Extruding! Yeah! Next issue is lumpy extrude. Need another drive screw.

So, finally got my Darwin extruding! Here's the first widebar.stl outline test:

As you can see, it's pretty lumpy even in the straight sections, disregarding the pauses at the corners, which I hear is a software issue that might be fixed already.

I can hear the GM3 speeding up and slowing down with every revolution, and looking closely I can see the two halves of the extruder open and close slightly with each revolution, and the threads on the extruder drive screw raise up and down. So, it looks like the bearing surfaces are not quite centered on the screw axis.

I may be able to smooth this out in software; as I calibrate the extruder I'm realizing that just building an encoder on the motor is going to be about as easy as getting the GM3 speed calibration right once. After that calibrations are free, so I'm going to go that route. But, having a funky drive screw is going to make that job quite a bit trickier.

I don't have a lathe handy, but does anyone have any more extruder drive screws they might like to sell me? Alternatively I'll fire up one of Vik's Afghan lathes, but that will take a lot of time, as I don't have the space for that right now. Probably going to go with a direct connection this time too, as I'm happy with ABS and don't want to deal with the extra looseness and breakage of the flex drive.

Wade

Wade Wrote:
-------------------------------------------------------
>Alternatively I'll fire up one of Vik's
> Afghan lathes, but that will take a lot of time,
> as I don't have the space for that right now.

Hell, I put a length of 1/4-20 threaded rod in my electric drill and turned it into a polymer pump in about 15 minutes. It's not a real slow process. I will suggest a set of safety glasses, however.

Heh, good point Forrest! I don't have regular access to a workshop, so I sometimes forget what can be done just around the house. Not sure how I'd cut the hollow end out without a vise and a drill press, but I can probably work something out, or just convert it to a direct drive.

I'm back to building in the kitchen, so I have to keep my metalworking to a minimum. Can't wait to move to a proper place with a workshop!