Tuesday, November 29, 2011

New Electronics

Sorry I've been gone for a while.  I finally threw up my hands and gave up on the Techzone electronics.  It seemed that, no matter what I did, I could not get any firmware to work correctly on it.  When I looked online I found that very few people were working with or supporting it so there wasn't the community that I needed to help me through it.  Given that sad situation I ordered a Sanguinololu and I have been waiting for it to arrive.

The new board arrived last night so I am back on track.  I will be using the Sprinter firmware since it seems to be fairly mature and has a good support community.  I hope to have time tonight to get things hooked up and tested.

Tuesday, November 8, 2011

More Progress, Same Problem

Last night I modified the heated bed and got it installed.  I attached the silicon heater element to the bottom (it's a simple peel and stick) so I just need to install a thermistor and wire it up to my control box and that will be ready to go.

Of course, a heated bed does me no good unless I can get this thing to extrude.  I switched out the thermistor again and got the same result.  Temp reads as 875 degrees at room temperature so the heater does not kick in.  I know that the thermistor is fine (I guess the previous one was OK as well) so I have another problem.  It wasn't until this morning on the way to work that I realized that I probably have the wrong temperature table in my firmware.  I will check that next.

Monday, November 7, 2011

Replacing the Thermistor

I finally got some free time to work on the Mendel yesterday.  I removed the extruder and replaced the thermistor with a spare one that I had laying around.  It involved carefully cutting away the Kapton tape and removing the thermistor leads from the crimped fitting that Botmill uses to connect it.  Not an extremely complicated procedure and it only took me about 20 minutes to replace it and re-crimp the connectors and tape the new thermistor in place.

I thought that I would do some testing prior to bolting the x-carriage back on the Mendel and it's a good thing that I did.  The temp showed as 875C so the heater never cut in.  When I checked the resistance of the thermistor I found it to be about 115K Ohms rather than the 80K that it should be.  Should have checked it before I installed it.  Either it is a bad thermistor or I picked up one with the wrong values at some point.  Luckily I have another one and it tests at the correct 80K so I will switch it out again.

Since I was dismantling things anyway I decided to switch out the build surface for the aluminum one that I bought to prepare for adding heating to it.  I removed the old one and then found that the aluminum plate blocked two of the holes in the plywood frame piece.  I will drill them out tonight.

I also made a cable with two female connectors so I could add a ground cable between the main and extruder boards.   I don't know if my problems with the extruder motor are due to grounding issues but this certainly can't hurt.