Cam Module - Work over the Weekend

Git Repo:

I have created a GIT Repo on github that the other guys are going to push back their changes to, so look here if you're interested in seeing our progress.

Weekend Work:

I spent the last weekend laying the ground work structure for the FreeCAD Cam Module - inadvertently helped by my student house mates being away, making it calm around here. Essentially the hardest or laborious task was creating the source structure. There are several classes which require both the declaration and definition just to work. This leads to a file tree in the module like so:

And there's more GUI stuff too!

This was created based on the design document we created over last week outlining a proposal for how all this stuff could fit together.

The Dependency Graph:

FreeCAD has a fairly intelligent system of managing updates through the document. Each document object can be referenced by a series of links which behave as dependency. When a Document Object changes or it's property. When this happens the property or Document Object is 'touched' and this indicates it should be recompute the hierarchy tree.

Any dependencies that reference this object will automatically be requested to recompute and update themselves. This is what drives parametric design but being transparent to the developer.

The first attempt at fitting these classes together wasn't entirely successful and in its process also made the discovery of some good fixes in the base FreeCAD application. The end result for the dependency chart (below) for the structure seemed logical but introduced several difficulties.

Logically the structure makes sense in terms of the object hierarchy. However, for the program it doesn't. When the StockGeometry, or CamPartList features update, the tool paths will not automatically update. It took me two hours to figure that one out and it didn't look pretty. Boo hoo.

I had two beers and a night off to think about this on Sunday. It became apparent that the CamFeature was simply a top level container that would provide a general interface for accessing and managing the other features - it didn't control the actual CAM process.

Instead I created an object hierarchy like so. Essentially GCodeFeature is the result from the combined results of the TPG. However we get the all the glorious updating mechanism with this.

The ToolPaths manages the Input and controls the process of updating the TPGFeatures eventually more intelligently.

The TPGFeatures are quite dumb. They behave like blackboxes and are given an input, do their thing and spit back a result. The nice thing is thing about this it will allow new TPG's to be more quickly developed since the developers don't have to set up the document feature, but only have to provide the input and in return can get the GCode back.

CAM Module

FreeCAD CAM Module.  Take 2:

After a fair bit of discussion through the Google Docs, Blog Entries, Forum Posts and ofcourse some IRC chatting Ideas we have pushed again and started the CAM 2 Module. Perhaps it's incorrect to say CAM2 but we are definitely putting the new source files in a new folder since we are essentially starting from scratch. We have even been blessed with a new subheading on the FreeCAD forums.

Objectives for this Module:

Essentially we aim to integrate the whole CAM workflow into FreeCAD.  The tool algorithms are developed  already in many libraries and are already useful but there is no practical integration within FreeCAD.

Secondary Objective : To cut out Sliptonic's spider!

The rough workings of CAM from a newbie:

The module will take your 3D Part within FreeCAD as the primary input. We provide a set process this with tooling algorithms which generates machine instructions (tool paths) known as GCODE. These are post-processed manually by the user and can be visualised within FreeCAD to check for any problems. We are basing a lot of the design on the work already achieved by HeeksCNC.

CAM in this Module will be a subtractive process -we remove material from a piece of Stock - such as sheet of steel by a series of operations. Each operation will be generated by a TPG - a Tool Path Generator. These are plugins which can be written in c++, python perhaps other languages and use their own algorithms to generate paths for the CAM Machine to remove material. These TPGs aim to be flexible, so we can call a  process to proprietary application allow this to do the hard work and then import it back into FreeCAD, but this process being entirely transparent. 

How I fit into this:

The strangest experience with this side project is that I have very little practical knowledge and experience working with CAM so I am very reliant on the wisdom of our CAM experts who have set up their requirements and how the perceive it working within FreeCAD. This is what makes it interesting in respect but also a difficult task. It is good practice working in an environment like this because I still yet to find a job that involves team work at such level haha.

My role in this project is to try and build up the basic FreeCAD infrastructure and then this will allow the other developers such as awallin, arobinson, dfalck to work on this independently, integrating the tools in.

Additionally work to build an awesome GUI interface into this ofcourse!