Monday, October 02, 2006

 

Mothra moving, mostly

I'd been caught in a bit of a dead-spot, waiting for gearmotors to arrive after my early tests showed way too little torque to move any axis. I broke out my quick-built uln2803-to-printerport interface
and it turned out I had soldered the capacitor in a bad configuration. Bypassed the cap, and the motors sprung into action, way better than before! So I brought in mothra and retested it with the steppers.















The X (bottom platform) and Z (updown) axis were running just fine once I cranked it up to 12v.


As you can see, I had to gear-down the Z axis because of the weight of the dremel tool. No matter though, it dosen't move much and gearing can be corrected in software.


The Y axis was still pretty sticky, and would not drive at 12v, so I'll probably have to put some better slides in it, probably drawer slides someone suggested previously. Those should make it very smooth.



Just for this test, I'm using extremely hackneyed vb6 code to move the platform, hooked directly to a uln2803, attached to the printer, that's driving the steppers. If I get all 3 moving, I might try and make a simple script for doing a real-life test with the dremel tip. Then it's down to the extruders.

In short, I have X and Z movement. Good enough for side-scrollers, but not enough for my reprap, yet.

Comments:
***The Y axis was still pretty sticky, and would not drive at 12v, so I'll probably have to put some better slides in it, probably drawer slides someone suggested previously.***

Just out of curiosity, from your pic it doesn't appear that you're using bearings on your drive rod. Are you having to overcome a lot of friction as a result of that?

That's why I use 3/8 inch studding for drive rods. You can buy cheap bearings at that diameter.
 
I didn't go for the all-out ball bearings on it, just brass bushings and nylon washers. It probably does give it a little more friction, but I didn't feel like waiting x days for a catalog order if I didn't need to.

Works fine with the other 2, at least.
 
***I didn't feel like waiting x days for a catalog order if I didn't need to.***

I can sympathise with the sentiment. I mentioned the 3/8ths because you can buy bearings for those in a good hardware store off-the-shelf.
 
If you have 1/4 inch rod, and bearings with 3/8 inch dia, you can cheat by wrapping wire (copper, steel, aluminium) along the threads of the rod. Just follow the grooves. If you've found wire with a diameter that matches well, the bearings will fit nice and snug. :)
 
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