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Circles on a CNC Whats the accepted tolerance ? Are my circles good enough?

adamfromayr

adamfromayr

New Member
Hi

Im using Mach3

And i know that making sure a CNC is good, well one way is to make a perfect circle?


After i set up Mach3 Using "Set Steps per Unit"

And "Motor Tuning"

99.5 vs 99.8 mm

Ive made a few Test circle cuts and measured them afterwards using my Calipers!


Im just wondering to ask CNC Pros is the circle attached good enough?


It measures a difference of around 0.3mm in different areas!

So its like 99.7% good but is not 100%

Do you need it to be 100%?

I wonder if others do this test also?
DSC06404.JPG
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DSC06401.JPG
 
G

GaSouthpaw

Profane and profane accessories.
If you're okay with it, and the customer's okay with it, then they're okay.
For signs, they're probably okay.
For precision parts, that would be out of tolerance for most applications.
It all depends on the end use.
 
adamfromayr

adamfromayr

New Member
Thanks for replying thats what i was thinking also

Like steel parts even more reason to be precise i think the Hugo stick circle i made is maybe 1-2 sheets of paper thinner on one side its hardly noticeable but was just wanting to know if others were similar or not i think on signs it will be even better its just from my experience circles were the one to make perfect first!

Many thanks!
 
JBurton

JBurton

Signtologist
Circles are great, but I usually do squares. Any CNC is going to have some chatter as it transitions axis', so even on a perfectly tolerant CNC, a little variation across sides of a circle is acceptable. Doing 2 squares of equal dimensions, laid one on top of the other at 90 degrees, this will tell you how accurate the machine is in a slightly easier to measure way. Also, cutting two identical shapes at opposite diagonal corners of the machine will help tell you if it's got slop closer to one axis or the other, if working with something doglegged like my old router.
 
adamfromayr

adamfromayr

New Member
JBurton said:
Circles are great, but I usually do squares. Any CNC is going to have some chatter as it transitions axis', so even on a perfectly tolerant CNC, a little variation across sides of a circle is acceptable. Doing 2 squares of equal dimensions, laid one on top of the other at 90 degrees, this will tell you how accurate the machine is in a slightly easier to measure way. Also, cutting two identical shapes at opposite diagonal corners of the machine will help tell you if it's got slop closer to one axis or the other, if working with something doglegged like my old router.
Click to expand...
Thanks for the valuable input

that's a good idea i will try doing squares shortly

Thanks again i will try that soon

adam
 
JBurton

JBurton

Signtologist
Another thing to consider, these are very small measurements to calibrate from. At 100mm, with an accuracy of 99.5, at 2m, you'll be missing 1.08cm. That's pretty significant, right? (I'm so bad at metric I honestly am uncertain how much that is) Depending on what you're doing, you may want to tune the machine further. I like to drill a pair of holes as far apart as I can, measure, crunch the steps/in, and repeat until I hit the distance to within a 1/16", which my math says is 1mm or less. You'll want to do this on both axis, as well as the Z, depending on how you will be using the machine, 3d carving vs ACM cutting.
 
adamfromayr

adamfromayr

New Member
Hi

Thats a great idea ! I will try everything you guys have mentioned and update some pics etc soon

Its a Belt system im using Mach3 with Aspire 9.5
 
adamfromayr

adamfromayr

New Member
WHOOPEE So Happy

Super happy, I tuned it in again using "Set Steps per Unit" in Mach3

A very sm
DSC06430.JPG
DSC06429.JPG
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DSC06426.JPG
all tweak and double-checked all the Nema Couplers were 100% tight

So now I've made the perfect circles

The square although its spot on size wise has one dodgy corner? also all bevelled edges but size wise its 100%

I think the square is something to do with how its saved in Aspire?

Maybe?
 
adamfromayr

adamfromayr

New Member
WHOOPEE So Happy

Super happy, I tuned it in again using "Set Steps per Unit" in Mach3

A very sm View attachment 169061 View attachment 169062 View attachment 169063 View attachment 169064 View attachment 169065 all tweak and double-checked all the Nema Couplers were 100% tight

So now I've made the perfect circles

The square although its spot on size wise has one dodgy corner? also all bevelled edges but size wise its 100%

I think the square is something to do with how its saved in Aspire?

Maybe?
 
adamfromayr

adamfromayr

New Member
More pics of the dodgy square

Circle View attachment 169066 View attachment 169067 View attachment 169068 View attachment 169069 i think is perfect thoughCircle View attachment 169066 View attachment 169067 View attachment 169068 [ATTA
Aaron Hunter said:
Your dodgy square looks to be the result of a lead in cut.
Click to expand...
Aaron Hunter said:
Your dodgy square looks to be the result of a lead in cut.
Click to expand...
ive not familiar with this saying what does it mean?

CH=full]169069[/ATTACH] i think is perfect though
 
N

netsol

Active Member
dodgy corner?
tramming isn't perfect?

adamfromayr said:
WHOOPEE So Happy

Super happy, I tuned it in again using "Set Steps per Unit" in Mach3

A very sm View attachment 169061 View attachment 169062 View attachment 169063 View attachment 169064 View attachment 169065 all tweak and double-checked all the Nema Couplers were 100% tight

So now I've made the perfect circles

The square although its spot on size wise has one dodgy corner? also all bevelled edges but size wise its 100%

I think the square is something to do with how its saved in Aspire?

Maybe?
Click to expand...
 
adamfromayr

adamfromayr

New Member
Im going to watch some videos on tramming but is that really the reason for the corner in one being so off?

I thought it was maybe the saving in post proccessor
 
JBurton

JBurton

Signtologist
Upload the file you used for the square. You'll have to rename it .txt or .pdf to get it to upload here.
 
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