Having issues with tracing to create pocket cutouts

[fritter63]

Ok, having a heckuva time getting this to work. I'm trying to create a "cutout" in a box bottom to precisely match a pair

of wine bottle openers. My POC is not doing so well. See attached pictures. I've taken a picture of the openers and loaded them into F360, then scaled them along a known dimension.

Then I used splines to create a tight outline of the shapes, and then offset the shape by .5 mm to give me some play in the cutout.

When I cut it on the CNC machine though, the cutouts aren't very accurate. Actually, ONE of them is, but the other isn't. There seems to be discrepency in the 3D recess after I have push pulled the sketch outline into the surface! 

Picture 1: Canvas with trace outlines. YOu can see that the offset outline leave plenty of space around the opener

Picture 2: 3D model showing that I have correctly selected the outer outline to extrude into the solid

Picture 3: A "bleed through" of the 3D shape, with the canvas visible. Note that the top of the outline does not appear to be the right offset curve, it is the tighter of the two, even the bottom seems to be fine. NOTE that the end of the corkscrew has plenty of room.

Picture 4: Picture of hte actual part after machining. Note that that tool barely fits, and that the end of the corkscrew is off by a good 4 mm. It is just to long for the cutout.

What is going on here? The differences are inconsisent and couldn't be chalked up to innacurracies in my machine (which I doin't believe there are).

[fritter63]

Here is the fourth picture since it wouldn't let attache more than 3 images....

[HughesTooling]

Can you export the f3d file and upload, can't help much without the file.

Mark

[michallach81 · Accepted solution]

I suspect that it's caused by lens distortion. To see difference try scan your corkscrew, and I do mean to make a scan in your printer/scanner device. There will be some distortion, but at least main body outline will fit.

[fritter63]

@michallach81

I considered that, but wouldn't lens distortion have made the outline larger not smaller?

[michallach81]

Not quite, it will distort image. Mainly, whatever is in focus will appear bigger, and what's no edges will be smaller. So, depend on how you've scale it it will be to thick in middle or too short on the ends.

[fritter63]

@michallach81

That was exactly it. I re-scanned and re-did the tracings and they came out perfect.