The Shop => CNC => Topic started by: awemawson on March 08, 2017, 05:22:21 AM

Title: Cutting Linear Rails
Post by: awemawson on March 08, 2017, 05:22:21 AM
I am re-working the Z axis on my CNC Plasma Table (will update that thread when anything to say!) and part of this is to incorporate a 'Floating Z' touch sensor that requires a sub-slide on Z that only needs about 15 mm of travel (just to operate a limit switch). Current set up uses a single rail that is quite chunky, and as it only has a single sliding shoe there is a tendency for it all to wobble a bit in use.

I'm going to use a pair of parallel THK 10RM rails that are nice and low (only 13 mm overall height over slider) but I want to cut a rail in two to get the short length that I need. I have two rails, each equipped with a slider, and had intended to wrap the slider in sticky tape then carefully cut the rail with a 1 mm disk on an angle grinder.

OK enough waffle - now the question  :clap:

..If I butt my two rails end to end, can I temporarily slide a slider off one rail to park it on the other while I perform surgery, thus totally avoiding getting grinding grit in the bearing  :scratch: If so not only is there less chance of grit getting in the bearing, but I preserve one entire rail uncut as a spare  :ddb:
Title: Re: Cutting Linear Rails
Post by: seadog on March 08, 2017, 05:32:48 AM
Why do you think this would not be possible Andrew? It seems straightforward to me from looking at the drawing. Provided the ends are butted squarely, I'd certainly give it a try. After all, it was assembled. But then again, I don't have them in front of me.

Interesting to note that it says on the data sheet that if you want two rails running in parallel, then you need two rails  :Doh:

Or am I missing something?
Title: Re: Cutting Linear Rails
Post by: PekkaNF on March 08, 2017, 06:17:07 AM
THK. The good stuff.

Some years ago all THK railing I met had a little acid etching at the end. Just to remove the burr and to make sliding the linear bearing over the rail possible. You see a little darker brownish silver lined hairline at the end of the rail. If someone has cut it later, you should see the difference, hopefully other end is clean and original.

If you are afraid of loosing the ball bearings, press gently grease on the bearing until track is releasing the grease when you move the bearing and then innards are sufficiently sticky to keep the grease balls together.

The grades of the THK we used allowed adjusting the preload with different size balls (that you could order another set with the unit). Another thing to note is that sometimes longer rails were put together from shorter pieces. You had to order the whole thing with one "number" and each rail was marked to put together correct direction and order.


Title: Re: Cutting Linear Rails
Post by: efrench on March 08, 2017, 12:06:02 PM
When sliding the carriage off of the rail, do it with the carriage resting on a towel on the table, not with the rail resting on the table. 
Title: Re: Cutting Linear Rails
Post by: hanermo on March 09, 2017, 03:51:55 AM

I routinely move cartridges on and off the rails.
There is a little plastic keeper that comes with new hiwin blocks, that keeps the balls in.
I have slid cartridges form rail to rail and rail to keeper.

And off course, all from keeper to rails, originally.

It is delicate, but not hard to do.
Title: Re: Cutting Linear Rails
Post by: awemawson on March 09, 2017, 04:19:31 AM
Thanks all for the encouragement  :thumbup:

I'll give it a try and move the carriages onto one rail, then I'll make up a simple slotted guide for my hand held 1 mm angle grinder disk and 'have at it' into two pieces  :bugeye:

I post the results - either success or tears !