hf 7x10 cnc

[brave_ulysses]

slowly modifying my minilathe for cnc operation...

currently has closed loop steppers and ballscrews on z and x axes - both addressable with 1u resolution. yes, this is overkill on this lathe

looking to machine an aluminum blank to be finished as an f10, 150mm spherical telescope mirror (finishing not by me)

of course i know that without pix it didn't happen, so with no further adieu:

 

[TomS]

Nice! I'm putting the finishing touches on my 7 x 12 cnc conversion. Hopefully will have it running soon.

 

[brave_ulysses]

hi tom,

i think we are gonna need to see some in-progress pix! any details on lead screw, motors, software, etc?

thanks,

clay

 

[TomS]

Well, if you insist. LOL. I'm using 1605 ball screws with double ball nuts on both X and Z. Probably overkill but I had a spare ball screw and ball nut laying around and wanted to put it to use on the Z axis. Linear Motion Bearings provided the X axis screw machined to my specs and both ball nuts.

The motors (270 oz in), drivers (DQ542MA), and power supply (350w, 36 vdc) came from Wantai Motors. I've had good luck with their equipment on my CNC vertical mill conversion. Been running about 5 years and no failures.

Control software will be Mach3. CAD/CAM will be a mixture of Fusion 360 and CamBam. I've heard good things about Ezilathe. I may give that a try.

I'm going to start out using a UC100 motion controller and a BoB left over from my vertical mill conversion. If that doesn't work out I'll probably go with a ESS Smoothstepper and upgrade the BoB. We'll see.

I'll take some pictures and post them tomorrow.

Thanks for your interest.

 

[TomS]

I didn't want to hijack your thread so I created a thread on my conversion in the CNC section. Here's the link. 7 x 12 Mini Lathe CNC Conversion

 

[brave_ulysses]

found that carriage was racking (rotates around y axis) and had lost motion in x (~0.2mm), so disassembled to find the cause

tightening up the gibs fixed the racking - had to move ballnut attachment for easier accessibility. bottom of ways are uneven (worse on back way) and will need to be addressed later. i found some nice tapered gib upgrades for the minilathe, but that will have to wait for my next lifetime

lost motion in x is due to flexure to the ballnut attachment extension (far left in first pic). i'll rebuild the attachment with 1/2" 6061. not as nice as toms', but better that what i have now

the current retrofit was constructed using scraps that i had on hand to see how it worked and how i liked it before i commit to using better materials

on my budget indicator (clockwise ditr 0105 on amazon), z axis is repeatable to a few microns. x should be similar when it gets rebuilt

 

[brave_ulysses]

got the new piece installed and the carriage flex is gone

it looks good enough to try some machining. subsequent fixes/improvements for another day

 

[brave_ulysses]

python code to generate gcode for an f10, 150mm mirror
sample (untested!) gcode included