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Re: importing coordinate list
« Reply #30 on: September 24, 2011, 12:23:53 PM »
What your asking is a little beyond the basic CNC (;-) .  What points you are gathereing will create lines not arcs on curves.  You would better off using the COPYCAT function and use a probe tip profile the same as your wheel diameter. This will auto comp the profile back to the wheel diameter . You would use the COPYCAT to create arcs and lines in G CODE  not just a series of points.

I thought that skates were just ground on specifc contours (;-)

(;-) TP


Yes they are ground on a specific contour at the factor originally but done
mostly by hand.  The sharpening process is done by hand which gradually destroys
the proper shape.

I can't find Copycat.  What you describe is just what i need with arcs being created.  Is there
any docs on Copycat and do you mean using G31?

Thanks
Keith

Offline BR549

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Re: importing coordinate list
« Reply #31 on: September 24, 2011, 12:56:07 PM »
Keith your encoder will work fine BUT you need to create a contactpoint that touches the blade that is the same radius as the wheel. You really don't want to get into the math to do a wheel comp on a curve with a linear infeed axis it will make your brain hurt. That is a CAM grinding problem as well.

I'll round up the info on the copycat for you.

SO would you not want to restore the factory contours or grind in a CUSTOM contour  OR are you just trying to collect contour data??

(;-) TP
Re: importing coordinate list
« Reply #32 on: September 24, 2011, 01:10:03 PM »
TP, i found Copycat and the documentation.  I will begin to study it but maybe the best idea
is to load some kind of probe in place of the grinding wheel that is the same diameter and
do the probing with Copycat like you suggest.  I am not sure how that probe would be
designed.  Is there anything like that available?

Yes we want factory specs on the shape but from measuring blades have discovered
that the factory does not put out consistently shaped blades.  I hope to create an
environment to describe the blade and indicate graphically or numerically how it differs
from the ideal then correct gradually to the original design or to a custom shape. 
Naturally I need to be able to leave the shape constant if desired and not introduce
changes over time by mistake...

Offline BR549

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Re: importing coordinate list
« Reply #33 on: September 24, 2011, 01:41:38 PM »
NOW you are talking CNC(;-)  It can replicate the exact shape over and over again.

There is also a free plugin called Jcode on the plugins page that may be of interest.

ALSO I had an idea standing here loading the pen plotter and watchin it FIND the paper.

Useing the encoder approach you could move back and forth across the blade to locate the key points ,staight lines(inside a deadband value say +/- .005 )
Then locate the startpoint  and end point of the arc. Then calculate the MIDPOINT of the arc (startpoint - endpoint /2) then use the startpoint ,endpoint, midpoint offset to create the arc.  

You then can then use these values for the program to write a Gcode GRINDING program based on those values. IF you used the contact tip of the encoder that was the radius of the wheel then NO further comp needed. You would then have a very GOOD (corrected for bad grinding ) grind profile. that represents what the PROFILE should have been. AND you can replicate it exactly over and over again (save the Gcode file(;-) ).

AND this should be doable inside of MACH3 and CB

What do you think, (;-) TP
« Last Edit: September 24, 2011, 01:43:22 PM by BR549 »
Re: importing coordinate list
« Reply #34 on: September 24, 2011, 11:21:17 PM »
TP,

By George, I think you've got it!  It seems so obvious now. No Dxf convertor,
and no Cad/Cam software needed. Excellent!javascript:void(0);

If we know what the blade's arcs should be we can probe in the 3 critical spots for each
sub-curve then calculate an array of coordinates for the ideal blade  if
I can identify staight lines inside a deadband value say +/- .005.  See comment below. 

Then do a comparison between the theoretical array and the actual blade probed array using
a sharp tipped encoder probe. Then come up with descriptive stats for the
variance to allow us to tell how good or bad the blade is. 

We could start correcting the discrepancies slowly over future sharpenings or just keep
current shape. 

We can use arcs and generate a tool path then mount the pseudo-grinding
wheel probe tip and run the blade collecting
the points for a compensated toolpath!  I could make several probe tips in
different size ranges to match smaller wheel diameters to account for wheel wear because
eventually the wheel will get much smaller.

The biggest problem we have is the difficult of finding the deadbands.  I ordered
an encoder that is +/- .0005".  The one I have is +/- .001"  Plus the current probe tip
is not pointed so the raw values are off because the shoulder of the probe tip hits the
blade

I will get going on the Jcode and Copycat learning curve.  Thanks!  It is making more sense
to talk it through.  I really appreciate the careful thought!

Offline BR549

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Re: importing coordinate list
« Reply #35 on: September 24, 2011, 11:31:59 PM »
NOW you got your thinking cap on.(;-)

How about instead of using a standard grinder wheel you could use a rigid carburumdiumdumbdumb (;-) wheel that never wears down(to a point) it is a solid wheel that is COATED with that funny sounding stuff. It works well on certain grinding as the wheel never looses dimension over its useful life.
Or use a belt grinder system, just replace the belt when needed.

Never have to worry about wheel diameter as it will always be the same AND the Zero point will ALWAYS be the same.

AT least I will know WHERE to send my ICE skates when Florida freezes over and I need to get around.

Just a thought, (;-) TP
Re: importing coordinate list
« Reply #36 on: September 24, 2011, 11:45:41 PM »
I wish I could use a permanent wheel but the blades have a hollow ground that varies with the blade type.
3/8, 7/16, 1/2, 9/16  Have to shape the grinding wheel for each blade...

Keith
Re: importing coordinate list
« Reply #37 on: September 25, 2011, 12:20:17 AM »
How to get Copycat and Jcode?  I have installed Jcode to plugins directory but only
video plugin is showing on drop down in Mach.  Can't find Copycat in wizards.

Thanks
Keith

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Re: importing coordinate list
« Reply #38 on: September 25, 2011, 12:26:29 AM »
the Jcode plugin has to be turned on in Config/Pluginconfig then restart mach3 and you should see in the top bar the plugin tab.  I will have to look for copycat for you. Be right back

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Re: importing coordinate list
« Reply #39 on: September 25, 2011, 12:28:54 AM »