Linear Bearings Vs Dual V Setup

[CKerttu]

I'm in the process of designing a laser engraver/cutter with a work area of 50" x 34" for the ability to cut a 1/3rd of a sheet at a time with pass thru for longer pieces. The XY stage will be T slot extrusion and heavy wall aluminum square extrusion. The frame will be welded square tube with the XY stage being bolted on with plenty of adjustment. I am not worried about mirror alignment or fabrication (Machinist by trade with a full fab/machine shop at my disposal)

I have on hand some USED nsk lu15 linear bearings and rails but I'm afraid that being used they will not hold up for very long with the speeds I'm shooting for (+1000mm/sec raster). I know I could replace them with some Hiwin 15mm bearing in the future but that would require dismantling the whole machine just to replace the linear bearings.

What I would prefer to use is some bolt on anodized aluminum V rails and metal or delrin wheels. I know they aren't as rigid a true linear rails but there isn't much force on them other than acceleration forces. (Which could be high as I would like to upgrade to NEMA 23 servos in the future.) I was wondering what peoples thoughts on this would be.

Should I design around a true linear bearing setup or should I go with the dual V setup where it is easy to work on and easy to replace parts?

Thanks for any advice
Carl

[TLHarrell]

I wouldn't look to breaking the sound barrier while rastering. You go too fast and the tube simply won't be able to switch fast enough. I usually raster at a lower speed (my machine has wheels on an aluminum track) to keep the quality up. Closer to 100% on my machine the quality drops too far for my tastes.

Aside from that, the THK style rails should hold up fine in your application. I'd rather have those. Less adjustments to have to make.

[CKerttu]

Thanks for the reply TLHarrell. I will probably have to agree with you on the true linear bearings. I really like the looks of v slot and v rail setup for simplicity but there is a reason most manufactures go with a THK style linear bearing setup. Things are already very straight and tight, there isn't much other than alignment you have to deal with.

I'll have to take a look at speeds. I was hoping for higher speeds but the switching rate of the laser is going to be the weak point as I see.

Carl