Trouble with core can't get all bearing engaged

I am having trouble getting the core properly set up. I can’t get all of the bearings to touch the bars. one side sort of touches(More like intermittently touches), the other side is close (a business card fits but you can’t pull it out). The outside bearings are snug but you can spin them by hand.

It’s a common problem, and i dont know the solution unfortunately. I’m on my 3rd core and 4th set of core sports, printed on the 3rd machine and i still have some wiggle.

I backtracked a bit, I did print out the big test print, y was OK, x was a bit out and z was out by what I think is a lot (just about 2mm). I adjusted x and z and another test print is on the way. I also adjusted the flow rate so my line was a bit thick.

Thinking hard about switching the outer wall print order from inside out to outside in.

the wife came up with an interesting thing to try I tend to print things with the long axis of the part aligned with the x-axis, but I may try turning the part 45deg to share the error… or magnify the error.

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You might take a look at this thread…

Full Printer Accuracy Tuning

Specifically the vector 3D skew test. I have used it personally and it’s a great test. Don’t bother getting the short one. Get the one for all 3 axis.

Its worth a shot. I did my 1st 2 cores on ender 3, most recent on a new bambu. Same isssue on all 3.

I bought the califlower test and that was the basis of my thinking I was good with calibration. The V1 test finished printing and to be honest I wish Marlin had a second decimal place for steps/mm. but that is me splitting hairs. I will get the calilantern and print that test just to confirm the last test.

The nice thing about the calilantern test is it lets you put in whatever skew correction you already have set. Then gives you what you should change it to based off the measurements you take. And tells you exactly how to make the changes in each firmware.

So after a couple of calilantern test prints, I have the core on the printer now 1 day 4 hours of print time.

And hey I have the latest Marlin firmware on my printer for the first time.

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1: Have them unsubscribe from any Andrew Tate social media
2: Convince them to actually listen to the rails
3: Remind them that the rails are fully functional pieces of hardware as well, and they have usefulness and purpose as well
4: Tell the rails that the bearings are rich

Quick test fit last night and it looks like I have decent contact the inner bearings do contact but still seem loose. I will go through my bearing supply and try to find the fattest four for the inside bearings. I am not sure how much variance is in the bearings but there must be some and a couple of thousands could help.

You can also try tightening your front screws for the struts (the strut that runs behind the core) if your core is still loose. Go just a little bit at the time and do it evenly across the entire X beam. That will spread the 2 conduit tubes apart a little and let the core fit a little tighter on the beam. Its very easy to over do it so take your time and just go a little bit.

Do you actually have all the bolts installed? I recall someone admitting they had everything installed and even run a few jobs, and discovered that they hadn’t installed some of the bolts (and maybe bearings?) in the core… A testament to @vicious1 that it ran well enough until then.


No, I was nowhere near fully assembled, Just the z-axis, and the top 6 bearings on the core did not want to bother doing a full assemble if it was another dud print.

Jonathan, I am not sure I follow what you are saying. but let me get the core reassembled properly and go from there.

Yes definitely get it fully assembled and adjusted per the docs before trying what I suggested. I did not realize you didn’t have it fully assembled yet. Good catch @kvcummins

Fully constructed, and everything is in contact.