Experiment Engraving Machine Dials

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awemawson:
So now the 'length of the wrap' is dictated by the lines and not the numbers - so did it work?

... well I've not cut metal to prove it, but if you look at this version of the G code you'll see that the A values are incrementing now by 3.6 degrees. 100 x 3.6 = 360 = one revolution which is what it should have been all along.

... as I've said before, it's a learning exercise - and I'm certainly learning things that I wouldn't previously have considered :med:

raynerd:
Cracking post Andrew, learnt a lot. I may invest in cambam and will be trying the carbide pointed engraver. I currently use a diamond but I see the carbide works well.

Chris

DavidA:
Andrew,

I was really surprised when I read your line stating that diamond doesn't conduct electricity.

So surprised I looked it up. And it seems..

...The electrical resistivity of most diamonds is on the order of 1011 to 1018 Ω·m...

That should read 10E10 to 10E18 Ohm per square Cm.

As diamond is carbon and carbon is used in conductors (Brushes etc) it was unexpected.

We learn something new every day.

Dave.

awemawson:
:bugeye: ARGH I Have a PROBLEM :bugeye:

I've been chasing tiny errors in the engraving line spacing for what seems ages - convinced I got the wrapping program set wrong, or something in my original drawing like too many or too few lines, so in desperation I decided to to a manual test:

a/ I skimmed off one of the 'doughnuts' to 48.5 mm o/d and mounted it up on the 4th axis

b/ I sent the 4th axis to -10 degrees, then to 0 degrees to eliminate any back lash

c/ I then manually drove the engraver into contact and scribed a line then raised it again.

d/ I then drove the 4th axis to 360 degrees then manually drove the engraver into contact and scribed a line then raised it again.

e/ I then drove the 4th axis to 720 degrees then manually drove the engraver into contact and scribed a line then raised it again.

f/ I then drove the 4th axis to 1080 degrees then manually drove the engraver into contact and scribed a line then raised it again.

Now all those lines that I scribed SHOULD fall on the same place and over lay each other BUT THEY DON'T :bang:

As you can see there is an increasing cumulative error. To try and quantify it the gap between lines is of the order of 0.833 mm on a circumference of 152.367 (Pi x 48.5) so of the order of 0.833 x 100 / 152.367 or 1/2 % which is far too large to tolerate !!!

Back lash has been eliminated by travelling in the same direction all the time so what the heck could cause that :scratch: :scratch: :scratch:

BillTodd:
Your 4th axis settings must be wrong too many (or too few ) pulses/steps per rev. (has someone swapped encoders by any chance) . What make of 4th axis BTW?

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