pacific bearings integrated v rails

[harryn]

Hi,

I am working on a DIY wood router, and would like to get some opinions on this rail type.

In particular, I am considering making the Y axis from the pacific bearings IVTAAE bolt on linear guide: (one of them, not a pair)

IVTAAE Bolt-On Linear Guides - Double Width | Integral V Technology

The tables show "ratings" for these guides, but they don't give any information on how much deflection there is under load. For example, I roughly estimate that during a router operation, the forces will be about 100 lbs at a 1 ft distance, so about 1200 in-lbs of torque on the Y rail.

The fixed gantry will be about 7 ft long, and I will make it as stiff as possible, but of course any gantry will twist a little.

Even if the gantry does not twist at all, the rail will twist some under load - but - how much ? My target is to have less than 0.010 inch total error if possible, so I would like to have no more than 10 - 20% from Y rail deflection.

Any suggestions or prior experience with these rails ?

Thanks

HarryN

[harryn]

I guess thinking about it some more, the ability of these to deal with torque is going to be about the same as any other V bearing setup, at least to a first order of magnitude.

[jharvey407]

I'm using a couple different form factors of the IVT rails. I'm using the IVTAAB on both sides of the X axis.

I find them to be very sturdy and stable. They aluminum extrusions that the rails are built around are quite substantial. I have mine bolted to 8020 extrusions which adds to the strength.

[harryn]

Thanks for the reply. On the X axis, their use makes a lot of sense, as the side and torsion loads are relatively small, compared to the down / up force.

Not just on these, but some V bearing builds have had challenges, and I am just wanting to make sure I understand the limitations.

I called Pacific Bearing on Friday and spoke to a product specialist, but he was actually the specialist for a different part of their product line, so he was not ready to really step out and tell me life would be fine for a Y axis type application. Early next week I will be calling in again to talk to the IVT specialist for a discussion.

( I am using 100 N-Meters as my calculated force in the X direction on a Y axis ) This might be high, but it seems like a good starting point.

Assumption for the 100 N-M number
- 1 rail + 1 carriage mounted on the Y axis of a fixed gantry system
- Option - 2 rail system

- 0.5 meter (about 19 inches) long distance from the center of that carriage to the tip of the router bit (yes, very long, but things can be scaled down)
- 200 newtons = 20 Kg x 10 M/s x s, so the equivalent of a 50 lbs force pushing sideways on the bit in the X direction during cutting

Post here if you have any other specific questions you would like asked. Maybe I can get them to post on cnczone - who knows.