Official Luthiers Forum!

Fella's, I posted the following over at CNCZone last night and since I still have not had a repsonce I thought I should bring the subject home and see if any of you have experience with this stuff:

Hello,

I have been dropping in every now and then but most of the stuff discussed here is WAY over my head! My name is Shane and I run a part time business supplying wood and parts for musical instruments(full time really but I have a day job as well). Recently I have added two computer controlled devices. The first is a mini mill with drives attached by a previous owner (I have no clue who he is) so one day I am hoping to discuss that machine for advice on what I need to do to get it to do what it can do after you all inform me of just that!. But, I also recently acquired a 1999 Precix 5100 3 axis cnc machine (4 x 4 table, 3hp perske spindle). When I took possession of it I didn't really have much time to check it out. Well recently I decided that it should be working and I ran over the machine and had to change all of the XL belts from the servos. The "X" access runs off a timing belt, it is metric, 5mm, 1650 mm long, 25 mm wide, AT5. The ones on the machine are black with a steel band core. I think, because they are black, that they are neoprene. The ones that I ordered for replacement are white with a steel core and I believe they are urethane. So I am seeking advice on the pros and cons of either. I am about to install the urethane ones but thought I should ask before I did that. Also, are there torque specs somewhere to tension these belts or are they just tightened enough to remove sag.

Thanks in advance!

Shane

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Canada

Hi Shane, I can't speak to the specifics of your equipment, but in general tension is not as much of an issue with a toothed belt/timing belt as it is with a V-belt. As long as those servos operate within the acceptable range for the belts you have, I would think they would operate pretty similarly. One possible difference could be a difference in stiffness that may cause you to change the accel/decel values??

I'd swap them out, run them slow to check...and increase from there to see what I could get away with!

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http://www.PeakeGuitars.com

Thanks Trev,

Good advise (as usual!). I will install the new urethane timing belts (probably no different than the original 'black' ones) and just snug them up. Although the old ones were in rough shape I may have over torqued them which resulted in broken steel bands and ultimately distorting the belt. The machine does move quite fast when I was moving it around with the controller but liked to jump a bit where the belt was buggered. The smaller xl belt from the servo to the main pully om the "Y" axis was missing a section, maybe that is why I got the machine so cheap, it wasn't working for them any more. $200 worth of belts and it will be running like new!

Thanks again

Shane

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Canada