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jakk100
06-12-2003, 09:12 PM
Can someone advise me on where to find servo motors and encoders.
I’ve looked at Camtronic’s- look good, but need more rpm.
Also looked at Cnckits-rpm good, but seems to lack encoders.
I want to rapid at 600 ipm, would settle for 300.
I would like to use 5 turns per inch lead screw.
Thanks

HuFlungDung
06-13-2003, 12:43 AM
Baldor, or Glentek come to mind.

There are a couple of considerations to bear in mind when trying to make a fast moving machine. You did not say what the load would be like, but usually people want pretty short acceleration/deceleration ramps so the thing will be up to rapid speed quickly. This requires a fairly large amp to supply the juice to do this, otherwise you get nuisance tripping of the amp on overload. Servo motors are pretty tough, and can stand brief applications of high current. Best go bigger on the amps and smaller on the motors, rather than the other way around, IMO. Of course, having plenty of $$ makes this easier to decide :)

Also, don't go "ape" on the encoder resolution. Depending on your controller, it can only handle so many encoder feedback pulses per second. So an ultra high res encoder can actually cap your rapid speeds at a lower rate, if your controller cannot handle what it is putting out.

A lot of controllers can read 4000 pulses out of a 1000 line encoder, so do your research on the controller before you buy.

I know that a lot of Galil motion cards can handle 12,000,000 pulses per second, but some of what these other guys are using for controllers, can only handle maybe 4,000,000. Whatever the number, divide this by your encoder pulses per rev, and this will give you your max motor rpm. How long a duration that the acc/dec ramps are is totally dependent on matching your motors and amps to the load.

jakk100
06-13-2003, 01:47 AM
Thanks for the reply.
The servos/encoders will be for a heavy duty, putting bread on the table, home made CNC router.
About 60” in X, 36” in Y, 8” in Z.
I am new to building machines and have just now started to research. I have been in the CNC machinist biz for 20 years. So I think I can grasp new ideas/concepts if pointed in the right direction.
Any suggestion would be appreciated for any aspect of CNC router parts/design.
Thanks

marting
06-13-2003, 06:52 AM
Hi Jakk
I fully agree with HuFlungDung and further more consider that if the axis is running at high speeds the ramps mentioned have to be anticipated early enough so as not to run out beyond the desired route. This is caused due to the inertia of movement. In other words it's like when you hit the brakes hard in a car, although you mean to stop it ASAP it takes it's time to come to rest due to the velocity at which it was speeding. Like wise if, you are going too fast you might go off coarse and ruin the work you are doing and possibly damage the cutter.
For servo drivers, which can handle the load, have a look at http://www.rutex.com. I have ordered a combination of drivers for my CNC that I am building aswell.

jakk100
06-13-2003, 01:03 PM
Thanks for the reply,
I’m hoping the software will be similar to commercial cnc’s that have a special G code to initiate “high speed look ahead”. This high speed look ahead will slow the machine, (regardless of prog’d feed) to ensure all programmed points are hit within the set parameters.
Has anyone experienced this with their software?
Thanks,
Jakk

HuFlungDung
06-13-2003, 03:08 PM
Jakk100, check www.camsoftcorp.com I used the CNC Professional software, and it has this type of look ahead option.

HomeCNC
06-13-2003, 10:02 PM
Hu, Your link says it has been disconnected! Jakk, you might want to look at Mach 2. It has a great look ahead feature. It made my router work so smooth. See my review in the review section of this board.

marting
06-14-2003, 04:03 AM
Yes it seems like it’s an excellent software from what I have seen on it’s manual but I do not know exactly how the cutting paths are created. That is whether one can import 3D IGES or DXF files into Mach 2 and create the cutting paths there or if these have to be created on another software and then import into Mach 2. I do not know if you have used it to create 3D cutting paths in this manner however would appreciate if you could share your experience in creating such cutting paths. I intend to use Mach 2 on my CNC when I finish but at the moment I’m have difficulties to find Brush type DC servo motors at reasonable prices. Does anyone know of any suppliers?
Cheers

HuFlungDung
06-14-2003, 12:17 PM
Originally posted by HomeCNC
Hu, Your link says it has been disconnected! Jakk, you might want to look at Mach 2. It has a great look ahead feature. It made my router work so smooth. See my review in the review section of this board.

Twas probably the period after the com that was screwing it up :)