MGN12 missing balls

o_lampe

MGN12 missing balls
June 21, 2016 02:07PM

Registered: 8 years ago
Posts: 5,232

I got 3 linear rails from robotdigg. They are all showing one or more gaps in the row of balls. One rail is particularly bad with two gaps of 6-8mm each.

Has anyone disassembled these rails and replaced or upgraded the balls?

THX
Olaf

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MechaBits

Re: MGN12 missing balls
June 22, 2016 04:58AM

Registered: 8 years ago
Posts: 1,671

I had a smaller rail & carriage, bought some small balls but they where too small so I took the balls out of my dodgy LM8's and they seemed to be correct size, so I'd give it a go. 6-8mm gaps going to take a few balls to sort out, thats pretty bad.

Edited 1 time(s). Last edit at 06/22/2016 04:59AM by MechaBits.

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o_lampe

Re: MGN12 missing balls
June 22, 2016 01:41PM

Registered: 8 years ago
Posts: 5,232

Here on ePay.de we have listings about balls in practically any size ( 0.1mm steps )
I wonder if the MGN12 is based on metric dimensions?

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cozmicray

Re: MGN12 missing balls
June 22, 2016 02:35PM

Registered: 11 years ago
Posts: 1,049

Hummm?

A set of calipers on the existing balls would give a good indication of what size balls you need?
Consider ball finish --- polished, plated, chromed very smooth balls --- very smooth ride

See:

koenejet [ PM ]
Re: Linear bearing upgrade

[forums.reprap.org]

confused smiley

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o_lampe

Re: MGN12 missing balls
June 29, 2016 12:34PM

Registered: 8 years ago
Posts: 5,232

FWIW, I measured the balls: 2.38mm or 3/32".
I ordered 200 of them. Not sure how many I'll need, but a few will disappear anyways while I try to fill the rails with my clumsy hands winking smiley

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the_digital_dentist

Re: MGN12 missing balls
June 29, 2016 02:55PM

Registered: 11 years ago
Posts: 5,780

Quote
o_lampe
I got 3 linear rails from robotdigg. They are all showing one or more gaps in the row of balls. One rail is particularly bad with two gaps of 6-8mm each.

Has anyone disassembled these rails and replaced or upgraded the balls?

THX
Olaf

It sounds like Robotdigg isn't doing much to ensure the quality of the parts they are drop shipping from China. I'd definitely complain to them. Either they shipped from China with too few or the Robotdigg people managed to lose them. Either way they should provide the balls need to fill up the empty spaces.

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

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Origamib

Re: MGN12 missing balls
June 30, 2016 07:03AM

Registered: 8 years ago
Posts: 601

Quote
the_digital_dentist

Quote
o_lampe
I got 3 linear rails from robotdigg. They are all showing one or more gaps in the row of balls. One rail is particularly bad with two gaps of 6-8mm each.

Has anyone disassembled these rails and replaced or upgraded the balls?

THX
Olaf

It sounds like Robotdigg isn't doing much to ensure the quality of the parts they are drop shipping from China. I'd definitely complain to them. Either they shipped from China with too few or the Robotdigg people managed to lose them. Either way they should provide the balls need to fill up the empty spaces.

this was my first thought too. These chinese sellers are often quick to deal with dissatisfaction in my experience, so its worth letting them know. Aside from missing ball bearings, what is the quality of these? Any noticeable slop or backlash? I would love to upgrade to linear rails, but I've found them difficult to source at good prices in the UK, and we don't seem to have surplus places that sell them.

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the_digital_dentist

Re: MGN12 missing balls
June 30, 2016 09:03AM

Registered: 11 years ago
Posts: 5,780

I buy used linear guides on ebay. I look for deals with at least one more bearing block than I need to use just in case balls are missing from any of the blocks I will use. Sometimes I find deals on NOS parts in unopened packaging. I tend to buy Japanese made stuff so there will be no doubt about quality.

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

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o_lampe

Re: MGN12 missing balls
June 30, 2016 02:55PM

Registered: 8 years ago
Posts: 5,232

Quote
Origamib
Aside from missing ball bearings, what is the quality of these? Any noticeable slop or backlash?

No slop or bashlash so far. But when you move the block slowly, you can feel it rumbling inside. But moved by a stepper the movement is smooth.
Tomorrow I'll replace the balls from one block and test the difference.

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o_lampe

Re: MGN12 missing balls
July 02, 2016 04:44AM

Registered: 8 years ago
Posts: 5,232

No more rumbling
The slider blocks now fall down from gravity, but they still show no signs of slack.
The new balls are visibly smoother ( shiny surface compared to the dull grey original balls )
Cheap and easy tuning, I'd say grinning smiley

Makes me wish, I could replace the balls in my Prusa LM8UU bearings too ...

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