Engraving small font - the bit digs deeper and deeper as the job goes on. 6040z

Rob,
Re-reading I should have worked out that it wasn't the spindle motor but it was the only thing I could imagine moving on a halfway logically assembled machine :-(
I suppose all the vendors of ball screws should have a recommended shopping list of Ball Screw, Ball Screw Supports, Ball Nut and optionally Motor Mount, Motor Coupling and Motor, with a brief explanation of how and why, the market has clearly moved to a point where there is no research prior to shopping,

- Nick

The Chinese vendor sent me a reply to an email that I sent them telling them about the issue.
Their response was:
"Dear friend.
Please can you buy such a coupling to change it. The problem will be solved then. This coupling is cheap only about 3usd. Can you get it in USA local? If yes. We can refund you 10usd. Then you can buy it. If you can not get it local. We can ship you 1pcs. It will cost about 12days. Please check if ok for you.
Waiting for your confirmation. Thanks a lot.
Nice day."
___________

I am unsure about what coupling I can buy in a hardware store to fix the issue.
Does anyone else have any recommendations on where to get similar couplings?

Thanks...

Mark

You didnt take a look at the fixed end of that ballscrew, which is on the bottom. There are two bearings on either side of the bottom plate, secured with a 17mm locknut on the ballscrew. The top bearing near the stepper motor is the floating end.

Quote:

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Originally Posted by xoneeleven

The Chinese vendor sent me a reply to an email that I sent them telling them about the issue.
Their response was:
"Dear friend.
Please can you buy such a coupling to change it. The problem will be solved then. This coupling is cheap only about 3usd. Can you get it in USA local? If yes. We can refund you 10usd. Then you can buy it. If you can not get it local. We can ship you 1pcs. It will cost about 12days. Please check if ok for you.
Waiting for your confirmation. Thanks a lot.
Nice day."
___________

I am unsure about what coupling I can buy in a hardware store to fix the issue.
Does anyone else have any recommendations on where to get similar couplings?

Thanks...

Mark

---

They are talking about this type of coupling https://buildyourcnc.com/images/rigi...01-4%20200.JPG
As we have said - this uses the stepper motor bearings to fix the position - it is not the proper solution - the Z axis leadscrew needs to be in a fixed bearing at one end and a floating bearing at the other end.

A better compromise would be to have a collar on the top end of the leadscrew, but we would need better pictures of the leadscrew mounting arrangement to be able to advise you properly.

Best regards,

Rob

I assume I have the same machine, and this is where the ballscrew is fixed.

Atleast on my machine, no motor-coupling would have anything to do with it.

Yes, we really need to see what is going on at the lower end of the Z on the OP's machine

Hello All,
Here are some photos of the bottom of the screw, the mid point, and another of the upper section per your request.

Thanks again for these tips and info.

Attachment 18237 Attachment 18238 Attachment 18239

Check the bottom bearing is not loose in the plate. It just looks like a push fit and it could have gone sloppy.

In the photo in post #4 there's a gap between the red buffer and the driven section of the coupling, either the ballscrew moved down or the driven section of the coupling moved down.
If the driven section of the coupling can move down then it's not tight enough and would also slip in rotation, and because more torque is required to lift Z than lower it the axis would slowly slip down.
If the coupling driven plate is slipping then stripping, cleaning, then reassembling with a stud & bearing fit compound may provide a temporary fix,

- Nick

I cannot see this being the problem more likely the simple options, ER11 thread damaged and not locking collet properly, material insufficiently secured if clamped at edges acrylic will lift in centre with any sort of up cut helix, wrong collett size used, whatever is causing a 3.75mm shift is gong to be measurable so measure collet protrution, relative position of ballscrew, deflection in frame or material plane with dial indicator etc and identify movement.
Before trying to remedy a problem identify it and save a lot of unecessary speculation.