Nema 17 - stronger motor alternative

... I was driving Precitec stepper drivers and NEMA-23 steppers with 325Volts DC pretty fine with an ArduinoMega and RAMPS ... if your drivers have 5V inputs, then they should work too.

Depending on your setup 3 Motors+drivers are enough -- you can use a stronger motor and chain-synchronizing two spindles for Y ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Quote
Arnold
Hi Jim,
I am thinking about at final 2x1,5m work area. I would like to cut just boards from wood, plastic, maybe aluminium. But firstly I want to make a little cnc for tests. Frame and linear rails will be aluminium, threated rods m8. Everything must be cheap so I dont plan to use some special components. I dont want to safe money on motors because I will sure make upgrade, so that is for future - I dont want to buy motors again. My idea for start is connect some strongs universal motors with arduino, but dunno how. I am total noob in electricity. Speed is now not so important but again, strong fast motors would be good for future upgrade. Spindle I would use some casual for wood at start, so no controling through pc. At the end I would like to choose special electronic for pure cnc working with mach3, but my vision for start is just testing with arduino.

If you haven't yet, check out the hundreds of DIY cnc designs at CNCZONE.COM.

Threaded rods will work ok for a very very small gantry router but anything approaching 2x1.5m, I would use 5start acme leadscrews. Ballscrew if possible. Check out dumpstercnc.com for antibacklash nuts.

I use the 276oz-in stepper from automation direct and gecko drives for my gantry router. Does 300ipm rapids. Stay away from the bigger 400oz-in steppers unless you can afford a higher voltage power supply and very good stepper drivers. The smaller 276oz-in can spin pretty fast, a big plus if you are using threaded rods.

Gantry Type Machine Building Lots of good info can be found here for routers.
[www.mycncuk.com]

Quote
Jim Fong
I use the 276oz-in stepper from automation direct and gecko drives for my gantry router. Does 300ipm rapids. Stay away from the bigger 400oz-in steppers unless you can afford a higher voltage power supply and very good stepper drivers. The smaller 276oz-in can spin pretty fast, a big plus if you are using threaded rods.

What voltage are you powering the 276 oz-in at, and how many amps are your drivers?
What difference, or gains would I see switching from 12v, to 24v? Does the torque increase, higher speeds, quicker acceleration?

I was looking for a ~400 oz-in motor, but based on your comment I'm now I'm unsure if that's what I should get. NOTE: I'm using 15 mm wide belt, with 4:1 pulleys, no screws. Worse case, I probably have about 12 lbf to move, so I'm looking for a motor that can move ~24 lbf.

Is it possible to use the $10.00 drivers that most RepRaps use? I've been looking at the ~$50.00 drivers, I welcome the savings if it's possible.

Automation Direct motor comparison:
[www.automationdirect.com]

Tks.

Quote
A2
Gantry Type Machine Building Lots of good info can be found here for routers.
[www.mycncuk.com]

Quote
Jim Fong
I use the 276oz-in stepper from automation direct and gecko drives for my gantry router. Does 300ipm rapids. Stay away from the bigger 400oz-in steppers unless you can afford a higher voltage power supply and very good stepper drivers. The smaller 276oz-in can spin pretty fast, a big plus if you are using threaded rods.

What voltage are you powering the 276 oz-in at, and how many amps are your drivers?
What difference, or gains would I see switching from 12v, to 24v? Does the torque increase, higher speeds, quicker acceleration?

I was looking for a ~400 oz-in motor, but based on your comment I'm now I'm unsure if that's what I should get. NOTE: I'm using 15 mm wide belt, with 4:1 pulleys, no screws. Worse case, I probably have about 12 lbf to move, so I'm looking for a motor that can move ~24 lbf.

Is it possible to use the $10.00 drivers that most RepRaps use? I've been looking at the ~$50.00 drivers, I welcome the savings if it's possible.

Automation Direct motor comparison:
[www.automationdirect.com]
Tks.

Lower inductance stepper motors are better if you have lower voltage power supplies. You usually are able to spin them faster therefore you will end up having more torque at higher rpm. I use gecko stepper drives so they are top notch for performance. They can drive steppers up to 7amps/phase. I recall testing the 276oz-in on my electronics bench with my 24volt lab supply. It was easily spinning over 1500rpm. The motor performs pretty well with only 24volts. Using a different stepper driver will probably not run as good.

However when I installed the steppers on the gantry, I ended up using a 48volt power supply because that was what I had in my junk pile. Anything 24volts or higher would of been fine though.

You can use the pololu type drivers but you won't be able to maximize the stepper holding torque. I think the maximum output current is around 2.5 amps while the steppers are rated at 2.8amp. Even if you drive the steppers with only 2.5amps, you will still get really good torque. Much more than any nema17 stepper you can currently buy. You may have to active cool the pololu drivers somehow if you run them at max current.

The ballscrews on the gantry is 5tpi. I can bear down my entire weight on the gantry while it is moving at 50ipm. You cannot stop the axis from moving. It will easily snap a endmill bit if it runs into a hold down clamp. My gantry is pretty heavy with a big cast iron/steel z-axis.
[www.embeddedtronics.com]

You can probably find some online calculator that will calculate the force a 276oz-in stepper with 4:1 pulleys will give you. See if that will work for your CNC.

I have a single pololu driver. I need to bench test it one day and see how good it runs compared to a gecko drive. Increasing the power supply from 12volts to 24 will not give you any more holding torque. However it will give you more torque at higher rpm. How much depends on the motor inductance and other factors. Motor datasheets sometimes will give you torque curves vs power supply.

Edited 2 time(s). Last edit at 06/24/2014 03:24PM by Jim Fong.

Got around to testing a pololu drv8825 stepper driver on my test bench using a automation tech nema17 stepper motor.
[www.automationtechnologiesinc.com]

This is a 1.5amp 76oz-in 4.8mh nema17 motor. Using a 12volt power supply, I was surprised that I can get the motor to spin over 2000rpm. Driver was set at 8 microstep mode. Im not sure if a Arduino can output a step rate that fast so I used a external Tektronix frequency pulse generator. 2000rpm pulse rate is about 53Khz. At that speed there is hardly any torque and you can stop the motor just by touching the shaft. The pololu driver doesn't have any kind of mid-band compensation so around 600rpm the stepper motor easily stalls. It has good torque up to about 500rpm, very difficult to stop the shaft with my bare hands at that speed. The range that a stepper motor stalls from mid-band resonance varies between 300 and 600rpm. For this particular motor, it is at the higher end range. I mostly use stepper drivers from geckodrive which does have mid-band compensation and are they able to drive a stepper very smoothly throughout its entire rpm range. They are expensive but worth it if you have issues with lost steps due to resonance.

For a 20tooth gt2 pulley, 500rpm with give you about 320mm/sec speed if my calculation is correct. Thats pretty fast for a 3D printer so you wont run into the mid band resonance range with this motor. Pretty decent stepper motor for only $12

The Pololu driver does get hot driving more than 1.5amps so I'm not sure if you can really output more current without active cooling of some sort.

Motor RPM speed was measured with a Ametek model 1726 tachometer and verified with a Fluke frequency counter.

This morning I dug out one of my industrial Parker E-DC stepper motor drives just to see how well it could drive the same nema17 motor. With the drive set to 10microstep mode, 36volt power supply I was able to spin the stepper 3300rpm. The drive has anti-resonance and was able to compensate for mid-band instability. Perfectly smooth travel from zero all the way to 3300rpm. Has great torque up to around 1200rpm. I couldn't stop the stepper shaft with my finger tips at that speed. This goes to show how well a high performance stepper drive works for even small motors. Anti-resonance works really well.

The Parker drive doesn't have an 8microstep setting and minimum input power supply is 24volts. The 36volt power supply was used since it was already sitting on my test bench. I wanted to test one of my geckodrives but they were all installed on my CNC. From my experience with using them, they should perform similar to the Parker drives.

Edited 1 time(s). Last edit at 06/26/2014 12:33PM by Jim Fong.