text:
Through what methods and mechanisms can a multi-material FDM printer operate?
I now own the Prusa3D MMU2.  The benefits, costs, and experience others have had is well documented.  I am interested in rebuilding my large, home-designed delta machine to be multi-material, and don't want to overlook strategies I haven't considered.
My original implementation used an E3D Kraken as the hot-end, and handled the inevitable delta tilt by adding two additional degrees of freedom to the head to lower the selected nozzle to the bed.  I've been through three generations of mechanisms, and I think the third will work.
But, I feel that I am not seeing obvious and better alternatives.
So, the question:  Through what methods and mechanisms can a multi-material (different polymers, different temperatures) FDM printer operate, and are there available designs or examples of best practices for those methods?

Let's look at various methods:
Multiple Hotends
The oldest version and one of the best to print materials at vastly different print temperatures (like printing a cheaper PLA infill into a Polycarbonate shell - the print temperature difference is 60-100 °C) is to have 2 or more hotends. This way also avoids the need for purging towers. It does, however, limit the maximum size of the used printbed and few 2-printhead machines are cheap.
Y-Coupler
Using a bowden setup, a Y-coupler could be used to feed the filament from 2 extruders into one hotend. On the switching tool command, E0 would pull the filament back some couple millimeters beyond the coupler and then E1 would push forward back into the meltzone. One will need a purging tower/object.
Special, multi-entry hotend
Some Hotends had been concieved that have 2 or more ways into the meltzone and the multiple extruders push along them. They generally are quite complex and hard to clean, but they allow to seamlessly blend between two filaments of the same material and create pretty much a controlled fade by precisely directing how much of either side is used on any layer. For clean cuts, a purging tower is necessary.
Splicing filament
This is what the Palette 2 and the Prusa MMU do: they push pieces of filament into a feeder tube that then are consumed by the printer via its own extruder. If they melt the filaments together like in the PAlette, it's proper splicing, if they just line up the next filament piece without merging into a spliced filament it's more like instant color switching.
This method is good for multi-color prints or using materials that have the same or similar1 melting temperatures. It might or might not need a purge tower/object to get rid of the residue in the zones between the filaments.
This could btw also be done manually but should be avoided.
1 - or rather not too dissimilar, if the slicer is set up to do it right. By setting up the slicer cleverly, one can have the extruder retract the filament, then adjust the heat over the purge tower and then resume extruding in the purge object at the changed temperature. PLA/PVA from a Prusa MMU is known and advertised to be doable, PLA/ABS might be possible this way. For extreme dissimilarities like PLA/PC (60-100 °C) I have my doubts though.
Usability
All of these variants are basically viable, but some have benefits over others. Service is in this comparison meant as repairing a broken extruder, maintaining as the operations needed to keep it in printing order.

multiple fully independent hotends is among the easiest to services. It could be direct drive (good for flexible filaments) or bowden. It is however heavy and usually not an option for delta printers. It has a downside that you have to perfectly level two hotend nozzles to be exactly on the same height, putting it in the hard to maintain category.

multiple hotends on the same carrier is harder to service and maintain in comparison to multiple independent hotends as the components are very close together. Especially nozzle height adjustments can be more finicky.

Y-Coupler needs to be a bowden and has problem with materials that are very stringy. That makes it especially bad for flexible materials. Maintaining is like a normal hotend and servicing is almost the same.
Special hotends are hard to come by but could be available for direct drive, making them possible for flexible filaments. They are, as already noticed, very hard to service.
Splicing filament can be done with either direct drive or bowden setups. It is probaby the most convenient to use after setup and has the maintenance and serviceability of a single hotend and a fully separate machine. Their biggest downside is price and setup time needed.

Deltas are tough to use with multiple nozzles since the plane of the central carrier is not parallel to the bed over the whole x-y range.  This is due to tiny manufacturing errors,  wear, and other errors which are compensated through bed leveling.

@cmm Y coupler and splicing are the best choices for Delta.

I'm a fan of Y couplers for things like deltas where you're trying to hit minimal effector mass. My own coreXY build I swapped the 8mm rods for 8mm CF tubes, and I'll be using Y couplers on a bowden setup for multi-material printing.

The Prusa MMU2 prints materials with somewhat different temperatures, and heats or cools the heat on filament switches.

@cmm Similar temperature doesn't mean same. I don't expect it to have very good results with extremely dissimilar materials though. Think PET (200°C) to Polycarbonate (260°C) or even higher.

I'll have to try it.  How about PLA (215°C) and ABS (255°C)?  That would be a 40°C difference.  I don' think it waits fully until the head is cool enough before feeding the next filament.  It does wait until it has withdrawn the filament to the cold end before heating the extruder.  But more importantly, you can print polycarbonate at 260°C?

@cmm 255-300 according to seller ; adjusted to reflect the operation of the splicing/filament switching. Good you brought it up.

I hadn't heard of nor seen Y couplings until you mentioned them here.

One of the easiest ways that I've seen, which I'm a fan of, is simply putting Y splitters on your Bowden tube and having multiple feeds to a single hot end. The main benefit is that you only need a single hot end, so you don't have to worry about extruder offset or alignment or anything like that, but you do have to worry about material blending somewhat. Basically you end up needing to build a "purge tower" next to your printed items that you use to transition from one material to another.
There's the Diamond hotend setup that basically moves the connections into the hotend itself, which reduces the size of your purge tower but increases the risk of burning if you're trying to print with materials with vastly different printing temps, like PLA and PETG.
You could also have swappable hotends but that requires you to be there to manually swap the print head twice per layer. Don't recommend.
Unfortunately there's only so many solutions to the multi material problem, either you put multiple materials through a single hotend, or you have multiple hotends. I'm a fan of the single hotend approach personally, especially on deltas where weight and space are at a premium and alignment becomes problematic.

Have you found a good way to use flex materials with Bowden extruders?

Not without ridiculous retraction settings. That said, you can also technically have your extruder mounted to the hotend, but still fed through a short 4-6 inch Bowden tube with Y connectors. It's kind of the worst of both worlds but a bowden that short shouldn't have substantial issues with flex filament.

@cmm: I'm using flex fine on the Ender 3 (bowden). See my question and answer here: https://3dprinting.stackexchange.com/q/8512/11157

Another way to combine the simpler geometry of a single nozzle, and to get the reduced mass of a single extrusion tool would be to make it like a CNC machine with a tool changer.  One material is printed, then the hot end, extruder, and feed tube are swapped out for another which is primed and ready with the next material.
Lots of mechanical precision problems exist for arranging for the nozzles to be in the very same place, plus or minus a small tolerance.  This is worsened by the presence of filament bits and strings which seem to eventually pollute the workspace.
If that could be worked out, one could have a plethora of extrusion tools, nozzle sizes, materials, multi-material mixing chambers, and other complexities.
E3D was talking about such a printer, but I haven't seen a product... only an invitation to send money as a show of interest in such a printer.


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Why have heater blocks on hotends?
I understand that heater blocks act as kind of “low-pass-filter” on the temperature change of the hotend, but why do we need that?
Wouldn’t it be better to have as little metal as possible in order to be able to control temperature changes quickly and precisely (using PID, PWM plus maybe some predictions based on printed G-code)?

Deltaprintr has a mini hotend that doesn't really have a heater block.

Let's look at the elements and what they do:
The Heater Cartridge (blue) is the device that converts electric to thermal energy to melt the plastic. 30 and 40 W are common.
The Thermosensor (red) is there to give feedback to the mainboard.
The Filament Path (gold) in this area is made up of the nozzle and the heatbreak, it contains the meltzone.
The Heater Block (transparent green) is the mounting for all parts. It also acts as the medium to transfer the thermal energy from the Heater Cartidge to the Thermo Sensor and the Filament Path. It also acts as a dampener for the control circuit.
Now, let's put things together and omit the wires and cold end (and internal geometry of the filament path, cause I am lazy):

Now, the construction gives us several reasons for the shape of the heater block:

Ease of construction. Taking a simple block and adding a couple of holes and one cut allows very fast production.
Maximum contact surface. To get the maximum contact surface to the heater cartrige, the heater block has to make contact along its whole length, dictating a minimum size in 2 direction. The same is true for the thermosensor.
The heater block transmits temperature pretty much radially from the heater cartridge. Because it is metal, the gradient between areas is very low, but it is measureable. These would be the thermal equivalent lines on heating up:

You may easily notice that the temperature lines appear more straight as they come closer to the filament path and thermosensor. This helps to give the filament in the heatbreak and nozzle more even heating and better printing.
The mockup I made has a deliberate flaw though: a change in temperature first affects the filament and then shows up on the sensor, making the temperature in the filament path wobble to the extreme. The Heater Block acts pretty much as a transmitter just as much as a time dilation between the heating command and the pickup.
Because this arrangement is not very good, let's swap sensor and filament path around and look at the same lines.

Now we have a much shorter feedback loop, allowing our printer to react quicker to temperature changes and the filament path also gets heated more evenly. The temperature inside the filament path does change less around the target temperature. The whole block now acts mostly as a distribution medium but also as a storage for heat energy:
Up to this point, we did not take into account a very simple fact: the hotend drains thermal energy via two areas:

The outer surface of the heater block emits heat to the air.
Filament gets molten and extruded.

Factor 1 is simple and here a bigger heater block actually is positive: The thermal 'storage' capacity is dependant on the volume, so goes with $xyz \approx a^3$. The surface to emit heat from goes with $2\times(xy+xz+yz)\approx 6\times a^2$. Plotting a graph of that shows us the square-cube law: the capacity increase for one unit does increase the surface just by a fraction of that, so the storage gets better the larger the heater block is.
Factor 2 is why we need to have a storage of thermal energy in the first place: the flow of filament is not exactly the same all the time. Of course, we have moments of even flow, but we also have moments of low or no flow when the printer moves between parts of the print. This alteration of the drain of thermal energy from the heater block means that if we would go down to a bare minimum size, we'd heat up the block fast whenever we are on a move action and cool as the extrusion starts till equilibrium is achieved again. The more thermal capacity is there to store energy, the less the lack of extrusion will immediately affect the print and the more even the temperature will be in the filament path.
Fast printing?!
How is faster printing achieved with a special hotend? Well, 4 factors are used in hotends meant for very fast or very hot printing:

Longer, more powerful heater cartridge.
Longer filament path.
Extra large Heater Block to even out the temperature changes under extrusion more.
Insulating the Heater Block to the air.

One of the prime examples would be an e3D-Volcano.

These pictures are fantastic.  I which I could vote more than once.

@user77232 all the mentioned parts, yes

Bigger block also means more oozing.

@VincentAlex no. Oozing is a result of bad installation

I think the idea is to not change the temperature fast. You want it to maintain a certain temperature so you have consistent flow. The extra mass at the hot end provides the mass which is needed to maintain the heat. If you don't maintain the heat while you print, you'll have inconsistent filament flow, which will screw up your print.

But if we want to extrude fast, we have to heat the filament faster. One way to do that is creating longer heat zones (volcano), but that leads to more oozing as well as increased friction (larger contact area). It seems a better approach would be to pump in more heat - but then we need to be able to stop quickly if extrusion stops or slows down

@user1282931 - If you want to "extrude fast" you need to keep heat in the hot end. You can't do that unless you have mass. Without the mass, the faster you extrude, the faster you're going to cool the hot end and the funkier the extrusion is going to be.

It seems all the heat that exits the hotend needs to be provided by the cartridge anyway, whether there is a block or not. Can’t I compensate for that by keeping the heater cartridge on and having the nozzle always a bit over the target temperature?

It doesn't seem I'm going to convince you that's why there's mass in the hot end. You have mass to keep the temperature constant. You DON'T WANT it to be changing temps fast ... you want it to be constant. The only reason to change temps is when you change filaments (ie: say from PLA to PETG or whatever). Running the heater cartridge all the time will be hot spots. The closer to the cartridge, the hotter it'll be. The mass in the hot end also helps to distribute the heat so hot spots won't happen.

We don't really care about the temperature of the heater block.  We care about the temperature of the molten plastic.  We want the plastic temperature to be constant, which is difficult under varying extrusion rates.  We aren't measuring temperature, and we can't change the temperature of the heater block fast enough to use feed-forward compensation.  We can't change the heater block temperature as fast as we change the extrusion rate.  Instead, we compromise and try to limit the thermal resistance between the thermistor and the plastic.

Heater blocks are used on hot ends because they are the current engineering compromise between the design factors of cost, reliability, lifetime, maintenance, and performance.
Ideally, there would be no heater block, the heater would have infinite wattage, the nozzle would heat and cool instantly while transferring heat to the filament, and the temperature of the molten plastic would be measured instantly.
But as this is engineering instead of magic, none of these conditions is the ideal.  The engineering problem is to find the right compromise.
Each of these can be treated separately.  How do we measure the temperature of the plastic?  Assume we have a tiny thermocouple in the plastic flow.  Why thermocouple?  Because it is smaller, less prone to manufacturing tolerance, and is good for higher temperatures.
Imagine a heater where the heater wire forms the threads into which the nozzle screws and also where the nozzle has thinner walls to reduce the nozzle's thermal mass.  Further, the nozzle is made of diamond which has almost ten times the thermal conductivity of brass.  Yes, machining diamond is not easy, and the supply of large enough diamonds is limited, but we're trying not to compromise yet.
In this scheme, there is no heater block.  We instantly know the temperature of the plastic, and we can dump large amounts of heat into the system to get a high enough temperature.  We still must hold the nozzle in place and connect it with the filament source (typically the job of the "heat break"), so let's make that of thermally insulating ceramic so it stays out of the heat transfer process.
With this, we have a hot-end where we would have great control.  We are directly measuring the parameter we care about -- the temperature of the plastic.  We can deliver heat rapidly.  When the extrusion rate increases, the temperature drops a little and we dump in more heat.  The thermocouple is fragile (don't try a cold-pull), and is subject to wear.  The nozzle is very expensive and difficult to make.
Ok, move the thermocouple to the outside of the nozzle's tip.  Now we have a heater intimately wrapped with the threads of the nozzle.  That is probably hard to make, so let's use a conventional heater cartridge that is very close to the nozzle threads.  Let's put in as many heaters as we can pack together near the threads.  If we angle the heaters they won't hit each other, so suppose we can put in four heaters spaced around the nozzle.  More heat, less distance from the heat to the nozzle.  Make this new heat block of silver, just like the nozzle.  Silver has 80% higher thermal conductivity than aluminum.  (Or we could use diamond, but really, who has diamonds that big?)
I was assuming a thermocouple to measure the nozzle temperature, and it is small enough that it could nestle into a small home in the nozzle.  We could use a thermister pressed into a hole in the nozzle, but experience has shown that thermisters are fragile.  We have found that the tiny glass beads are prone to either breaking of the glass, separating from the thin leads.  The electronics to measure temperature with a thermistor is simpler and less expensive than a thermocouple and seems to have good enough resolution, accuracy, and temperature range.  If we follow that experience, we will package the thermistor in a cartridge housing that is easier and more reliably placed and protects the thermistor from damage.  But the cartridge is too large to connect directly with the nozzle, so we'll put it in the same block with the heaters.  After all, they are silver and conduct heat very well.
This may be a better hot-end than the conventional system.  It heats faster and more accurately measures the temperature of the plastic.  But there are problems. Silver is heavier, and four heaters and their wiring have more mass than one.  And, the holes for the heater cartridges are each in a different plane, so it is more expensive to machine.  And the price for the silver may be a factor.  Silver costs (today) \$215/lb, where aluminum is $0.80/lb.
In this answer, I have tried to show how heater blocks are useful for coupling the heat from the heaters to the nozzle and to show that there are alternatives with perhaps superior performance but problems with reliability or cost.
Edit:  In a comment, the OP asks why we do not machine away extra material that is not required to couple heat to the nozzle, and correctly raised the issue of cost.  There may also be a performance issue.
The conventional heater is only on one side of the nozzle.  When the heater is cooled by the filament, it draws heat from all sides.  The thermal mass on the non-heated side helps with stability by providing a source of heat from which the nozzle can draw.
On the heater side, a factor to consider is the coupling of heat from the heater cartridge to the heater block.  Removing additional material should be evaluated to assure that it does not increase the thermal resistance from the heater to the rest of the block and the thermistor.  This is important to help with thermal stability, and also to assure that the heaters do not overheat themselves.
For thermal conductivity values, I used this reference.
For metals pricing, I used Google to find spot metal prices on 6/3/2019.

This is a great answer, thank you! It does suggest though that less mass in the block is in any case desirable. One question remains then: why not machining away any material from the block that isn’t necessary to directly connect nozzle, heater cartridge and termistor? Is it simply the added machining cost of cutting away corners/drilling holes that is preventive or is there some other reason?

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

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Cura settings for Fabrikator Mini V2 Turnigy or Malyan M100
I am trying to run this 3D printer:

Fabrikator Mini V2 Turnigy/Malyan M100

Does anyone have the Cura settings?

Look here for a similar question.

These setting should come from the manufacturer of the machine.

The settings of a printer are set in a different section and describe the printer specifics  (bed size, G-code flavor). The profile posted as answers below is a print-profile, it is only valid for something you print on the machine, e.g. in PLA, hence this might not work for ABS as that requires a different profile. This question already has been asked how to add specific printer parameters in Ultimaker Cura for a printer.

I googled your machine name and found this HobbyKing page.  There is a link here to CURA settings.
Page with CURA settings

I thought it better if I included the Cura profile settings, pointed to in cmm's answer, here, in case of link death:
[profile]
layer_height = 0.2
wall_thickness = 0.8
retraction_enable = True
solid_layer_thickness = 1.2
fill_density = 20
nozzle_size = 0.4
print_speed = 60
print_temperature = 200
print_temperature2 = 0
print_temperature3 = 0
print_temperature4 = 0
print_temperature5 = 0
print_bed_temperature = 60
support = Touching buildplate
platform_adhesion = Brim
support_dual_extrusion = Both
wipe_tower = False
wipe_tower_volume = 15
ooze_shield = False
filament_diameter = 1.75
filament_diameter2 = 0
filament_diameter3 = 0
filament_diameter4 = 0
filament_diameter5 = 0
filament_flow = 100
retraction_speed = 30
retraction_amount = 3
retraction_dual_amount = 16.5
retraction_min_travel = 1.5
retraction_combing = All
retraction_minimal_extrusion = 0.02
retraction_hop = 0.0
bottom_thickness = 0.3
layer0_width_factor = 100
object_sink = 0.0
overlap_dual = 0.15
travel_speed = 100
bottom_layer_speed = 20
infill_speed = 0.0
solidarea_speed = 0.0
inset0_speed = 20
insetx_speed = 0
cool_min_layer_time = 3
fan_enabled = True
skirt_line_count = 2
skirt_gap = 4.0
skirt_minimal_length = 150.0
fan_full_height = 0.5
fan_speed = 100
fan_speed_max = 100
cool_min_feedrate = 10
cool_head_lift = False
solid_top = True
solid_bottom = True
fill_overlap = 15
perimeter_before_infill = False
support_type = Lines
support_angle = 60
support_fill_rate = 15
support_xy_distance = 0.7
support_z_distance = 0.15
spiralize = False
simple_mode = False
brim_line_count = 5
raft_margin = 5.0
raft_line_spacing = 3.0
raft_base_thickness = 0.3
raft_base_linewidth = 1.0
raft_interface_thickness = 0.27
raft_interface_linewidth = 0.4
raft_airgap_all = 0.0
raft_airgap = 0.22
raft_surface_layers = 2
raft_surface_thickness = 0.27
raft_surface_linewidth = 0.4
fix_horrible_union_all_type_a = True
fix_horrible_union_all_type_b = False
fix_horrible_use_open_bits = False
fix_horrible_extensive_stitching = False
plugin_config =
object_center_x = -1
object_center_y = -1

[alterations]
start.gcode = ;Sliced at: {day} {date} {time}
    ;Basic settings: Layer height: {layer_height} Walls: {wall_thickness} Fill: {fill_density}
    ;Print time: {print_time}
    ;Filament used: {filament_amount}m {filament_weight}g
    ;Filament cost: {filament_cost}
    ;M190 S{print_bed_temperature} ;Uncomment to add your own bed temperature line
    ;M109 S{print_temperature} ;Uncomment to add your own temperature line
    G21        ;metric values
    G90        ;absolute positioning
    M82        ;set extruder to absolute mode
    M107       ;start with the fan off
    G28 X0 Y0  ;move X/Y to min endstops
    G28 Z0     ;move Z to min endstops
    G1 Z0.2 F{travel_speed} ;move the platform down 15mm
    G92 E0                  ;zero the extruded length
    G1 X75 E10 F{travel_speed}       ;extrude 10mm of feed stock
    G92 E0                  ;zero the extruded length again
    G1 F{travel_speed}
end.gcode = ;End GCode
    M104 S0                     ;extruder heater off
    M140 S0                     ;heated bed heater off (if you have it)
    G91                                    ;relative positioning
    G1 E-1 F300                            ;retract the filament a bit before lifting the nozzle, to release some of the pressure
    G1 Z+0.5 E-5 X-20 Y-20 F{travel_speed} ;move Z up a bit and retract filament even more
    G28 X0 Y0                              ;move X/Y to min endstops, so the head is out of the way
    M84                         ;steppers off
    G90                         ;absolute positioning
    ;{profile_string}
start2.gcode = ;Sliced at: {day} {date} {time}
    ;Basic settings: Layer height: {layer_height} Walls: {wall_thickness} Fill: {fill_density}
    ;Print time: {print_time}
    ;Filament used: {filament_amount}m {filament_weight}g
    ;Filament cost: {filament_cost}
    ;M190 S{print_bed_temperature} ;Uncomment to add your own bed temperature line
    ;M104 S{print_temperature} ;Uncomment to add your own temperature line
    ;M109 T1 S{print_temperature2} ;Uncomment to add your own temperature line
    ;M109 T0 S{print_temperature} ;Uncomment to add your own temperature line
    G21        ;metric values
    G90        ;absolute positioning
    M107       ;start with the fan off
    G28 X0 Y0  ;move X/Y to min endstops
    G28 Z0     ;move Z to min endstops
    G1 Z0.2 F{travel_speed} ;move the platform down 15mm
    T1                      ;Switch to the 2nd extruder
    G92 E0                  ;zero the extruded length
    G1 X75 E10 F{travel_speed}       ;extrude 10mm of feed stock
    G92 E0                  ;zero the extruded length again
    G1 F200 E-{retraction_dual_amount}
    T0                      ;Switch to the first extruder
    G92 E0                  ;zero the extruded length
    G1 X75 E10 F{travel_speed}       ;extrude 10mm of feed stock
    G92 E0                  ;zero the extruded length again
    G1 F{travel_speed}
end2.gcode = ;End GCode
    M104 T0 S0                     ;extruder heater off
    M104 T1 S0                     ;extruder heater off
    M140 S0                     ;heated bed heater off (if you have it)
    G91                                    ;relative positioning
    G1 E-1 F300                            ;retract the filament a bit before lifting the nozzle, to release some of the pressure
    G1 Z+0.5 E-5 X-20 Y-20 F{travel_speed} ;move Z up a bit and retract filament even more
    G28 X0 Y0                              ;move X/Y to min endstops, so the head is out of the way
    M84                         ;steppers off
    G90                         ;absolute positioning
    ;{profile_string}
start3.gcode = ;Sliced at: {day} {date} {time}
    ;Basic settings: Layer height: {layer_height} Walls: {wall_thickness} Fill: {fill_density}
    ;Print time: {print_time}
    ;Filament used: {filament_amount}m {filament_weight}g
    ;Filament cost: {filament_cost}
    ;M190 S{print_bed_temperature} ;Uncomment to add your own bed temperature line
    ;M104 S{print_temperature} ;Uncomment to add your own temperature line
    ;M109 T1 S{print_temperature2} ;Uncomment to add your own temperature line
    ;M109 T0 S{print_temperature} ;Uncomment to add your own temperature line
    G21        ;metric values
    G90        ;absolute positioning
    M107       ;start with the fan off
    G28 X0 Y0  ;move X/Y to min endstops
    G28 Z0     ;move Z to min endstops
    G1 Z0.2 F{travel_speed} ;move the platform down 15mm
    T2                      ;Switch to the 3rd extruder
    G92 E0                  ;zero the extruded length
    G1 X75 E10 F{travel_speed}       ;extrude 10mm of feed stock
    G92 E0                  ;zero the extruded length again
    G1 F200 E-{retraction_dual_amount}
    T1                      ;Switch to the 2nd extruder
    G92 E0                  ;zero the extruded length
    G1 X75 E10 F{travel_speed}       ;extrude 10mm of feed stock
    G92 E0                  ;zero the extruded length again
    G1 F200 E-{retraction_dual_amount}
    T0                      ;Switch to the first extruder
    G92 E0                  ;zero the extruded length
    G1 X75 E10 F{travel_speed}       ;extrude 10mm of feed stock
    G92 E0                  ;zero the extruded length again
    G1 F{travel_speed}
    ;Put printing message on LCD screen
    M117 Printing...
end3.gcode = ;End GCode
    M104 T0 S0                     ;extruder heater off
    M104 T1 S0                     ;extruder heater off
    M104 T2 S0                     ;extruder heater off
    M140 S0                     ;heated bed heater off (if you have it)
    G91                                    ;relative positioning
    G1 E-1 F300                            ;retract the filament a bit before lifting the nozzle, to release some of the pressure
    G1 Z+0.5 E-5 X-20 Y-20 F{travel_speed} ;move Z up a bit and retract filament even more
    G28 X0 Y0                              ;move X/Y to min endstops, so the head is out of the way
    M84                         ;steppers off
    G90                         ;absolute positioning
    ;{profile_string}
start4.gcode = ;Sliced at: {day} {date} {time}
    ;Basic settings: Layer height: {layer_height} Walls: {wall_thickness} Fill: {fill_density}
    ;Print time: {print_time}
    ;Filament used: {filament_amount}m {filament_weight}g
    ;Filament cost: {filament_cost}
    ;M190 S{print_bed_temperature} ;Uncomment to add your own bed temperature line
    ;M104 S{print_temperature} ;Uncomment to add your own temperature line
    ;M109 T2 S{print_temperature2} ;Uncomment to add your own temperature line
    ;M109 T1 S{print_temperature2} ;Uncomment to add your own temperature line
    ;M109 T0 S{print_temperature} ;Uncomment to add your own temperature line
    G21        ;metric values
    G90        ;absolute positioning
    M107       ;start with the fan off
    G28 X0 Y0  ;move X/Y to min endstops
    G28 Z0     ;move Z to min endstops
    G1 Z0.2 F{travel_speed} ;move the platform down 15mm
    T3                      ;Switch to the 4th extruder
    G92 E0                  ;zero the extruded length
    G1 X75 E10 F{travel_speed}       ;extrude 10mm of feed stock
    G92 E0                  ;zero the extruded length again
    G1 F200 E-{retraction_dual_amount}
    T2                      ;Switch to the 3rd extruder
    G92 E0                  ;zero the extruded length
    G1 X75 E10 F{travel_speed}       ;extrude 10mm of feed stock
    G92 E0                  ;zero the extruded length again
    G1 F200 E-{retraction_dual_amount}
    T1                      ;Switch to the 2nd extruder
    G92 E0                  ;zero the extruded length
    G1 X75 E10 F{travel_speed}       ;extrude 10mm of feed stock
    G92 E0                  ;zero the extruded length again
    G1 F200 E-{retraction_dual_amount}
    T0                      ;Switch to the first extruder
    G92 E0                  ;zero the extruded length
    G1 X75 E10 F{travel_speed}       ;extrude 10mm of feed stock
    G92 E0                  ;zero the extruded length again
    G1 F{travel_speed}
    ;Put printing message on LCD screen
    M117 Printing...
end4.gcode = ;End GCode
    M104 T0 S0                     ;extruder heater off
    M104 T1 S0                     ;extruder heater off
    M104 T2 S0                     ;extruder heater off
    M104 T3 S0                     ;extruder heater off
    M140 S0                     ;heated bed heater off (if you have it)
    G91                                    ;relative positioning
    G1 E-1 F300                            ;retract the filament a bit before lifting the nozzle, to release some of the pressure
    G1 Z+0.5 E-5 X-20 Y-20 F{travel_speed} ;move Z up a bit and retract filament even more
    G28 X0 Y0                              ;move X/Y to min endstops, so the head is out of the way
    M84                         ;steppers off
    G90                         ;absolute positioning
    ;{profile_string}
support_start.gcode =
support_end.gcode =
cool_start.gcode =
cool_end.gcode =
replace.csv =
preswitchextruder.gcode = ;Switch between the current extruder and the next extruder, when printing with multiple extruders.
    ;This code is added before the T(n)
postswitchextruder.gcode = ;Switch between the current extruder and the next extruder, when printing with multiple extruders.
    ;This code is added after the T(n)

Note these are some customer uploads, from the HobbyKing page for Mini Fabrikator V2 3D Printer - Silver (US Plug), under the Upload Files tab, click the CURA PROFILE_3.ZIP zip file.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
How to create supports for the parts hanging above 45 degrees?
Do you have any specific process recommendations to achieve support for the parts hanging above 45 degrees, using open source software?

Hi VampishWolf, welcome to 3D Printing.SE! Sorry, but this question cannot be answered as SE is not about product recommendation please read [help] and take the [tour]. All slicer software applications are able to do this for you, some are free (e.g. Ultimaker Cura, Slic3r, etc.). It will be a setting in the huge pile of settings to set the support angle. Alternatively you can create the supports in the program you designed the object in or open the model in a program that can add or change the design.

As it stands your question is a bit broad so could you clarify your question with a specific example, using a model, images, diagram? We can't really recommend software brands, but process recommendation is permitted. BTW, don't any of the other support structure questions answer your question?

I thought the slicer software like Cura or Slic3r did that for you, either automatically or with a minimum of effort. There are plenty of youtube videos to walk you thru using either too. In my famity, we (i.e. my wife) are using Cura at the moment. We've only printed 1 part that needed supports so far, it was a file we found on thingiverse and I don't know if it includede the supports or not in the file that she downloaded.

PrusaSlicer has support enforcers you can place on areas that need support.
See this video: Prusa Slicer Support Enforcers.
Automatic supports
There are automatic supports, in the Supports dropdown menu, select Everywhere:

Click Yes in the resulting dialog:

Click on the Slice icon in the bottom left:

You will end up with a lot of supports:

However, this method generally results in too much support...
Custom Suport Enforcers
So turn off Supports in the drop down menu, select None:

Now, in the Print Settings tab, under Support Material, disable Auto Generated Supports and enable Generate Support Material:

Then right click on the model and select Box from the Add Support Enforcer menu item:

You can move by clicking the Move button in the left hand palette,

resize by clicking the Resize button

and re-shape the Box as necessary, to support the difficult overhanging parts parts only. Here we can see three boxes have been added - pale blue for the previously added boxes and green for the current box:

And a fourth final Box for the tail:

Now, when you hit the Slice button, there will be much less support structure than when using Automatic supports:

Parts of the model that the slicer thinks still needs support will be highlighted in dark blue (such as the elbow and back of the head):

Add a cylinder support enforcer:

Resize and re-shape as before and move into position below the elbow:

Adding a second cylinder as a support enforcer

Upon hitting Slice:

Now in Print Settings - Support Material - Pattern change it from Rectilinear to Rectilinear Grid:

For prints with curves and details Rectilinear Grid works better, than Rectilinear (which is fine for supporting a plain cube in the air). It is easier to break the support off the print.
Now save your hard work as an AMF file:

This file maintains all of the support enforcers so that they can be modified if the actual print needs some adjustments - without having to re-add all of the support enforcers all over again.

I've updated your answer for you :-)

@Greenonline You've been busy! Nice addition to the answer.

@Greenonline Perhaps it's better to make your own answer when editing that much though...

@Jeroen3, Yes, sorry about that but you found the video and I didn't want to take credit for that... :-) I must admit that when I started adding info I didn't realise that there would be so much of it! I expected only one or two screenshots. Lol. But yes, you are right, for such extensive edits, it would have been better for me to refer to your answer and add the process as my own answer. Ah well, next time I will. Thanks for finding the link anyway... it was a useful learning experience :-)


text:
PTFE detoriation temperature
I read that PTFE starts to deteriorate past 260 °C. Does that mean heating to 250 °C is no problem at all, or will that destroy the PTFE material over time to?

Degradation starts at 260 °C and shifts towards full blown decomposition towards 350 °C. 250 °C is technically fine, but you should keep in mind that you've got little to no wiggle room for error at that temperature. Your thermistor and board may not be accurate enough to guarantee you'll never overshoot that temperature, and the way 3D printers often handle temperature adjustment exacerbates that risk. You can print at 250 °C, just be aware you've got basically no margin for error.

how fast does ptfe detoriorate at 260°? is that something that takes seconds or days?

More like weeks or months.

yeah if you're exactly at the temperature it's going to take an extended amount of time. I still wouldn't try printing at those temperatures though, because PTFE breaking down isn't an issue because it's wearing out, it's an issue because of the highly toxic and corrosive compounds that teflon degenerates into. Check this link out:
https://www.ewg.org/research/canaries-kitchen/teflon-offgas-studies

"Highly toxic" is meaningless without specifying concentration and exposure. Non-stick pans regularly get around or above 250°C in cooking use. I'd be a lot more concerned about the fumes from the materials being printed at these temperatures than from the PTFE.

Also, the PTFE end is not supposed to be getting that hot - if it were, the filament would be melting inside it. Assuming your cooling is working right (and if it's not, you'll have catastrophic failure regardless of what your hotend temp is set to), it should be at least a few degrees, and ideally a few tens of degrees, cooler than the set temperature.

Also note that 260C equals 500F. It might be a less exact limit than we think.

High temperature rated PTFE tape is rated for up to 288°C (550°F).

authors: اصيل الخيبري


text:
High temperature flexible filament
I need to cool some liquid (250 °C) while it’s flowing through a tube which has to be able to bend and flex.
My idea is to make a flexible tube with a second tube spiraling around it through which coolant will flow.
I’d like to 3D print this tube if possible so I wonder if there is some printable filament that:

doesn’t melt at 250 °C
is flexible enough that it can print some tube that can bend (bending radius of 30 cm)
optimally also has good heat conductivity

Is there any 3D printer filament available that has these properties?

Are you looking to print the first straight tube, or the second spiral tube, or an object with both?  It matters because a filament with supports a 250°C operating temperature will be hard to print on most printers.  If you want the spiral tube to be printed, that is easier since it is not exposed to the 250°C liquid.

Googling "high temperature TPU" suggests that there are forms that withstand up to 300°C or higher, but I'm not aware of any printable filament, and you'd need an extreme hotend to print it.

simple: no, not even close, at least in the consumer/maker sphere; it's possible that the military or specialized industries have a proprietary method, but certainly not something we can order.

Is there a reason you can't use a PTFE tube?

Ok, so to answer the primary question: What flexible filament will operate consistently at 250 °C?
Man, this is a tough one. Some filaments, like PEEK and ULTEM 1010 can operate up in the 200 °C range, but they're not flexible at all.
Silicon might be able to work, but you're still pushing boundaries.
Now, I'm lucky to be in a 3D printing company and we're testing a super-high-temp flexible material, very similar in temperatures to ULTEM. I'll definitely check back and let you know how it goes, but...
Honestly, that's so hot! Readily available thermoplastics may not be an option unless you're in aerospace with an unlimited budget which, based on the requirements, would make sense, lol!
I'd say the most readily available way to get this done would be 3D printing a mold, in which to put your silicone, and bam -- you've got the part.

3D printing nerd showed a couple of filaments that fits this in his latest video "Printers at RAPID + TCT 2019":

Firstly a Nylon 6 high temperature filament:

Another part of the video shows another flexible print, created on a four axis 3D printer, using TPU filament:

Whilst your answer may be technically correct, it is rather terse, and, as such, it has been recommended for deletion, unfortunately. If you could expand it then you may get a more positive response, add some screenshots & text explaining the process. I would recommend that in addition to reading some highly voted answers to gauge the standard expected, that you take a look at the help section relating to answering questions, in particular [answer], and take the [tour] for more information on how stack exchange works. Thx

Are you sure these filaments are able to withstand 250 °C without deforming?

To support the comment of @TomvanderZanden, the last edit you made (@Greenonline) included normal TPU but printed on a 4th axis (ideal to withstand the hoop stresses and prevent printing of support material if printed upright), I don't know if this answers the question. I'm still in doubt if the first part of the answer answers the question. 250 ºC is pretty high, even Nylon would not take that IIRC that stops at about 120 ºC, higher temp thermoplastics exist, but the question is: "Are they printable and flexible?".


text:
How is E value calculated in Slic3r?
I want to know the math behind how Slic3r calculates E values. $E_{value}$ represents amount of filament in mm (unless volumetric extrusion is selected) that has to be fed into the hotend to obtain a road of specific extrusion width.
Consider an example with following parameters:

Nozzle diameter = 0.6 mm
Layer height = 0.35 mm
Extrusion width = 0.61 mm (for external perimeter)
Length of the line segment (distance of the deposition path) = 98.2 mm
Diameter of filament = 1.75 mm

First part of the question: How is $E_{value}$ calculated for this case?
Second part of the question: How is velocity of extruder motor calculated for this case?
The Slic3r manual has limited information on flow math but is not comprehensive.
Let's assume volume of plastic fed in equal volume of plastic comes out
$$Volume_{in} = \pi\times{(\frac{d}{2})}^2 \times E \times x = \frac{\pi\cdot d^2}{4}\times E \times x$$
Where,

$d$ = diameter of the filament
$x$ = extrusion multiplier
$E$ = $E_{value}$ to solve for

$$Volume_{out} = (A_{road} \times L)$$

Length of path, $L$, is obtained from start and end coordinates
Area of the road, $A_{road}$, is calculated according to this link (Slic3r flow math; Section: Extruding on top of a surface). The formula for area of the road according to Slic3r manual is:

$$A_{road} = (w - h)\times h + \pi\times{(\frac{h}{2})}^2 $$
Where,

$w$ = Extrusion width
$h$ = layer height

Seems like I am missing something. Math doesn't yield me same result as Slic3r $E$ value.

Many of you have marked this question duplicate. I know the first question is similar to what has asked before (calculating E value) but the answer doesn't match actual E value in G-code.
Also there is a second question on how to calculate extrusion speed given an E value
I have added G-code from actual Slic3r with the same settings as above to check the math.
The advance extrusion width settings in slic3r are as shown in the picture below:

The settings are from a Prusa config for 0.6 mm nozzle
Consider a 100 mm x 100 mm x 5 mm part (X x Y x Z dimensions). Following is the output G-code from Slic3r:
; generated by Slic3r 1.3.0 on 2019-06-04 at 16:36:24

; external perimeters extrusion width = 0.61mm (6.55mm^3/s)

; perimeters extrusion width = 0.65mm (10.54mm^3/s)

; infill extrusion width = 0.70mm (15.25mm^3/s)

; solid infill extrusion width = 0.65mm (8.78mm^3/s)

; top infill extrusion width = 0.60mm (6.43mm^3/s)

------ Values of parameters defined in Slic3r -------

first_layer_acceleration = 1000
first_layer_bed_temperature = 60
first_layer_extrusion_width = 0.65
first_layer_speed = 30
first_layer_temperature = 215
first_layer_height = 0.35
max_print_speed = 100
nozzle_diameter = 0.6
external_perimeter_extrusion_width = 0.61

------ some initialization lines above --------
G1 F1800

G1 X78.400 Y169.100 E8.21483 ; perimeter

**G1 X78.400 Y70.900 E8.21483 ; perimeter**

G1 X176.600 Y70.900 E8.21483 ; perimeter

G1 X176.600 Y169.010 E8.20731 ; perimeter

G1 X177.175 Y169.675 F10800.000 ; move to first perimeter point

The above code snippet refers to the perimeter of the very first layer in the print. Let us consider the highlighted line in above G-code. According to equations we have above, the values of the variables are:

$d$ = 1.75
$x$ = 1
$E$ = $E_{value}$ to solve for
$w$ = 0.61
$h$ = 0.35
$L$ = 169.100 - 70.900 = 98.2

Area of the depositied road is:
$$A_{road} = (0.61 - 0.35)\times 0.35 + \pi\times{(\frac{0.35}{2})}^2 $$
$$A_{road} = 0.187211 mm^2 $$
For calculating $E_{value}$, We use volume equality
$$Volume_{in} = Volume_{out}$$
$$E_{value} = \frac{A\times L \times 4} {\pi\times d^2 \times x} = \frac{0.187211 \times 98.2 \times 4} {\pi \times 1.75^2 \times 1} = 7.6432 $$
The $E_{value}$ in the G-code is 8.214
This is a big difference isn't it? I know about the die swell effect and expansion of molten plastic at the tip, but there seems to be no uniform compensation factor for this!

Slic3r is open-source. You don't have to assume anything.

Closely related to, but not duplicate of How is the E argument calculated for a given G1 command?

@Oscar, I saw this post earlier. still the calculations dont match with those of actual values output by slic3r

@Rock It should, I've calculated it before in a different answer, it should match or at least very close as there might be some second order effects in play. You should edit the question with an example piece of G-code from slic3r and your calculation. Then we can verify it, now it is guess work. Bit still, the numbers should add up, fortunately, this isn't rocket science ;). A second order effect is die swell, the lines are thicker than the nozzle size on extrusion, there might be compensations in play.

To answer your first question:
Your calculations are not wrong, they are correct for a normal layer (uncorrected) layer. These calculations should get you very near the solution. The problem is that there are default modifiers at play that modify the extrusion process which become apparent when you change them or look at the hoover hint in the advanced printer settings section. E.g. see the image below of the "Print Settings" graphical user interface; specifically look at the hoovering hint:

The hoovering hint tells you that there is a 200 % modifier at play. What! a default modifier without me knowing? Well...., if we had looked at the
Slic3r Manual (The Important First Layer) a little better, we read that:

Fatter extrusion width. The more material touching the bed, the better
  the object will adhere to it, and this can be achieved by increasing
  the extrusion width of the first layer, either by a percentage or a
  fixed amount. Any spaces between the extrusions are adjusted
  accordingly.
A value of approximately 200 % is usually recommended, but note that
  the value is calculated from the layer height and so the value should
  only be set if the layer height is the highest possible. For example,
  if the layer height is 0.1 mm, and the extrusion width is set to 200 %,
  then the actual extruded width will only be 0.2 mm, which is smaller
  than the nozzle. This would cause poor flow and lead to a failed
  print. It is therefore highly recommended to combine the high first
  layer height technique recommended above with this one. Setting the
  first layer height to 0.35 mm and the first extrusion width to 200 %
  would result in a nice fat extrusion 0.65 mm wide.

Tada! There we have the modifier from the screenshot; 200 % (this is expressed as a percentage over the layer height, and causes that an additional filament scale factor bigger than 1 is at play; the $x$ in your equations).
To answer the second question:
That should be rather straight forward, you know how long the path is and at which speed the head is moving (either at constant speed, decelerating or accelerating) and how much of filament you need to deposit, at the end point all filament needs to be deposited so you can calculate how fast the extrusion needs to be to accomplish that.

If you calculate back from a volume of 8.214 mm2 and solve for unknown $w$ you see that this yields $ w = 0.65\ mm $, and that is exactly what is stated as first layer width in your Slic3r settings; I quote:

first_layer_extrusion_width = 0.65

P.S. When you look into the source code of Slic3r, if you dig deep, you find that extrusion width is bound by minimum and maximum values, it could well be that that is causing the value to differ from 0.70 mm (200 % of 0.35).

Excellent..! :-)

Very nice. I know it's a quote, but... "Setting the first layer height to 0.35 mm and the first extrusion width to 200 % would result in a nice fat extrusion 0.65 mm wide." - gets out calculator...

@Davo Yep, my HP-48 G says 0.70, please don't shoot the messenger ;)

@0scar Thank you for the explanation. The calculations match up when I use extrusion width = 0.65mm. I checked my slic3r config (edited my original question to add the picture). I am using a config from Prusa for 0.6 mm nozzle. Although its not set to auto, the value still corresponds to 200% (default). What was throwing me off was that the lines of g-code in my question correspond to external perimeter and there is a specific value for external perimeter width for external perimeters (0.61 mm). Does, the "first layer" width overrides the perimeter width too?

@Rock Yes first layer overrides other settings.

@0scar can you give me an example for the second part of the question that you answered above? Maybe use a trapezoid velocity profile for this?

@Rock A trapezoid profile is not possible, it is constant, accelerating or decelerating, there are no other options. I'll update the answer with an example.

@0scar doesn't the trapezoid velocity profile contain all the three segements (accelerating, constant and decelerating) you mentioned? . . . waiting for the answer for second part of the question


text:
Power consumption of filament extrusion
I'd like to calculate the power lost through the filament being extruded (or in other words, at how many Watts I'd have to run an ideal heater that loses heat ONLY through filament so that it stays at constant temperature).

Power is defined in Watts as $\text W =\frac{\text J}{\text s}$
Specific heat capacity of a material is defined as $C =\frac{\text J}{ \text K \times\text{kg}}$

When extrusion happens, the filament of higher temperature leaves the hotend while the same weight of filament of lower temperature enters the hotend.
Let's say the specific heat capacity of the filament is $C$ and the extrusion rate $r$ is given with units kg/s. The temperatures are $T$.
Is it correct then to say that the power consumption of filament extrusion is $W = (c\times T_\text{Nozzle} - c\times T_\text{Environment}) \times r$
meaning that if I would run a heater cartridge at exactly "W" watts and extrude filament with rate "r" and the block would not loose heat through any other means than through the filament extrusion, then the nozzle temperature would stay constant?

Specific heat of a material is drastically different in solid and liquid phase. In addition, there's the heat of transition: the energy required to change from solid to liquid (with no change in temperature). And remember that the hotend heats the liquid phase to well above the transition temperature.

@CarlWitthoft: The materials in question don't have discrete solid and liquid phases involved (no discrete phase change and thus, at least AIUI, no jump in energy without a change in temperatures) but a glass transition temperature at which they begin to soften.

This is very simply stated, in fact the specific heat is a function of temperature and state of the material (liquid or solid). Also you need to consider which type of specific heat you use, e.g. the one for constant volume $C_V$ or for constant pressure $C_P$. Constant pressure is probably preferred considering the mechanics of the printer (pressing filament into the nozzle-heatbreak assembly).
A very interesting source of information is the PolymerDatabase.com.
This source confirms that:

In the case of polymers, we have to distinguish between the heat capacity of liquid, rubbery and glassy polymers. The heat capacity increases with increasing temperature, therefore, a liquid or rubbery polymer can hold more energy than a solid polymer. All materials show this increase in heat capacity with temperature.

also:

Specific heat capacities as a function of temperature have been published for only a limited number of polymers. In many cases, the heat capacity (at constant pressure) as a function of temperature can be approximated by straight lines.

In such cases you can use the value of the specific heat at a predefined temperature (in thermodynamics that is frequently 298 K) to get approximations for your thermoplastic material. These formulae can then be used to integrate over the temperature rise.
Please remember that a cartridge is of a certain value of Watt; to have a lower power, the cartridge modulates voltage to keep the heating block within a predefined temperature range.

No.
Your formula is quite off, and it starts with the nomenclature:
Watt
Watt is the unit of energy transfer which equals power.
The commonly used term "wattage" does not exist in science. It is a very despised shorthand only used in terms of electric power $P=UI$.
Both power $P$ (like work over time) and heat energy transfer $\Delta Q$ (which is one variant of power) use the unit $\text W=\frac {\text J} {\text s}$, which is confusing but a necessary distinction. Always remember that $P_\text{total}=\sum_{i=1}^nP_i$ - the total power in and out of an object is the sum of all partial powers!
Heat Energy transfer
The Heat energy transfer through an object is defined as the change of the heat energy $Q$ stored inside an object. $Q$ is given in $\text J$, so its change $\Delta Q$ is given in $\text J$ too. To get to the power, the energy change needs to be measured at several spots in time, so we make the derivate over time and get the power in $\text W$. We're looking at $\dot Q=\frac {\delta Q} {\delta t}$.
The absolute change of heat energy of an item is defined as $\Delta Q(t)=m(t) c \Delta T$: Increasing the temperature $T$ of an object with the mass $m$ and specific heat capacity $c$ by $\delta T$ (between times $t_0$ and $t$) results in a change of the stored energy by $\Delta Q(t-t_0)$.
So, we know $Q=c m \Delta T$ and $P=\dot Q=\frac \delta {\delta t} c m \Delta T$
Problem in question
We know that the drain (loss) of thermal energy from the system is via three ways:

melting plastic (phase transition)
extruding heated plastic
convective heat loss to the air
black body radiation of the heater block

We know that the total balance in equilibrium should be $P_\text{total}=P_\text{heating}+P_\text{melting}+P_\text{extrusion}+P_\text{convection}+P_\text{bb}=0$.
heat deposited into the system
Let's start at the simplest: we simply know the nominal heating power of the cartridge, it is usually written upon the cartridge itself, usually something in the area of 20 to 40 W. In praxis, it is not exactly that, but the ballpark fits. Otherwise, we'd plug in $P_\text{heating}=\epsilon \frac {U^2} {R}$ for our specific resistor, where $\epsilon$ is a coefficient between 0 and 1 telling us how good it is in converting electric to heat energy. Remember that since $U$ is technically a function of time (it is modulated to control heating behavior), our heating power also is, even though not explicit!
black body radiation loss $P_\text{bb}$
Black body radiation: $P_\text{bb}=A \sigma T^4$ where $A$ is the surface area of the object, $\sigma$ is a constant called Stefan-Boltzmann Constant. That much thermal energy is just lost due to radiation via photons, even if we don't see it glowing.
convection loss $P_\text{convection}$
The change of heat energy via heat convection is roughly defined as $H=\theta A (T-T_f)$ which brings us another coefficient $\theta$ about how good the block heats the air and the temperature of the medium (air) around $T_f$ - which we can replace as $(T-T_f)=\Delta T_a$.
And then we get to the biggest can of worms: the thermal heat transfer for melting the plastic and how much thermal energy is extruded from the system. For one of them, we can estimate some ballpark numbers, for the other, we will get into problems.
extrusion loss $P_\text{extrusion}$
The heat energy removed from the system by extruding plastic we can estimate from what we already established about thermal energy back in the Heat Energy transfer paragraph: $Q=mc(T_0+\Delta T)$ using the specific heat capacity $c [\frac {\text{J}}{\text kg K}] $ of the molten plastic as it is extruded (more about that later). But that's not the loss per time, but the heat energy stored in it in Joules. What factor is changing? In this case, it is the mass $m=r\times t$ where $r=\frac {\text kg} {\text s}$ is the extrusion rate. So $Q_\text{extrusion}=rtc\ \Delta T_\text{extrusion}$ and subsequently $P_\text{extrusion}=rc\ \Delta T_\text{extrusion}$
This leaves us with the big problem: as 0scar correctly pointed out by directing to the PolymerDatabase the specific heat capacity is not a constant and not linear but changes depending on the aggregate of the substance. We can make some estimate about it though from how we formulated the total power and adding a few absolutes for convenience:
$$P_\text{total}=P_\text{heating}+P_\text{melting}+P_\text{extrusion}+H_\text{convection}+P_\text{bb}=0$$
$$P_\text{heating}-H_\text{convection}-P_\text{bb}-P_\text{extrusion}=P_\text{melting}$$
$$\epsilon \frac {U^2}{R}-\theta A \Delta T_a-A \sigma T^4-rc\ \Delta T_\text{extrusion}=P_\text{melting}$$
Remember, that $U$ is a time-dependent factor (because of the control board activating it or disabling it), $T_f$ is also not a steady thing and changes depending on the airflow (though we can just pin it for our thought experiment) and thus $T$ itself might change over time as a result. $T$ is not equal to $\ \Delta T_\text{Extrusion}$ but is the temperature of the heater block system as a whole. $\ \Delta T_\text{Extrusion}$, on the contrary, is the temperature increase of the filament and not necessarily the same $\Delta T_{air}$, the differential between the heater block and the air. Why this differentiation is necessary becomes apparent if one realizes that the path of the filament might benefit from the heat that is lost from the heater block along that path, pre-heating the filament.
Phase Transition $P_\text{melting}$
$\propto$ is the proportionality sign and indicates that I might skip factors or constants.
What is that last part? That $P_\text{melting}$? It is the power of the Phase Transition. Matter does not shift between phases freely. There is energy stored in the state itself! So when transitioning from one phase to the other, that energy either has to be added (when going from solid to liquid or liquid to gas) or removed (when going the other way).
The "heat of fusion" is a material constant. For this look, I'll call it $\phi [\frac {\text{J}} {\text {g}}]$. We can make an estimation for the power that is put into melting the filament: there's an amount of filament that gets an amount of heat and undergoes the phase transition per time increment $$P_\text{melting}\propto \frac \delta {\delta t}\phi m_\text{melting}=\phi*\dot m$$ Now, we have the product of specific "latent heat" and melting mass derived over time... We had earlier the flow rate of material $m=r\times t$ and the "latent heat" is a constant. So, we pull out $\dot m=r$ again. So in the end we get that the power that is needed to melt our filament is proportional to the flow of the material and the material constant. $$P_\text{melting}\propto \phi r$$
Conclusion tl;dr
When eliminating the loss via convection and black body radiation and assuming them 0 or neglectable, we assume our heater is packed in perfect isolation - and call them losses. Assuming $\epsilon=1$ for a perfect heater, we are left with this equilibrium situation:
$\frac {U^2}{R}-P_\text{losses}=P_\text{melting}+rc\ \Delta T_\text{extrusion}$
The sum of the power of the phase transition (melting of the filament) and the energy stored in the extruded filament per time $(\frac{dQ}{dt})$ is equal to the energy deposited into the hotend over time [minus losses over time]

Explanation: is Textrusion changing over time? no, it's the same final value. Therefore if's a constant, and derivative does not touches it. Is Tinitial changin over time? no, as well. Conclusion: deltaT is a multiplicative factor, like c, and is not affected by the derivative. Is m changing over time? yes, the total mass that has passed through the extruder is increasing over time (or you would not be extruding at all), therefore you can derive over time that one, and get m'.

@FarO Correct, I think I found the last errors now.

Pmelting is a bit hanging there without much explanation (the only one without a section for it), but in general it's ok.

@FarO Not sure if I got it down to the last factors, but I get something akin to $P_\text{melting}\propto \phi r$ where $\phi$ is energy that is needed/released for one gram doing the phase transition and $r$ is the flow rate of our filament. I am not entirely sure if I might have missed some offset or other factor, that's why I only point to the proportionality.


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Printing PLA on PEX surface - is heated bed needed?
I have a WhamBam build system on order. A magnet attaches (glues down I think) to the Aluminium printing bed (or add a glass sheet? Separate question), then PEX material on flexible steel sheet gets slapped down for the print surface.

I have been printing PLA on a cold PEI sheet from Vertex, using 4 binder clips to hold it in place vs peeling the backing off and sticking it down. The print job wants to keep heating the bed to 60 °C, I turn it down, a couple minutes into a job it cranks it back to 60 °C and I turn it down again.  A few times I missed the second turn on, and the PEI has been kinda warped now (or maybe it's just the plastic over the sticky backing), and has also peeled off some surface chunks in the middle, so we've been trying to print around the damaged section.  The warping has now made the PEI unusable, so I'm hoping the WhamBam arrives soon.
We've been printing for a couple of weeks now (I printed a chess set, largest has 4 cm diameter and is 10 cm tall, some pieces on blue tape, some on the PEI) and are starting to venture into our own designs.
Intended project is box tops & bottoms that are ~90 mm x 65 mm x different heights with openings.  We tried one on blue tape (a bottom with no openings) and ended up chiseling it off the bed with a steel putty knife (I don't recall if heat was on or not). We tried a top with openings on the PEI, missed that the heat had turned back on, but between the bed not quite level (forgot to re-check it) and the PEI being warped we killed it after the openings were printed around. It was not going to be usable, but we did print enough to be able to confirm the opening spacings (needs work still) so it was not a total loss. Came off the PEI easily (<2 mm thick when we stopped), we managed to miss the damaged parts mostly.
So the question: when the WhamBam arrives, is it better to print PLA at 60 °C, or do I keep playing the game of turning it down (and saving the waiting time of it heating up)?

Received and installed the WhamBam system, and it works great! Have been letting it heat to 60C, which I'm pretty sure is not making it all the way thru the magnet, flex steel plate, and the PEX surface, but parts are adhering great and pop right off the PEX just by the act of picking up the plate, even a large box bottom (~68mm x 95mm) came off so easily I thought it had lost adhesion - my wife printed several items earlier and they came off the same way. I am impressed with the system!
We had lost a blade off the hot end fan (and turns out it was 3 blades), initial prints had failed to adhere on the PEX, the PLA didn't appear to be extruding properly, and the fan irregularity was very irritating. Internet searches indicated the plastic melting temp was not accurate enough.  Replaced the fan and every print since has been great.
EDIT 6/14/2019  Here is a youtube clip of a freshly printed door knob (screen door latch) coming off a 60C bed, no problem!

And a larger box, ~65 x 98mm, that popped right off.

I print PLA on a PEI bed at 60°C.  I have also printed PLA on an aluminum bed at 60°C with Elmer's Glue Stick for bonding, which worked better for me than PLA.  I recently switched to Aqua Net Hairspray on the aluminum bed at 60°C, which also worked well.
I have found no reason to avoid bed heating with PLA.
If the object is stuck too tightly on the PEI bed, you could try adding hairspray.  It acts as a glue, but also as a release agent, and, being soluble in water, you can help release the object with a few water drops.


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Overhangs lift up
My printer is exhibiting a problem wherein it's as if the nozzle pulls up on layers.  I don't think it used to do this - it seemed like it manifested after I replaced the broken x-carriage with a printed one, but I don't see how that could have caused the issue.  It's possible something else I did or replaced caused it; not sure.  Allow me to give an example:
I'm trying to print a worm gear, with a tooth size of about 2mm.  The teeth, as they appear in the stl, look kinda like
 ____________
<            >
  >        <
<            >
  >        <
<____________>

However, when printed, the edges are pulled upwards, looking more like
____________
\          /
_\        /_
\          /
_\        /_
\          /
 \________/

I originally noticed the pull-up in the surface finish of flat things - there was a grid of raised bumps on the top layer, I believe corresponding to the empty points between infill walls.  That wasn't an effect that mattered to me, though.  The effect on the worm gear is much more significant.
Anybody know why my printer is pulling up on layers, or whatever it's doing?

props for amazing ascii art. Does this happen when printing larger overhangs as well?

@Nach0z Yes it does, you see this effect many times, e.g. at the bow of the Benchy, myself I experienced this with X-axis idler mounts with 45º slanting slopes.

@Nach0z Haha, thanks.  Mine seems to happen primarily with thin layers - but on the other hand, I don't usually print large overhangs, anyway, so that may just be data I don't have.

If you print (overhanging/slanting) fine edges too hot with too little print part cooling, they curl up. Please increase the part cooling fan percentage or try printing with a lower hotend temperature. Another possibility is to print slower, this way the filament cools better for the same fan RPM settings (fan spends more time in the hot region).

The Simplify3d slicer website has a print quality troubleshooting section that describes the up-curl of edges, they also hint to overheating as the source of your problem.

This is absolutely correct. On my Ender 3 I get the effect only on one side of the threaded shaft due to unequal air flow. Going to do a custom fan duct to mitigate it, but short of that, longer cooling and slower printing mostly suffice.

Well, I reduced the temperature all the way down to 175, but there was no change.  I do have a cooling fan enabled, though it's kinda homebrew.  I'll try slowing down the print.

Yes slowing down also should work, for similar print cooling fan settings, cooling is more effective.

Alas, I cut print speed in half (to 30 mm/sec), turned temperature down to 180*, and the cooling fan speed is at 100%.  No change.  It's possible my cooling fan is inefficient?  I did just tweak it slightly and reprint it, though (https://www.thingiverse.com/thing:3676251) - no change.

@Erhannis Adding some pictures of the prints and the setup you use by [edit] of your question would help out. Indeed, ineffective cooling can prevent the print to cool properly. You could try a desk/table fan to see if it helps. Sorry it does not work for you, but this up-curling is a temperature problem, fixed as addressed in the answer.

That looks like a hotend fan setup not one for cooling the part...?

@R.. I think the right part is the print cool duct, and indeed it is a very bad design, the area narrows too much for the fan to push air through. There are way better print cooling ducts to be found.

@0scar: Oh I see. Yes. These ducts that concentrate the air flow are awful and bend the deposited material with the pressure while it's still soft. I tried the popular ring one on my Ender 3 and it shrinks threaded cylinders by at least 0.3 mm.


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3D printer and design software for creating propellers for a toy airplane/drone
I would like to begin designing and 3D printing propellers for both a toy airplane and drone that I own. I want to do this for experimental purposes.
I have never used a 3D printer nor have I used any 3D printing design software. So as a beginner to both of these things, I would like to know what would be the best type of 3D printer to use to create propellers for toy aircraft and I would like to know what is currently regarded as the easiest-to-use 3D design software for creating objects such as airfoils.
Also, at this time, the most I want to pay for a 3D printer is $500.

I'm voting to close this question as off-topic because shopping and recommendation questions  without a very narrow scope are out of the scope of any Stack Exchange

The 3d printer is irrelevant here.  What you're asking is 'how to use CAD programs' , and even that is a small part of the problem.  You can easily design a propellor that works, but if you want it efficient and low-noise, then you need a lot of knowledge about fluid dynamics.

Hi HRIATEXP and welcome to SE.3DP..! Unfortunately your question has been closed as both a [shopping] recommendation and for being too broad. However, it won't get auto-deleted as it has some up votes. In future try to ask questions that are specific to one particular issue. You can join us in [chat], have a look at the on-topic page (although that is in a state of flux) and don't forget to take the [tour]. Thanks :-)

Thingiverse.com has  a bunch of propellers you can download and print. Choice of printer varies from kits you need to assemble, a great way to learn what's really involved, to more expensive ready to go systems.

First, welcome to 3D Printing SE.  This is a great place to ask questions and get answers from people who have walked the same path.  I see from your profile that you are not a stranger to StackExchange and the available sites.
This question may be too broad for this SE Group, as it is asking for opinions rather than facts.  We try not to ask questions about "what is the best printer", or "what software is the best".  We avoid it both because it will change frequently, and because the answer needs to be gauged in your context, not the answerer's. We have some tools and community guidelines that suggest how to formulate the best questions.
Never-the-less, it is very hard when starting to even know how to make the first step, so with the indulgence of the group and your patience, I will make a suggestion or two.  These come from my experience and your's is surely different.
To try out 3D printers you may have resources the don't require buying one yourself.  It doesn't seem that 3D printing is the end goal for you.  You want to use 3D printing as a way to manufacture several experiments.  To access a 3D printer, it could be productive to check for local makerspaces, public libraries, or high schools with 3D printing capability.  You may find a friend you 3D prints who would be happy to run some objects for you.  You might even find it cost-effective to send designs to a service bureau such as 3D Hubs.  Note: I have no relationship with the company, although I did use their services once.
With the printing side temporarily in abeyance, you can focus attention on the design side.
If you are familiar with programming, you might be able to use either OpenSCAD or SolidPython as a design tool.  If you want something graphical, it might be worth trying OnShape.  NOTE: I know at least one of the founders of OnShape, but have no investment nor role in the company.  There are many design tools available.  For designing technical parts, I think you want tools more focused on technical than aesthetic content.
I would avoid purchasing a printer unless you want 3D printing and 3D printers to be part of your project.  People have mixed stories with many brands of printer, and lower-cost printers often become projects in themselves.  They can be satisfying, rewarding, and learning-driven projects, but can distract you from your prime intention for a long time.  In my case, I wanted to print boxes for projects, and prototypes for larger wood carvings.  I designed a printer, acquired materials, built it, and spent 3 years playing with it.  Along the way, I made some useful prints.  Eventually I was tired of not having a reliable 3D printer, and I wanted to reliably make things.  I needed a printing appliance.  So I bought a mid-range printer (which works very well for me), and I don't mess with it (much).
So, a broad answer in response to a broad question.  Welcome to 3D printing, the hobby and the StackExchange site.

thanks for those suggestions. Now that I think of it, it would be a good idea to first learn how to use design tools/software and then send my propeller designs to someone, or some 3d printing service, that will 3d print my propellers and then ship those to me.

I'll second the learning to design aspect of your quest. It will be the most productive use of your time and effort, in my opinion. Consider also to search for makerspaces in your area, which will have members to print for you and possibly advise for your design goals. There are as many design programs available to the common man as there are 3D printers.

At the current price you can get a decent 3D printer ($200 or less), making trips back and forth to a maker space for each round of prototyping really doesn't make sense unless you're operating on an extremely tight budget. IMO we're to the point where dedicated spaces are more for taking a look at the tech before you start and for occasional use of specialized higher end equipment you don't otherwise have access to. Nobody uses computer labs/cyber cafes anymore...


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What pins do I use for UART control on a RUMBA board for tmc2208?
I have been looking in the Marlin firmware for about an hour or two now to find what pins I should use for UART for my tmc2208 drivers and I have come up with nothing.
Does anyone know what they are or how to assign them? BTW, I am using the regular version of the RUMBA board not the RUMBA+ version.
For somereason i didn't put that i want to control my stepper motor drivers through uart they are tmc2208

Why do you need the UART? What are you trying to achieve? Do you want to reflash the firmware?

Is it a genuine RUMBA or a Chinese clone. I have both RUMBA boards and found that the Chinese clones cut corners and as such some things don't work. E.g. the exposed USB pin header on the RUMBA+ is totally unusable when you properly connect it, the board stops working...

sorry i didn't put that i wanted to use uart for my tmc2208 drivers my bad.

The RUMBA schematic is available on the RUMBA wiki.

From the schematic, I see that UART3 (with +5V logic levels, not RS232) is presented on the EXP3 connector.  I don't know if Marlin firmware can be controlled through a UART other than UART0, which is converted to USB through an FDDI chip.  The Arduino bootloader is not expecting another UART, so you may still need to program it through the USB port (and UART0).

Did you mean FTDI (i.e. FT232RL) and not FDDI? Also, the RUMBA appears to use a 16U2 to implement USB, not an FTDI.

Yes to both.  I didn't spend enough time with the schematic.  Thank you.

Sorry i didn't put in there that i wanted to use uart for my tmc2208 drivers sorry about that... But are you saying that the chip only expects uart from the usb does that mean i cant use uart for my drivers?

You can use those pins as you wish, if they are otherwise free.  In Arduino, it will be Serial3.begin(baud_rate) to start it.  The other port will work as it normally works.

how do i setup the pins.h to tell the Arduino that those pins will be used for uart connections for the stepper drivers?

If they are using the Arduino libraries and have not changed things, all you should need to do is Serial3.begin(baud_rate_you_need);

Of you are using the new motor drivers for real-time motion control, you may face significant challenges adapting the firmware.  This discussion should probably be moved to another forum, as comments are not intended for ongoing discussion.


text:
Pololu - connect motor supply ground and logic supply ground
Is it okay to directly connect together the grounds of the logic supply and the motor supply when using a Pololu style stepper driver?

If yes/no, why so?

(This is more of an electronics.stackexchange.com question btw).
It is not only ok, it is absolutely necessary. The systems won't operate correctly unless all the gnds are tied together. Since this is a stepper motor, you don't have to worry about noise getting back onto the power supply lines for the logic supply, since the stepper board has a decoupling capacitor(s) to keep stabilize the power to the motors and the VCC of the logic supply will be unaffected by the GND of the other supply that its tied to.

That depends on how much noise you have on your motor power supply ground.  You definitely want the 100 µF capacitor to have a good high frequency response.  Motors turning on and off can be noisy, and that noise can cause false clock signals in your logic circuitry if you tie the grounds together.

I could not find a schematic of the Pololu A4988 stepper motor driver, but I did find a photo of the board that includes the ground planes for both the motor and logic.  On the reverse side of the board, they were not connected.  They should not be connected on the driver cards.
Instead, all the motor ground lines should be brought together at a point, and the Motor supply ground connected to that point.  The V-motor should also be run radially to each stepper driver and connected to the V-motor supply.
There should be a single connection point between the motor ground and logic ground.  No motor current should flow through any logic ground wire or circuit board trace.  The motors are switching high voltages and high currents.  If these currents pass through a logic ground line, they will introduce voltage spikes into the logic which can result in unexpected operation.
The 100 μF capacitor in the schematic is good for supplying low frequency energy needs, but it should be paralleled with a 1 μF capacitor and a 0.01 μF capacitor placed as close to the radial feed points as is practical.  A larger capacitor tends to have higher leakage inductance, which limits the high-frequency response.  A range of capacitors in parallel will perform better.

I can confirm that the motor ground and the signal ground are connected in the ground plane. See https://forum.pololu.com/t/a4988-gnd-question/6575

I'm not sure how to comment here.  The multiple driver board motor ground signals should be connected together and to the motor supply ground.  The driver board logic grounds should also be connected together and to the logic ground.  There should be s single connection between the two ground systems.

Is it okay to directly connect together the grounds of the logic supply and the motor supply when using a pololu style stepper driver?

Most stepper drivers don't have separate ground pins for the logic and motor supplies. The two ground pins on the A4988 board you've shown are electrically connected on the board. The question is moot.

Circuitry like this may explain why a uninterupted power supply (UPS) with a surge protector isn't good enough during short power outages, because their power transition isn't as clean as a power conditioner.  I often get x and/or y offsets during power outages.

@PerryWebb Your comment seems completely unrelated to this question or to my answer.


text:
StepStick Protectors
How do StepStick Protectors work and what exactly do they protect?
If I use them with Pololu style stepper drivers, can I unplug for example the motor while the driver is powered without damaging the driver?

The linked drivers protectors use flyback diodes, a very good article can be found here. It is fairly complicated to explain in other words (I'm no electrical engineer); someone with an electrical engineering background might be able to explain it more simple. You can also try posting the question on EE.SE.

To Protect, or Not to Protect
From the web site you reference:

The SilentStepStick Protector is an add-on module for StepStick and
  Pololu A4988 compatible stepper motor drivers. The board provides
  flyback diodes (freewheeling diodes) for the motor outputs, so that
  they are also protected against induction voltages in the unpowered
  state of the driver.
The v2 protector also contains a diode from the logic voltage (anode)
  to the motor voltage (cathode), so that the power supply order of all
  SilentStepSticks is always guaranteed.

Since I assume you've read this, please indulge some explanation of the electrical engineering.
Motors
Every motor has a part called the "rotor" that rotates, and a part called the "stator" that is stationary.
In the stepper motors usually used in 3D printers, the rotor is a permanent magnet and the stator consists of coils of wire.  In normal operation, the current flowing through the coils creates a magnetic field.  The rotor aligns itself with the field of the stator.  To move, the stator field is shifted by changing the current in the coils, and the magnetic force causes the rotor to rotate to align the fields.
Generated Voltages
As Faraday discovered, a changing magnetic field induces a voltage in a wire.  There are two ways that the magnetic field changes.  The first is that the current changes or stops.  That introduces little high voltage blips into the motor coils.  The motor drivers are well prepared to handle this blips.  The second is when the rotor is forced to turn by an outside force, such as sliding the bed.  As these voltages are not related to action the motor driver is causing, some of the techniques used to handle the voltage spikes may not be as robust.
The protection boards you point to consist of diodes to limit the magnitude of the voltages that the coil can produce.  This is redundant with the diodes and protections built into the driver chips, but it may offer stronger protection.
Benefits?
In this responder's opinion, you are unlikely to see a great benefit from these boards, but perhaps there are vulnerabilities I am unaware of.  You are also unlikely to do any harm.
You asked specifically if, with the protectors installed, you could unplug the motor while it is passing current.  The protectors may help with that, or they may not.  Interrupt the connection creates a spark, and arcing through the air, that makes many high-frequency components which may not (or may) be effectively clamped by the diodes.  For best results, you could add the protectors, and also avoid interrupting the motor current while powered.

The community shows various result using these protectors. I always thought that print heads with a lot of mass (e.g. direct driver extruder mounted on carriage) benefit more as a high mass will not stop instantaneous causing flyback currents (motors become generators).

There is a maximum deceleration rate based on the torque the drivers can cause in the motors.  This is related more to the strength of the magnetic fields then the motor acting as a generator.  In particular, the drivers are controlling that by the currents they are passing through the coils.  The movement of the rotor does induce a reverse voltage in the coils, the back-emf, which somewhat limits the maximum speed the stepper motor can attain, although the greater limit is the ability of the drivers to change the current in the coils fast enough.  That ability is driven by the supply voltage.


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Ender 3 Random Axis Shift
My printer has been doing weird things lately.  It used to print fine, but now it's like the Y or X axis after a certain percentage time.
ie on a 24 hour print: it got off at 5 hours
on a 42 print it got off at 16%
Thoughts?

Good morning, and Welcome to the 3D Printing SE site.

I am sure what you are asking.  The best questions have lots of details in the questions, such as the type of printer, the material being printed, temperature settings if you have them, anything that might have changed, and, if at all possible, one or more pictures of the defect.

The usual suspects are overheating stepper motor drivers and over-tight belts. It can also be caused by belts coming loose in their mounts.

I've had similar problems printing overnight using a computer and suspected network activity causing the problem.  Energy savings settings can also cause it.  I print overnight using an SD card to print the gcode file to solve the problem.


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Creality CR10 S5; the Z dimension is wrong after switch from 0.4 to 0.2 mm nozzle
So I tried to print a model with a 2 mm thickness main area, and a couple 4 mm parts that stick out.
Instead the 4 mm is 3.05 mm and the 2 mm is 1.07 mm (0.042 inches measured with a caliper).
The only physical thing I changed was the nozzle from a 0.4 mm to 0.2 mm.
I changed to Ultimaker Cura 4.1 (from 4.0) and entered a 0.2 mm nozzle size in the settings. Just as before with the 0.4 mm nozzle, I used a 0.1 mm layer height.
The X and Y dimensions are good, and the screw holes line up perfectly.
I auto homed and used the bed leveling mechanism built in one many times.
Any suggestions why the height of the printed part is too small?
I don't have the model with me, but this is an example (without the holes):

I am manually using the GUI of Ultimaker Cura, not the slicer engine embedded in another program or from command line.
Do I need to increase the filament temperature up from 200 to have the filament liquid enough to flow through the smaller tip?
Here is representation of it.

The old models are rigid, and the new ones bend because it is so thin.

update 6-10-19
I re-installed 4.0 to no avail.
I think the problem might be related to the filament feeder because otherwise there should be filament everywhere.  I am going to try different filament temperatures to see if that changes anything.  Trying 205. Unless the feeder motor is damaged.

Can you add a photo or diagram? It's not clear which dimensions you're talking about.

@R..     The vertical dimension or Z is not correct   Approx 6" by 1" by 2mm rectangle laying flat on the bed like a sheet of paper with holes, and bits that stick up 2mm (or there supposed to.)

Did you re-level the bed after changing nozzles? i doubt it could make this much difference though. A pic would still help.

@R..  I re-leveled 5 times.  I have included a picture of the basic design.

Your dimensions between the flat part and the step seem consistent (ie: it's very close to 2mm difference), which is what you'd expect if you were getting the right print height altogether. Was this print successfully done prior to the nozzle change? Have you tried any other prints since the nozzle change?

Have you checked the slicer output? Is it possible that your model somehow got below the XY plane and the slicer just cut off that part? I know Cura will do that if you use CuraEngine from the command line and the STL file has negative Z coordinates, or if you manually position the model below the XY plane in the GUI. Not sure if there's an easy way for it to happen accidentlaly in the GUI.

@Pᴀᴜʟsᴛᴇʀ2  Yes, the prints were correct prior to the nozzle change, and the upgrade from 4.0 to 4.1.  The main body was 2mm, but now it 1.06mm.  I will have to check if its below the 0 point.  Something else is printing now, but won't be done for hours so I will have to check it when its done.

What do you mean with "I am using the GUI", does it really add something to the question? PLA should perfectly be extruded at 200 ºC.

@Oscar User "R.." said in the comments using the CuraEngine from the command line has issues like that.  Is 200C enough even at the smallest tips sizes?  200C was fine for 0.4mm, but maybe not for 0.2mm

But that has nothing to do with your issue, you should post pictures of the prints, else it is guess work.

@cybernard: Your picture doesn't look like there's any extrusion problem. It's possible you have some kind of Z-axis binding issue going on that's mashing all the low layers together, but I think it's more likely that the slicing went wrong. Can you check the layer count in Cura or a gcode analysis program (or just reading the gcode file) to see that the number of layers and final Z matches what you expect?

By looking into the G-code you can find out if it is sliced correctly, look up the last layer move G1 Zxx.xx, xx.xx should be the height of the model. If that is correct, then your Z might have a problem.


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3D printer part clones from china - legality
What's the legal status of Chinese 3D printer part clones such as Hiwin linear rail clones or E3D hotends?
While it's clear that Chinese clones are certainly sub-par in quality, no question, what I wonder is whether they violate any laws (they don't use brand names or claim to be the genuine product).
In particular, I’m interested whether it is in any way illegal to order such parts in the U.S.
Given that there's hardly any 3D printer that doesn't contain at least one Chinese part, I really think this is on topic.
I also don't seek legal advice but any information other 3D printer users on here have.

Hey I put this on hold, this is a legal question, which honestly I think you know the answer to if you should buy printers that use knock off IP. We unfortunately cannot give legal advice, and must stick strictly to direct questions about the application and use of the printers, not international laws.
That said, buy the real hotends, not a knock off, the knockoff is going to be junk, and who knows might explode due to sub par quality.

No I really don't know. It's clear that chinese clones are certainly sub-par in quality, no question. What I wonder though is whether they violate any laws (they don't use brandnames or claim to be the genuine product): Given that there's hardly any 3d printer that doesn't contain at least one chinese part, I really think this is on topic. I also don't seek legal advice but any information other 3d printer users on here have.

The case is very different for some parts: some parts are non patented and non patentable and can't be trademarked, thus customs can't do anything. Other parts are patented and their (non functional!) shape or color trademarked, allowing customs to crack down on them. More information and cook down to one part - and don't frame it as asking for legal advice.

This is hugely dependent on what part you're talking about though. Thankfully, many components are open-sourced, meaning the Chinese clones are just legitimate, as long as they don't maliciously attempt to fool people into thinking they're buying the real deal ("Genuine Arduino" branded clones"), which does not usually seem to be the case.

This question is really a legal question, and could apply to any cloned parts/devices rather than being 3D printer specific, and a generic counterfeit consumer goods based question should be asked on SE.Law. However, as you rightly state, a lot of 3D printers from China may contain (whether knowingly sourced or not by the manufacturer1) counterfeit parts, be that ICs, hotend designs (i.e. E3D clones), controllers (i.e. Arduino Mega boards or stand-alone non-RAMPS Arduino shield boards),or what have you. As such this is an issue that may be faced by any unwittingly innocent consumer.
Prefacing any statement with I am not a lawyer (IANAL), these sections from Wikipedia entry on Counterfeit consumer goods might help answer your question:

Growing problem as will this
Enforcement- US.

In short, if they have a mind to, Customs could seize it at the border; if your house was raided (for whatever reason) law enforcement could seize your printer (although this seems unlikely, unless they were explicitly raiding your house for knock-offs); and (more worryingly) there is a proposal to fine those people who purchase knock-offs.
Of course this is not the only legal issue that may be encountered when buying Chinese devices/parts from less-than-reputable suppliers o eBay or AliExpress, for example, what if:

it breaks and what legal recourse do you have as a consumer;
it produces a poor quality or dangerous print;
it explodes, what legal recourse do you have;
and so on, etc.

These questions lead into rather murky grey and legally complex areas, and really would need to be dealt with by a legal professional (solicitor/lawyer).

Other Stack Exchange posts worth reading
These deal more with quality not legality but see

Can cheap hotend parts sourced from China actually produce good prints?, and;
Vaguely related - What are the pros and cons of collecting parts yourself, versus getting a DIY kit and then modifying it?
Also, which respect to the electronics:

Some Arduino components seem ridiculously cheap and;
Compatibility between Arduino and Arduino clones.
This answer to Arduino Clone - A request for the USB device descriptor failed interestingly points out that if the device is licensed appropriately (CC, open-source, etc.) then they may not be any legal issues at all related to cloning (but not counterfeiting - See What's the difference between a clone and a counterfeit Arduino?.

1 A bone fide low end oscilloscope manufacturer got stung by a batch of fake regulator ICs just last year, see Re: JYE Tech DSO150 oscilloscope troubles

Fake parts is another big problem since stolen parts from original shipments are committed, then to be sold has to cover de original marks and in the process the robber offers the product as the same part or like substitute. I saw that on manufacturing companies.