Linear Rails

[heepofajeep]

I am in the design/parts accumulation stage of building a 4x8' plasma/torch table. A friend recently gave me a bunch of phased-out automation parts from his work. The caveat with these parts is that his company has an unwritten policy that you cannot make a profit from any scrap parts you take home-- I'm not complaining though-- it's free!

So for my first question... do you think a 53" linear rail will be sufficient to get 48" of travel? I would really like another 6", but I am trying to work with what I've got. Basically, the biggest concern is the fact that I would only be using one 'car' per rail, of the two rails for the axis. My thinking is though, that I should be okay, as the unit will not be seeing enough side loads to cause it to lose precision.

2nd question: What is the best bang-for-your-buck linear guide solution for the 8' x-axis? I like the affordability of the custom DIY 'angle iron mounted bearings riding on tubing' that I've seen on here, but I am a little concerned with deflection over an 8' length. Another option is a linear shaft combo, especially since I do have some cars that will work, but I am wondering, (question 3 ) where is the best place to buy supported linear shafts?

Thank you very much in advance, and I am sure this is just the first of many questions to come as I get deeper & deeper into this project!

[Torchhead]

Personally for "bang for Buck" I like the V groove bearings and matching hardened rails. Bishop-Wisecarver makes them and so do others. You bolt the rails on any structure and you can make that as stiff as you want.

[Dirtbos]

Originally Posted by Torchhead Personally for "bang for Buck" I like the V groove bearings and matching hardened rails. Bishop-Wisecarver makes them and so do others. You bolt the rails on any structure and you can make that as stiff as you want.

I to like the v-groove design (have not built yet) but noticed on the B-W site that they only mention sliding doors, etc under "applications" for the v-groove design. Does this design have the necessary durability for linear motion?

[Torchhead]

Sure has been a lot of commercial machines built with the V-grooves. Get a copy of the "Handbook of Inch Drive Components" from www.Sdp-si.com. There are several pages with interesting graphs and formulas about bearing life with different loads. One states the life in "miles" of travel VS load in lbs. Graph starts at 112lbs load and goes to 1293 lbs. Life with a 112lb load is 6.2E+4 (62,000) miles. That would run your table for a while..........

[Dirtbos]

Originally Posted by Torchhead Sure has been a lot of commercial machines built with the V-grooves. Get a copy of the "Handbook of Inch Drive Components" from www.Sdp-si.com. There are several pages with interesting graphs and formulas about bearing life with different loads. One states the life in "miles" of travel VS load in lbs. Graph starts at 112lbs load and goes to 1293 lbs. Life with a 112lb load is 6.2E+4 (62,000) miles. That would run your table for a while..........

An excellent research website. Thanks for the information. It will be very helpful.

I have done a search on this forum regarding v-groove bearings and don’t come up with much info. I was unaware that commercial machines use them.

The easy adjustment, the claimed “self clean” feature and relative low cost makes them a good candidate in my mind. If they maintain close tolerance, they will be my choice.

I am planning a plasma table of 48 x 48 (or possibly smaller). We tend to make small runs of tabs, brackets, etc. so I do not feel it needs to be very large.

Thanks again for the info. I will be ordering other publications from them also.