A peek inside the THK KR20

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enricosavazzi
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Location: Borgholm, Sweden
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A peek inside the THK KR20

Post by enricosavazzi »

The THK KR20 linear actuator is not news to many of us. However, it may be interesting to peek inside and see a little of how it is built, especially since disassembling your KR20 just to see what is inside is "not recommended" (for good reasons).

http://savazzi.net/photography/THK_KR20 ... uator.html
--ES

chris_ma
Posts: 243
Joined: Fri Mar 22, 2019 2:23 pm

Post by chris_ma »

I love that rail, looks so simple but incredibly precise.

thanks a lot for your interesting insights, and also for the rest of your webpage which I always enjoy to read!
chris
chris

Adalbert
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Joined: Mon Nov 30, 2015 1:09 pm

Post by Adalbert »

Hello Enrico,
Great job, many thanks for sharing!
BTW, I have already tried to determine the smallest, stable step of the THK KR2001A
https://www.photomacrography.net/forum/ ... 7&start=30
BR, ADi

ray_parkhurst
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Location: Santa Clara, CA, USA
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Post by ray_parkhurst »

Hi Enrico,

Nice page describing the KR20!

You may want to also reference the full catalog/spec for the KR series rather than just the mechanical pages linked at bottom of your page. I refer to the following quite often:

https://tech.thk.com/upload/catalog_cla ... _kr_en.pdf

I didn't see it mentioned but the "SKR" types have caged balls rather than loose. This keeps the balls from hitting each other as the rail moves, and allows faster speeds, and longer life. I'm pretty sure they can be taken apart much easier and without loss of the ball bearings, but I'd still be hesitant to do it.

I've moved idler carriages from one rail to another with success. I have not moved a ball screw carriage, only idler types. It is just a matter of lining-up the end of the donor rail with the end of the target rail, and sliding the carriage across. It's a little disconcerting first time you do it, but no big deal after that. I've contemplated moving a ball screw carriage a few times, but have always found other solutions.

kaleun96
Posts: 193
Joined: Sat Oct 20, 2018 3:47 pm
Location: Stockholm, Sweden

Re: A peek inside the THK KR20

Post by kaleun96 »

enricosavazzi wrote:The THK KR20 linear actuator is not news to many of us. However, it may be interesting to peek inside and see a little of how it is built, especially since disassembling your KR20 just to see what is inside is "not recommended" (for good reasons).

http://savazzi.net/photography/THK_KR20 ... uator.html
I "accidentally" disassembled my KR26 the other week. Took about 3 hours to get all the ball bearings back in, may have missed a couple though :oops:
- Cam

mawyatt
Posts: 2479
Joined: Thu Aug 22, 2013 6:54 pm
Location: Clearwater

Post by mawyatt »

Nice article, I wouldn't think of disassembling these rails, like taking a complex lens apart, way outside my skill level!

These THK KR types are likely some of the best performing rails based upon a screw thread and carriage design, and your article shows why.

Control these with a Trinamic controller under "Motion Control" and you have a setup that's about as good as it gets for this type of screw thread rail. Closed loop piezo stages can take this to another level of precision, into the nanometer regions, but have very limited range.

Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

mawyatt
Posts: 2479
Joined: Thu Aug 22, 2013 6:54 pm
Location: Clearwater

Re: A peek inside the THK KR20

Post by mawyatt »

kaleun96 wrote:
enricosavazzi wrote:The THK KR20 linear actuator is not news to many of us. However, it may be interesting to peek inside and see a little of how it is built, especially since disassembling your KR20 just to see what is inside is "not recommended" (for good reasons).

http://savazzi.net/photography/THK_KR20 ... uator.html
I "accidentally" disassembled my KR26 the other week. Took about 3 hours to get all the ball bearings back in, may have missed a couple though :oops:
This reminds me of accidentally letting the smoke out of a chip, and then trying to get it back in so the chip will still work :shock:

Hope you got all the ball bearings back in, maybe they have a couple "spares" :roll:

Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

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