Z Axis Stalling

LowRider CNC Troubleshooting
1

So, I finally got a table built and the LR3 mounted, and am now testing, squaring, and trying to get ready to cut strut plates. BUT - when I mounted the router (Kobalt) and did a Z axis up/down, I found that the Z servo at one end will stall if the router is toward that end. In other words, with the core at X=0 the Z axis at the 0 end will stall. With the core at Xmax, the Z servo at the Xmax end will stall. With the core in the center, everything is good.

Thinking this through, I wondered if the driver current was too low. I found the settings on the SKR board and increased the current from 900mA in increments until I got to 1200mA and everything smoothed out.

So I’m really a newbie at this, and I’m wondering if I did the right thing? Or is there something else I should be looking at?

2

Measure the top of your leadscrew to the YZ plate. If the number is different at the top vs bottom you are binding.

4

Since I’m new at this, I’m going to ask what might be an obvious question to some.

“Different at the top and bottom”. Top and bottom of what? Do you mean if the number is different on the 2 Z lead screws?

5

Measure the distance the top of your Z leadscrew is away from the YZ plate. If there is something funky it will actually get closer or further away.

If that does not make sense post a picture of your plate from the front and I can draw on it.

6

Did you lube your Leadscrews?

7

Ok - here’s a photo.
IMG_5025

8

I didn’t see anything in the docs about lube on the lead screws, so no. But reading your question, I put some TopCote on them.

9

I think he was wanting a picture showing a close-up of the lead screw where it goes through the threads (easier to explain if you have two photos - with the threaded part at both the top and then the bottom of the travel)

10

Ah - I think I understand. If for example the motor mount was loose the top of the leadscrew would move vertically relative to the top of the YZ as the mount “climbed”. Assuming that’s correct, I did measure with the beam up and down and got identical measurements from the top of the YZ to the top of the leadscrew - on both ends. In any case, here is a close up photo to draw on in the event I’m still confused - please pardon the sloppy initial wiring…

After letting the TopCote dry, I restored the default current drive level(900mA) and tested and it works fine. I used the TopCote thinking sawdust would bind to white lithium grease or an oil and bind up the lead screws. If there’s a better way let me know.

While poking around on this, I found a possible contributing factor. I didn’t have clearance between the top of the Z couplers and the bottom of the lead screw nut when the beam was all the way down. Fixed that

IMG_5026
IMG_5026480Ă—640 133 KB

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