Help! Advice needed to convert stepper to servo!

[designit]

Hello:

I am wanting to convert my stepper-run mill to a servo-run. I am a teacher, and have a very limited budget (around 1000), and do not want to make any mistakes with the public's money!

Questions:

1. How mush power/torgue do I need? We ONLY mill 1/8" thick soft plastics (Sintra) in 2D shapes. I ONLY want to move at 100 IPM speeds? (By the way, is it safe to go that fast and reverse directions????)

2. Can I simply bolt the new motors on the old NEMA 23 base holes? I thought I read about having some kind of adapter/coupling?

3. Can I mount a dial on the z axis which would allow my students to carefully lower the bit to the work surface. We do a lot of fine engraving, and I think this would help.. Can you "spin" servo motors without damaging them?

4. Anyone know a person (or company) who will sell me a plug and play system for about $1000?? I need them to be a fully-licenced business entity or the school district will not pay out!

Thanks. If you have answers, please either post them here or better yet email me directly at "dpwysen@seattleschools.org"

[HillBilly]

I have the small CL system and have used it with the CNC control software included and with Mach 3 demo software with good results.

http://www.maxnc.com/page13.html

Darek

[imserv]

What size is your mill? What is the leadscrew pitch?

Fred Smith - IMService
http://www.cadcamcadcam.com.hobby

[MHINK]

If you want the least expensive solution, try building your own.
I hope not to be too self serving, but you can find a pretty good little book to answer your questions and be a good reference for your students, right here at CNCZone classifieds. There is a section on calculating torque and related formulae, drivers and how to build a simple Z axis, plus where to get free CNC operating systems, write G-code and make the machine work. You can probably get the whole thing built and running for under $300. To see more click on this URL
http://www.cnczone.com/classifieds/s...&cat=11&page=1
Good luck.
-Mark

[Stevie]

I think you guys are missing the point; he wants to change what he has; not build a new system from scratch

[ESjaavik]

Originally Posted by designit 1. How mush power/torgue do I need? We ONLY mill 1/8" thick soft plastics (Sintra) in 2D shapes. I ONLY want to move at 100 IPM speeds? (By the way, is it safe to go that fast and reverse directions????)

You need to give more information! What size is it? Make, model?
The torque that will be fine for an Emco F1 will not be able to move a Bridgeport at all. When reversing you need to go through zero speed. Any other way would involve infinite acceleration.

2. Can I simply bolt the new motors on the old NEMA 23 base holes? I thought I read about having some kind of adapter/coupling?

As an example, you have several motors to choose among from this manufacturer.
http://www.worldservo.com/html/as.htm
The price for 3 motors + 3 drives from this manufacturer will go beyond your budget unless they have a special deal for schools.

3. Can I mount a dial on the z axis which would allow my students to carefully lower the bit to the work surface. We do a lot of fine engraving, and I think this would help.. Can you "spin" servo motors without damaging them?

Yes, but you may damage the drive unless the rotation is very slow. And you would of course have to disable the drive or it will oppose your moving the motor.

4. Anyone know a person (or company) who will sell me a plug and play system for about $1000?? I need them to be a fully-licenced business entity or the school district will not pay out!

It seems that if someone that price their time as a professional would leave very little for the cost of hardware after charging for their time.

Have you considered just modernizing your stepper system? If it's based on an old non-chopping driver, there is a lot of performance (speed) to gain by just changing the driver(s) to a modern microstepping chopper design.

[peternielsen]

there is a company that has very inepensive servo drives they typically have a torque of around 280oz.in which should be enough for what you are doing.You will require to do some software however it is not rocket science and would even give your students some experience with machine code....I also know that there is some software out there that will help you.

check out their web site:http://www.coolmuscle.com/Motors

I am neither affiliated with this company but have used their product in machine applications and consider their product to be very robust


Pete Nielsen

[ViperTX]

...so, you got something working with a stepper....and you want to be frugal.....why do you want to switch to a servo for the application you stated??