PROXXON mini Mill MF70 conversion to CNC

[limor]

We found this famous small European made mill on the web for 200EUR so we decided to get one and go through retrofitting it with motors and trying to print out some metal brackets and PCBs.

MF70 specs: Spindle speeds 5,000 – 20,000rpm. Table 200 x 70mm with X-Y travel of 134 and 46mm respectively, with vertical travel 80mm. Footprint size 130 x 225mm and overall height 340mm. Weight approx. 7kg.

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[billyzelsnack]

Do you think you'll be able to get away with low amp steppers? Ones that could use the MUCH cheaper stepper drivers?

[limor]

I have been reading about the Mf70 convertion to CNC and it seems like a very popular platform in europe. I think you are right about the nema23 not being powerful enough.
sparkfun have some low cost 3A stepper drivers that look ok.

Do you think a RC Crawler sensed motor can be used instead? Or a "supermodified" rc servo with 360° magnetic encoder? I haven't found any such references online so the idea must be flawed.

Here are good links about mf70 to cnc convertion:

http://dangerousprototypes.com/forum/vi ... =19&t=2414 

http://www.indoor.flyer.co.uk/millingmachine.htm

http://www.civade.com/post/2008/05/10/3 ... xxon-mf-70

http://www.jarkman.co.uk/catalog/cnc/russmf70.htm

[billyzelsnack]

If they're the ones I'm thinking of you're not going to get 3A out of those drivers. You might be able to get away with the makerbot 3.3 stepper drivers. They supposedly will do 2.8A per coil. Using your thingomatic bits + RepG to bootstrap is probably smart too as it'll let you take baby steps.

Another option might be these:
http://www.geckodrive.com/g250x-p-37.html
I paid $41 each during their annual sale last year. Checking my email looks like the sale is in November.

I'd just stick with the classic steppers otherwise you might end up doing more R&D than actual milling in the next year.

[Meltdown]

You are going to have a hard time milling alu plate with that.
You will spend a fortune on broken cutters.
I build several cnc mills over the years to know that.

First the X-Y table is made out of pressed alu, it will give way when side pressure is applied, same for the mill collumn itself resulting in bad surface finish and broken cutters.
What you need is a cast iron construction for mass stability really.

Wile it's possible to mill alu you won't be able to take off more material than 0.05/0.1mm at maybe 1mm/second a pass.
It will take like forever to cut through 1.5mm alu plate.
Also with high speed cutting and tiny 2mm cutters you need a cooling pump otherwise your cutter will burn up fast, become dull and will break due to the high speed motor.
Another problem is getting rid of the debris which will clod up your cutter which also results in broken cutters.
This machine is best used for making pcb's and maybe carbon cutting.
Metals need a strong slow cutting motor and cast iron contruction, or a strong high speed one like a kress.

[billyzelsnack]

This video makes it looks like it'll work out.

http://www.youtube.com/watch?v=wmB8Z_ZQepc

What am I missing?

[limor]

The idea is to experiment and learn.
I will have to spend now at another 200EUR or so on steppers motors, stepper drivers, switching power supply and parallel port paraphernalia.
Until few days ago i would have never believed that a CNC relies on a real-time patched Linux PC that flips around parallel port pins to control a mico-stepped stepper motor (blindly). So i actually look forward to learning more about this watch-maker's technology and see this thing eat through aluminum sheet hopefully

[Axelen_Ran]

You are going to have a hard time milling alu plate with that.
You will spend a fortune on broken cutters.
I build several cnc mills over the years to know that.

First the X-Y table is made out of pressed alu, it will give way when side pressure is applied, same for the mill collumn itself resulting in bad surface finish and broken cutters.
What you need is a cast iron construction for mass stability really.

Wile it's possible to mill alu you won't be able to take off more material than 0.05/0.1mm at maybe 1mm/second a pass.
It will take like forever to cut through 1.5mm alu plate.
Also with high speed cutting and tiny 2mm cutters you need a cooling pump otherwise your cutter will burn up fast, become dull and will break due to the high speed motor.
Another problem is getting rid of the debris which will clod up your cutter which also results in broken cutters.
This machine is best used for making pcb's and maybe carbon cutting.
Metals need a strong slow cutting motor and cast iron contruction, or a strong high speed one like a kress.

Not quite true ... usually I do 0.5mm DOC (Depth Of Cut) and run at
70 - 120 mm per min. when using 3mm cutter I do 1mm DOC.
End mills (cutters) usually break because of user error (My errors....)

I have been using this maching for milling 7075 allu', and it cuts it
very nice:
http://www.youtube.com/watch?v=1-1I5Htx ... re=related

Cheers
Ran Amir

[peeer]

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