CNC4NEWBIE Z Axis Upgrade Issue

Hello everyone. I want to start by thanking everyone in this community. This is my first post, but I have been lurking for a while and have been able to solve many issues and learn a lot about my machine through all of the posts here.

I have a SO3 XXL that I have been working with for about a year. Overall, I have had a lot of success and, other than a few setbacks, haven’t had any real issues. That said like some have posted, I was having some issues with the z-axis skipping a tooth from time to time and throwing off the job. This led me to invest in the Z-Axis slider by CNC4NEWBIE.

The install was mostly painless thanks to all of the documentation here, but I have run into an issue that I can’t seem to find any other reports of. Basically, the downward z-axis movement is not smooth. I can raise the z-axis at any speed and distance and the movement is very fluid and accurate, as it should be. I can make small downward movements of the z without much issue, however, if I try to move the z-axis a large amount, it seems to stop/hang up in the middle of the movement.

For example, if I try to run the z-axis down 1 inch, it will go down ~3/8" then hang up, then continue down to the -1" of travel. From my testing, the total movement appears to be accurate in terms of distance, but I can definitely see this leading to issues.

I have tried removing the stepper and turning the screw by hand, which feels normal and smooth. I have tried jogging the z-axis with both Carbide Motio as well as cncjs (which I normally use) and have the same issue. I have not been brave enough to try running an actual job to see if the same problems show up.

Has anyone ran into this type of issue? Any advise or tips would be greatly appresited. Thanks in advance!!

Try turning down the acceleration in GRBL, I had the same issue. GRBL -> $122 . Take a look at what it is current set to, and cut it in half, and try that. You can likely go faster, but you’ll need to see what works.

I will try turning down the speed. It is very quick moving up, so slowing it down should still be plenty fast enough. Thanks!

This will only turn down the acceleration, the speed will stay the same. That would be the next thing to turn down though.

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Thanks for your help. I changed $122 from 750 to 300 and took care of 90% of the problem. I think I will be able to work through a few other slight adjustments and get smooth movement on the Z. Thanks again!

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