Hi,
I have a RF31/clone and I want to convert to CNC. Unfortunately it's the round column version but I read that Mitch? did a conversion to square column and sounds like he did what I thought of doing. I can't seem to find that thread now but when I did look, I could not get the pictures to load/links to work. So I'm only guesing from what I've read that it was indeed a success.
Anyways, my main questions are what size motors/ball screws and slides/rails to use.
I seem to recall he used 20mm wide rails for te new Z, is it really needed or will say 2x MGN15 also work?
From reading it seems 5/8" by 0.2": or 16mm by 5mm pitch ballscrews is what most use. Is this the right size or can/should one go bigger? What about the Z axis?
Motors I have read anywhere from 450oz/in to over 1600oz/in. I was originally looking at a 1600oz stepper kit on ebay but from experience I know steppers have their drawbacks. I have also found some closed loop 2 or 3phase steppers which should be an improvement but looking at the motor specs, the torque falls off quite rapidly as you increase the speed.
Here is the link of the closed loop steppers: http://stores.ebay.com/cntop201301/C...ub=10987359015
The other option I have considered was either Brushless DC or AC servo controls from Omron/Yaskawa or others but came across this: https://store.dmm-tech.com/collections/all
It is a bit pricey but when you look at the specs, you get 1.27Nm (~180oz/in) continuous or 3.1Nm (~450oz/in) peak, the continuous rating is constant from 0-3000RPM so this speed can easily be reduced and then the torque multiplied. I'm thinking 1:3 so with a 5mm pitch screw you will end up at 540oz/in (1350oz/in peak) and get 196ipm which is probably good enough?
Anyone use these servo drives before and can comment on the torque specs/life/comparable price?
Has anyone done all the proper calculations to see how much torque is really needed for these little machines? I would hate to re invent the wheel but I also don't want to buy twice, rather do it right the first time. Excel spreadheet anyone?
My purpose for the conversion is to make small injection moulds for parts I want to make, mostly aluminum molds but the machine might also see some steel (maybe even proper mould steel).
There is also a company in town that is handing out CNC work to subs so it will be nice if I can also stand in the queue to get some work for it. Obviously the machine will have limited capacity but it would be nice if it can also earn me some money. I have a big knee mill that will be used to make parts but currently I don't have the time or energy to stand in front of it for it to make me some money so the CNC is a nice alternative option. I'm not really considering converting it as it will cost alot more and as far as I can tell the nut will be a problem as the XY is very close together, its a Lagun FTV-1.
Comments/advice/warnings welcome!