7 Kg of plastic, and my X & Y linear bearings are warn out.

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DAP
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7 Kg of plastic, and my X & Y linear bearings are warn out.

Post by DAP » Mon Jun 04, 2018 8:28 pm

I have at least 1mm vertical play (I can see the bearing shift relative to the rod) on the y axis, and a small but visible play in the x axis. I am rather surprised that these bearings wore down after only 7 Kg of plastic.
Excuse me while I go shopping for replacements.

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piercet
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Re: 7 Kg of plastic, and my X & Y linear bearings are warn out.

Post by piercet » Mon Jun 04, 2018 9:57 pm

Those bearings are designed to be press fit into a housing with a preload. The 3d printed parts cant take that much force. The usual way to get a better contact pattern is to loosen the bearing holders and move them onboard or outboard until play is reduced. You can also change to other setups. If you decide to try metsl bearings, swap the rods out AT the same time for harder ones or else you will chew up the stock ones. One person had good luck with somewhat spendy oilite bushings. Or there are openbuilds rail alternatives.

DAP
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Re: 7 Kg of plastic, and my X & Y linear bearings are warn out.

Post by DAP » Tue Jun 05, 2018 8:37 pm

piercet wrote:
Mon Jun 04, 2018 9:57 pm
Those bearings are designed to be press fit into a housing with a preload. The 3d printed parts cant take that much force. The usual way to get a better contact pattern is to loosen the bearing holders and move them onboard or outboard until play is reduced. You can also change to other setups. If you decide to try metsl bearings, swap the rods out AT the same time for harder ones or else you will chew up the stock ones. One person had good luck with somewhat spendy oilite bushings. Or there are openbuilds rail alternatives.
I don't think this has anything to do with the 3D printed parts. I took a video to show that the wear was on the purchased bearing.

I'll know more when the replacement bearing arrive and I take the machine apart.

(Weird, the youtube link did not work until I removed the "s" from the https: part of the link. Apparently, Firefox is adding an additional "s" so it gets "httpss:" and it gets confused. Anyway if that link does not work here it is in plain text: https://youtu.be/18L_bJcZ_i8" )

kmanley57
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Re: 7 Kg of plastic, and my X & Y linear bearings are warn out.

Post by kmanley57 » Tue Jun 05, 2018 9:21 pm

Vertical play in the Y bearings like that is caused by gravity pressing the bearing against the rod. Look more for horizontal movement on the bearings. Left and right movement on the Y table ones and backward and forward movement on the X axis ones. The weight of the bed and extruder pretty much force the bearings to ride on the top surface of the rod all the time.

Unless you are printing in a zero gravity situation then you might think about replacing them for vertical movement like that.
I will express my CRAZY ideas at any time! So you have been warned. None of my opinions are Lulzbots and can be wrong at any second.

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piercet
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Re: 7 Kg of plastic, and my X & Y linear bearings are warn out.

Post by piercet » Wed Jun 06, 2018 9:10 am

DAP wrote:
Tue Jun 05, 2018 8:37 pm
I don't think this has anything to do with the 3D printed parts. I took a video to show that the wear was on the purchased bearing.
Ok. If you measure the height of those bearing fins on that bearing, and on a brand new one, you will find they are identical. But if you don't think thats what the issue is, thats fine too. Its your printer.

DAP
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Re: 7 Kg of plastic, and my X & Y linear bearings are warn out.

Post by DAP » Fri Jun 08, 2018 8:32 pm

Update: I got the replacement bearings today. The new bearings have almost, but not quite as much play as the original, so Piercet is right. At least the lesson I learned was rather inexpensive.
I am very surprised to find equipment like this with as much designed in play as this one has. If this were a milling machine, it would be scrapped as warn out.
I guess I will look into one of the upgrades that have been designed.

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tetralite
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Re: 7 Kg of plastic, and my X & Y linear bearings are warn out.

Post by tetralite » Mon Jun 11, 2018 9:03 pm

I have the same play on Y axes on both my TAZ6s and it just doesn't seem to cause any print problems. I was shocked when I first noticed it, but since I get good prints I have just ignored it. Haven't tried it in an anti-gravity situation, but wouldn't the extruding plastic push the bed away so that it rides on the same bearing surface in a zero G environment as in one G?

DAP
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Re: 7 Kg of plastic, and my X & Y linear bearings are warn out.

Post by DAP » Thu Jun 14, 2018 9:33 pm

Now that I have two sets of bearings, I'm thinking of running a hacksaw between the fins to cut the outside frame. Then print a set of modified mounts that allow me to squeeze out the play with a hose clamp. This would also allow me to tighten up the bearings as they wear.
This would be a reasonable stop gap until I can figure out a better solution.

DAP
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Re: 7 Kg of plastic, and my X & Y linear bearings are warn out.

Post by DAP » Sat Jun 16, 2018 12:15 am

I went and looked up the specifications of the bearing.
The bearing has a tolerance on the shaft of 10 mm -0 +.04mm.
The shaft measures 9.982mm
The bearing is supposed to be 19mm in diameter, (no tolerance given). The diameter is different depending on where you measure it, but it is close to 19mm.
The hole for the bearing should be H7, which for a 19 mm hole is 19mm -0 + 0.021mm.
I should see at most 0.08mm movement, but I'm seeing significantly more than that with just the bearing on the shaft.
I need to measure the movement of the bearing on the shaft, but that will require disassembling my printer again. Something for another day.

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mrvanes
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Re: 7 Kg of plastic, and my X & Y linear bearings are warn out.

Post by mrvanes » Sun Jun 17, 2018 3:25 am

There's a topic about upgrading the bearings on the Mini:
viewtopic.php?f=43&t=4761

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