Help me figure out why I can't flip my guitar and it stay straight - I am about to pull my hair out

[evanDXG2P]

I have run this three times where I have the fixtures included in the sketches, I get through the front, flip to back on the Y axis, have the Z flipped, etc. Doing all the right things, but the cuts are just about a half inch off. Please take a look at the file and help me figure out what I am doing wrong here. 

[laughingcreek · Accepted solution]

half inch which way?

did notice you're using the center of the program generated stock box for your origin.  it's not lined up on the centerline of the guitar, so there will be some shift b/c of that (magnified 2x because of the flip).  good idea to create the geometry for your origin yourself when ever flipping is involved.

[evanDXG2P]

But since I don’t have any additional stock beyond the edges wouldn’t the c enter of the stock box be the same as the center of the guitar?

[laughingcreek]

the centerline of your neck (which is what you based the center of your fixturing sketch on) isn't the center of the volume of the guitar body, ie the stock material.  your intending to flip it on the center line of the neck, but the origin you define isn't on the centerline of the neck, it's in the center of the stock.

it's only off in the x direction .766mm (it's off in the u direction some also), but that differance will be 2x since you flip it, so you will see a 1.5 mm difference between sides.  that's way less than the .5 inch your saying you have, so there may be something else happening also.

[evanDXG2P]

 

So I did an experiment with this. The two holes in the first picture are equidistant from the center of the fixture line like you mentioned. I used the center line of my blank to set zero thinking it was the middle of the stock. 

then I measured the distance from one hole to the center and the other hole to the center. One is 6.125” to center. The other is 5.75”. The difference between these is 0.375” which should theoretically be the difference it creates when flipping it over, right?

so I measured the amount of space between where the neck cut on the back and on the front (second picture). Calipers said 0.38”. I’m trying to make sense of this but that’s definitely not a coincidence. 

[evanDXG2P]

Are you sure that 0.766 isn’t inches because divide that by two and you get 0.38”

[laughingcreek]

I don't see a tool path for cutting the index pins.  how is that being done?

[evanDXG2P]

I removed it after I exported its gcode.

[laughingcreek]

unfortunate.

next-how are you locating blank on table for first cut?

when you zero x,y are you using the absolute values you zeroed at to cut the fixturing pinholes or doing something else?

[evanDXG2P]

I would run the dowel insert OP for the wasteboard, insert dowels, clamp a template to my blank, and drill holes for the wasteboard attachment using the template all the way through the blank. 

then I would attach that to the wasteboard. 

[evanDXG2P]

Also, all I did was extrude the fixture pieces, create a setup with program generated stock box, and then post process code

[laughingcreek]

would be a good idea to check that your template is right.

I would redo the tool paths for creating  fixturing holes and template.  and leave them in the model.

also, you said above-"I used the center line of my blank to set zero thinking it was the middle of the stock. "

this is an opportunity for errors.  x,y zero is set to what was used for the waste board when you drilled the index holes into it, not off the stock.

the CenterPoint of the generated stock box for the extruded fixturing sketch looks to be where you had intended it to be, meaning it's off from the CenterPoint of the generated stock from the guitar body.