Cutting outside a sketch with variable offsets

Here's the place for discussion related to CAM/CNC and the development of the Path module.
burgerking
Posts: 5
Joined: Wed Feb 19, 2020 9:47 pm

Cutting outside a sketch with variable offsets

Postby burgerking » Wed Feb 19, 2020 10:08 pm

Hi,

I would like to cut the outside edge of a sketch with different offsets. E.g. 1mm from the edge, followed by 2mm from the edge, etc.

I am using a laser mill (ultrafast, pulsed), and trying to cut pre-defined shapes into metal. The FreeCAD files are given to me with the shapes defined, and I need to cut them out of thick metal. The laser mill will not cut all the way through without some finite thickness to the cut. So I could create a border region, and use the "profile faces" option on that border region. That requires major modification to the drawings.

Ideally, the array option would allow adjusting the offset (or equivalently tool radius), rather than just allowing X, Y, Z offsets

Is there any way to achieve this using the Paths/CAM module currently?

I realize this is a fairly uncommon setup. Any help would be appreciated.

Thanks!
m0n5t3r
Posts: 105
Joined: Fri Feb 03, 2017 2:55 pm

Re: Cutting outside a sketch with variable offsets

Postby m0n5t3r » Thu Feb 20, 2020 7:26 am

I'm not aware of anything that would do this out of the box; you can probably use multiple single pass contour operations with manually set extra offset (positive for leaving material, negative for removing material), possibly automated with a bit of scripting.
RatonLaveur
Posts: 695
Joined: Wed Mar 27, 2019 10:45 am

Re: Cutting outside a sketch with variable offsets

Postby RatonLaveur » Thu Feb 20, 2020 7:41 am

If it really is variable offset within the same single contour, then I'm afraid the ideal is to retrace the contour with the offsets at the locations you want.
If it's generating several contours with different offset to optimize your taper/tolerances, then FC can do it by default or you can use your CNC's G41 command.
If it's only to optimize taper and tolerance, why not cut a few circles in a non-used area of your stock to figure out the right compensation?
chrisb
Posts: 24399
Joined: Tue Mar 17, 2015 9:14 am

Re: Cutting outside a sketch with variable offsets

Postby chrisb » Thu Feb 20, 2020 9:18 am

burgerking wrote:
Wed Feb 19, 2020 10:08 pm
I would like to cut the outside edge of a sketch with different offsets. E.g. 1mm from the edge, followed by 2mm from the edge, etc.
I would use for each distance one profile or contour operation with a tool of appropriate diameter, i.e. in your case 2mm and 4mm.
RatonLaveur
Posts: 695
Joined: Wed Mar 27, 2019 10:45 am

Re: Cutting outside a sketch with variable offsets

Postby RatonLaveur » Thu Feb 20, 2020 9:51 am

This is actually interesting. It would be difficult to do that on a single edge/segment the way the selection works and the GCode is output.

However i wonder, could we integrate the parametrically placed datum points found in Work Features WB to reference for G Code selection? This could also help with start point selection, lead-in/lead-out positions....etc.

Essentially creating a set of tools to operate one layer above the virtual workpiece to reference path events and behaviours.
CoderMusashi
Posts: 39
Joined: Mon Nov 19, 2018 8:26 pm

Re: Cutting outside a sketch with variable offsets

Postby CoderMusashi » Thu Feb 20, 2020 11:09 pm

I have created youtube videos that show this very thing. There are several ways to achieve what you want but out of the box FeatureArea is your best choice or doing custom sketches / wires for the tool path. This is the forum link to check for the youtube video link https://forum.freecadweb.org/viewtopic.php?f=36&t=41781
chrisb
Posts: 24399
Joined: Tue Mar 17, 2015 9:14 am

Re: Cutting outside a sketch with variable offsets

Postby chrisb » Fri Feb 21, 2020 12:44 am

I hadn't realized that you wanted to include only certain edges in the path generation. If you want to go the GUI way: Russ is currently working on this: https://forum.freecadweb.org/viewtopic.php?f=15&t=43434 and hopefully we will soon see some results. Besides that you can use Profile and Contour plus PathBoundary dressups.
burgerking
Posts: 5
Joined: Wed Feb 19, 2020 9:47 pm

Re: Cutting outside a sketch with variable offsets

Postby burgerking » Tue Mar 03, 2020 4:40 am

I really appreciate the answers here. I am still new to Freecad, scripting, and even python, so I am still trying to unpack all the suggestions here. But as far as I can tell, the magical "FeatureArea" button and code from realthunder would solve all my problems. Really the only issue seems to be that I have no idea what I am doing. The button that is used in the tutorial videos linked by CoderMusashi -- it is no where to be found. I am running FC 0.19, the daily builds on linux mint. Would someone be so kind as to point me to a tutorial or explanation as to how I get the FeatureArea button. Many thanks.
chrisb
Posts: 24399
Joined: Tue Mar 17, 2015 9:14 am

Re: Cutting outside a sketch with variable offsets

Postby chrisb » Tue Mar 03, 2020 7:43 am

burgerking wrote:
Tue Mar 03, 2020 4:40 am
Would someone be so kind as to point me to a tutorial or explanation as to how I get the FeatureArea button. Many thanks.
Path_Area.
burgerking
Posts: 5
Joined: Wed Feb 19, 2020 9:47 pm

Re: Cutting outside a sketch with variable offsets

Postby burgerking » Tue Mar 03, 2020 2:25 pm

Thank you! Following the instructions found at https://wiki.freecadweb.org/Path_experimental worked.