How does everyone snug their linear bearings without them binding with the rails?

I purchased a desktop cnc mill so I can prototype my own PCBs. Just the same as when I assembled my 3D printers, when I tightened the bearings for this machine, they bound up tightly with the rails. Everything could be moved but the movement was not smooth by no means whatsoever. If I completely loosen up all the bearing bolts, its so smooth, but the machine is obviously wobbly.

This machine uses the through-hole style linear bearings. What's the trick? If this a normal thing? Any tips? I'm thinking I'm going to sand the mating surfaces some to make sure there are no dings that caused material displacement. I'm thinking maybe I'll try some kind of gasket that has a little give to it. I'll just snug the bolts with locktite.

Need opinions.

Could you tell us a little more about the machine, what movement platform does it use? Are the belts tensioned equally? Does the X-axis skew maybe? Can it be the frame is not squared? Or maybe one rod or extrusion is longer than the other?

It is not supposed to be binding. Linear bearings are supposed to run smoothly.

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http://www.marinusdebeer.nl/

... in a "good" CNC-mill the bearings are "compressed" to eliminate play -- for this you'll need high torque motors, to overcome the friction - typically 2-10Nm torque ... or even more!

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Viktor
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What kind of rail, what kind of bearings?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

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the_digital_dentist
What kind of rail, what kind of bearings?

I would assume LM8UU bearing blocks, but I think we need more info in order to give useful advice.

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http://www.marinusdebeer.nl/

Sorry for the late reply everyone.

This is the machine I bought:
[www.banggood.com]

The rails are 0.5" rods. The bearing housings are the through hole type. The whole thing is made and aluminum and it's heavy. I know that the bearings are to be tight to eliminate play while cutting, but they bind to much. The movement isn't smooth at all. It uses NEMA17 steppers.

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CVRIV
Sorry for the late reply everyone.

This is the machine I bought:
[www.banggood.com]

The rails are 0.5" rods. The bearing housings are the through hole type. The whole thing is made and aluminum and it's heavy. I know that the bearings are to be tight to eliminate play while cutting, but they bind to much. The movement isn't smooth at all. It uses NEMA17 steppers.

Those bearings should definitely move smoothly. But it's really hard to see the problem without being there physically.

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http://www.marinusdebeer.nl/

I understand.

I took apart the machine and I'm working on the z-axis right now and I noticed that the bearings, ever so slightly, are misaligned. It's such a small misalignment but it's so devastating. I made a washer/spacer using craftboard (flat thin cardboard) and sandwiched it between the bearing the the z-axis housing on only the one side. I tightened one bearing down nice and tight as usual, and I snugged the other bearing with the craftboard spacer. Is was still supper tight, only only till the point that I fine tuned the snugness of which ever bolts were needed to get the bearings aligned. Now with the bearings fastened very well, the rod is very smooth and there's no play. I think I will do this for all of them.

The purpose of this post..... is it always like this? Does everything have to finagle the bearings to get them to work right out of the box?

Machine is fully built and I nailed it getting to move smoothly. The spacers worked great. Took some time to get it done but it's together tight and moves smoothly.

Is it a problem on all axis, maybe the bolts need to be tightened in diagonal pairs, maybe loosen(or check) rails.

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CVRIV
Machine is fully built and I nailed it getting to move smoothly. The spacers worked great. Took some time to get it done but it's together tight and moves smoothly.

Cool, I don't know about the new machines. It seems every machine has it's own quirks. I have only done DIY machines so far. And I got an old 3D-printer, a Replicator 2x that had pretty bad bushings on it that I fixed and now it runs smoother than ever.

I guess it's all down to the user to make sure it works. Share some of your first work when it's done, I'm curious what this machine can do!

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http://www.marinusdebeer.nl/

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MechaBits
Is it a problem on all axis, maybe the bolts need to be tightened in diagonal pairs, maybe loosen(or check) rails.

Yea it was all of the axis bearing, some worse than others. I could see the misalignment when passing the rod through one bearing to the next. I basically used one hand to slide the rod back and forth continuously while gradually tightening all the bolts down. The cardboard spacers allowed for some tilting of the bearings while tightening the screws. The spacer is fully compressed, aka bolts tight. The machine moves very nicely now.

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Ohmarinus

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CVRIV
Machine is fully built and I nailed it getting to move smoothly. The spacers worked great. Took some time to get it done but it's together tight and moves smoothly.

Cool, I don't know about the new machines. It seems every machine has it's own quirks. I have only done DIY machines so far. And I got an old 3D-printer, a Replicator 2x that had pretty bad bushings on it that I fixed and now it runs smoother than ever.

I guess it's all down to the user to make sure it works. Share some of your first work when it's done, I'm curious what this machine can do!

I figured this, but I wanted to be sure that I wasn't missing something. I will surely post some pics once I have it running. I still have to print out some custom parts to finish the build. I can't wait. After this I have to start designing a CNC platform for a 5W 450nm laser I bought. That's going to be interesting too.

Posted to pics of the machine so far. If you look closely you can see the spacers smashed between the bearings. This little machine weighs 16.8lbs. The entire thing is made of aluminum; even the knobs are solid aluminum.

The Chicom 3D printers have a flexible frame that prevents to some degree, the bearings from binding too much. They are just noisy, the time it takes to grind the guides enough.

Here, the frame seems sturdier, therefore binding is as normal as the poor alignment. It is cheap, isn't ? 0.5" diam is quite strange, not standard, is it US made ?
Check if the rods are hardened steel, not soft stainless. In SS, better plan their replacement.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

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MKSA
The Chicom 3D printers have a flexible frame that prevents to some degree, the bearings from binding too much. They are just noisy, the time it takes to grind the guides enough.

Here, the frame seems sturdier, therefore binding is as normal as the poor alignment. It is cheap, isn't ? 0.5" diam is quite strange, not standard, is it US made ?
Check if the rods are hardened steel, not soft stainless. In SS, better plan their replacement.

This machine was shipped from Canada, I don't know if it was made is China and just came from Canada, or what. I don't know what is the standard, but I know the rails need to be of a larger diameter do to the the cutting forces experienced with milling.

I got my Red 1419 CNC router cutting. Works great. I had an issue with the z-stepper it came with and the z-stepper replacement I purchased, but I fixed the replacement and its working great.

[youtu.be]

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CVRIV
I got my Red 1419 CNC router cutting. Works great. I had an issue with the z-stepper it came with and the z-stepper replacement I purchased, but I fixed the replacement and its working great.

[youtu.be]

Look at that. Now it's time to learn all about feedrates. I think you're going way too slow. Speeds are essentially the most important factor in tandem with depth steps. Too slow and everything will get too hot and you run the risk of fire, faster wear on the mill bit etc.

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http://www.marinusdebeer.nl/

Exactly. This is literally my first CNC cutter so i purposefully ran it really slow because I didn't know how the machine was going to behave. I ran it super slow and even though I thought I was only cutting a tiny bit, in height per pass, it was still a little bit to much. I'm trying to dial in the distance per revolution now.

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CVRIV
Exactly. This is literally my first CNC cutter so i purposefully ran it really slow because I didn't know how the machine was going to behave. I ran it super slow and even though I thought I was only cutting a tiny bit, in height per pass, it was still a little bit to much. I'm trying to dial in the distance per revolution now.

I hope there are good guides on the subject. We have one at work, but it's a beast with a 2,5m*1,35m bed. Want to build my own desktop cnc some day with the leftover frame bits and other parts that I have laying around.

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http://www.marinusdebeer.nl/

It's not super hard to design and build these. The biggest thing with cnc routers is that they are rigid and heavy, which is the opposite, except for rigidity, of how one may design and build a 3D printer.

I am thinking I may get a spindle that supports a greater RPM and I want to get some fluted bits to cut with so I can see how they compare with the rasping kind.

Here's another video after having sped up the feed rate, decreased the cutting depth, and I fixed the distance per revolution. Definitely want to try some fluted bits.

[www.youtube.com]

Edited 1 time(s). Last edit at 08/24/2020 12:37PM by CVRIV.