Z-Axis dives in 2mm to deep after probing correct

LowRider CNC Troubleshooting
1

Hi,

I’m a bit desperate with my LowRider V4 at the moment. I am using ESTLCAM for gcode generation. I load the finished gcode into fluidnc and start the job there.
Now I do the homing and then the probing. After probing, I start the job.
However, the milling cutter always plunges 2 mm too deep into the workpiece. I have entered a depth infeed of 1 mm for the tool in my job in ESTLCAM. Nevertheless, the milling cutter plunges 2 mm into the workpiece in the first pass and the offset of one millimeter then continues throughout the entire job.
What could I have set incorrectly or what can I check?

2

Please link your gcode, specifically the probing instruction.

What are you using as a probe?

3

this is my gcode i use right now and where the problem can be reproduced.

Kinderfeuerwehr_Schild_V1.gcode (480.7 KB)

I use the probe from v1engineering - Shop (" Tiny Touch Plate ")

The probing-part should be this:

G21
G90
G94
G92 X0 Y0
M0 (MSG Attach probe)
G38.2 Z-110 F200 P0.5 (probe down set thickness )
G1 Z10 F900
M0 (MSG Remove probe)
G00 Z5.0000 F900

And if it’s important to know: I’m using a Jackpot Controller.

4

Your gcode looks fine, I was checking you had probe thickness set correctly.

Maybe check if this is related to cutting load. What happens if you probe/zero the machine (you can enter the G38.2 Z-110 F200 P0.5 in the console) home it ($HZ), and drive it back to 0 (G0 Z0)? Does it push into the material/lift your Y-cart up?

5

That works fine. G0 Z0 brings it back perfectly to where it was probed Z0.

6

I have just done a simple test:

3 different pockets milled in soft wood (to be sure it’s not overstressing router or z-axis in any way). Milled pretty slow with a 1.5mm flute.

first with exactly 1mm depth
second with exactly 2mm depth
third with a depth of exactly 3 mm

result:

Pocket 1 (target 1mm) 1.72 mm deep
Pocket 2 (target 2mm) 3.59 mm deep
Pocket 3 (target 3mm). 4.78 mm deep

Looks suspiciously like a factor of 1.6 to me?

I’m not really familiar with all the settings and stuff yet. Do you have to calibrate / adjust the board in any way like z-steps or so ?

7

If you got the leadscrews from the V1 store and are using the V1 config files, you shouldn’t have to do anything.

I’m guessing this is a case of either the Z motors skipping steps (need to lube the leadscrews) or the leadscrews slipping (need to tighten the grub screws). When either of these occur, they are more likely to happen when Z is at the bottom and moving up. You might not have seen an issue with the earlier test because homing is slower.

8

I think Jason is on the right track. I had a similar issue with my Primo but it was stairstepping down. I am not sure of the final solution, but I checked grub screws, lubed, and increased my stepper current and the issue went away. Here is the post if you are interested. Z height issue

9

ok, thanks, will check that.
But if the Z-motors would skip steps, would that not happen moving the gantry upwards? The first pocket with 1mm depth is also 1.5 mm deep and the gantry moves down all the way to the 1.5mm. As this pocket is milled in only one layer, there is no movement of the gantry - and so the z-axis motors where steps could be lost?

It’s reproducable, ran the same job three times and homed everything inbetween and also did the probing.

How do you increase the stepper current at the Jackpot board? I’m pretty sure there is a documentation somewhere explaining that and in which boundaries the current should be set?

10

After probing, the gcode you listed is moving up to 10 after probing and then back down to 5. You could be losing that half a mm in that G1 Z10 move.

11

oh yes … thats true.
Didn’t lube the leadscrews till now cause i thought the lube would catch all the dust :smiley: Do you also lube the Linear rails?

12

I would bet lubing the leadscrews solves the problem. I haven’t done anything to the linear rails.

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13

The linear rails should be lubed a bit from the start, but you can lube them. The leadscrews need to be lubed.

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14

My theory, and maybe others don’t agree, is that with an upcut bit and gravity, it will pull the gantry down. In my case it was going deeper when it hit corners which is where more of the bit is in contact. Again, your case may be different. One thing you could try is to ramp down instead of a straight plunge and see if that makes a difference.

15

This should absolutely not be happening. I put 10kgs on the gantry before and it didn’t lose steps. Also, my gantry is 3mm thick pipes with 1220mm cutting area, so significantly heavier than those with 1.5mm walls and there is no dropping or losing steps because of that. So no, an endmill can’t pull it down.

16

What is more likely happening in that case is that the work piece isn’t attached well enough to the spoilboard, so it’s pulling the work piece up from the spoilboard.

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17

My workpiece is attached to the spoilboard with several screws (one of them 1.5 cm away of the first pocked drilled). Also the endmill is a very small one (diameter of 1.5 mm, 4 flutes). Shouldn’t pull that much at the workpiece?

18

That is not a good endmill for these machines. You ideally want a single flute, 2 at most.

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19

Yes i know, still looking where to source endmills here in germany. I’m using the MAKITA RT0702C. My endmills with a little bigger diamater are single fluters or 2 fluters. Didn’t get one with such a small diameter till now :frowning:

20

Sorotec? There’s no debate there… Great quality, good price.

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