How to cut a dished shape with nothing around it.

[iacomputerguy]

Hi,
I’m new to the whole CNC thing, so please forgive me if this is totally novice. I’ve watched a few tutorials and did a bit of searching, but did not find what I was looking for.

I’m wanting to cut a dished shape out of the top of a board (like the inside of a spoon, see attached file). I created the shape I want and saved it as a 3DS file. I then imported it into Cut 3D. The tool path created attempts to cut out the shape around the dish cut which I do not want. I am cutting this shape into an existing piece so all I want to do is clamp it down, set my xyz above the place to cut and then cut only the dish. If I used the tool path created, it would dig in to the object around the outside of the dish shape.

I tried making a large flat surface around the dished shape and setting my Z0 slightly above the object. This helped, but the router would be goes back and forth like crazy over areas not cutting.

Any suggestions would be appreciated. Thanks!

[tmerrill]

Try this:

Just model the dish shape and bring that into Cut3D. Be sure it is positioned at the top of the material block (Set "Depth of Model below Surface" in Step 2 to 0.0).

This is normally the key - in Step 2 be sure the Symmetrical box is checked and a very small value in the input box as shown in the first picture below. Do not enter 0.0 here, but a small number as shown.

Set up your toolpaths and both the roughing and finish should stay within the dish. The second picture shows the finish toolpath and it is only over the dish shape.

My example Cut3D file and .stl dish model also attached should it help. The dish model was done it Aspire but that should not make a difference.

Tim

[iacomputerguy]

Thanks a lot tmerrill!

[steina81]

I think this answers my question. I guess the small value needs to be smaller than the cutter. At that point the tool will not drop into the perimeter.

[adze_cnc]

I guess the small value needs to be smaller than the cutter. At that point the tool will not drop into the perimeter.

Remember that the larger the value the more the finish cutter (probably a ball-end bit) will "roll over the rim" hence the use of 1/10,000"

Steven

[JHSheley]

tmerrill,

The solution that you posted might be able to help me with a problem that I have. If you have time, will you please comment on the following problem?

I have 7 fractions (images/reliefs) of an original image/relief. For now I will name them A,B,C,D,E,F, and G. Theoretically, I can execute each of the fractions in any order and the original relief is formed.

In practice all of the images have the zero plane included. The effect of this zero plane is that the end mill will remove material from the portions of the block that I want dedicated to the remaining fractions. So if I execute “A”, then A is made, but all of the material above the zero plane is removed and is no material remains for fractions B,C,D,E,F, and G. (GRRRR!)

The desired effect:
When I run “A”. I only want material directly above (z-axis) removed for “A”.
When I run “B”. I only want material directly above (z-axis) removed for “B”.
.
.
.
.
When I run “G”. I only want material directly above (z-axis) removed for “G”.

After "G" has been executed, the original relief is visible.

There is a 2megabyte limit on this web page, so I can not post the miscreant files.

[Adrian]

Tim (tmerril) hasn't been here for over a year now but hopefully someone else will be able to help.

Have you tried zipping the file or putting it on a service like DropBox and linking it to here?