two sided machining offset problem

[PlaneCrazy18]

I am doing my first two-sided machining job. The top and bottom are the same profile rounded over. When I use a round-over bit I have to offset the profile the radius of the round-over. If I offset both sides the same they do not meet in the middle in the simulation. I have to offset the top side by .4375 inches and the bottom .325 inches. A difference of .1125 inches. I am wondering first, why is this so and second, does this mean that I would have to do this for the machine as well or is this a problem just in the simulation? When I use an endmill this does not occur but there is no offset for the end mill. Any suggestions?

Thank you,
Steve

[garylmast]

The bottom side probably is not in the correct position. If you post a picture, it might be more helpful. Did you import the model or copy and paste the bottom part?

Gary

[Jim_in_PA]

Not relevant to your two sided issue, but if you use a point roundover tool, you can do your vector "on the line". I do this all the time and no offset is required. Depth, obviously, has to be calculated to avoid over cutting.

[martin54]

If you can post the file then it makes it a lot easier to help out, saves having to keep asking questions about how you have the project set up & what toolpaths you are using

[Rcnewcomb]

Can you upload your file (.CRV or .CRV3D) to the forum?

Here is a link describing how to upload your file. (How do I upload files or photos to the forum?)

If the file is too large to upload here you can use a file sharing site such as drive.google.com, onedrive.com, or dropbox.com. They all have free accounts available

• Upload the file to the file sharing site
• Make the link shareable
• Share the link to the file here

[adze_cnc]

PlaneCrazy18 (Steve): Try taking a look at the attached file and compare it with your project. Included is the profile used to create the round-over form tool.

Steven
 

[ohiolyons]

Nothing happens to the file?

edit

You have to select the vector and recalculate the toolpath

[PlaneCrazy18]

I have solved the problem. Instead of using the offset allowance I used an offset vector to the center of the bit and had it profile "on the vector". It works fine now. Thank you all for your input.

Steve

[adze_cnc]

While offsetting the vectors and profiling on the line can work. There are some (many) vectors that when offset have unexpected shapes and therefore the cuts can be different.

The two images show:

1. cutting outside the line with a tool offset
2. offsetting vectors and cutting on the line

Note the little chunk missing on the offset vectors cut. Admittedly this example was contrived to fail but there are many potential failures out there.
 

Outside the line using tool offset

 

Offset vectors on the line