How to solve ABS deformation at the bottom? I am printing small mechanical pieces in ABS:

100 ºC bed temperature
70 ºC Room temperature
250 ºC nozzle temperature
0.4 mm nozzle, at 0.15 mm per layer.
100.8 % scale to compensate ABS dimensional innacuracy.

The first layer is printed correctly, but later, corners warp and first 10 mm get deformed (See images).


How do I solve this? Unfortunately, I cannot increase room temperature over 70 ºC
Here is a picture while printing, we can see that the edges get warped even far over the first layer. (Sorry, the picture quality is not so good):
The up-curling of overhangs is frequently seen when printing PLA or PETG when the just deposited layer hasn't been cooled enough. The residual heat will allow the curling as the plastic has not been fully set (above the so called glass temperature) because of insufficient part cooling.
Knowing that ABS doesn't need much cooling (to improve the inter-layer bonding), you most probably will not require full power of the fan (depending on the cooling power of the fan). You do need a little cooling though, but not for the first (few) layer(s), so keep the fan off at the first layer. Be sure it is up to speed at the layer you require the cooling as the first few percentage of the fan is generally not enough to rotate the fan. E.g. my fans start spinning at about 20-25 %.