Interesting Linear Drive System

[TravisR100]

This is my first post here. I've been reading the threads here for several months and am planning to build a CNC router at some point. Like most, I've been busy scrounging parts. A couple of days ago I found a salvage computer dealer here in Houston. I dropped by to see if they might have anything of use. Apparently I stopped by the right day. They had a surplus robotic tape library. This wasn't one of the little ones. It's about 6 1/2' feet tall by 2' wide by 2 1/2' feet deep. I took some pictures before I started the process of taking it apart but haven't had a chance to pull them off my camera yet. What was amazing to me was one of the linear drive systems I pulled out of this thing.

I'll try to describe it as best I can. It appears to be an aluminum extrusion much like an 80/20 extrusion. The extrusion is about 2"x2.5". On top of the extrusion rides a plate that's about the same width of the extrustion and 6" long. Where you would normally be able to see into the track of an 80/20 extrusion where the t-nuts would go is a belt. The belt is a continuous belt that runs through the extrusion and is attached to the plate that runs on top of the extrusion. At first I wasn't too thrilled because I couldn't imagine this thing would be able to hold any kind of tolerance. After playing with it I was amazed. The plate that runs on top of the extrusion appears to have no detectable play in any axis. At the end of the extrusion a shaft protrudes from the side which is coupled to a servo motor that drives the plate up and down the length of the extrusion using the continuous belt inside. I was baffled at how this little 2"x6" plate could possibly have no play and yet was used to support the entire robotic head inside this machine that weighed at least 20 pounds. I figured it out after looking at the manufacturer information on this thing and looking it up on the Internet. This thing actually has a hidden rail system INSIDE the extrusion! Take a look at this link:

http://medias.ina.de/medias/en!hp.ec...R;aI1XmOQuCHhc

That's a picture of it. The one I have is an INA MLFI25ZR. I don't see that exact part number but it appears to be identical to the INA MLFI20ZR which is listed in the link above. So what do you guys think about this piece? It seems like it would be a combination lead screw and rail system in a packaged piece that could simply be bolted on for a complete X or Y axis. Any thoughts?

-Travis

[TravisR100]

As promised, here are some photos. In the 3rd picture you can clearly see a U shaped panel attached to the back of the extrusion. This isn't part of the extrusion. It's simply attached with double-sided tape. No comments on this???

[higgrobot]

I guess there's a price to pay for having a neat little setup like that and the double sided tape gives a clue of what that is. The maximum load capacity seems to only be 120N, about 27lbs. This doesn't sound like a lot when you compare it to a conventional linear bearing that may handle ~30,000N at around the same size. The belt inside looks like it will only handle 2.3Nm or 325ozin from the servo or stepper so be carefull not to break it. Remember most belt or rack servo/stepper setups have a geared drive system that multiplies the torque so you may be limited to say 80ozin peak steppers at 4:1. also, the feed is 81mm/rev so at 4:1 with 200 step/rev steppers you would be moving 0.1mm per step, that's not very accurate.

[TravisR100]

Thanks, I appreciate the comments. I'd just never seen anything like it before so I was quite surprised to find it. I went ahead and listed it on eBay.