"V" bit over run to complete a square .

[myshop1044]

I notice just lately when I did a set of coasters there was a slight over run when the
"V" bit completed the sq. It was in the same place every time, bottom left corner when it tries to complete the square on each one.
I did a test at different depths (4 sq.s) , .093 and .031, same mpc. I notice the .031 did not appear to have the over run or it was not as noteiceable.
Attached are the PTN and 1 pic( out of focus) note the bottom right had corner in the pic where I placed an arrows.
Any help would be great as to why to look to fix this problem.
Myshop

[AskBud]

I notice just lately when I did a set of coasters there was a slight over run when the
"V" bit completed the sq. It was in the same place every time, bottom left corner when it tries to complete the square on each one.
I did a test at different depths (4 sq.s) , .093 and .031, same mpc. I notice the .031 did not appear to have the over run or it was not as noteiceable.
Attached are the PTN and 1 pic( out of focus) note the bottom right had corner in the pic where I placed an arrows.
Any help would be great as to why to look to fix this problem.
Myshop
Myshop,
I'm sorry, but I don't think this MPC is the one that applies to your carved photo.
Do you have another MPC, or know how the images got reversed?
AskBud44113

[myshop1044]

Bud, I just turned the board around when I took the picture, if you rotate the pic. 90 deg. to the right the biggest sq should
at the bottom left corner just as it would have come out the machine.

[Digitalwoodshop]

2 thoughts while not fully understanding the problem....

Did you use the bit selected? Designed in V90 use V90.... Designed in V90 use V60 get strange Text and line effects.

How many hours on the Y Gear Box bearings? 450?

AL

[AskBud]

Bud, I just turned the board around when I took the picture, if you rotate the pic. 90 deg. to the right the biggest sq should
at the bottom left corner just as it would have come out the machine.
OK, I had to turn the photo 180 degrees to get it to match the Designer. This places your deep spot on the upper corner of the Left side (on the design). Now, the question is where did the bit start, and did it travel clockwise or counter-clockwise? Is the deep spot at the beginning or end of the cut (known only by watching the process)? My first guess is that it's at the start, and you may have a dull bit. I know you are on some sort of a sled or extended board (as the design is too short to stay under the rollers).
AskBud

[AskBud]

I know, by the Design, that you are using 3/8" stock. However, I/we don't know what the material is. By your photo it appears that it may be Corian, is this a fact?

Since I have not played with Corian, I can not say for sure, but I thought that there were restrictions as to bit usage on Corian.
AskBud

[myshop1044]

The plot thickens, the material is 3/8 plywood for the test. The miss alinement is at the end of the sq. in a counter clockwise motion. I watched the whole process and each time it came around to the start point of the sq. and covered the first line for a short time, is when it seems to be missalined. When it started the first line it nevers goes as deep as it should until it comes back around and cleans up the the first 1/2" or so .
I used a 60 deg bit thru bit selection. I'm not sure how you tell the hours on the gear box. I drew all the sq.s and selected all of them and
selected the 60 deg option after.
yes it is in a sled.
I also thought the plywood might have been loose in the sled, but I had to press it down hard in the sled for a good tight fit.
I just replaced the x 1 and 2 gears because of a broken tooth on the x2, but first this happen 2 weeks ago, that why I tried the test today after the gear replacement.

[AskBud]

If it were me, I would keep the .031 depth and use a virgin V-bit. Assign the proper bit in Designer. If I have no trusted V-bit, I would consider something like a 3/8 Ball Nose, as what we want to know is "does the depth or the alignment change" or "was the problem due to a dull bit".

Once I/we know that time can be taken to narrow the problem.
First of which would be to substitute a (single) thicker and longer board. Thus I'm eliminating the sled after I have changed the bit in the step above.
AskBud

[myshop1044]

Thanks Bud, I have 2 new "V" bits comming next week, so I will put the test on hold untill then.
Thanks for the help.

[Digitalwoodshop]

2 more WAG's... Wild AL Guesses....

1. If you have 450 cut Motor Hours then you have 450 Gear Box hours.... About 450 is when the bearing go out and thin the shaft.... Do you have any clicking at the bit flag? That is a sign of worn bearings. If you replace the bearings before they fail and wear the shaft thin then you save from buying a gear too....

2. Run the same project but use the 1/16 carving bit.... Assign the V60 but use the 1/16 th carving bit. My thinking is that the spin of the bit could be walking the Y like it does when you use a hand router in the WRONG direction... It feeds and leads.....

Just another in a long series of WAG's for the shop of AL who....

AL

[liquidguitars]

This is a simple pattern no reason that it would not cut correctly. Check your sled for warps and bad joints that could make a uneven base. I use a drum sander to level the sled and I use brass screws to fasten the plywood to the sled to remove any chance of movement. Also your MPC layout is not the best for sled work I recommend including the overall dimensions of the sled.

[bergerud]

I have had the same problem before. My machine would also not carve in the center. I noticed the calibrate Y-offset had a strange (not default) value. I changed back to the default and carves were centered again. I cannot say for sure whether the non closing problem had the same cause but I do not have that problem anymore either. Have a look at the calibration menu.

[myshop1044]

Dull 60 deg. bit, go figure.
I tried a test with the carving bit first and had no deflection, second I tried the same project with a 60 deg and it still showed
a little deflection. I them tried it again with a 90 deg. and had no deflection, finally I got my new 60 deg. bits and did the same thing again with my sled and low an bewhole there was no deflection. I guess I finally wore out that bit.

I have 684 cut hrs on my machine, is there a PDF that showes the removal of the "Y" gear gear box for inspection and replacements of the bearings, I just want to inspect the gear box and maybe head off trouble down the road.

Thanks for all the help fellows

Myshop