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Bridge mill / Twin column mill
so i had to sell my old cnc router as im moving :S
but once ive settled down again i would like to build something again
i have an old cast bed 900x900x120mm weighing in at around 400kgs ....
ideally it would be nice to have a fixed gantry, but i dont have the space for it ... so its going to have to be a moving gantry
my idea is to have something like in the picture ... i would like to maximize the 900 width , so therefore the rails extend onto the gantry risers allowing the z carriage to have maximum travel
i have seen a couple ground ballscrews, 25mm c5's with a 6mm pitch .. going to have two of them to move the gantry on a twin 400 watt servo (still to do the math ) can see im gonna need the 750w
again would like to go direct drive onto the servo to avoid belts and pulleys
Re: Bridge mill / Twin column mill
It's possible to use servos in direct drive mode, but it takes a bigger motor to get the same effect as a smaller one using belt reduction. The reason is that servos have a "sweet spot" at a fairly high RPM; they don't have as much torque at low speeds. The belts let them run significantly faster and convert that speed into torque.
Re: Bridge mill / Twin column mill
while im busy on my drawing ive been looking at servo systems ....
ive heard good reports about the dmm kit , but ive also read that a 'named' brand is so much better
what would the difference be between using either ? ive only had two systems and both were steppers ...
DMM AC Servo Motor&Drive 4Axis-750W for CNC Router Plasma Mill kit | eBay
and the other
MITSUBISHI SERVO 1KW 750W,3-AXIS KIT,DRIVER MOTOR,MR-J2S-70A,CNC,ROUTER WORKING | eBay
is it going to be a 'nightmare' to setup the servo's ? or is it something a logical person can do :D
Re: Bridge mill / Twin column mill
Quote:
Originally Posted by
Bl@ckrat
[Setting up a proprietary servo system like this is definitely verging into nightmare territory, especially if you don't know much about servo motion control. There's a logic to it, but it's not immediately apparent to mere mortals. Of the two systems above, I'd lean towards the DMM if I had to chose. For one thing, it's new, while the other is used "in excellent wroking condition" but sold as-is. It's good to be able to get tech support from native English speakers, unless you happen to speak Korean. But I'm still not sure you'd get much help from DMM, since this probably isn't their current system and you're not getting it from them.
If I were you, I'd avoid both systems, though, and get some brushed servo motors with rotary optical encoders. These are not too hard to find, cost much less than these proprietary systems you're looking at, and can be driven with Gecko G320 drives, which work off step-direction signals a lot like steppers do. A system like that would be a lot easier to set up, and you'd get support from Geckodrive if you had problems.]
Re: Bridge mill / Twin column mill
been reading about the DMM package and im really liking the sound of them .....
needs to get the calculator out and start throwing some numbers about ... number crunching is not my kinda thing though
