Questions from TOM Stepstruder newbie

[Jwo Lee]

I just finished building my TOM this weekend and I'm trying to calibrate it properly.

Flow Rate question:
No forum or wiki talks about the flow rate on a stepstruder, since they all assume 255 PWM on the old DC motors.
I noticed the default settings in Skeinforge is set to 5.0, and I'm trying to figure out what that number even means.
Is it RPM? If so, anyone knows what the max flow rate is on the stepstruder?

ABP questions:
Also, I noticed that the heated ABP does not register the correct temperature.
It always shows 127 degrees at room temperature. Even the makerbot wiki shows a screencap of the control panel showing 131 degrees at room temp.
Anyone know why the thermocouple on the ABP does not register the correct temp? I had to change my start.gcode to set it to 132 to even stay on during the entire build.
I think this also causes the ABP to not eject the part because it's waiting for the build platform to cool back down. I ended up taking out that line in the gcode to just wait 90 seconds instead.

Also, anyone with the ABP notice that the belt is not completely flat against the heated platform, especially near the edges? It seems the rollers are slightly higher than the platform.
This doesn't seem to matter that much when making something small in the center, but I seem to need a raft when making larger, flat objects.

Raft Question:
I had a hell of a time trying to remove the raft from my model. It seems to be stuck on pretty well. I tried reducing the Interface Infill Density, but that only decreases the amount of material sticking, not the sticking issue itself.
Perhaps letting the raft cool more before laying down the first Object Layer?

I couple of things I did notice, is that using the 1.75mm filament, I wasn't planning on it, but I did see it make a horizontal line spanning over 4cm in midair, which is neat and sure opens up a lot of design/model opportunities.

Sorry I have so many questions. Any help or insight is appreciated.

- Jwo Lee

[Rick Osgood]

I'm not sure what the max setting is for flow rate with the stepstruder, but I played with mine a bit and increased it by just 3 or 4 and it was spitting out plastic way too fast for my prints.  Each layer was getting way too thick.  Of course, I didn't mess with my X/Y speed setting to compensate.  I can't remember what I currently have it set too but I can check when I get home tonight.

My ABP shows the correct temperature at room temperature.  It usually shows around 20 degrees C.  I have not had the problem you describe.  You definitely have the heat board plugged in the right way?  Sounds obvious but you never know.  I don't even know what would happen if it was plugged in upside down.

I haven't noticed my belt sticking up anywhere, but I did notice that my belt started to warp after a few days, specifically in the middle where each roller splits.  I can see condensation forming there when the build platform heats up so I think the water collecting there is causing the problem.  I have been thinking about getting a de-humidifier for that room and seeing if that helps.  Was your belt almost impossible to put on?  I find that I dread changing it because it's such a pain since it is so tight.  I have to unscrew all six screws without losing any nuts, and to get the next belt on it always feels like I'm about to break something.

I have been unable to print a raft that will actually peel off of my model so far.  I tried changing a few settings around to make the raft less dense but I have had no luck so far.  Rather than fussing with the raft settings I have just been printing raftlessly.  I was surprised at how well the prints actually came out with no raft.  I attribute this to the HBP.  For smaller prints I will usually enable Outline in Skeinforge so the extruder can get rid of some of the oozing plastic before the print.  But I find that for larger prints the outline will often try to print off of the platform.

I have been using the 3mm filament but I might have to pick up some 1.75mm so I can give that a shot.

[Rick Osgood]

Also in regards to the raft, I think perhaps if you were to let the raft cool a bit it might help the sticking problem as you suggested.  I haven't tried this myself but it sounds like it could work.  I'm also wondering if there is a way to raise up the first layer of the actual print.  That way, it squishes the raft to the build platform but the first layer of the object doesn't get squished into the raft so much.  I haven't been able to find this option yet, if it even exists.   There are so many options in Skeinforge!

[Jwo Lee]

My current settings are 45 for feedrate, and 7.5 for flowrate (150% default values), and it seems to still work well. I'm sure your settings are different since you are using 3mm filament. I did try to push the flowrate up to 10 earlier, but my filament somehow broke and started to get wrapped around the drive gear. But this was done under manual testing, and I had only set the extruder head to 220 degrees, instead of 226 during builds.

Both ends of the connectors for the ABP heat sensor are flanged or clip, so I'm sure I wouldn't have even been able to plug it in if it were the wrong way. I'll try flipping it in case the cable was made wrong.

I have the same problem with the ABP as you have, wrinkle that forms in the belt in the center where the rollers split, the condensation, and the near impossible task of getting the rollers on during the initial build. Perhaps it being too tight is causing the wrinkle in the center? The only solution might be to sand or dremel the divots where the rollers sit to allow a little more slack.

Thanks for the tip about outline. I saw it briefly mentioned somewhere and forgot what the setting was. I'll give that shot, since it does always seem the initial (raftless) extrusion makes a mess and throws everything off.

- Jwo

[Jwo Lee]

I think I fixed the problem with the belt being too tight and wrinkling.
I ended up taking out the center spacer, pushing the two tube halves together, and adding a spacer's width of addition tubing to the end. Then I trimmed off the little tabs on the wooden platform.
To make the entire thing looser, I removed the two flanges from the rear rods, and just let it roll on the metal.
There is enough friction from the silicone tubing that I highly doubt it will come loose without the flanges.

Now I have a very smooth rolling belt on my ABP.

- Jwo

[Rick Osgood]

How long have you been running it like this? Id be interested to hear how it lasts after 10 to 20 print cycles. Sounds like it might be worth trying. The wrinkling is starting to bug me.

>>>>> shows a screencap <http://www.flickr.com/photos/makerbot/5238929586/>of the control panel showing 131 degrees at room temp.

[Jwo Lee]

The new roller setup works great. I've done a dozen or so prints now, and the belt still looks crisp and new.
I'm not sure what the reasoning was ever to have that gap in the roller.

- Jwo