Cutting Measurement

[James RS]

Ok I did a project where I set a rectangle to cut at .25" deep and 7" long and .777" wide.
The depth of .25 is fine, but the 7" added a 1/16" and the .777" measured out at .866" It's not a huge deal for this project, but I'm wondering what happened.

Thanks,
Jim

[Digitalwoodshop]

Are you talking Physically measured.... After the cut holding the wood in hand?

Remember ZERO in the center of the bit... What is 1/2 of 1/8?.... The bigger the bit from ZERO the smaller or bigger the cut.

Did you FLIP the cut?

Both effect what you get....

AL

[AskBud]

It would help to see the MPC.
If you assigned a bit rather than doing a Carve Region, you must consider the thickness of the bit and the "Inset" in many situations. In a Carve region you must watch the "Feather" as well.
AskBud

[James RS]

Hi Bud, Hi Al Happy 4th,
Al I physically measured the board after the cut with a digital caliper,Bud here's the file.


Thanks,
Jim

[AskBud]

Sorry, I can not open the MPC as I have not converted to the higher version as yet. I'm still on 1.132.
Someone will need to look at this file and determine your solution.
AskBud

[blantz]

Jim,

You have the rectangle being cut out with the tapered 1/16 cutting bit. The walls of the rectangle are tapered and I would bet that the bottom of the recess is closer to the correct dimensions.

[James RS]

Jim,

You have the rectangle being cut out with the tapered 1/16 cutting bit. The walls of the rectangle are tapered and I would bet that the bottom of the recess is closer to the correct dimensions.

I should of used the 1/8" straight cutter, I can't check the bottom of the rectangle as I glued the tray in already. I'm going to do some playing around tomorrow

[James RS]

I was just in designer and wondered this, If I make a 2" square and select the 1/8" cutting bit should I split the difference so as to maintain the 2" outside dimension?
After doing this I made another square inside where the 1/8" left off and selected carve region
at the same depth of .25".


Thanks,
Jim

[blantz]

Jim,
I believe the center of the tool follows the tool path, so the dimensions will have to be smaller by 1/8” for the 1/8” cutting bit.

[James RS]

Jim,
I believe the center of the tool follows the tool path, so the dimensions will have to be smaller by 1/8” for the 1/8” cutting bit.


That's what I was thinking, but if the center of the tool follows the line wouldn't it be half of the tool on the outside of the line so it would be a 1/16" over. I'm going to go give it a shot
I'll post my result

Thanks,
Jim

[ChrisAlb]

Remember like Al just said, the "center" of the bit follows the vector path (by default).

You can either adjust the size of the box, circle, line whatever by half the diameter of the bit, or you can use the "Inset" dimension box to offset the bit itself up to an 1/8 (.125) either way.

A positive number will offset the bit to the "inside" of the line.
A negative number will offset the bit to the "outside" of the line.

So for example (picture), here are three 2" squares with the 1/8" straight bit applied to the paths.

The first is the bit cutting down the center of the line (default)

The second is the bit offset (positive) half it's diameter (.065) and it cuts to the "inside" of the line.

The third is the bit offset (negative) half it's diameter (-.065) and cuts to the "outside" of the line.

If you were using a 1/4" bit, half of it would be .125 which is the max we can go with the "inset" as of now. If you need any more than an 1/8" offset like if you were using a 3/8 or larger bit (on anything but an automatic cut out) , then you'll have to start resizing the shape.

When using the automatic "cutpath" (for cutting the piece out) you can simply "flip the cut" to the inside or outside of the line.

Hope that helps with sizing.

[James RS]

Thanks,
I did find the offset setting and did this for my little test made 2 squares at 2"x 2" using the 1/8" cutting bit with a depth of 1/4" with no offset. The second box exactly the same except I used the offset of 1/16", I ran this twice and got different measurements on both tests.

Test 1: (No Inset X axis 2.076" / Y Axis 2.046") (Inset .062" X Axis 1.99"/ Y Axis 1.959")

Test 2: (No Inset X Axis 2.137" / Y Axis 2.118") (Inset .062" X Axis 2.042"/ Y Axis 2.020")

Jim

[ChrisAlb]

Thanks,
I did find the offset setting and did this for my little test made 2 squares at 2"x 2" using the 1/8" cutting bit with a depth of 1/4" with no offset. The second box exactly the same except I used the offset of 1/16", I ran this twice and got different measurements on both tests.


Jim

Everything mechanically on the CW is correct...i.e, head pressure/alignment, belts, clean and smooth moving Y...etc...?

Have you calibrated it lately?

[James RS]

Yes, clean after every use I have a Jet dust collector hooked up with a bottom exhaust feed
mounted on a table.Now I just did a 3rd test, using the measurements from the previous 2 and adjusting accordingly. And I added a 3rd square.


Test 3 Took the differences from the measurements on A & B of the previous test


Block A No Inset (Y Axis 2.0-.118=1.882 / X Axis 2.0 -.137 =1.863) Result Y-1.998 X-1.992

Block B Inset.062 (Y Axis 2.0-.020=1.98 / X Axis 2.0-.042=1.958) Result Y-2.005 X-2.008

Block C No Inset (Y & X 2.0-.125=1.875) Result Y-1.996 X-2.013

Kinda interesting
Jim


Edit Never calibrated as I don't have the 3/8 bit

[ChrisAlb]

Interesting. I see you have 1.15 as I can't open your MPC on my system. I haven't done a size testing in the new version but all the tests I did in 1.134 came out right on the money.

I'm not saying this is it but I recommend getting the 3/8 so you can do the calibration every once in a while.

[James RS]

lol I knew you were going to say that, oh well for now I can adjust the A block result until I can get the bit and do a calibration.

[ChrisAlb]

lol I knew you were going to say that, oh well for now I can adjust the A block result until I can get the bit and do a calibration.


Ok, I have the new version on my laptop. Now I take it you're measuring the block left "inside" the cut??

Or are you measuring the outside cut?

[James RS]

Ok, I have the new version on my laptop. Now I take it you're measuring the block left "inside" the cut??

Or are you measuring the outside cut?

Chris,
Yes I measured the outside cut with a digital caliper

[ChrisAlb]

Chris,
Yes I measured the outside cut with a digital caliper

This is one of a few tests I usually run. It tests inside and outside square and accuracy for the X and Y directions.

I can't get to my machine but if you have the time and wood, try running this one.

[James RS]

Chris I'm sorry I want to cut out the whole square, but I noticed when I did my last project that it was off slightly, So I just used the boxes as a test with selecting the 1/8" bit to check.