Thursday, December 22, 2011

The Never Ending Story

Well, not quite never ending but it sometimes feels that way.  

I adjusted the pots on the stepper controllers last night.  It fixed all my problems with the steppers except for the Y-axis which just sat still and jerked a bit no matter what I tried.  I eventually moved the motor over to one of the other controllers and found that it worked fine so I guess I have one bad controller.  I actually thought about ordering a couple of spare Stepsticks when I ordered the Sanguinololu but decided against it so now I have to wait again for a delivery.  The genetic predisposition to being a cheap bastard which I inherited from my Scottish ancestors has undone me again.

The good news is that everything else seems to be working finally.  Extruder, steppers and hot end are functioning as they should so I am able to do a few things while I wait.  The opto-endstops are not working yet but that is because I have not yet soldered the bridge for the 5v power to them.  I also need to clean up all of my wiring but I was waiting to do that until I got everything working.  After I do that I am going to switch the controller for the Z-axis to the Y and then I can do a couple of tests while I wait:
  • Lay down a line in a single layer so I can confirm that it is extruding the correct length of filament.
  • Lay down a square in a single layer to confirm that everything is square.  Should get right angles at the corners and sides of the same length in both the X and Y directions.
  • Lay down some complex curves in a single layer just to confirm that ethe X and Y axis are moving as they should and are coordinated properly with the extruder.
Since the Stepsticks are coming from the Netherlands I expect it to be a couple of weeks yet before I will be able to build anything but success is definitely in sight at last.

Wednesday, December 21, 2011

By George, I think I've Got It!

Just a quick update.  

Based on some online posts that I found, I believe that I have identified the problem with my steppers.  I think I just have to adjust the current potentiometers on the Pololu driver cards.  I haven't had time to try it yet, hopefully tonight.  If this works I will have solved my last problem with the machine itself.  Very exciting.

Monday, December 19, 2011

Hot Damn! Melted Plastic at last!

Over the weekend I finished re-assembling the Mendel and tried it out.  The Sanguionololu works great and so does the Sprinter firmware although I still expect to have a lot of tweaking for my specific machine.   Here's a quick pic of my first mess of plastic:

I think I will keep this blob on my desk as a post modernist sculpture

At first I could not get the filament to feed into the extruder.  I was trying to get it in by hand-turning the gear on the wade's extruder but it just didn't seem to be able to pick it up.  It was late and I was just going to give it up for the night when I realized that I was turning the gear the wrong way!  As soon as I turned it the other way the filament loaded into the hot end easily.  One more boneheaded move among many.

With the ATX power supply and the single board electronics my wiring is much cleaner.  I still seem to have a problem with my steppers though.  The X axis moves very slowly and the Y and Z axis don't move at all.  They just hum and jerk a bit.  I think that I may have them wired wrong but it was getting too late to get into troubleshooting last night so I will check it out tonight.

But, in general, it looks like I am finally ready to build some things.  Life is good.

Monday, December 5, 2011

Finally, Some Good News!

I wired up the Sanguinololu board last night and things went very well.  I jumpered the power enable pins on my new ATX power supply and then clipped the connector off of the 4 wire power connector and twisted the two power and two grounds wires together.  These were inserted in the screw terminals on the Sanquinololu board and then I plugged in the USB cable.  I got a steady green light so it looked like everything was ready to test.

I loaded up the Sprinter firmware that I had modified for my Mendel with no problems.  Then I confirmed that Pronterface can connect to the board.  I probably still have to do a lot of tweaking of the firmware but that can wait until I have a test print to use as a baseline.

My extruder is still disassembled from fixing the broken thermistor wire but I was able to wire it up on the bench to test it.  I had been holding off on reassembling it and mounting it back on the machine until I could confirm that it was working correctly since it is a major pain in the ass to remove.  I removed the 4 pin connector that came with my Botmill extruder and replaced it with two 2 pin connectors.  The heater and thermistor connectors on the Sanguinololu are on opposite ends of the board so their arrangement just wouldn't work.  After connecting with Pronterface the temp reported as 25C, which is about correct for my basement workshop so I went ahead and sent a command to heat up to 185C (PLA melting temp).  The heater worked and the thermistor immediately began reporting the correct temps as it rose  I confirmed that it heated up to the correct temperature and that it then started the regular on-off switching cycle in order to keep the temp stable.  Being fairly certain that I could melt plastic safely I then moved on to the steppers.

The Sanguinololu board expects 4 pin connectors and my old boards had screw terminals so I can't hook up the steppers until I get the correct connectors.   I had bought some locally only to find that I had the wrong ones.  I have a set coming in the mail but they have not arrived yet.  Luckily I have one stepper that arrived with the correct connector already attached so I used that one for testing.  I attached it to the extruder controller  and sent a command to extrude 5 mm.  The stepper kicked in and ran for what seemed to be the correct time period.  Hot Damn!

I then moved the motor to each of the X, Y, and Z controllers in sequence and tested them with the jog commands.  All seemed to be working correctly.  The only thing that I did not test was the opto-endstops.  I have to solder a joint between two pads on the board in order to set the voltage for them.  In my case this is 5v but I forgot to do it before I hooked everything up so it will have to wait until I take everything apart again prior to the final assembly..

So it looks like I am finally ready to print.  As soon as my connectors arrive I can do the final hookups of the steppers and move on the the really interesting part of this whole thing, the printing!