Building CNC Plasma/Router - Help with steppers and controllers

[tjb1]

I have to do a senior project in college, seeing as we have a Hypertherm 4 for the family business and are looking to get a plasma table I was thinking of building one for cheaper and getting my project done. I get the basic idea of the design with racks on x-y and a ball screw on z for THC. One I seen over at pirate4x4 is using a spring to keep tension on the rack and most I have seen are all using belt drives to gear the stepper motor down then putting a drive on the rack from that. Next semester I get my electrical and plc class so hopefully I will understand the wiring a little better, currently a manufacturing engineer so thats really all I need before I can dive into this project.

Being that plasma has no load, I can use pretty small steppers like this G723-280-4 Stepper Motor and the spring tension on the rack would be fine. I havent decided if I would like it to be router but what kind of changes to a design would be needed to handle the forces of the router?

Also, are there any articles or anything explaining resolutions of the steppers and explaining the controllers as far as full step, half step, or 5uStep operation. I see a bunch of drives listed but it looks like most are using the G201.

Finally, what is the interface between the drives and the computer?

[ssutton]

Lots of questions.......you may need to park here for a few weeks and read, read and then read some more. All of this starts to make since after a while of digesting all of this information.

To get you started;

"forces of the router?" This will depend on what you want to cut and how fast you want to cut it. Many machines on this forum operated just fine with a R&P system with nema 23 motors at about 300 oz. in. holding torque. This includes my machine. We cut everything from aluminum to wood.

"are there any articles or anything explaining resolutions of the steppers and explaining the controllers as far as full step, half step, or 5uStep operation"
Go to Gecko drives website and read in the support area of the site about steppers and drives, LOTS of great information there.

"what is the interface between the drives and the computer" Generally this would be a breakout board. It is a circuit board that accepts the pulses from the parallel port and directs them to the stepper drives.

Scott

[tjb1]

So you wire the drivers into the breakout board which connects to the computer via serial cable? Im guessing the breakout board will decode the signal for x-y and z and distribute them to the drivers. Thanks for your help!

[acondit]

Originally Posted by tjb1 So you wire the drivers into the breakout board which connects to the computer via serial cable? Im guessing the breakout board will decode the signal for x-y and z and distribute them to the drivers. Thanks for your help!

Not a serial cable -- a parallel cable.

[tjb1]

Also, what is the name im looking for on these rails. I found rails on McMaster Carr but they are super expensive, $.43 a MM.

McMaster-Carr

or would these t-slot rollers work?

http://www.mcmaster.com/#roller-bearing-rails/=ekcj8q

[RossMosh]

Go on CNCRouterParts.com and look at their stuff. Their parts are commonly used on DIY builds and they actually have a 4x4 and a 4x8 design you can use.

Joe's 4x4 CNC is another popular DIY plan you should look into. It can be expanded to 4x8 fairly easily.

To add a plasma option you're really looking at adding steel grates and a water bed.

[tjb1]

Thanks a lot for that link. Looks like I can grab the steppers, driver and supply from there for under $600. CNCRouterParts Looks like everything is taken care of there, can you still interface THC with that kit?

[tjb1]

Anyone know a cheap place for rails? To get a 4'x4' cutting area im going to need like four 5' rails for x and y and each rail is like $400. Can i use square tubing rotated 45* and a roller on top and bottom?

[RossMosh]

Originally Posted by tjb1 Anyone know a cheap place for rails? To get a 4'x4' cutting area im going to need like four 5' rails for x and y and each rail is like $400. Can i use square tubing rotated 45* and a roller on top and bottom?

Again, look at CNCRouterParts.com. They have their own linear rail system which uses cold rolled steel. If you want to do something a bit more "precise", V-rail is commonly used on a lot of light commercial machines. Shopbot, EZ-Router, Mechmate and several others use it. Joe's CNC also uses it (except they just call for grounding angle iron into a V).

[tjb1]

Alright, sorry I did not see that. I understand it now. Ive been looking some more and talking to some people and someone showed me The MakeSlide Project but this is a kickstarter project and he has not begun selling to the public yet but I am also not ready to begin building yet so this may be an option for just plasma cutting.

Also, I have begun to look at the controller more. The kit from CNCRouterParts is most likely what I am going to buy. It has 3-Nema 23 steppers and a G540 controller. From the TexasInstruments page the Nema 23 has a 1.8* step so that is 200 steps in the motor correct? And looking at the manual for the Gecko 540 I see it has 4 inputs on the card and 2 outputs. My memory is a little fuzzy on inputs and outputs but if you set an input on the card, it will send that input though the parallel cable back to the computer and I assume you can do something with these inputs in Mach3 so are these the inputs I would use to Home the Axis?

http://www.geckodrive.com/images/fck...4%20MANUAL.pdf