salvaged stepper motors

[javafiend]

I'm building my first benchtop CNC based off of this one on instructables. I've been tearing apart every secondhand printer I can get my hands on to get the stepper motors. My question is, do they need to be identical for my x, y, and z axis?

Thanks

[Hirudin]

I'm also a beginner, so take this with a grain of salt...

It's OK if the motors are different. I would imagine you'll want to put the strongest on the X (the axis with the most weight), second strongest on the Y, and the last one on the Z.

I'd guess it would be preferable for the steps per inch/mm to be the same for the X and Y at least. So assuming the screws on the X and Y are the same you probably wont want to mix motors with different amounts of steps per revolution.

[High Seas]

javafriend - don't overlook the other good stuff in those printers - the rails and brass bearings that the printhead rides on! You get several sets of those and -- instant rails for the axis.
If tempted to use a belt drive system - those bits are there too.
BTW welcome to the CNCZone!

I'll go look for some pics of what I mean....
First one is an example of printheads salvaged and mounted to make a mini-mount for a Z axis.

The second is a draft of a vinyl cutter using bits and pieces from printers - track feeds etc.

You are only limited by your imagination -- well, and the size of the printers too
Jim

[CanSir]

Mixing motors with different resolutions (steps per revolution) isn't a problem because the controlling software (EMC2, Mach3) can easily be adjusted for that. If you get lower resolution motors (ie: 3.6 degree per step) then you can improve your machines final resolution by half-stepping them and/or coupling them to slower screws (ie: 10tpi single start screw instead of 10tpi two start screw). You lose top end speed, but gain precision.

Power requirements can be an issue though. I prefer to have all the motors matching so I can swap things around and not have to remember to adjust POTs or change power resistors before turning things back on.

Long before I got into CNC, I remember letting dozens of those really old, giant dot matrix printers slip through my fingers. I can only imagine how hefty those steppers must have been!

Good luck!

- Dean

[javafiend]

@ High Seas: I've been saving nearly every useful part - motors, electronics, gears, and the rods. I seem to have missed the boat on the print carriage and other structural materials, though. Guess it's time to get bigger bins to start holding those too.

@CanSir: Thanks for the input on stepper control with different size motors. I was afraid I would be out of luck.

Another question now, how do you go about calibrating your axis? Is this something done through software? I will be using a Linux system, most likely an Ubuntu variety.

[Hirudin]

Here's another thread with some more discussion on this subject...
http://www.cnczone.com/forums/showthread.php?t=35382

[CarveOne]

Yes, calibration is done in software settings. You move it some distance of travel and measure it to confirm that the distance moved is correct. EMC2 requires Ubuntu 8.04 currently.

CarveOne