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CNC Stepper Motor and Controller Board Inquiry: What is the torque, motor size, threshold for dremel tool to engrave ? Answered

CNC Stepper Motor and Controller Board Inquiry:

Even with the extensive research and links I have visited it seems I got the cart before the horse with a bit of ebay bidding fever in purchasing my stepper motor.

I just purchased 4 pieces new SHINANO KENSHI Co. ball bearing stepper motors Part # STP-42D201-36, 1.8 DEG, 200 Step/Rev, 3.7V, 3.1A/Phase, Size 17 with a 5mm shaft.

I will be making a computerized dremel tool ENGRAVER (not cutter) to start.

I do understand that a CNC, for cutting out shapes, requires more torque than the STP-42D201-36 will put out.

I however wish to engrave, only partially cut into the surface of wood to render my artwork, some which can be seen at http://designermite.net/. These will initially consist of line work but then later I will render halftone work.

I do own and work with Gerber Advantage 6.0 Premier and Omega software with Gerber HS/15 PLUS plotter creating vinyl graphics and logos that you might see on store windows, car, truck and van lettering. So I do have a working knowledge of the basic skills needed.

I need help on what sort of setup I should be leaning towards that would work with my CURRENT purchase.

What is the torque rating, motor size, specs threshold for dremel tool to engrave properly?

Some have been very helpful via email and for that I thank you and others have just lived up to thier names of being cranky, claiming they invented everthing under the sun, with short two word sarcastic answers when I actually wished to purchase their plans.. go figure.

Thank you in advance for your time

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7 Replies

willnrach (author)2009-10-17

<p>Having stepper motors its easy to change the torque, With these type of motors and drives, you will have either high velocity (speed) and low torque or Low velocity and high torque, there are various ways of connecting the motor, unipolar, bipolar series ( high velocity ) or bipolar parallel ( high torque ), on the motor you should have eight cables, without knowing the motor config im guessing at colours. however A* would connect to A on drive, A- and C connect together, and C- and A- connect together and go into the A- on the drive, the other side of the windings i.e B* B, D* and D- would connect the same way, with B* into B on drive and D-/B- into B- on drive</p>

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True: I like 8-wires steppermotor as they can be used as bipolar paralell, bipolar serie or unipolar. All of these have advances and disadvances. The stepper controller can only use unipolar OR bipolar. It depends on the hardware, sometimes one want have high velocity but low torque to get the maximal IPM. Right now I need a axis with high torque and I am okay with low speed. (It's why I like bipolar drivers - one can fit the motor to the CNCmachine) But Unipolars drivers does not mean that it's bad, it just a design, and one can build the hardware around the driver/motor. There is no clearly disadvance to run bipolar paralell (high voltage/low amp) in contrast with the biopolar serie. (eewww, I run bipolar series here!) :p

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alfredhenriksen (author)2010-06-20

Well. A dremel is not accurate enought for fine CNC-work. (play in the ball bearing) BUT, it depends at the details (resolution) in your cutting/engraving. It can be fine. It can suck. Up to you. In my case I had to abandon the Dremel. There is no clear answer for your queston, try to run it dry-run (G0 in G-Code) without skipping steps to see the topspeed. Cutting speed can be between 25-75% of that. It depends. Use a bigger powersupply (12V is nothing. 20V is okay. 30V is fine, up to your stepperdriver, most have ~35V limits) and the cutting speed will increase. And what about backlash? :) ... RPM, IPM and which materal you're cutting/engraving is more important than the type of cutting tool. Get a bigger one and CNC-machine may be slower due to more moving weight. Get a smaller one and it may be faster due to less weight and faster accel. .......................................... To make it simple, I recommend that you're setting a side a lot of time to TEST. Run it slow and nice and see how it will go. Which IPM (inch per minute) does the engraving mess up? Then you can find solutions to increase the speed later. There is a lot of formulas out there but I am too lazy to point out the correct direction for you. Sorry. :)

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frollard (author)2009-08-18

Another solution of course - if you're stuck with the motors is to run the motors with reducing toothed pulleys/sprockets to get the torque you need, or finer pitch on the drive screw.

I really have no experience with the exact torque/settings necessary to get a specific result with a specific materials. I bet those motors are PLENTY strong enough to engrave or even route softer materials.

http://www.diycnc.co.uk/ has a WEALTH of free information.

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steveastrouk (author)frollard2009-08-18

Seconded. Link quality and products there are second to none. The site owner is very helpful, and his stuff is first rate.

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seandogue (author)2009-08-18

Not sure exactly, but to get that info, I;'d suggest calling or emailling Dremel. I;'m sure they;d be glad to help you realize your design using their equipment.

However, as others have noted before (in other topics)...a small air die grinder might be a better option for your tool...The stepper for translation, yes, but a die grinder has much higher sustained speeds for engraving and other similar work, although it *does require an air supply.

I believe they can be purchased for a very modest investment of well under $50 US

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seandogue (author)seandogue2009-08-18

one more thing to consider for the tool motor...in both cases, optimal material removal is performed using a specific shaft speed for a specific tool, material, depth of cut, and linear speed. Since shaft speed must be controlled, an adjustable pressure regulator would be needed with the die grinder. In either case, some type of tachometer would be nice to include in your final design for measuring and setting shaft speed. To get nit-picky, one might want a shaft speed controller (fee run speed will differ from working speed, and depth of cut and linear speed will alter that even more....

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