Home Built CNC Project


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Bryan1

Guru

Joined: 22/02/2006
Location: Australia
Posts: 1219
Posted: 08:51am 07 Aug 2011      

G'day Guy's,
I pulled apart the z-axis stepper today to see what was wrong and 2 of the main pad's were cut so I soldered on a bit of wire and tested it. No movement from the shaft but one could feel the ramp up and sudden stop. Pulled it apart again and had a closer look and one of the winding had burnt out, tried to solder it but on the next test still didn't work.

Anyway I have 4off of those 16mm split bearings so I'm going to make a new Z-axis complete using the 16mm bearings and rod's and I do have a 5 volt 1 amp bipolar stepper motor I'll use as the drive.

As I will need to make a new driver board I'm going to make up some A3977 boards so I can go the micro stepping route. The only set back is I need to source some 3 watt 0.2 ohm smd resistors for the circuit design I have here. I do have a transparency so as most of it is smd it will be a fun job to make with only one good hand. Hopefully on Tuesday the cast will come off an I will have more use of my right hand but looking at the dressing before the wound has weeped again so I reckon the 20 or so stitch's won't come out on Tuesday.

This cnc has been a long term project and with going the ball screws on both the X and Y axis I might have to have another look on fleabay and get a ball screw for the z-axis. Then the cnc will be totally driven by ball screws and accuracy won't be a problem.

Like I've said once this small cnc is done I aim to start on the big one and when my tax return comes in I'm buying the RHS to make the frame. As I already have the steppers for the big one I will need to find a new driver circuit as they all are rated at 250 volt, the X and Y are rated at 11 amps and the Z is rated at 7 amps. In order to get the full capacity of these 8 wire steppers homebrew micro stepping circuits are hard to come by so if any guys have a link or such and can provide details I will appreciate it.

Cheers Bryan