Printing in ABS

I recently received a roll of ABS from Czech and decided to 3D print squirrel with it. For some reason the squirrel has become a kind of calibration cube for me.
 First impressions are quite positive. ABS is a lot more dimensionaly unstabler that PLA. To prevent severe warping a good heated bed and preferably heated chamber is a must. Also ABS smooths small details so the print comes out a lot cleaner but it lacks some detail.
 I will publish a full review of the Czech ABS but currently it feels quite good and my reprap seems to like it also.

Printing settings where as follows:

• layer height 0.2mm
• perimeters 3
• bed temperature 105 C
• hotend temperature 
• 265 C first layer
• 245 C all other layers
• printing speed 45mm/s
• infill 0%
• solid layers 4

I suspect that my termistor is a little off, so temperatures are indicative not absolute.

Slic3r, the new application for skeining models

Until now I have used SkeinForge for all my slicing and g-code generation needs. Most people complain that is is rather slow, but if you use pypy it is rather snappy(more on how to get a 2 - 5 times speed boost with pypy in a later blog post). Quality has been good but the configuration is a bit more repetitive that I would like. 

Now there is a new kid on the block. It is named Slic3r and it claims to be 10 times faster than SkeinForge. It is lacking some frequently used features like, hexagonal infill and support material, but it promises to be better in other aspects. 

For testing I processed the squirrel model with Slic3r and printed it. 

First impressions:

1. Get the first layer height right. 0.02mm can ruin the print.
2. The speed is nothing too fenomenal. SkeinForge with pypy is somewhat slower but not by an order of magnitude.
3. Get your e-steps and filament diameter right.
4. Now that your printer has heated up, go to step 1, do not press print.

The final setting where: nozzle 0.35, layer height 0.15 and 40mm/s perimeter speed.

The print result looks fenomenal. I can see and feel the surface roughness from the model. Layers are also almost invisible to the naked eye. Now I just need to try to print 0.15mm resolution with SkeinForge.

The heroic MOSFET.

Today one of my MOSFET power transistors heroically sacrificed itself to save 2 protection fuses. Ironically the MOSFET was rated for 55 A but my power supply in rated for only 30A. A strong power supply, heroic transistor and a lazy fuse do not make a good combination. I wonder if I should replace my fuses with cheap transistors instead.  

The acrid smell of failure in the morning

Having finished all the mechanical stuff, I proceeded to the promised land of electronics. My yet_to_be_named prusa mendel uses RAMPS   1.3 for all of the heavy lifting. For firmware Sprinter was chosen because the "just works"™ feature looks damn compelling. There was one small hiccup trough . Sprinter firmwares Makefile is hardcoded to search for gcc in /usr/bin. Sometimes the distro provided gcc is a bit buggy so it is recommended to use arduino IDE to compile it.

So everything was fine in the evening. Firmware was booting communicating and reading the termistor. I did not connect the 12V power supply yet because stepper testing "might/will" require quick reflexes.

So this morning I decided to start with endstop calibration. I was quite puzzled when the firmware refused to boot and the 5V regulator on the arduino board almost went up in smoke. It turns out that all my pololu a4983 drivers have shorted their power supplies to the ground. I did not have +12 supply connected yesterday, yet I saw no warning in datasheet about not connecting the motor power supply. The most puzzling part is that, I managed to kill all 4 of them in one go. I wonder if the A4983 are so fragile or did I do something extremely stupid.

A bit of debugging on a breadboard confirmed, that all the A4983's are quite dead and show no recognizable signs of life. Oh well that was not even a learning experience, because I have no inkling what killed them.

Plan B


I will scavenge the stepper drivers from my CNC mill and try to use them. Luckily there is a 4 axis driver board on the CNC.

Is it here yet ??? how about now ???

Last  week I decided to join the ranks of the reprap crowd. It turns out that is is quite hard to find "someone near you" to print the plastic when you live in Estonia. To make matters worse thanks to the EU import tax everything coming from outside EU gets taxed the living hell out of.

Luckily I was able to find NOPHEAD's fantastic offering and UK can be stretched to fit the definition of "near you". The parts arrived in just 4 days. Astonishing considering I have been waiting 2 weeks for the electronics.   

Up Next: building the prusa day 1.