King Midas mill conversion

[Swarfing]

Ezecnc Roger had this issue when he converted his viceroy, he did not suffer any damage luckily but did have a huge issue with resistance. Made it hard work to mill by hand. He was using large steppers but goes to show that the issue is there no matter what size steppers you use. It would be worth whipping out the DTM to check on any back current flow?

[Jonathan]

The back-emf from stepper motors is significant - they're good little generators. The protection diodes in the stepper drivers will rectify the back-emf and if you turn it fast enough power up the driver which is clearly bad news. I found that below a certain speed they manually turn quite easily, but when that threshold is exceeded it gets a lot harder. Clearly it will vary significantly with the size of motor.

Easily solved - just unplug the motors.

[Robin Hewitt]

The sensitive drill part is really useful when you come to hammer a collet out of the taper, it gives you something to hammer against.

Best if you can release the Z axis screw before you hammer so you aren't bashing against expensive ball nuts and bearings.

[diy-john]

Good point Robin. Thanks!

Alternatively, perhaps one could use the lever on the left hand side of the quill, to lock it (during hammering)
- Not sure though is it strong enough / meant for that purpose.

Hoping to receive some bearing mounts, before weekend, so would have something to play with..

[diy-john]

Status -update:

[x] received six (6) bearing mounts for the ballscrew -bearings
- a small local workshop made them for me.
- these are temporary bearing mounts, but very good at such.



- Holes for bearing are 32mm in diameter. Used heat to expand the mounts, so that bearings would go in easier. Holes are quite tight and precise, think it is impossible to remove the bearings in one piece.



[x] continued with a temporary, crude build
- in particular Z-axis

- Z-axis now looks like this

- Z-axis lower bearing mount. Used an electric drill to fabricate some supports



- Purpose is to make a mock-up of the build, write down anything that needs changed, and then hopefully make it a nice looking mill.

[x] an un-necessary side-step was when I dropped balls from a ballnut. Thought first oh well, that was 100 quid down drain. But to one's surprise, managed to find all balls and with instructions found from internet, put it back together. For record, took out the remaining balls, and used a plastic straw from a WD40-bottle to put them back in, one by one. Used bearing grease (like Vaseline) to make the balls stick to the plastic straw / and also stick onto the inside-walls of the ballnut.

[diy-john]

Latest is:
1) At garage, have a crude build ready to plug motors in
2) At home, have a pc with with LinuxCNC + motors running on table ( this has in fact been ready already for months)

Next steps are
- put 1) and 2) together... by Christmas time will take pc, monitor, motors, drivers, to garage and plug them in.
-- before that, need to study calibrating LinuxCNC X, Y, Z -axis

Lessons learned recently:
- making crude build takes more time than expected. Probably spent 4 days x 8 hrs = 32 hrs to make it, over a few week period.
-- need to buy small sundries here and there
-- compressed air die grinder similar to this is helpful. I find it safe to use (no sparks + quite difficult to cut yourself accidentally), and cuts material quite quickly, but not too fast. Makes a nice sound, too. Of course not a CNC -machinist / milling machine operator approach, but hey, one haven't got a mill running now.

- have already noticed a few design errors by making a crude build, so it has been worth it.

- Longer term plan:
-- Once machine is running, make revised intermediate parts. Use possibly less thick Aluminium than one would have in final build. Cheaper. One expects there will be errors as I am a newbie in all this.
--- want these parts to be relatively rigid, so that it is possible to make good quality "final parts" later.
- Hope to submit more photos next weekend + a compulsory video

[diy-john]

Well she runs now, albeit slow and ugly, though to my eyes it is pretty



Is this it? CNC -virginity lost?

My smallest milling bit is a 10mm wide end mill, so the letters are fat beyond recognition.



Machining marks are quite visible, and think all the axis give way when pushed hard.
- Think the cut aluminium chips are around 0.2mm thick.
- Have to check what sort of feed rates I used actually, and how fast the mill bit was turning. With my zero experience I just set them to something that didn't seem overly fast.

Happy New Year to all!

[diy-john]

Things have been moving slowly, due to work etc. commitments.

I have now officially begun an intermediate -build of the CNC -conversion.
- Focus is making now parts more rigid, and more like the final, beautiful build.
-- One is using less thick (cheaper) materials here, than in what will be the final build.

Today I have been using the mill as a manual machine, with LinuxCNC, using DRO's and Power feeds.
- Trying to get used to G-code, use simple commands like G0 somewhere, G1 elsewhere... while cutting aluminium.
- Measuring with a digital vernier, cutting a tenth here and there.

Perhaps one had thought I am going to make a fancy drawing and export it into G-code. Send chips flying and ta-da, bolt everything in place, and have a ready CNC conversion.

But it has not been like in dreams. Need to take one step at a time. It was fun cutting aluminium today. :)

[diy-john]

Small update:
- have been getting more familiar with G-code, LinuxCNC, QCAD, dxf2gcode.
-- Also have Heekscad / HeeksCNC + Blender installed (http://www.mycncuk.com/forums/cad-ca...hat-i-did.html).
--- However so far,I have not transferred anything useful to work-piece from Heekscad/Blender.

- This weekend I started to make X-axis parts.
-- use QCAD to make DXF.
-- use dxf2gcode to make G-code.
--- each task I do in several smaller tasks.
---- I could not get dxf2gcode make one long piece of G-code, with climb-milling.
---- So instead, I have chosen to create individual smaller G-code -scripts, that I run in series.
----- Let mill return to home between each G-code script.
-- Getting used to mounting a work-piece.
--- Working with coordinates
--- Zeroing coordinates. Touchoff. In short: mount a work-piece, and practice how one can get cuttings exactly where one wants them.

-- On Friday bought a new 4mm and 6mm carbide end-mill. Smallest I had before this, was a 10mm end-mill.

It is slow progress, however rewarding. Would just love to go back to garage and start cutting again. At this stage, the machine is crude but it does what it is told to do.

[WandrinAndy]

It's looking good John! ...Thanks for a great thread.