Need Help!- stepper motors from a printer/scanner

[Gerbrand Nel]

Hi guys
My name is Gerbrand, and I've been lurking on this forum for a while now. My goal is to build my own little engraving machine to be used for knife making. At the moment the knife making hobby is costing me a pretty penny so I'd like to build this machine as cheap as possible. It seems like stepper motors and controllers are the most expensive parts on a cnc, so I would like to see if I can salvage these from old printers. The problem is that I have very little knowledge of electronics. I have a old HP psc1215 printer/scanner ( HP PSC 1215 All-in-One Printer - HP Customer Care (United States - English) )and would like to know if someone could instruct me on how to get the motors and whatever else I might need, out of it.
I hope this is the right place to ask this. If not, feel free to move this post
Thanks
Gerbrand

[JD_Mortal]

Printers usually only have one decent stepper, on older printers. Newer printers have faster running, less accurate steppers. They use, and depend on, the encoder strip for accuracy. Some of the newer printers also use optical sensors for alignment, since a fact of printing is that there is always an unprinted edge to watch. (Think of optical mice following your desk surface as an encoder.)

Back to the subject...

Yes, you can use some printer steppers for a CNC. The best motors come from old dot-matrix printers, the paper-feed motors. Newer printers only have to move light printer-cartridges, and paper-feeding is done with a normal DC motor and a line-advance encoder. If there is a stepper motor, it will have a difficult time moving it's own weight, but it can advance a single sheet of paper quite well.

I suggest that you search ebay for decent components. Since you are focused on smaller detail, on blades, you have the advantage of using the best small motors. A large stepper motor would be complete overkill.

You can find decent china-setups with "Nema 17" size motors, and "3-axis" controllers, with power-supplies, for about $150 - $300 shipped.

The CNC frame you need, is more in tune to a PCB-CNC or an Engraver-CNC. You will be using higher gear-ratios, and slower speeds, with tighter tolerances for drift, play, and alignment. You will need accuracy/resolution of around +/- 0.01mm for a decent etch that will fit on an 8" x 2" blade.

You will do best with a laser-etcher, or an equally expensive diamond-drill. (The laser may ultimately be cheaper, but the diamond-drill will have ultimately better control, at the same cost. EG, laser-etching setups increase exponentially more than any diamond-etching setup.)

There are also alternative etching methods you may consider...

Using an etching wax, and the CNC as the wax remover, you can burn etchings in layers, with chemical etchers. Ultimately, those etchings can be filled with paints, dyes, or discolored with tempering heat. (You would restore the discolored blade, which is not etched, with diamond-polishing.)

You can also use some diamond-coated or some high-carbon PCB blades as an etching tool. (You can't effectively etch, with good results, using a high-carbon steel blade with a similar metal drill-bit, you would need diamond-coated.)

If you limit your work-area to a 12" x 6" milling area, you should have no trouble finding cheap or alternative parts that can give you the accuracy you need, within a reasonable budget.

[Gerbrand Nel]

Thanks for the reply and info JD
Maybe I should clarify what I want to do with the cnc concerning knives. I'm a 3D artist by profession and have allot of experience with 3D organic modelling. I've played with cnc machines a bit and would like to cnc artwork as 3d forms into handles of knives I make. I would also like to cnc wax carvings to be cast in silver as ornamental hilt fittings. I suppose it comes down to accuracy and detail for me.
I live in South Africa, so parts like steppers are pretty expensive down here. Do you have any links to these china set-ups you mentioned?
Thanks
G

[JD_Mortal]

Ok, I was thinking that you were talking about blade-etching, like engraving scenery or names on the blades.

If you only intend to use this on soft-items, like woods, then you might be able to use printer/scanner motors. However, the cnc will not win any speed-records. The slower speeds required to gain precision and power, will result in longer spindle operation hours, which will result in excessive wear and increased inaccuracy of the spindle. EG, it might take you a week of solid operation to get something worthy of sale, resulting in an electric bill and repair bill for the spindle that does not justify the additional effort put into the blade. The blade value would have to be hundreds times more expensive, for a sub-par 3D carving.

This is where tried and true technology out-weighs the DIY hacks. You can get it to work, but it will not compare to the results you would get with spending a little money in the right place.

Have you looked at the ZEN CNC? For about $500 you can get a decent 7x7 work area and a decent spindle. It comes with the 3 motors, which can be upgraded later, if desired. You only need to add a power-supply and controller/driver for the motors. (Another $70 for the all-in-one controller/driver, and a simple CPU PSU hack, or x-box brick-hack will give you adequate power to drive it for wood-milling.)

If you must have printer-motors, you should also know that they will have a belt or gear on the shaft, which would need removal for the cheaper direct-drive of a screw-shaft. (It will be nearly impossible to find matching gears or belt-pulley's for the scanner motors, for use in the CNC. Not to mention, expensive and difficult to rig-up.)

You can use a gear-puller to remove them, sometimes. Other times they are sonically bonded to the shaft or reamed with a mushroom or compression expander.

At $20.00 for a decent stepper online, I don't think it will be worth the effort involved to gut a printer. However, if that is your only option, it may work, for another $50.00 in effort and time. Just start unscrewing it, and pulling apart anything that is not a motor! Then hope that you can find a data-sheet for that exact "custom" motor online. You will have to match the motor demands with the controllers ability to supply those demands.

In the end, you would be spending the same amount of money, trying to "fix" and "re-fix" the design and setup to work 1/10th as good as something that cost that much with known results. If you invest $500.00 into the right tool, here it will result in a direct turn on investment, reducing your overhead cost to produce great results fast. You can be cranking out high-detail carvings, sellable quality, within a day of carving, as opposed to something possibly sellable, within a week of carving. (Not to mention all the waiting for trial-and-error on a slow carver.)

Links:
NOTE: for the TB6560 they have multiple versions, for printer-steppers, you need to tell them that you want the 1.5a version. For nema-17 to nema-32, this 3.0a board will be fine as it is listed on ebay. However, the larger nema-32 style motors may like the 5-6a version of the controller/driver board. (Those are more for milling metals.)
3-axis TB6560 http://shop.ebay.com/i.html?_nkw=3+a..._BIN=1&_sop=15
ZEN CNC http://shop.ebay.com/i.html?_nkw=zen..._BIN=1&_sop=15

You can search for similar items using those search-names. Also try "Nema 17" or "Nema 23" or "CNC driver controller" on ebay or google shopping, or your favorite shopping search website of choice. Paypal is the most universal dollar since gold. The only hard part is coming up with the money to use. Spending is easy!