need some help.

[needleworks]

To get back to your original request, I drew a small oval given the sizes you specified

Any small shape would do a oval around 40mmx10mm 3mm deep would be good

The dxf was then put into Cambam and this is the resulting code :-

0,0 would be set right in the centre of the oval, and Z0 would be the top of your part, it is set to go down at .5 depth of cut, so for a total depth of 3mm, should go around 6 times.
Give it a try and see if it works?

Oval.Part1 [Profile1].nc