Fighting with computers

Computers are not always friendly.

Sunday, May 31, 2015

Making sense of toolpaths

On my CAM project I am using the intersection of a part with a given plane to determine later the proper tool-path for three-axis machining. But sometimes, parts are such that the intersection line contains some concavity.




So I detect whenever the tool cannot reach that line and create a suitable solution. In the picture the red line in the top removes any concavity as seen from Z-axis top, converting that polyline into another that might be machined from the top.

It is interesting to note that one extra point needed to be created and appears marked with a dashed circle, though strictly speaking both bottom corners of the red line are new points too, but they are not over any of the original polyline space.

A second problem appeared once I obtained not one polyline but several of them as a result of objects that contain holes or several domains with respect to the cutting plane as it is shown in the image below.




In this other case, the different polylines need to be consolidated into a single one, that will ignore the holes (as the gray one) contained within another area and that will join the polylines that can be joined (which may or may not be possible depending on whether or not they overlap in the sweep direction). Again the red line will be the result of combining the three different polylines above.

Friday, May 01, 2015

Getting the hang of it

I have been using for a couple of weeks the web-based CAD system OnShape. I did this robot just as test to see how to use the different tools.

I have been using OpenSCAD for quite some time and I was not very keen on using some fancy CAD systems like Inventor or Solid Works because I could not afford them but also because they would force me to use Windows, which I prefer not to. But even if AutoCAD can do OSX besides Windows, I do use Linux most of the time.

So when I learned that there was a new game in town that was based I was first skeptical that a browser could to the job, but after some testing I am now a believer. And I love to be able to jump from a Linux workstation to a Mac to continue editing my designs.

The free version of the service has certain limitations in the number of private projects you can have, storage and something else, but given the fact that can not only import but it exports to popular CAD formats like STEP or IGES it means your work is not locked in. And the easy export to STL makes it perfect for 3D printing (it can also export 2D sketches to DXF equally easily for laser cutting parts too).

I am by no means a CAD expert so maybe some important features are missing but it seems these guys really are experts in the field. If you liked Gmail, I would say this tool is to CAD what Gmail is to email.