CNC Burning Table

[johnplctech]

I am looking into building a CNC burning table. What is the best kind of drive system for the X,Y axis? Stepper or Servo motors? I need this to be PC controlled and to read a DXF file. Any tips on where to start

Thanks
John

 

[SERVOCAM]

How big of a burn table are you looking to build? Ever think of using Laser instead?

The bigger burn tables I see out there use rack & pinion and servo. I would deffinately use servo as well. There are many mfgs that have CNC controls.

My controls are CNC and I have precision tables. I have done a lot w/ lasers (have seen Burn & EDM). There are many Post-Proccessor programs that can take the DXF and ker-chunk out the G-Code.

Give me some more details (Load, Speeds, XYZ Travels) and I will help you out.
Cameron Anderson - Sales & Applications Engineer
Aerotech, Inc. -

http://www.aerotech.com

"Dedicated to the Science of Motion"

 

[johnplctech]

Why would you use a servo motor over a stepper motor?

What programs will ker-chunk out G-Code?

Thanks
John

 

[SERVOCAM]

I would use servo because of the efficiency, speed, and torque, and better precision and control over the stepper. It is not very typical to see steppers on CNC machines.

I have heard a half a dozen or more names of Post Processor programs that customers use, just can't remember any of the names. SIM CAD is one, I think BOB CAD is another. Maybe some of the other readers know? Cameron Anderson - Sales & Applications Engineer
Aerotech, Inc. -

http://www.aerotech.com

"Dedicated to the Science of Motion"

 

[MotionRat]

The major reasons for considering steppers in this type of application are cost and lack of following error. This assumes properly selected steppers with adequate torque to run in open loop mode. The actual requirted torques are important and thereffore some understanding of the inertial loading, frictions and acceleration is required.

Servos are great where higher speeds justify the cost, but they will need to be properly tuned to minimize following error inherent to any servo control which will show up as machine error.

If the machine engineering is not totally rigid and exteremly low backlash gears are not used, it may be impossible to get accurate shapes cut. If high speeds are required, servos are certainly the way to go, but burning applications generally imply relatively low speed.

The bulk of the CNC router market runs on steppers for most of the above reasons.

Look at Ability Systems for an LPT port driven indexers software selection and probably the ability to translate DXF files.

You can use this type of control with Step and Direction type of servo drives, and you should look at some of the new hybrid options Notably the PB series from MotionOnline.com which is a closed loop stepper servo hybrid.

Peter Ratcliffe
President
RPT Motion Inc.

 

[SERVOCAM]

I work a lot in laser processing and we use servo for everything. I have not sold a stepper system in a long time. I'm in speeds of a few mm/second holding amazing accuarcies. A lot does have to do with the mechanics of a system, how good the control are, and how well the system is tunned.

I guess the world MotionRat is in versus what I am in are 2 different places. All my CNC customers are all servo.

Steppers systems have their places, I know, I have sold $millions of them, just not into CNC applications. Also with steppers, once you get above a 34 or 42 frame motor & you put an encoder on it, a servo system starts to look really cost effective.

You have to watch steppers in contouring applications because of low speed resonance & cogging. There are stepper systems from companies like IDC, Oriental, and Compumotor that have Anti-Resonance. Micro-stepping will also help eliminate this problem.

I guess it all comes down to what exactly your trying to build. How big? How fast? How heavy loads? How accurate? How much $ do you have to spend?

Oh, and I also remembered a few names for Post-Processor programs for DXF to G Code:
SigmaNest:

http://www.sigmanest.com/

Tech Soft America:

http://hoops3d.com/

DigitalCAD:

http://www.digitalcad.com

Cameron Anderson - Sales & Applications Engineer
Aerotech, Inc. -

http://www.aerotech.com

"Dedicated to the Science of Motion"

 

[Jazzenjohn]

Like motionrat said, stepper systems are good when price is a primary consideration. They are easy to set up and in a burning application they wouldn't run into problems with missed steps which can occur when larger driving forces are required and the stepper motor selected is too small. Another possible company for help would be ah-ha group.

http://www.ahha.com.

with their system you could put together a complete hardware and software microstepping package for about $3000. I don't know how much a complete hardware and software package for a comparable servo system would cost. Perhaps servocam can give you a quote.

 

[SERVOCAM]

If we look at my newest controller, Automation 3200, w/ drives, cables, & 23 frame sloless brushless servos, CNC MMI...etc, your looking at ~$7K completely configured & tested.

If that Ah-Ha system is what your looking for....have fun.


Cameron Anderson - Sales & Applications Engineer
Aerotech, Inc. -

http://www.aerotech.com

"Dedicated to the Science of Motion"