Thursday, January 15, 2015

Improved Printing Quality with the Stratasys BST 1200

As I've talked about before, using the right filament with your printer's settings is important for getting parts that come out. After trying out several different combinations and brands we've found a combination that works even better than the original filament from Stratasys. It's the 1.75mm ABS and 1.75mm HIPS from SainSmart for the model and support material respectively. The stuff is also available on Amazon. Obviously you will have had to either modified your 3d printer to refill cartridges or set up a Raspberry Pi to reflash the EEPROMS.

As you can see the HIPS holds to the build plate well enough to prevent curling but comes off much more easily than the standard filament from Stratasys.

Wednesday, January 14, 2015

PCB for Stratasys Cartridges

There's a *very* long list of things that I have yet to update on the blog, but this is something I'm going to stay on top of.

I recently found out from the Have Blue website that there is a way to flash the EEPROMS from scratch with a Raspberry Pi for the Stratasys 3d printer cartridges on the Dimension BST series printers. This means that you can refill the printer with 3rd party filament without modifying the printer, something that is going to become very useful since Stratasys is dropping support for the BST 1200 series on June 30th, 2015. I had already modified the 3d printer at my school in order to make student printing affordable, but this method requires the printer to be reset after reloading the cartridge EEPROM, which is a problem if a cartridge runs out during a print and all of the chips are empty.

After seeing all of this I thought that while people who already had EEPROMs from used cartridges would still be able to use the printers, those who had returned their used cartridges for a discount wouldn't be able to use this workaround without paying through the nose for a used cartridge, which would only continue to become more expensive and scarce. So I went to a friend of mine who is a whiz at making PCBs and asked if he could make a board for the EEPROMs that could substitute the originals. Since the circuit is only two pieces and the layout is straightforward he was able to make it in less than an hour in Eagle. Using OSH Park to make the boards gets you three PCBs for $6.65 (while the screenshot below makes it appear that the notch in the middle is missing it is present in the board outline). A suitable 4.7k ohm resistor can easily be found on DigiKey.

However, the original Maxim DS2433 EEPROM chip has been replaced with the DS24B33. The previous link contains details about the differences between the chips. Of particular note is the increased max current draw from 500 micro amps to 2 milliamps and the increase in recovery time. This may make the chip unusable with the Stratasys printers. DigiKey does have the DS24B33 available if you would like to try this chip. I will order one and will post results when I have them. It is also possible that if the new chip does not work out of the box there is a config file for the 1-wire interface on the Stratasys that could be edited to make it compatible.

The Eagle board and schematic files can be downloaded here. Note that these files may not be used for commercial sale and all use is AT YOUR OWN RISK. While the boards have been ordered from OSH Park and the schematic is very simple this board has not been tested and verified as of 1/14/2015.

Update 5/11/2015:
It has been a while since I've had time to work on this project. The PCBs came in the mail, and I've stuffed the boards with the parts. Unfortunately I wasn't able to communicate with the new chip using the bus pirate, although I'm not sure if this is because of a hardware problem or because the script I was using had an error trying to read a cartridge from a blank chip. Here is a side by side comparison between the original PCB (green) and the replacement (purple):