Cutting board blood route - alignment issues

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termite07
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Cutting board blood route - alignment issues

Post by termite07 »

I have been asked to use my CNC to create blood routes on a cutting board for a friend. Not wanting to mess up his piece, I cut some boards the same size as his to practice on. I am struggling with the correct alignment between the software and the CNC. As you can see with both pictures, the cut is out of center (even though I have measured this multiple times) with the edges of the board. I am probably missing something basic, but I can't figure it out. I have attached pictures and the CRV file. Any help, suggestions or improvements would be welcome.
Attachments
Board 1.jpg
Board 2.jpg
Cutting Board with Blood Rail.crv
(26.5 KiB) Downloaded 73 times

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Aussie
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Re: Cutting board blood route - alignment issues

Post by Aussie »

My thoughts are that your material is not square to XY.
For a test I would use an oversize piece of material. do a full depth profile cut around the material to square it up, then measure the center point of the material, set X0 Y0 and cut your groove.
Ron
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Charlie_l
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Re: Cutting board blood route - alignment issues

Post by Charlie_l »

Looked at the file. Zero must not be set at center, that’s probably what is driving you crazy. If you put the machine at x/y zero and manually move to the edges, do the values make sense?

Can you compare machine locations to the gcode/ text file that the machine is using?
Charlie
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RalphPitz
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Re: Cutting board blood route - alignment issues

Post by RalphPitz »

Not sure what type of bit you are using in setting up X0 Y0 , but try a 60 deg or better yet something like a 22 deg V bit to accurately center the router on the center point drawn on your board and then change bits to your .5 " core bit.

Daniel S
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Re: Cutting board blood route - alignment issues

Post by Daniel S »

I had similar results with my HD4 Shark and never did solve the issue. When trying to leave a boarder on a carved file I could not get the boarder to be equal on all 4 sides. I would measure the square or rectangle for being square and it was always off to some degree. This past spring I decided to purchase all metal CNC machine with rail drive system and welded frame and it solved those issues for me. Now I have very close tolerances, and when I measure diagonally it has equal measurements. I not sure what is causing this to happen, when watching the X drive rod on my HD4 it appeared to me to wobble. I sent video to manufacturer they said it was optical illusion, so I moved on still not sure if that was the problem in my case.
Dan

cncfan
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Re: Cutting board blood route - alignment issues

Post by cncfan »

Been away from cnc cutting for a long time, just getting my machine back in running order. So I am not sure this is what you need but have you tried the "Drawing menu" function? It at the bottom of the layout menu.

JeffZ
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Re: Cutting board blood route - alignment issues

Post by JeffZ »

One way around this is to make the cutting board slightly oversized and have the cnc cut the profile too. This would only work if you didn't need the blood ditch on both sides of course.
If you did need it on both sides you can make a fixture out of some scrap to mount it on in the machine, and make a shallow pocket in the fixture first so you know exactly where the machine thinks that spot it. I would just use a piece of scrap plywood or whatever was lying around.

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adze_cnc
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Re: Cutting board blood route - alignment issues

Post by adze_cnc »

termite07 wrote:
Mon Jan 11, 2021 12:37 am
I have been asked to use my CNC to create blood routes on a cutting board for a friend. Not wanting to mess up his piece...
This precludes modelling and using an oversized piece of material as it is for an existing sized piece.

termite07: I'll post how I would approach this (and have in the past) in a bit.

Steven

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adze_cnc
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Re: Cutting board blood route - alignment issues

Post by adze_cnc »

termite07:

In the following I am presuming that the CRV file you posted represents that precise size for the existing cutting board. Although, looking at your test pictures above they don't look to be the same size as the file.

Rather than trying to do two tricky things:
  • align the XY datum to the center of the material
  • align the material to the XY axes of your machine
I suggest cutting a locator jig at a known place. That way the edges of the jig can represent preciesly the X and Y travel of your gantry. Work from the known to the unknown.

See attached locator jig file ("cutting board locator.crv").

The XY datum for the actual cutting board file will now be at the lower left and not in the center (I have changed that in the attached "Cutting Board with Blood Rail (XY datum lower left).crv" file).

For the jig material use one of your test pieces of plywood picutred above.
  • Attach the jig material to your machine bed (align it a close as possible to square but don't obsess about it). Note: avoid attachment points where the cutting path will go.
  • Using a pencil mark a point 5 inches from the right edge and 5 inches from the top edge.
  • Set your XY home position to that point on your machine.
  • Cut the locator jig file.
  • Remove the offcut and replace with the cutting board---butting the left and bottom edges against the leftover jig.
  • Apply your hold-down method to keep the board from moving.
  • Cut the blood gulley file---the one with the XY datum at the lower left!
Things you will need to change in the locator jig:
  • material thickness (I just used the 3/4" from your cutting board blood gulley file).
  • I set a document variable called OC to 0. This is an overcut amount as some people like to cut an extra few thousandths of an inch into their spoilboard (Edit > Document Variables). If you're one of those people you can set that value to however much you want or leave it at zero.
  • You'll need to change the tools used for the two toolpaths. I just arbitrarily chose a 1/4" bit that I've set in my tool database for plywood. I have a toolchanger so the bit will use my tool number. Just be sure to recalculate your toolpaths!
I hope this makes sense.

Steve
Attachments
cutting board locator.crv
VCarve v9.519
(29.5 KiB) Downloaded 52 times
Cutting Board with Blood Rail (XY datum lower left).crv
VCarve v9.519
(27.5 KiB) Downloaded 63 times

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