What is a good way to estimate the impact on material strength different printing methods will have? I'm going to 3D print a part that needs to meet certain strength requirements, due to its usages. I know how strong a particular plastic (eg. comrpessive/tensile/shear strength) is when dealt with in a solid chunk, but not when it is 3D printed. What is a good way to estimate the change?
It's hard to tell without actually testing the part. There are many ways you can 3D print a part, even on the same machine, that can yield different results.

Here are some tips to help uphold strength requirements:


Identify where your stresses are and avoid allowing the natural "grain" of the print (i.e. each layer) to coincide with the stresses of the part. For example, I just printed a part with hinges today. I set my part up to ensure that the circular profile of the hinge on each layer, instead of having the machine "bridge" the circular profile.
Make your part more solid by increasing the infill. Note that somewhere around 35% won't really provide much more strength than say 50% with a standard infill pattern (i.e. hexagonal, diamond, catfill). However, I would imagine that if a spherical infill pattern was ever designed, that would be the strongest.
An easy way to beef up small areas of a part is to increase your shell variable (how many profile layers for each layer). Again, referencing my hinge design, I made sure that my hinges were completely printed using shell instead of shell/infill.
Don't be afraid to do some post-processing such as adding epoxy/epoxies in high-stress areas.


If it's not an expensive part to print, I would suggest playing with some of these ideas yourself and conduct controlled tests to see what setups work best for your application(s).