How to install linear rails accurately

[WayneC]

I want to upgrade my CNC router that now uses Bishop/Wisecarver rails and wheels to use linear guides.

I have two questions about how to do this. This is on my X axis, and the rails will be mounted onto a horizontal surface.

1) How do I make the horizontal surfaces flat and CO-PLANER so that the rails are mounted on a flat surface that is on the same very level plane? I can use self leveling epoxy as a way to get a single rail surface flat, but how do I make the other side coplaner?

2) How do I get the linear rail installed straight along its 120" length? I understand how to install the second rail based on the first. But how do I install the first rail to be within a few thousandths over its length? I read a guide to installation that suggests using a tensioned wire to create a reference straight line, and to mount the rail just touching this wire. Would this work, or is there a more accurate way?

I'm concerned that if I upgrade to linear guides but don't do a good job on the installation I'll get binding and not get the accuracy and smooth travel that I'm looking for.

Any advice is welcomed!

Wayne C

[Eurisko]

Hi Wayne,

Just some food for thought. Linear rails aren't straight or true right out of the box. The rails should be clamped to a straightedge to hold them true while mounting. The second rail can be trammed in with a dial indicator, mounted to a beam attached to the trucks on the first rail.

A 10 foot axis is going to be a challenge. Finding a 10 foot parallel bar to use as a straightedge is a challenge in itself.

I'm sure that it can be done. Just make sure that you know what to expect before taking your machine apart.

[bri-guyCMFGT]

Wayne,

The castings on production CNC machines are machined with a vertical step as a locating reference edge for the square rail to be mounted against. If it is possible you can machine a step for the rail to locate against.

For flatness you may consider having the surfaces ground. If your horizontal surface is a steel plate you can send out for blanchard grinding to make the entire surface flat to a few thousandths of an inch.

[ger21]

Have you read this?
http://www.oneoceankayaks.com/madvac/machine_frame.htm

[vger]

Wayne,
If you want to use the tensioned wire method, you might try electricly insulating the wire from the frame and attach an LED with appropiate power (auto parts store 12 V LED with resistor) to the wire. Wire it up so that if the tensioned wire touches the frame, the LED lights up. Put a bearing truck on the rail with a micrometer temporarily attached such that adjustement of the micrometer will allow the moving face to run out to touch the wire. You should be able to dial in the first rail pretty straight this way.

Steve

[esdios]

Have you checked out IVT? It would save you the time and hassle of trying to mount linear guides.

[rowbare]

This doesn't really cover frame preparation and all but is a good overall guide:

https://tech.thk.com/en/products/pdf/en_a1_322.pdf

[15mgtar]

Am now scratching my head to mount 25mm 2 meter long LM rail. Making holes evenly 60mm apart and straight was a challenge already as the rail holes don't align.

[luca.sl]

Originally Posted by WayneC I want to upgrade my CNC router that now uses Bishop/Wisecarver rails and wheels to use linear guides. I have two questions about how to do this. This is on my X axis, and the rails will be mounted onto a horizontal surface. 1) How do I make the horizontal surfaces flat and CO-PLANER so that the rails are mounted on a flat surface that is on the same very level plane? I can use self leveling epoxy as a way to get a single rail surface flat, but how do I make the other side coplaner? 2) How do I get the linear rail installed straight along its 120" length? I understand how to install the second rail based on the first. But how do I install the first rail to be within a few thousandths over its length? I read a guide to installation that suggests using a tensioned wire to create a reference straight line, and to mount the rail just touching this wire. Would this work, or is there a more accurate way? I'm concerned that if I upgrade to linear guides but don't do a good job on the installation I'll get binding and not get the accuracy and smooth travel that I'm looking for. Any advice is welcomed! Wayne C

Never try with a laser level? put the laser on a stand and align the two rails...