Looking for a source of Stepper Motors for ramps electronics

Hi I am new to reprap, but am in the middle of building a mendel prusa machine, I want it to be as accurate as possible, so I plan to use the ramps electronics with 2.5 belts. But I dont know what motors to buy yet? I was looking at the steppers in Makergear which i think is the most accurate machine you can buy, and I think they are 0.9 degree steppers is this the best option for me?? if anyone has any sudjestions of where is could buy these in or near the uk, as I dont want to pay a fortune on electronics?
Or any other sudjestions of parts that will make this machine more accurate?
thanks

There's no visible/proven benefit to need for 0.9 degree steppers when we're using 16th microstepping, so 1.8 degree steppers is perfectly fine, as well as cheaper.

You might be able to find a good deal on steppers from ebay, I personally prefer to use a RepRap vendor so I know the motors will be powerful enough.

XYZ printers is located in the Netherlands, and I have good experience with them.
Lulzbot in USA also have a good reputation.

Edit: See comment by Viktor

Edited 1 time(s). Last edit at 03/19/2012 09:44AM by Nudel.

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-Nudel
Blog with RepRap Comic

... the positioning error of a stepper is specified in fractures of a single full-step, regardles which microstepping resoulution you use, as it's the 'elasticity' of the magnetic field between two fullstep-positions.

So a 0.9-deg stepper will have better positioning accuracy than a 1.8-deg one ... but with the overall accuracy of the mechanics and the extruded material it's not really needed.

But it will be of interest, when replacing the extruder by e.g. a dremel or laserhead ...

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Viktor
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Ok in that case I will probably go with the 16 step, i am also buying the ramps electronics kit off xyz, but it says it comes with mechanical enstops, are the opto endstops better quality and more accurate? Would this be easy to change?
Do you have any other tips as I would like to build a precise machine?
I'm using 2.5 belt to drive the x and y would this help? Rather than T5
Thanks for your replies

I have been unable to spot any difference in the objects produced by T5 and T2.5 belt.

I don't think optical end-stops are any more accurate than mechanical. They have a 0.1mm slit that gets covered progressively by the flag. That produces a varying output from a photo-transistor that gets compared with a threshold. Since we need better resolution on Z than 0.1mm the repeatability is affected by stray light, temperature, supply variations, etc.

Micro switches work by pushing a spring loaded fulcrum past its tipping point. That seems to be to be a more digital effect than the optical effect. If the slit was 0.01mm instead of 0.1mm then the optical ones might win out.

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[www.hydraraptor.blogspot.com]

The biggest thing when buying steppers is to look for how much torque they have vs how much current they use.

kthx says:
ideal steppers are NEMA17 size, rated 1.5A to 1.8A or less, 1-4 volts, 3 to 8 mH, 62oz.in (44Ncm, 4.4kg.cm) or more of torque, 1.8 or 0.9 degrees per step (200/400 steps/rev respectively), for example the kysan 1124090/42BYGH4803 or the 17HS8401
I've just ordered some of these:
[www.aliexpress.com]
tiny bit high on the current, but loads of torque.
which will be replacing my current:
[www.sparkfun.com] which overheat a bit. I'm probably running them with too much current to counteract the low torque.