Non-circular boring. Nerd fun.

skunkworks · Mar 17, 2020

I thought you guys would get a kick out of some weekend playing I have been doing. (This is linuxcnc - so most of you guys can tune out now

)

One of my friends demonstrated creating a hex on his lathe by gearing the x axis to the spindle rotation. It was a sort of proof of concept.

I wondered if I could do it on a mill - gearing the x/y axis with the spindle. So - I created a component within linuxcnc that takes spindle position and moves x and y to create a polygon. This is just using a table top cnc (Tormach style) - so I am limited by the physics of the machine. (plus the machine has a gear for the spindle encoder - so it is only 152 counts per rev. I was honestly surprised it worked as good as it did considering..

You give the component the number of sides, polygon radius, tool diameter, tool orientation angle and other things that I cannot think of at the moment.

Here is the initial test. (video making isn't one of my strong points.. sorry)

Then I figured I could 'connect' the x axis to the radius of the polygon - to create profiles. - you can see the limitation of the low count spindle encoder.

And - sorta real-world application..

I need to try this on the K&T....

Scottl · Mar 17, 2020

Interesting concept. Thanks for sharing.

Am I correct that your machine has ball screws? Otherwise I would expect rapid wear due to the repetitive movements.

skunkworks · Mar 17, 2020

Yes - ball screws and auto oiler...

Scottl said:
Interesting concept. Thanks for sharing.

Am I correct that your machine has ball screws? Otherwise I would expect rapid wear due to the repetitive movements.

gregormarwick · Mar 17, 2020

This is not unlike the lathe retro I did with LinuxCNC years ago.

I used synchronised spindle and x axis with constant z feed to "turn" pins with an asymmetric ellipsis cross section.

LinuxCNC is fantastic for this kind of outside of the box experimenting.

eKretz · Mar 17, 2020

Scottl said:
Interesting concept. Thanks for sharing.

Am I correct that your machine has ball screws? Otherwise I would expect rapid wear due to the repetitive movements.

Going to be rapid wear regardless compared to normal longer linear movement. Local wear would be nasty if this was used much over time. I'd try to keep it to a minimum on a little machine. Something with box ways and it might be a different story.

DDoug · Mar 17, 2020

There is a "CNC Section" here.

Or better yet, try the zone.

Please.

skunkworks · Mar 17, 2020

It worked surprisingly well considering what I am working with...

gregormarwick · Mar 18, 2020

eKretz said:
Going to be rapid wear regardless compared to normal longer linear movement. Local wear would be nasty if this was used much over time. I'd try to keep it to a minimum on a little machine. Something with box ways and it might be a different story.

The one I did was just a basic cnc centre lathe (Harrison M400 CNC), typical dovetail and gib cross slide but all ballscrew driven. The x axis oscillation was fast but the reversals were relatively smooth because of the profile tangency. It had a very small amount of wear on the slides when I started, and it did not increase appreciably over a year of moderate use (lets say about 100 hours a month for a year until the job ended). Ballscrew was still perfect. I did increase the oiler frequency to cycle IIRC every 30 seconds, and changed the metering valves so it didn't just dump all the oil over the bed.

If it did not have an effectively constant flow of oil I'm pretty sure the slides would have worn out completely very quickly.

I did have to replace the x axis servo motor and amplifier shortly after we started production, but it was ancient already and might have been ready to pop before we even started. With a new ac servo and amp I was also able to increase the spindle RPM appreciably without sacrificing profile accuracy, as the servo inertia was much lower than the old dc servo, and therefore had much better dynamic response.

This is experience is how I was left with the firm opinion that LinuxCNC is a valuable industrial tool and not just a toy for hobbyists...

eKretz · Mar 18, 2020

gregormarwick said:
The one I did was just a basic cnc centre lathe (Harrison M400 CNC), typical dovetail and gib cross slide but all ballscrew driven. The x axis oscillation was fast but the reversals were relatively smooth because of the profile tangency. It had a very small amount of wear on the slides when I started, and it did not increase appreciably over a year of moderate use (lets say about 100 hours a month for a year until the job ended). Ballscrew was still perfect. I did increase the oiler frequency to cycle IIRC every 30 seconds, and changed the metering valves so it didn't just dump all the oil over the bed.

If it did not have an effectively constant flow of oil I'm pretty sure the slides would have worn out completely very quickly.

I did have to replace the x axis servo motor and amplifier shortly after we started production, but it was ancient already and might have been ready to pop before we even started. With a new ac servo and amp I was also able to increase the spindle RPM appreciably without sacrificing profile accuracy, as the servo inertia was much lower than the old dc servo, and therefore had much better dynamic response.

This is experience is how I was left with the firm opinion that LinuxCNC is a valuable industrial tool and not just a toy for hobbyists...

Keeping the oil supply much more constant was a good idea. Hopefully O.P. will take note so he doesn't chew up his machine.

EmGo · Mar 18, 2020

They used to make drill bits that would drill polygonal holes. Maybe still do ? You let the part shake around instead of the entire machine

jz79 · Mar 18, 2020

EmanuelGoldstein said:
They used to make drill bits that would drill polygonal holes. Maybe still do ? You let the part shake around instead of the entire machine

they still do make them, poly count is 5, works especially well with larger drill sizes and thin materials

regarding the OP, while fun thing to do, not much practicality in it, and seems that servo decel/acceleration might need improving to fix the geometry issues

skunkworks · Mar 18, 2020

Very neat! - exactly. The machine has its limits.

jz79 said:
they still do make them, poly count is 5, works especially well with larger drill sizes and thin materials

regarding the OP, while fun thing to do, not much practicality in it, and seems that servo decel/acceleration might need improving to fix the geometry issues

View attachment 282120

StinkyDan · Mar 18, 2020

digger doug said:
There is a "CNC Section" here.

Or better yet, try the zone.

Please.

Haha everyone ignored ur post.

To the o.p. cool stuff, keep it up

skunkworks · Mar 29, 2020

Aluminum.. Used feed per rev..

skunkworks · Mar 29, 2020

skunkworks · Apr 5, 2020

Just to see if it could be done.. 60deg twist in .5" - the vertical lines are the resolution of the spindle encoder...

atex57 · Apr 5, 2020

Sam, you are getting into some deep stuff!! I put an encoder on the spindle of my Well-Index CNC, maybe I can do this too. Now just have to find a use for it. I gotta come up that way sometime and see this thing.

Ed.

skunkworks · Apr 5, 2020

Someone said I could make pasta dies....

You are always welcome Ed.

atex57 said:
Sam, you are getting into some deep stuff!! I put an encoder on the spindle of my Well-Index CNC, maybe I can do this too. Now just have to find a use for it. I gotta come up that way sometime and see this thing.

Ed.

Cole2534 · Apr 6, 2020

I came in here to write a snarky, condescending comment but after seeing it this is pretty kickass.

Thanks for sharing.

skunkworks · Apr 15, 2020

Phase 2.. Higher resolution encoder.. (some actual K&T IIIb video...)

Non-circular boring. Nerd fun.

Aluminum

Diamond

Aluminum

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Diamond; Mod Squad

Diamond

Aluminum

Diamond

Diamond; Mod Squad

Diamond

Stainless

Aluminum

Aluminum

Aluminum

Aluminum

Aluminum

Stainless

Aluminum

Diamond

Aluminum

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