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X1 CNC convertion

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bogstandard:
Hi Peter,

I am glad you have made your way here. Welcome.

I think this is a place to show how well you have got on with your conversion, and it is coming along real well.

John

CrewCab:
Welcome aboard Peter, looks like your conversion's coming along nicely, it certainly seems nice and smooth under power.

CC

Chris_b:
A few notes about the electronics for Peter's mill conversion.

There's a driver box and a manual control box plus a 24 volt power supply.

The driver box (not in Peter's photos)  is basically a packaged up MD3AXSI8435N controller from www.mdfly.com which is intended to connect three steppers up to a PC running CNC software. He sells a few variations on the theme, and not all of them all the time. Eg the board above isn't on his site at this moment, but will probably return at some point. There's several other people who sell boards like this, which really just wire up three Toshiba 8435 driver chips which do all the work, and usually add some optoisolators plus inputs for limit switches etc. There's a 25 way D connector and a cable to connect to a PC parallel port. Mods I did to this board include:

- fit a decent size heatsink and a fan on the outside of the box
- replace some of the ic's Mdfly decided not to fit, mostly optoisolators but also a voltage regulator
- change a diode in the power feed which wasn't properly rated
- fit some pullup resistors so the unit sits in a guaranteed safe state if you pull the D-type plug out/power it up without the PC connected

The manual control box replaces the PC and is homebrewed to Peter's requirements.

- a 100-step rotary wheel which can drive X or Y axes. With Peter's 2:1 belt drive, 2mm pitch lead screws on the mill and the right settings in the driver box (half-step I think) you end up with one rev of the wheel = 1mm table movement
- alternative to the rotary wheel, buttons for +/- X and Y movement (speed variable)

- buttons for Z movement

- a few switches to select the above, and some lights to show what's going on

- a big button for the spindle motor (see below)

Mostly on account of the rotary wheel, the manual control box contains a microprocessor (PICAXE 28X1 - see www.picaxe.com) and about 15 ic's. The circuit is not optimum and there could have been less ics if I'd not used the Picaxe which contains a Basic interpreter and is thus slow enough that I had to do some functions in hardware that could have been done in software.

If you don't require a rotary wheel, it could be done with a few ics and I'm currently (err rather slowly) building one of these for myself. Incidentally this will run a different driver board to the Mdfly one as he stopped selling them for a bit. As all the stepper control work is done in the Toshiba 8435 chip that's not a problem.

I've reverse-engineered most of the X1 control box (nb for MY model, I'm sure there are several variations) so I have some inkling of how it works, including the zero-volt safety feature which is particularly devious.


If anyone is interested I'm happy to let them have the circuits and software for the Picaxe which I'd release under the Gnu Public licence ("once free always free"). I'd post it all them on a website but I don't have one (=too lazy to set one up and look after it).

I've got some photos of the innards somewhere which I'll post when I've found some which don't demonstrate my chassis bashing skills too vividly (Peter has been *most* polite about this  :thumbup:)

Chris

sbwhart:
Wow great job  :bow:  :thumbup:

Have fun
 :wave:

Stew

Chris_b:
Here's a couple of pics. I've added some explanation for those who aren't too familiar with electronics.

The first is the Mdfly driver board being built into its box. Things to note:

- More heatsink. The black one is bolted to the original silver one with a very thin film of heatsink compound between. The fan sucks air through the box from R to L. The inlet grill got a piece of loose weave filter gauze added later. Without extra heatsink and fan the driver chips would likely get too hot in this situation.

- The actual driver chips themselves are mostly hidden from view you can just see their legs to the left of the three capacitors in the big round cans

- most of the ics on the board don't do anything tricky. The little ones with 4 legs (black and white) are opto-isolators. When I received the board, they had been replaced by wire links (shows how important they were considered to be!). I happened to have some lying around so I fitted them. The general idea of optoisolators in stepper drivers is to protect the driver chips from any voltage "surprises" coming into the driver on the 25 way connector, and vice versa if there's a fault and the 24 volt stepper mtotr power gets fed back to the PC. The 20 pin ics on the left by the D type connector (you can see one and a half of them) will probably do as good a job of protection by acting as fuses!

- the 16 pin ics on the right of the picture drive some LEDs on the board to show when step pulses are being applied. The circuit is wrong and the LEDs don't work as intended so I ignored them!

- the red switches in the middle of the picture set the step mode for the three motors. This basically translates into how many pulses have to arrive at the connector to make the motors move one full step

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