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The purpose of the rib is to deform the pvc slightly as you knock it in, and to give it a bit more flexibility for different pipes. If yours fits snugly without the rib, more than good enough. You can use some PVC weld to fix it permanently, but be sure to be very careful with the captive nuts… If they fall out then, you are screwed. (Don’t ask me how I know)
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Belts used are T2.5 with matching pulleys on the motors. You can use any belt, as long as it fits through the holes on the drive wheels back to back. Best if it is a tight fit, because I don’t have to use any other mounting but friction on my two prototype machines.
I used chipboard screws to attach the Z mounting brackts, but this depends on the platform material. You could even glue it down with silicon… Be creative!
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I finally got the shaft (drill bit) wedged in tight enough that it no longer falls. The coupler is falling off of the stepper motor shaft. I’m using the 3 grub screws tightened to the point where it is actually deforming the coupler, but they still eventually loosen and the assembly falls off.
Any hints are appreciated.
don
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Ironically I just suffered the same failure…
I will properly tighten the screws with some thread lock. The problem is that it is relatively hard to get in there with an allen key to tighten it properly. The reason why I went for this design is that the plastic on metal couplers let loose far sooner. My original Morgan is still going strong, with not even a hint of slipping, and it remains my busiest machine.
If I need to change the couplers design to improve it, I will let you know.
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I think I may have it licked (hate to jinx it). I printed the coupler with 100% infill so it won’t deform as much. Used loctite on the grubs. Looks like I may get my first successful calibration cube.
One other question. What rates do you use for printing? I’m using the slic3r defaults which seem a bit on the slow side.
Thanks for such a wonderful design.
don
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Ok… next step. Take off the motor, and right on the grub screw level and slightly below, use a file and score a slight grove on the motor shaft, to prevent the screws from slipping past it.
Mine is holding on again.
Come to think of it, I actually roughened up the motor shafts with a hacksaw blade to see if I could get prusa couplers to stay put. I failed, but this might be why mine does not slip down when tight.
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I may have figured it out. My Morgan is printed in PLA. The z-axis motor gets very hot during a print. I think that the grubs get hot, heat of the nuts, and they press into the plastic, reducing the grip on the shaft. Since yours is ABS, you don’t have that problem. I’m going to replace the coupler with an ABS one and see if my problem goes away.
I’ll let you know so you can warn future builders. Ironically, I have no problem with my PLA toolhead.
Also, one last question. What speeds do you print at? I’m printing fairly slowly right now, but wanted to know how far I could push it once things are dialed in.
Thanks,
don
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Since I’m only printing PLA, my build plate is 1/4″ Lexan. Prints adhere a little too good initially. However, as it’s gotten scratched up, it’s working better, so I may “frost” the entire surface. It’s fastened simply with countersunk bolts. I built some 10mm spacers to give me enough altitude, but I’ll probably print something similar in shape to your universal build platform.
don
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