design advice for a new builder

[deft]

Hi-

I 've been interested in building a cnc wood router for a while and I just found this forum.

I have a number of design questions, I've read most of the posts here and it looks like you all might be able to help me out...

machine I'd like to build would have a 24" x 36" work envelope, and be used primarily for routing plywood, mdf, plastic, possibly aluminum but that isn't so important. I'm thinking of using a laminate trim router, or a pc 690 I have laying around. Ulitimately I would want to get something with varible speed but that isn't necessary right away.

I'm pretty confident on the mechanical parts, but the electrical parts frankly confuse me.

i understand the basics in that I need a driver for the motors but I don't know what driver - motor combo would be appropriate for the size of machine I'd like to make. In another post someone suggested 250-300 oz/in for a 5' x 9' machine. Is there a rule of thumb? Like 40 oz/in per 1/8" of material (I'm assuming plywood). Thus 240 oz/in for 3/4", 80 oz/in for 1/4"? Or is the mass of the machine (say gantry or moving table) more critical than the material cut?

The other part I'm unsure of is selecting a driver motor pair that will work together.

I'm thinking of building a cheap cnc router first (ie with stuff I have laying around) but i'd like to eventually migrate the motors and drivers to a better machine when I can afford it.

thanks in advance

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[WOODKNACK]

The way I started out, kind of like you. I bought a kit from www.stepperworld.com. It had the stepper motors the controller and a power supply. There are cheaper ways out there. But if you are not that good with soldering your own board, then your better off getting a complete controller, motors, power supply. If you do go with the stepper world one go with his FET kit the sp3-ht is going to be slow and you will get discouraged real quick!
You can check out www.hobbycnc.com to he has some good stuff.

I am now using a www.Xylotex.com board and I bought his power supply to. I already had some stepper motors, but at the time you could buy those off him to. For the money I don't think you will be able to buy a bipoler chopper drive anywhere for the price Jeff sells his for ($125). I am very happy with his service and his product. Also another good thing with that board is you do not need power resistors. As you will with the stepperworld or hobbycnc boards. The xylotex has pots on the board for each axis. You stick a multimeter to them and turn them to the right voltage for your motor. A very simple task!
Like I said his service is awesom too. Everytime I email him with a question, It seems like he is sitting right at his computer and I get a really quick responce. That right there is worth the money.

[HomeCNC]

You should make your choice NOW about going steppers or servo's. I personally will always go with Servo's and a G320's from Geckodrive. If you read the router posts then you must have seen mine. My router is 24" X 24" powered by my servo's I sell. I did a real world test with my router a few nights ago. I wanted to know how strong my servo's were. I did not have any measuring equipment but my cousin who is a large and strong guy leaned his weight and muscle on the Y axis to prevent it from moving. He could NOT stop it. He said he knows he put over 100 pounds on that. He said it would have crushed him if he was in the path. I am getting over 150 IPM and have plenty of strength.

[WOODKNACK]

Can he buy a complete Servo kit? Servos, controller and power supply somewhere? I think this is what he is looking for. And for someone just getting into this hobby, I think the servo may be to expensive to start out with. Dont get me wrong, servos seem like the way to go. Maybe my next investment. Just seems like a lot of money to start out in this hobby.

[HomeCNC]

I'm not sure it's a hobbie he is after with that size of a router. He may want to build a business with it.

Only the power box would be the challeng. It was for me too
My last power box went together without a hitch and I could post the parts needed and a wiring drawing.

[deft]

actually I was starting to look at servos-

If I was to use servo's I would need a driver for each of the motors, correct?

ie one g320 for each axis? would I need to slave a drive on the x-axis? and if so would I need to get an additional driver?

homecnc, what kind of motors are you using? and what is their cost?

I'm considering doing as woodknack suggested and starting small (with steppers) to get a feel for the software end and then going big with servos.

[balsaman]

I am all for steppers for your first machine. KISS



Eric

[ger21]

I'm building a similar size machine, and I went with the xylotex driver, and picked up 4 253oz-in steppers on ebay for about $65 each. I'm using 2 on the x-axis, so I also got the xylotex single axis board as well. It'll be a while before I have time to see how it works out, though. What Woodknack said about xylotex, all true Outstanding support. If you have any questions, just e-mail Jeff and he'll get right back to you. I hooked up my driver the other night, btw, with 1 of the motors and TurboCNC. Worked great, and very cool. Also, check Ebay for Power supplies. I got a 24V 12a supply for $5.

Gerry

[HomeCNC]

That's a steel for the power supply!!

[ger21]

Actually, I got screwed. It was a Dutch auction and I bought 2. The second was actually a dual output, 5V and 12V, no 24, and the 12V didn't work. He would have taken it back for a refund, but ... it was $5. The other one seams to work fine, though.

Gerry