CNC First timer, a little help?

[TheMobster]

Okay, so I'm thinking about making one of them new fangled CNC machines. I'm 18 and as such money is tight, so cheaper is obviously better (when isn't it?). I set an ad on craigslist and a guy replied with some stepper motors. They are Pacific Scientific Powermax II motors. The part number is P22NRXA-LDS-NS-02.

They have a holding torque of 138-214 oz-in. They are NEMA23 motors. They have double stacked rotors with a shaft on each end and no encoders.

What is an encoder? Is it a problem that there isn't one?

Someone else posted on this site about this particular model, saying "what would be a good driver for Model P22NRXA-LDS-NS-02NEMA 23
200 Oz-In
8 Wire
May be Wired Bipolar, Unipolar, Series, or Parallel
3.3 Amp Bipolar Series ~ 6.5 Amp Bipolar Parallel
2.71 Amp Unipolar Series ~ 4.6 Amp Unipolar Parallel
35VDC
1.8 Degree / 200 Steps Per Revolution
and i have a 24 v 6.5 amp power supply
would the G201 work for this motor ?
for xyz Central Machinery"

Think this is a good buy for a motor? I am still getting a grip on all this stuff, so progress will be slow, but hopefully I can get this done.

I am not sure what I want to build the structure of it out of yet, metal is more expensive but obviously more durable, but also harder to work with. My school sold all their nice metal working tools, so we only have a woodshop now. I think I might try a mix, but that could be a bad idea I think.

I will think and come back,

http://www.pacsci.com/support/docume...er/stepsel.pdf
That's the pdf for the motor. I might swing my local surplus store to see if they have any stepper motors.

[ger21]

I'm 18 and as such money is tight, so cheaper is obviously better (when isn't it?).

When you need to spend 2-3 times as much on drives to get the full potential of the cheaper motors. That's when. 3 Gecko 201's will set you back over $350. That same $350 will get you a 4 axis HobbyCNC with 4 305oz motors, and almost everything you need to build a power supply, too. Another $20 for a transformer and a case and you're ready to tun. A 3 axis kit is only $296 delivered.

[TheMobster]

Okay, so I have 2 of my 3 motors. This one is a 2.71 VDC/ 4.6 A unipolar stepper motor, 1.8 degrees. It only has four wires on the hookup end, but it seems like two were cut. There is also two wires rerouted back into the motor at the connection to the motor. I will post a picture later (no card reader at the moment). The wires are wired into the 15,14,13,12 ports, and the guy said he tried to test them and they worked. It was originally in an XY machine. On the end serial connection, 9/10 are also wired, but their wires were snipped. Anyone know anything? I bet this will be easier later with some pics. He said he would try to get the motor driver for me, he said it had 3 axes but the Z just had a signal output or something like that, but I don't know if it would be easier just to get hobby CNC.

[TheMobster]

And without further ado! The pics!

Motor

Serial Cable


Motor connector



It looks like it could be an 8 wire? or at least 6. Anyone able to shed some light?

[Konstantin]

Hi.
Please be more specific as to what do you expect from your CNC project.

That last pic of the conn looks like a bipolar to me.
You can make your own spepper drives, just get schemactics that suits your motor and make your own PCBs.
Going DIY route for the electronics will need lots of time, if you can afford to buy a kit of 3 or more axis it will let you focus on the actual mill/router. You can spend a lot of time making wrong decisions if you purchase old and different steppers and then fit them to existing open source drives, like http://pminmo.com/.
DIY is not a problem, but for a beginner can become a little cumbersome.
I bet you will progress way faster if you get a job or get 300 bucs for your drivers + motors kit than if you solder and learn how to use the electronics. There is alot of information to absorb.

Think about it, you will eventually have to purchase the motors, purchase and/or build PCB, purchase the electronics, solder, test the drive then fix whats wrong. There is money and lots of time to spend here. And I m pretty sure that you are going to spend there quite a bit of money.

There are a lot of steppers around there if you wan to play with them, salvaged from old copiers/printers and many of them are old and there are no specification sheets on the web for them.

You don't need encoders if you are using open loop system , drives with no feedback about stepper position. They just pulse and forget.

And keep reading the forums, look for the design that you like, maybe copy it.

Konstantin.

[TheMobster]

I'm just looking for another project really. I want to etch some plexiglass, but I have no specific thing I need to make. I'm in no hurry to get it done, so I think I might wait for this guy to see if he can get me the driver that came with the XY, and then make a single driver for the Z axis w/ the signal from the other driver.

I do have one question though, what exactly is backlash?

And why are Acme threaded rods/nuts so expensive?

And thanks for the reply konstantin.

[ger21]

I do have one question though, what exactly is backlash?

And why are Acme threaded rods/nuts so expensive?

That's two questions.

1) Backlash basically is looseness in the nut to screw fit. So that after moving in one direction, when the screw reverses direction there's a slight delay in the movement changing direction due to the sloppiness of the screw/ nut fit.

2) Depends what you compare them too. Acme screws are very inexpensive when compared to ballscrews. I think that demand for certain sizes dictates price, as well as the precision of the screw. You can get low quality 1/2-10 acme for about $1 a foot. Higher precision multiple start 1/2" acme can be over $10/ft, even more for stainless steel.

[TheMobster]

Okay. So I'm on the FIRST robotics team at school, and we made a steel frame. It was .5 inches too long, so it had to go in the trash! Although I was deeply saddened, I had other plans for the frame. Here it is.

[img]http://s7.photobucket.com/albums/y29...t=IMG_6293.jpg[/img]

[img]http://s7.photobucket.com/albums/y29...t=IMG_6294.jpg[/img]

[img]http://s7.photobucket.com/albums/y29...asurements.jpg[/img]

[img]http://s7.photobucket.com/albums/y29...t=IMG_6295.jpg[/img]

More after dinner.

[TheMobster]

Okay so that frame had to serve an alternative purpose. Back to wood.

Now I 'm trying to make this stepper driver (little over my head at the moment, hopefully I will get some bearing).

There are 8 wire slots on both of the motors. When I touch a wire to 1/5, hum. 2/6 hum. 3/7 hum. 4/8 hum.
http://www.kelinginc.net/34H.pdf
That looks like a helpful diagram? Supposedly this motor that I have can be wired in a variety of ways, I might run it over to the store by my house and see what they say.

Any Idea how I would wire this correctly in unipolar mode?
Going off this diagram
http://www.instructables.com/id/Easy...and-Driver-ci/

[TheMobster]

Okay, so I struck a deal on Craigslist. A really nice guy that is trying to help CNCers get on their feet sold me all this awesome stuff for $20.















So, now I need to figure out a few things.

Am I going to be okay mounting the screws to a pillow block even though the screw doesn't stop?
like this


Where on earth do I find wiring diagrams for these things?

So the big guy, his wires are red,green,black,white, white/red,white/green.

The little guys are black, green, red, white. Black is on 1, 2 and 5 are connected, 3 is green, 4 and 7 are connected, red is 5 and 8 is white.
Thanks in advance.

[KsiR]

Not sure if this will help you but I have a motor with same wire coloring connected to a unipolar driver (3 axis DIY descrete board from www.pminmo.com). The white & black wires are V+, red & white/red are A+/- and green & white/green are B+/-. You can switch As and Bs around to change the motors direction... I hope this helps

[TheMobster]

Etching copper does not work well in the Minnesota winter. The board should be etched by monday, ready to go by tuesday.

I got my main frame and will start on the gantry this week sometime.












36 inches of travel on the screw, and it's 19 inches wide. I think I am going to make it a 22 inch cutting envelope as I have 24" ball screws.
Now I need to figure out my drive mechanism, coupled or belt driven?