Optimum BF20L - I don't know how to fix belt pulley to Z axis ballscrew

Hi,

I have the MK F20DP kit with steppers, housings, belts and whatnot from Optimum.
Attachment 284226
I have recently replaced all the leadscrews with ballscrews and I borrowed one of the holding nuts from the original Z leadscrew to help me fix the belt pulley that goes on the ballscrew end. But upon trying to move the axis, I noticed two things:
1st: Even though I set the motor side pulley as far from the motor and down onto the housing as I could, the belt went upwards on the ballscrew side and like half of it was protruding the pulley. So maybe the pulley on the ballscrew side was too low, but then again... well see point 2
2nd: After the first test of lowering and raising the head, it wouldn't go down anymore... When I checked I saw this:
Attachment 284222
The belt was now in place, but the nut that I fitted on top had come loose, and I swear I made it tight
Attachment 284224
And the pulley is not even thoroughly inserted in the ballscrew. Also it's just threaded and has no bores for holding pins or something. So how am I supposed to fix it to the ballscrew? Oh and yes I drew the ballscrew up against the bearing... This doesn't make sense. It seems too short. And I don't see how the pulley is supposed to stay in place anyways.

Thanks for any help

I think I've solved the mystery among bad dreams. First, to solve the belt level issue, maybe the pulley needs to be installed up-side-down. And secondly I can barely recall having left a thin brass ring from the original leadscrew between the inner side of the bearing and ballscrew. So maybe if I remove that one, I might have room to fix not just one of the original nuts, but the two of them on top of the pulley. That's about the only thing I can think. Hopefully I'll get some help if I'm wrong before I start making these changes.

Nope. That brass ring was still on the old leadscrew. Anyways I did as I said.

I made sure the ballscrew block is tight against the bearing part:
Attachment 284280

I installed the pulley up-side-down and tightened it and retaining nut with strength only known to gods:
Attachment 284282

What you can see under the pulley is really a non-threaded block that can run through the bearing but not through the pulley. And it's the only reason the pulley isn't up against the bearing:
Attachment 284284

This is how it looked after installing the belt and motor this time:
Attachment 284286
Attachment 284288
The belt is pretty much centered onto the pulley.

I passed the first down and up test and the nut and pulley seem to be still in place. The belt however had moved downwards, to the point of reaching the lower edge of the pulley, but it hasn't protruded this time.

Now I'm going to try and code some lines of gcode to repeat the test a hundred times in a row. I just hope the pulley won't come loose this time...

But still, this all seems too awkward. Is this supposed to be like this?

Later

Yup, that did it. Hardest part was to find to-the-point info on gcoding and figuring out things like goto command not supported in mach3 and how to exit gracefully from instead-used subroutines. I still find it awkward and feel there must be a better way to fix it, and I'm open to such pointers.

Going for a well deserved drink! Bye

Edit: too many drinks... :violin::(

Thanks for sharing. While I don't have your kit, I'm building a BF20/G0704 currently and seeing these issues helps with my design.


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Glad it helps.
Actually I've had another sort of problem early in the day with another axis and I've found what the possible culprit was. When you're sitting the widest side of the pulley against the bearing, part of it touches against the bearing housing part, as such, the pulley might block when rotating and actually unscrew its way out.
Attachment 284774
A bit ashamed I didn't realize this earlier. I wish I had some sort of instruction manual, but hey they need to sell labor too...
I'm very close to finishing my CNC upgrade! Good luck with yours! :)