CNC Shaping Circle Out of Round

[Hardwoodcnc]

Hi,

I’m using Fusion 360 and Mach 4. I’ve confirmed my model and center point are correct in Fusion. I’ve confirmed my work offset is centered accurately in the center of the ring I’m shaping.

When I run my gcode my cnc is not cutting the ring evenly. Certain parts of the ring are being shaped while the cutter isn’t making contact with other parts of the ring causing it to be out of round.

Any ideas on troubleshooting this issue?

 

[Seesecurity]

What machine, what material, what cutters, what feeds and speeds?

 

[sinha]

Can you please post the sketch of the shape you are getting, with measured dimensions?

 

[rjwalker1973]

it would help tremendously if you could post a drawing and let us know what tools and machine you are running this on. By looking at you program it says 1.375 with no Cr in the description. Is that the tool or the finished ring size?

 

[Cole2534]

With Mach4 as your control I'm guessing this is a home-brew machine and that the error is in your motor tuning or in the machine itself.

The best solution would be to have it ball bar tested, that should highlight any issues you have.

 

[Hardwoodcnc]

I've attached the sketch I'm working off of. I'm currently shaping the inner ring of the sketch (12.625).
I'm using a machine that I built from scratch.
I'm shaping drum shells made of hardwood.
My feeds and speeds settings are attached.
I'm using this cutter (1-3/8X1/4"2FL CARB TIP MULTI-RABBET ROUTER BIT) which is mounted on to a tool extender (collet extension).
I've confirmed that I'm not missing any steps and that my center (origin point on machine) is accurate.
What is the best way to run a ball bar test on a budget?

 

[atex57]

Do you have a dial indicator to sweep the inside diameter?

Ed.

 

[BT Fabrication]

id be guessing its slop in the way your machine moves back and forth. most likely a cheaper belt driven machine.

 

[gmc1724]

Hi,

I’m using Fusion 360 and Mach 4. I’ve confirmed my model and center point are correct in Fusion. I’ve confirmed my work offset is centered accurately in the center of the ring I’m shaping.

When I run my gcode my cnc is not cutting the ring evenly. Certain parts of the ring are being shaped while the cutter isn’t making contact with other parts of the ring causing it to be out of round.

Any ideas on troubleshooting this issue?

Learn to read g-code before playing at being a machinist.

 

[Cole2534]

What is the best way to run a ball bar test on a budget?

I was being facetious, it would be a giant waste of money to hire one out. and there's not a very good way to do one at home.

Do a circle, diamond, square test. Here's a link to a Renishaw white paper on it- Renishaw C/D/S test

 

[memphisjed]

The shapes being cut are circles? If so and not concentric then either you are missing steps on rapids- which you do not have so I would guess material is shifting.

 

[MaxPrairie]

Lathes are good at cutting circles...

 

[gregormarwick]

I'm using this cutter (1-3/8X1/4"2FL CARB TIP MULTI-RABBET ROUTER BIT) which is mounted on to a tool extender (collet extension).

In your previous thread about this (removed by moderator) of an idea, I said without hyperbole, something along the lines of (removed by moderator).

Since you chose to ignore me at that point, I will reiterate, this is (removed by moderator).

Tiny toy spindle, long extension, relatively heavy cutter, 15000rpm - it is only a matter of time before that comes apart spectacularly.

 

[MwTech Inc]

Some people have no idea what's in front of them.......if you tell them and they ignore it.......well, it thins the herd eventually.......

 

[CarbideBob]

What is the best way to run a ball bar test on a budget?

Circle/Diamond/Square test. This how it was done before ball-bars and other fancy stuff on NC machines.
Axis backlash may be the problem.
Never used Mach so no idea of how or if it handles this fix.
The problem with any ballbar, laser or grid test is that it is done under no axis loading so one can dial in zero here and still get bad cuts.
All fine for a CMM. Machines cut stock and bend, twist, rotate while doing so.
On most machines some addition tweaking is needed to comp for this.

Think if you had a flimsy milling machine with .050 backlash. Not only do you have to take out the lash but now the axis itself deflects.
The lash is fixed at any give spot. The defection is dependent on cutting pressure so it varies with light cuts and heavy cuts.
Bob

 

[MaxPrairie]

In your previous thread about this (removed by moderator) of an idea, I said without hyperbole, something along the lines of (removed by moderator).

Since you chose to ignore me at that point, I will reiterate, this is (removed by moderator).

Tiny toy spindle, long extension, relatively heavy cutter, 15000rpm - it is only a matter of time before that comes apart spectacularly.

Reminds me of the guy that put the fly cutter through a block wall at 12k rpm's.

 

[camhead420]

Lathes are good at cutting circles...

If he has gotten this far without figuring that out it is pointless to help him.
The previous post asking this same question was awhile ago and he is still trying to make it work.

 

[70olds]

If he has gotten this far without figuring that out it is pointless to help him.
The previous post asking this same question was awhile ago and he is still trying to make it work.

Is this the keyseat cutter around the outside of the big chunk thing?

 

[TeachMePlease]

Is this the keyseat cutter around the outside of the big chunk thing?

Wasn't it a damn saw blade?

 

[charlie gary]

In your previous thread about this abortion of an idea, I said without hyperbole, something along the lines of "stop before you kill yourself".

Since you chose to ignore me at that point, I will reiterate, this is ridiculously fucking dangerous.

Tiny toy spindle, long extension, relatively heavy cutter, 15000rpm - it is only a matter of time before that comes apart spectacularly.

It can definitely be a life-changing moment.