Home settings varying

I have a small 4 sided project which is 41.5 x 190 mm in size. It is as perfectly square as possible and the home end is at right angles to all sides.
The work piece is held in a very secure machined jig and each side is machined in turn and the bottom left corner should be exactly the same coordinates.
First job is too rough cut with a 6.35mm end mill and then turned over and cut the back piece the same - I shouldn’t need to check the Z here but did do it
As it machines the back side it is noticeable that the figure machined is off one way so stop the job
When checked the X and Y home points are up to 0.5 mm off where they should not be.
Wondering if anyone has struck this before and if so anything to fix it.
Am using Vcarve Pro 11.5 ver
Any suggestions welcome Kerry

Hey Kerry,

you may be interested in this and this

Hey Kerry,

when you say “when checked”, you mean probed?

Do you probe XYZ after turning the piece over?

Do you home the machine once at powerup, or more often?

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Thanks for the replies and yes original machining was checked with probe but only the Z axis checked after turning over as the job was the same as a two sided one with locating spots for the reverse side but instead of pins it was a jig with extremely close tolerances to locate it so should not need X and Y probed.
Also machine homed always at startup

Hey Kerry,

do you use a g-code file that is for one side, and run the same file again after you turned the workpiece? Or do you have a file with the turning in it?

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Basically the same file but it is the other side of the 3D model but still should be the same coordinates etc .
Just thinking about the suggestions about homing causing problem but am unable to see how it could - I home the machine at startup and the axis’s never touch anywhere near the homing points except maybe for the Z axis so unable tosee how they could effect the difference in coordinates in any way

you run a file once, then you turn the piece over, and then you run the file again? Is this correct?

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Hey Kerry,

you run a file once, then you turn the piece over, and then you run the/a file again? Is this correct?

If so, after the program was run the first time, where is the router then?

Do you have to return it manually before running the other side?

If so, how do you do this?

The model is a four sided chess piece with different sides on each side - File is basically the same except the model changes as per side.
Each side starts at the same datum point - bottom left corner - and runs that side and then the next.
As I said the block of wood is exactly the same size and the bottom edge which is used as the datum corner is at 90 degrees as did want to rule out any variation there.
Did check that the Y axis is perfectly set up by running the bit along the length of the jig and almost exactly coordinates.
The jig is just large enough to allow the block of wood to fit with slight force and for two sides - ie front and back should be exactly the same as if using dowels to align the second side,
Have checked the software but will do so again but has got me beat haha

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Hey Kerry,

you did not answer my question:

After the first file was run, where is the router then?

Do you have to return it manually before running the next file?

If so, how do you do this?

Sorry once the file is run the router automatically returns to the datum point which is the bottom left corner and the next file is loaded after the work is tuned over to machine the back face - usually the datum is relocated but it shouldn’t need to be as in the case of a double sided job as the bottom left corner is in exactly the same position as for the first side - have done it both ways with the same result

I do 2 sided 3d cuts and i use metal pins (on both ends of material) and work off a predefined center point.

Thanks Vern but do think my trouble is worse then that in locating pins etc.

First figure shows how the figure is roughly 3mm out to the right side more then the left - thought has to be the X Y and Z settings from my probe are wrong - did check them when new and they were out slightly and fixed them - checked the probe again and the X setting was approx 0.5 mm smaller then should be so changed them in settings again and saved them and rebooted the machine, rehomed it and did the second figure.
This was a bit better but was still 2mm to the right too much.
Checked the starting datum point by eye and allowing for eye error the X< Y and Z were almost exactly at 0.00 so the variation is occurring after starting to run the file.

Would appreciate any ideas as got me beat Kerry

Hey Kerry,

generally I find it difficult to understand what you exactly mean.

And at the moment, I have not understood your workflow, since you don’t express it in a way that I can understand it. I think I could help you if I would better understand what you are trying to describe. When I ask you something, I am not sure if you answered yes, or no. The way you express yourself made me give up earlier, but that you still did not resolve your issue bothers me, especially because I believe there must be a simple explanation and a solution.

What do you mean witch this? Is it? Is it not? By what? By you?

Sorry for the confusion so let me lay it out as it happens
1 machine is homed on startup
2 datum point on wood is probed and set
3 file is run and as from the picture you can see it is 3mm out to the right more then the left side
4 at this point bit would be changed to a tapered ballnose for finishing and z zeroed on top of wood.
5 material would be flipped over and datum rescanned and the file for the back side run
6 rezeroed for tapered ballnose and finished
7 turned to one side datum rescanned and finished and then th final side finished

Of course haven’t been able to get past the front roughing and back roughing stage as carving is so far out.

I have checked the datum point after running th file by eye and very close to zero so it is still accurate .

Also used the same setup and size wood to drill a series of holes following the setup stages above and the holes are exactly where they should be and not to the right or left

Can only assume that something in the code with the stl model is causing the change to occur for some reason.

Have refferred it to Vectric so maybe they might be able to determine what is happening.

Thanks for all your help and maybe did call it the wrong thing when I said Home settings vary and should have said Settings just varying

Thanks Kerry
PS if they can help I will let you know the answer

Hey Kerry,

thanks for the explanations and also for the pictures!

Would you mind showing the jig you use and how it is in place in your machine’s workarea?

Not sure if you have found a solution to this yet but…

Almost all work I do on my 1F is two sided. These are the steps that best work for me:

  1. Mark a center point of cut on board and zero 1/4 drill bit on center point.
  2. Run a simple gcode file to drill dowel holes on both ends of board blank.
  3. Run a gcode that will move you to a predefined center point on waste board and zero machine.
  4. Drill dowel holes in waste board to match those in board blank.
  5. Now dowels (I use 1/4 x 1-1/4 steel dowels) can be set in waste board and wood blank.
  6. Now you should be able to use that predefined center point to work off of to machine both sides of wood blank.

Working off lower left will rarely work for two sided cuts.

If you have further questions please feel free to ask.

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Sorry haven’t got a picture as not near the machine but the jig was machined out using the demensions of the work piece and is screwed to the waste board.
It is sitting in a recess of 12mm deep and is a knock in fit so very secure and unmoveable.
Originally it was used with 3D tabs top and bottom and still didn’t machine accurately so was trying the way it is shown in Carveco Maker on Youtube.

Just got an answer from Vectric and they put it down to movement in the router but find that very hard to believe.
They looked at the Gcode in the file and say -
This is ruling out both the toolpath strategy and the post processor as the cause of your mis-alignment
here I’m afraid and pointing to an external factor, such as material movement or machine tool calibration / setup issues.

Hi Vern thanks for the suggestion and will try it at the weekend and see how I go - just something funny seems to be happening but hopefully work it out Kerry