AR8 Accuracy of Cutting

[Barry K]

I have had an AR8  2x4 machine for approx 2 years and love it but something has always puzzled me . Maybe someone can advise me 

When I go to cut a pocket or groove to fit another piece into I measure the piece I would like to insert  with my micromater  and use the data to program the size I want the pocket or groove to be cut   and it never works out accurately 

Example  I wanted to cut a groove in a piece of hardwood .735 In wide by .375 In deep  when I programmed these dimensions to a pocket cut with a 1/4 in end mill  groove was too small . I played around with it and had to cut the slot .76 in Wide by .04 deep for the slot to be the right size  The same thing happens when I cut holes for dowels etc always too small if I use measured data for cutting input 

Can someone tell me why that is ?  Thank you in advance for your help 

[kokopelli2020]

Could it be the postprocessor is in inches vs mm?

[Barry K]

Im using Vetric Aspire software and input is in inches as is the measurements . How could the post processor mess things up . How could I check that ?

[Barry K]

If this helps I have attached the pocket file that I needed to cut to achieve a pocket groove .735 In Wide by .375 in deep  You can see this file is using different dimensions than listed to achieve the required size of grooveTest pocket.crv3d (27 KB)

[toddd]

Dec 11, 2022 13:03:33 GMT -5 Barry K said:

If this helps I have attached the pocket file that I needed to cut to achieve a pocket groove .735 In Wide by .375 in deep  You can see this file is using different dimensions than listed to achieve the required size of grooveView Attachment

Are you measuring your end mill also and entering the actual size vs advertised size, bits can be off new or after sharpening and in a pocket any discrepancy is doubled

[Bob]

In addition: Have you cut a test groove across and with the grain, then measured the groove? This will verify the actual cut width.
Cut depth. Is your touch puck calibrated properly? Is the collet clean? Have you tried touching off Z with the paper method?
Also: Did you measure your dowel diameter? It's seldom what is expected...usually bigger.
Bob

[Barry K]

Really good comments . I have not mic'd my actual  tool but did mic the T-Trac. I am installing  so after cutting it either fits or doesn't .  It seem however if I Mic a dowel and then try to cut a pocket to fit it they are always to small 

[djl]

For the dowel circles you may want to adjust your feeds and speeds for circular tool paths as outlined in the following link.  
circular tool paths
Also try a finishing pass (or two) cutting conventionally.
Doug

[Bob]

In your tool database, have you checked the specifications for the bit you're using? Is the proper diameter entered?

[Barry K]

Bob
I have checked my tool database and I believe it may be part of the problem . When I upgraded to Aspire 11 I believe my tool database has changed . I use Amana bits almost exclusively and cut a lot of maple and pine The 1/4 Amana down cut mill actually was .229 rather than .250 and my 1/2 mill is closer at .495 rather than .5 which might be why my accuracy was off in some of my cuts. It looks like I need to rebuild my tool data base. Does Axiom publish a general tool data base that I could use as a starting point. I know Amana has one but it is more for industrial machines and I am using the AR8 Pro

[grossmsj]

I don't believe Axiom supports a tool database. I use the Amana tool database. I haven't been aware of accuracy problems from the Amana bits, but it could be lurking there and I just haven't noticed.
I may start buying bits from Bits & Bits, and they have a tool library for Vectric. bitsbits.com/tool-file-library/

[jgarciaa]

Dec 11, 2022 12:37:40 GMT -5 Barry K said:

I have had an AR8  2x4 machine for approx 2 years and love it but something has always puzzled me . Maybe someone can advise me 

When I go to cut a pocket or groove to fit another piece into I measure the piece I would like to insert  with my micromater  and use the data to program the size I want the pocket or groove to be cut   and it never works out accurately 

Example  I wanted to cut a groove in a piece of hardwood .735 In wide by .375 In deep  when I programmed these dimensions to a pocket cut with a 1/4 in end mill  groove was too small . I played around with it and had to cut the slot .76 in Wide by .04 deep for the slot to be the right size  The same thing happens when I cut holes for dowels etc always too small if I use measured data for cutting input 

Can someone tell me why that is ?  Thank you in advance for your help 

It seems like you're not factoring in the diameter of your cutting tool when programming your CNC machine. You need to compensate for this to ensure accurate cuts. Enable tool diameter compensation in your CNC programming to align measured dimensions with actual cut dimensions. Also, ensure your machine is properly calibrated for accuracy. monportlaser.com/collections/co2-laser-engravers/products/monport-40w-lightburn-ready-12-x-8-co2-laser-engraver-cutter-with-fda-approval?sca_ref=5031521.ka374VZjm3