Other Core won't tighten

I have this same problem using 23.5mm tubing and the “C” parts. Everything else on the machine fits great. But the if I grab the stepper on top of the core, it has about 1cm of play. It’s clearly because of the interface between the gantries and those four clamps on the core, which are all very loose. But I don’t think I can tighten them further w/o breaking something. I’m at a bit of a loss on what to do.

Take the core clamps off and bolts out. Be sure to follow the order of operations on the instructions. There is a note about it being too loose. Clamp the core clamps before installing them, make sure to install them without the rail in place.

Thanks. What do you mean “clamp the core clamps before installing them”?

I just removed and reinstalled these 4-5 times, paying careful attention to the instructions. I also reprinted one of the clamps to see if it made a difference (the blue one in the video). No joy. I’ve measured the tubing and the bearings and they were the right size. So I’m stumped. I’m starting to worry it might be my core itself. I really don’t want to reprint that!

I took a video to show the problem I’m having. If anyone has any ideas I’m all ears. The X and Y work great, the software works, I just need to get this part working and then I can move on to being frustrated by my lack of knowledge of CNC :slight_smile:

With the core clamp off, install and snug the tension bolt and bearing. Then put the core clamp back in place and snug it up. Loosen the tension bolt and insert the rail, then follow the instructions.

FI that doesn’t work you should be able to measure the exact Z height of your core print and double check it before reprinting. It is usually just snug bolts throwing things off.

Thanks for moving this, I was feeling bad having intruded in the other thread but thought we might have had the same problem.

Just to follow up, I was able to fix this by switching from the 5/16" bolts to M8. The M8 bolts I obtained locally were a little over .1mm in diameter larger than my amazon 5/16" bolts. Somewhat to my surprise this moved the bearings in enough that I was able to get all the slop (which seemed more on the order of 2-3mm) out of the system.

I almost didn’t figure this out, everything I had printed was measuring nearly perfectly what it should have compared to the models. I just assumed the bolts would not make a difference. I was wrong!

I’ve got to reassemble everything and re-test with a pen but I think I’m in good shape now. I guess it’s time to buy a 660!

Thanks,

-dave

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I wonder if just taking it apart and putting it back moved something into the right place.

Just wanted to follow up on this old post. I’d been doing a lot of detail work with the CNC and it became obvious that my Z play was still too much, and it was still because despite all my work to snug up the interface with the conduit, it was too loose.

In the process of rebuilding my machine I realized that my 3D printer calibration is slightly off. I still haven’t figured out why–all my calibration tests look good, although they are on much smaller objects.

Anyway, I scaled down to 99.5% and printed a new core. It is super solid. No doubt what it should have been all along. No play.

I’ve clearly got some work to do to figure out what the hell is going on with my printer but I just wanted to throw this out there as another really dumb thing that can cause this type of problem in a build.

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Yeah 20mm calibration cubes get you very very rough calibration. I do 100-150 mm to get a real picture of what is going on. You notice 1mm discrepancy way more than 0.2mm

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And, diagonals tell you more than any single axis could.

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