Motor Requirements

I'm trying to find out exactly what specs are needed for the stepper motors. I'm trying to build this on a small budget and I'm not willing to pay $60+ (

Hi Dylan

You need a Nema 23 motor this is the mounting flange spec and is 57mm x 57mm approx to be exactly the same as Darwin it should be 51mm long, but if longer it would be no problem on X or Y and would just reduce Z travel by the over size. The double shaft is needed on the Z axis only.

As for Voltage, Amps etc, if you run V1.0 electronics then ideally the motor should draw no more than 2 Amps, (but Bruce is currently running a Darwin with V1.0 electronics and pulling higher current with no problems just a big heat sink) this means a series resistance of 6 Ohms minimum, with Bipolar just double the specified resistance (if series connected) i.e. the motor you list above would be 3.68 Ohms, 0.84 Ohms and 0.92 Ohms respectively.

With V2.0 Arduino electronics they have current limiting so any motor will work (not sure if it is a fully working system yet, but if not it won't be long).

You want Bipolar 8 wire motor as they can be connected in either bipolar or unipolar so are the most versatile.

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Ian
[www.bitsfrombytes.com]

Ok, I have ordered the PCB kit from the rrrf site which uses the UC board v1.3. So I guess that means version 1 electronics.

size: NEMA 23
ok, this seems pretty standard as a sizing requirement between the different motors

bipolar: Why is this needed on the Z axis. what good is it for? extra torque?

amps: when you say 6ohms resistance, did you mean in the circuit control or the motor itself, and is that 6 only on higher amp motors? I ordered the big heat sink and have an extra fan I can put with it to keep it cool.

I'm sure the motor I listed would work for the torque (it's a little higher than the one on farnell).
Would this motor work for the project? (w/ the universal controller v1.3 board)
Also, would I need to adjust the input voltage to match the 3.8V it lists? Or would the 5V input work ok?

I know I have a lot of questions, but I'm new to motors, my experience is more in circuits and design.

thanks
Dylan

I really want to build a reprap, but one of the major barriers for me is the cost of a 400 step motor.
This might be a bit naive a question, but why not use a 200 step motor instead and design a half-step driver circuit?
The advantage is that 1.8 degree bipolar motors are really cheap on the surplus market - and can even be free if someone is willing to locate old industrial printers or large floppy drives.
True- half stepping can be kind of slow, and less efficient power wise - but the reprap is not a high speed milling machine,so I can't see those requirements as being a problem.
half-stepping capable driver circuits (with code) using PIC processors are fairly plenty on the net.
BTW What a great website! I have spent lots of time looking around, and alrady have some ideas on the way I want to build my "Repstrap"

Thanks

Fred

You can use 200 step motors: [blog.reprap.org]

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[www.hydraraptor.blogspot.com]

Could someone wiki the actual requirements regarding motors? Maybe some instructions on usage and identification of motors from different sources such as old printers etc.

Mostly everything else needed for making a rep(st)rap i could find.

Elmo

I just ordered some NEMA 23 400step (0.9 degree) motors from [stores.ebay.com]
It's under 2 amps, 2 phase, 8 wire, 5.4V, and from what I could find out the holding torque is about 118 oz-in which should be 0.8333nM (this is a little less than the one on farnell, but it might still work).
Best of all, they are only $28 + a few bucks for shipping. This is in USD and I'm not sure if they ship international. I don't know how many he will have in the future though.
I haven't gotten them yet, but I'll let everyone know if they work well when I get them.
Dylan

also, the RRRF is doing a bulk buy of stepper motors. we'll be attempting to stock them full-time in the store so that everyone can have cheap access to a 'standard' motor that is guaranteed to *just work* with the electronics.

the motors are ordered, and should be here any day.

The motors run at 12v but steppers are current devices not voltage I run my CNC steppers (3.6v) at 35v but control the current, a higher voltage gives better response. The V1.0 electronics doesn't control the current and as such the motor has to limit its own current due to its resistance i.e 12v 6 Ohms = 2A which is the continuous rating on the L298

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Ian
[www.bitsfrombytes.com]

At 2A the L298 drops around 4V leaving only 8V across the motor, so the minimum resistance is more like 4 Ohms to give 2A.

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[www.hydraraptor.blogspot.com]

That's interesting, I didn't know that kind of thing. So the motors I ordered have 5.4V and 1.5A as their specs. If I'm using the standard universal board at 12V would I need to add a resistor or anything for it to work efficiently?



@NopHead I saw your blog, great job. Have you considered replacing a few parts, closing the the box off and actually putting a heating element in there to bring up the ambient working temp to overcome the problem you had of speed vs heat?

Edited 1 time(s). Last edit at 12/18/2007 09:21PM by Dylan.

Dylan,
If they are 8 wire you have the choice of wiring the coils in series or parallel. If they are 5.4V per coil then wiring then in series should be fine. Parallel is generally preferred for speed but that would draw 3A, too much for the L298 and you would need resistors are well.

I am trying to avoid the complication of putting it in an oven. The layout of my machine does not really lend itself to that. If room temperature FDM does not work I will probably switch to another technology.

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[www.hydraraptor.blogspot.com]

ok, if serial will work better, for the current board, how is that hooked up? Is the tutorial and board made for serial or parralell? So far I'm just following the steps on the "how to make a reprap" section.



I know what you mean about the oven thing, but from the other systems too, it looks like most of the systems seem to do it this way. I plan on trying to convert this system into and SLS system with optional FDM capabilities.

The tutorial here [reprap.org] describes the wiring of the official motors which are also 8 wire motors and the coils are wired in series. I.e. four of the wires are cut short and linked in pairs, the other four wires go to the board.

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[www.hydraraptor.blogspot.com]

ok, thanks, I hope the colors will be the same.