Recommended Feed Rates for Nema23 Steppers??

[AssassinXCV]

I have some Nema 23 3amp steppers using some random 1/4" threaded rod from one of those hardware stores and i'm using an anti-backlash system using springs. The cutter i'm going to be using is a Dremel 4000 series and can range from 5000rpm to 35000rpm, i was wondering what i should set the feed rate to. Please help.

It's a 6"X 6"Y 5 1/8"Z cutting area. Could someone help me?

[atwooddon]

The correct feedrate is determined by a few factors.

1. Material being cut ie acrylic, soft wood, hard wood, mdf, aluminum, etc
2. Bit being used
3. Rpm ranges

If you could tell us a little more about what you are wanting to cut and what bits you have we can give yous some ball park ranges for rpm and feed rates.

Don

[ger21]

If your cutting wood and plastic, it's likely that the 1/4" threaded rod screws will limit the feedrate to something less than ideal. You'll also be limited by the power of the dremel.

Basically, if you're getting burned wood, or melted plastic, increase the feedrate or lower the rpm, or both.

[AssassinXCV]

Well, since i have a dremel tool, i can only go up to 1/8" sized bits unless i find a 1/4" bit wil a 1/8" shaft (can anyone help me with that too?). I'll be ordering some other these off ebay when i'm closer to being finished building the machine:

eBay Store on eBay Canada

Dremel can range from 5000rpm to 35000 rpm. Mostlikely going to be cutting stuff out of MDF, Foam, and i have a good 4 feet X 1 foot X 1" of pine Pine wood. I also have some black walnut that i got from my highschool.

I hope this is enough information.

[atwooddon]

What Ger21 said is a good general rule of thumb. If you are burning wood instead of cutting chips, then the rpm is too high, or the feed rate is too low, or both. Keep turning up the speed until you are cutting chips, not burning the wood. If you run out of speed on the feed rate, turn the rpm down on the Dremel. Same is true for plastics, if it is melting, you are going too slow on the feed rate or the rpm is too high.

Unfortunately, the Dremel looses power as you turn the rpm down so you will be balancing the rpm vs feedrate.

Foam isn't usually a problem, slow rpm and high speed usually is pretty easy to do because foam cuts so easy.

Best way is experiment with some scrap wood, foam or plastic to see what happens. Don't be discouraged if cutting isn't clean to start.

For bits, you will pretty much limited to 1/8" shank diameters. Try to find some 2 flute bits, or better yet, some single flute if you are trying to cut plastics. The Dremel bits are usually more flutes and are designed for grinding or cutting very light materials. You also want to use spiral bits, not straight flutes, the spirals help bring the chips up out of the cut and help cool the bit. If you leave the chips in the cut, they add to the load and heat.

Don

[AssassinXCV]

^
| That's one that i was thinking of getting. It has 4 flutes, but the seller has different number of combinations for the number of flutes.

here's a 2 flute extra long endmill:

[atwooddon]

I think the 2 flute model would be a better choice to begin your tests.

Don

[AssassinXCV]

okay. i'll just order maybe 3 endmills total until i find out what works best. thanks so much for your help. didnt realize how compicated it can be for something that seemed simple. but i guess once all the settings are determined, you wont need to change them around. (but it would depend on what ur trying to do)...

thanks again.

EDIT: Going to be looking around for some AMCE rods. Ballscrews are too expensive for me, and this non-name brand threaded rod from the regular hardware stores might end up not cutting it.

[AssassinXCV]

BUt something i REALLY need to know is the initial FEEDRATE. What would i set it at for the NEMA23 motors? i can always tinker with the RPM while it's milling. I dont want to burn out the motors if i try to turn them too fast.

6" x 6" xy

if feedrate is 40inches/min, then: t=D/V: 6inches/(40inches/min) = 0.15min = 9seconds...9seconds to move 6inches. Does that sound resonable?

[ger21]

You can't damage stepper motors. And I doubt you'll be able to get 40ipm. But that should be fine to shoot for.

[AssassinXCV]

Thank you

[awerby]

trying to use it as a CNC spindle. For anything but the shortest and shallowest cuts in the lightest materials, you'll need to find something else. Even just running it continuously for a couple of hours will heat up the plastic housing and cause the working parts to go out of alignment. And it's going to be the limiting factor in your feedrates, not the 23frame motors.

Dremel tools were designed to be inexpensive tools for short bursts of hand work. They work okay for that (but not great). If you want to make any progress in your walnut or whatever, swap it out for at least a hand router, which, although it's loud and also won't last forever, will at least be able to cut these materials (although aluminum is questionable with your setup.)

Feedrates are determined by factoring in the endmill you plan to use, its number of flutes, the depth of cut, the RPMs, and the material being cut. But if the spindle is going to crap out when pushed into the material (like your Dremel will) then you need to derate it substantially. You haven't provided enough information for anybody to suggest a reasonable feedrate, but given what you have shared, I'd suggest going very very slowly at first, and speeding up if it seems to be working (or burning up the wood).

When you give up on the Dremel (or destroy it) and are thinking about improving your setup, you might also consider replacing the hardware store all-thread with acme screws, which were designed for this sort of application, and will transmit motion from your motors more efficiently and accurately.

Andrew Werby
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