New Machine Build- Servo to PC?

[roger_e]

When buying servos...do they come with an encoder....I was hoping to get a servo package that could connect directly to a controller...for example the stepper motors I have came with a cable that plugs directly to a card.

Is this common when purchasing servos....(yes servos are required...feed rates are just not enough with steppers during interpolation))

Is the set up the same when building a servo driven system as a stepper? ie...cables from motor to board... then LPT to PC?...any ways this is the way I wanted to go.

Will be building a small mill/lathe combo....(I want to turn parts then machine them)


Thanks


My background:

CNC programmer in woodworking, OEM manufacturing (molds, paving machines)
prototyper for small electronics/optics company.

Besides working, I am in the third year of a mechanical engineering degree. Lots of experience with the "business" end of a CNC

Current resources in house:

Software:

Solidworks 2007
Unigraphics
Visual Mill 6.0
AutoCad
Mach 3

Hardware

Minitech 4 axis mill
Mazack VTC 20

I got what it takes to make a small machine

[acondit]

Originally Posted by roger_e When buying servos...do they come with an encoder..

Some do and some don't.

..I was hoping to get a servo package that could connect directly to a controller...for example the stepper motors I have came with a cable that plugs directly to a card. Is this common when purchasing servos....(yes servos are required...feed rates are just not enough with steppers during interpolation))

Not really.

Is the set up the same when building a servo driven system as a stepper? ie...cables from motor to board... then LPT to PC?...any ways this is the way I wanted to go.

More or less, it depends on what kind of board you're talking about and what kind of servo drives. If you use Gecko servo drives then the control loop is closed in the gecko drive, but if you use something less intelligent like an H-bridge driver then the encoder signals are routed back to the control board, like a Mesa 5i20 or 7i43 or a Pico Systems board.

Will be building a small mill/lathe combo....(I want to turn parts then machine them) Thanks

Part of it boils down to your choice of control software. If you choose Mach then your choice of hardware is limited by the fact that Mach doesn't have the facilities for closing the loop in the PC software. If you choose EMC2 you can still choose Gecko servo drives and run it like a stepper system but you can also allow EMC2 to close the loop itself. If you are using high count encoders, you will probably want a board that supports encoder counting in hardware. The PC is really not up to counting high encoder counts at high rpm.

Alan

[roger_e]

I am not partial to any controller software


EMC2 is loaded and I use it occasionally....so sounds like EMC2 is the way to go....


What about power? right now the small cnc runs off of 110, the spindle is on it's own controller(NSK E3000 1-50K RPM).

I cut stainless on it (small cuts etc...) with a bigger spindle and servos am I looking at different power arrangements? I guess I am having a hard time visuallizing 220 cable running in the controller....

[Al_The_Man]

One other closed loop option is Camsoft, this closes the loop through a Galil motion card.
You can pretty much do what the VTC20 will do.
With a motion card, you can use various servo types such as DC ,DCBL or AC together with analogue drives from Advanced motion etc.
Al.

[roger_e]

So....

Besides tearing apart my current functioning CNC is there another source for these builds?

[Al_The_Man]

You mentioned building a machine, or do you want to retrofit the machines named in the 1st post?
Al.

[roger_e]

No Al,

We intend to build a machine for several purposes:

Develop and test our own line of motion control sensors
Make a machine(just to say we did)
cut parts for our protoypes
production of master tools for our injection molded parts

We have the capabilities right now to do 3 of the 4. And have the time to get this right...so I thought it would be a better experience to build one than to buy one.

I do the manufacturing and prototyping for www.infraotica.com