Dogbone dressup modifies inside-corner cuts to remove material missed by a cylindrical cutter.
I have a whole pile of old Altoid tins that I use to store small screws and such. The tins had migrated into a physical pile on top of another storage container and were occasionally knocked over while I was looking for something. I thought it would be nice to have them in a rack mounted on the slat-wall.
Laser cut acrylic seemed the natural choice. The glued finger joints are plenty strong but need to be accurately cut. Since the project was pretty simple, I decided to try to do the whole thing in FreeCAD including the gcode generation with the new Path module. I know Path is still incomplete but I've been watching the improvements for months and thought I might be possible. Here's how it went.
The parts were simple sketches padded to the thickness of the acrylic - 3mm. The important thing is to make the depth dimension of the tabs match the acrylic thickness and the position match the corresponding slots.
I used the assembly2 workbench and built the assembly. Assembly2 is very slick and I caught several boneheaded mistakes that would have cost time and plastic otherwise.
I used Assembly2 again to make a second assembly. I didn't set any constraints, I just laid out the pieces to fit on the raw stock in the laser cutter. This way, if I need to change any of the parts, I can just refresh the assembly and regenerate the gcode.
Next I built the profile operations. This was the hardest part because Path is very new and only the simplest operations are working. I ended up with separate operations for each outside profile and each hole.
I hid the solids and just focused on the gcode backplot. It's very easy to see any problems with operations and make whatever changes are necessary.
When things started looking good, I tried exporting the gcode and loading it in LinuxCNC. There were a few problems that I could easily have fixed by hand but decided to try automating the process as much as possible.
My laser needs a couple commands in the preamble to set the power output. I copied the linuxcnc_post.py file to my FreeCAD macro directory and renamed it laser_post.py. For FreeCAD to see it as a post processor, it needs that name format. The first part can be anything you want but it must end with _post.py. Editing was just a matter of pasting the lines into the preamble section.
At this point, I could select the project node in the tree and use the export menu. Select 'GCode' for filetype and give it a name. FreeCAD will prompt with a list of post processors. I select my new customized post, and click 'ok' The code is written and ready to be loaded in to LinuxCNC.
That last part is a lot of clicks and I tend to repeat it many times as I'm working out the last little bugs. FreeCAD has a couple conveniences to simplify things. The project node has a property for the output file and the Machine node (see picture above) has a property to pre-select the post processor. With these set, you can click the 'Post process' icon on the toolbar and it's done!
The pieces cut out beautifully. I glued them together like so:
This was a quick one-day project while I was cleaning up the workshop. The toughest part of a project like this with my other tools would be the fine tuning to get the slots and tabs to align right. With FreeCAD, that was really easy. The Path workbench still has a long way to go and it's not usable for anything but the simplest operations right now, but it's improving fast.
For the last few months I've been helping out with a side project to write a CAM workbench for FreeCAD. Being a not-very-good programmer, I've focused on cheer-leading, testing, and trying to stay out of the way. The project has come a long way, but it will still be a long time before the average user sees it. Still, it's a good time to start talking about the workbench, setting expectations, and encouraging folks to take a look.
Don't we already have open-source CAM tools? Why do we need another one?
A quick Google search or browsing through the LinuxCNC wiki would make you think the field is already crowded with alternatives. If you've actually tried to find a functional solution though, you probably already know the answer. Most of the projects out there are stale, offer limited utility, or are very specialized. A lot of them are completely dead. To be fair, some of the projects like BlenderCAM, HeeksCNC, and the Inkscape plugin gcodetools offer decent hobby-level functionality but there's nothing that competes with the commercial alternatives.
To be competitive, an open-source alternative really only needs two things (and time):
First, the application has to be user friendly:
- Cross Platform
- Integrated with CAD
- Reasonably Intuitive
Cross Platform means the application meets the user half way. Learning the application means the user will have to understand new concepts, watch tutorials, read manuals, and suffer through bugs. Asking them to change operating systems or compile from source is unreasonable. Integration with CAD doesn't mean the user should change his primary design tool but the line between CAD and CAM gets kinda fuzzy in practice. Visualizing your tool path as it relates to your base geometry and making minor tweaks to the design to get a usable path are common. Switching tools for minor adjustments is annoying and leads to errors.
The application doesn't have to be a marvel of form and function but it needs to have a reasonable UI. By this I mean that it should work for a hobbyist who needs to set up a simple CNC router job but provide capabilities for an experienced machinist to set up more complex jobs as well. (multiple fixtures, tool tables, and selection planes). It should let users customize their configuration so the output is predictable and works with their machines.
And, of course, it's got to be fast. 'nuff said.
Second, the project has to appeal to the developers:
- Reasonably easy to learn
- Great community
- Clear license policy
Plenty of digital ink has been spilled discussing what it takes to make a great open source project so I'm only talking about those things that I've personally seen kill open-source CAM projects.
The number of people in the world that have both programming skills and machine tools is pretty limited. For open source CAM to succeed, the developers who show up need to be able to get into the project easily and become productive. A great open source CAM project would have a great architecture, robust community, thorough documentation and large user base. It should be easy for a new developer to understand the landscape and figure out how to improve application -even a little bit- and then get their improvements adopted by the project.
I'm not sure anybody including lawyers actually like dealing with licenses but they're a reality we have to live with. If the license landscape isn't unambiguous, packaging and distribution of the application is a non-starter. If the license doesn't protect the developer contributions and make it easy to distribute, why bother?
The things I've listed aren't rocket science and they don't, by themselves, make a great application. But together they create an environment in which a great application can mature. Obviously I'm writing this because I think the FreeCAD Path project has this particular mix.
So where is the project now?
Rather than trying to provide all the functionality of a mature CAM application, Path will initially provide only the basics. In fact, the real focus will be on the underlying infrastructure.
Like other workbenches in FreeCAD, the low level stuff is programmed in C++ and the high level, user-facing, functionality is written in Python. The low-level stuff includes the data structures to represent a single move (command), a group of moves (path) and other structures for organizing projects. It handles representing those things on the screen and provides the interfaces to Python so they can be manipulated by the GUI and macros.
An import framework is provided so path information created externally can be loaded and rendered within FreeCAD. Likewise and export framework exists to get path data out in a usable form.
If importing and exporting were only provided through the compiled C++ application code, it would mean that FreeCAD's ability to read and write gcode would be fixed and difficult to adapt. So the import/export framework is exposed through a set of pre_ and post_ scripts written in Python. This means FreeCAD can play nice with all kinds of other applications. If you already have a program that generates gcode, you can import the code into FreeCAD. If your machine needs gcode in a unique dialect or modified some other way, you can tweak the export post_ script to get exactly the what you need.
This is pretty handy but most users will want to create gcode directly from the things they design in FreeCAD and this is where things get interesting. Experienced CAM users opening the workbench for the first time will be asking questions like, "How do I create a profile or pocket a feature?" CAM operations like this will be implemented as a Path-Python-Feature (PPF). A PPF is a python script that uses the FreeCAD API to generate the path data. Almost everything you will see in the workbench GUI represents a PPF. PPFs can have have icons and dialogs and integrate seamlessly into the workbench GUI and power users can study and extend their functionality.
Now is the time to set expectations. The initial set of PPFs will be limited. Users just looking for a functional CAM system might be disappointed. There will be pocketing, profiling, and drilling operations, but they will have plenty of bugs and missing features. Other kinds of operations, like 3D surfacing, will be missing altogether.
CAM users will also be looking for tools to organize operations into a complete project -- Sequencing, tool management, part nesting, etc. Early users of Path will see some of this but it too will be buggy and incomplete. Users should expect things to change a lot in the near future.
Because all of the PPFs, project structure, and pre/post processing is written in Python its pretty easy to experiment with and improve. No doubt, an active community will mature the operations quickly and add new ones as well.
Once Path is merged into the Master branch of the FreeCAD development repository, it will still be quite a while before end-users see it. Users running the development version will see it, of course, but it might be a year or more before Path makes its way into a stable version. By then, the functionality should be more mature and usable for real CNC projects.
I got the chance to speak about FreeCAD at the Osmoces event near Chicago over the weekend. I had a really good time seeing some of the other presentations and exhibits and just hanging around with some pretty cool people. In addition to the talk, I also taught a workshop where we got hands-on with the software and modeled a simple part.
One theme in my presentation was that this stuff is really hard. It's hard to learn, hard to use, and mistakes have real consequences. This isn't just true of FreeCAD but of any CAD or modeling software. This fact was reinforced for me personally in the workshop where I saw frustration and confusion first hand.
Even though students struggled at first with the interface and the general concepts, most were able to make a lot of progress and judging by the number of students who stayed late and asked about areas I hadn't even covered, the demand for powerful open source design tools is growing.
This was the second time I've taught FreeCAD to a group of new users and I'm starting to get a sense for where they get hung up. I'm hoping to teach this again so I can build on that knowledge and perhaps find better ways to explain the core concepts. If you have anecdotes about learning CAD or teaching it to greenhorns, I'd be interested in your comments.
If you're looking for my slides or notes, they can be found here.
This is still early but it's too cool not to share. Yorik has added a WebGL exporter to the FreeCAD arch module (but it seems to work everywhere in FreeCAD)
Open a model in FreeCAD and select the objects in the tree
Export the objects (File -> Export) and select WebGL
Save the file and open it in a browser: WebGL export (will open in a new window)
(The default view is zoomed up close but clicking and dragging with the mouse buttons will zoom/pan/rotate the object. There's still plenty to be done with materials and lighting but being able to share FreeCAD models through a browser is very cool.)
I'm going to build an enclosure for my CNC mill to keep coolant and chips from going all over the floor. It took about ten minutes to model the mill table in FreeCAD but modeling all the aluminum extrusions was looking like a lot of work. Fortunately it isn't necessary
More and more vendors are providing CAD data in their online catalog. As long as they provide data in one of the non-proprietary formats, it should import very nicely into FreeCAD.
McMaster-Carr's catalog is legendary and many of their products have CAD data associated. You can download in a bunch of different formats that are compatible with FreeCAD, HeeksCAD, or probably any other CAD system on the planet.
Just click on the part number . In the item detail pop-up there's a CAD link that will take you to a page where you can get 2D and 3D CAD models and also see some dimension data online.
Misumi's site is maybe even better. Misumi will custom cut aluminum extrusions without a setup fee. The nice thing is they also provide custom CAD data for the parts you specify. For example, if you want a 330 mm extrusion, they'll cut it, but you can also download a 330mm model to use in your design.
In the design at the top of the page, I used three different length pieces and played with them in FreeCAD to verify that things would line up on the table the way I wanted.
I wish all vendors provided this, along with detailed specs, schematics, and illustrated parts lists. If you know other noteworthy vendors, drop a comment.
When I first started using HeeksCNC I was totally confused. It seemed overly complex. When I finally understood it, I realized what a great model it is. I still won't claim to be an expert but from my perspective it meets three really big objectives. One of these is compromised in every other solution I've seen:
1) It keeps the computationally intensive algorithms in C++ where they run fast. Other systems that are flexible and customizable are written in interpreted languages and that means they're slow for computationally intensive tasks. Generating a complex path can tax a processor and really needs to be fast.
2) It provides a scriptable interface in a friendly language (Python). No matter how good the developer was, there's no way he can anticipate every need. That's why we like applications like blender, inkscape, gimp, and FreeCAD. These apps assume that the user may want to extend the application. Making the tool path generation accessible through a scripting language unleashes a lot of power.
3) It allows customization for the machine specific output without recompiling. This is the Post-processor. Not all machines are created equal. Different capabilities and different controllers mean the final output must be tailored.
Dan Falck did a great write-up of how Python is used in HeeksCNC to generate tool paths using the C++ libraries. I hope a future CAM workbench for FreeCAD has a structure like this.
Dan Falck and I spent the last couple months working the Packt Publishing to write this book. The book is written as a series of recipes to guide new users through some of the basic concepts in FreeCAD. The later chapters get into how Python can be used to automate and extend the application.
I hope the book will be a benefit to the community and make it easier for new users to get productive with this great application.
BTW, Packt Publishing is very supportive of Open Source software. According to their website, a portion of the royalties will go directly to the project.
This is one I'm documenting here because it's come up twice on the #freecad channel and because I keep forgetting it myself.
FreeCAD has a bunch of different ways to change the appearance of solids.
You could change the properties on the objects view tab:
You could use the appearance... tool from the object context menu
You could use the random color button from the object context menu
You could use the appearance... tool from the view menu (this is the same as the context menu. Why it's in 'view' and not 'edit' I'll never understand.
You could use the random color item from the view menu (see above)
There's at least one more that's different than all the rest. If you select the object and right click over the tree (not the 3D window, but the object tree) you get a menu item called set colors...
This one opens a task panel. With the task panel open, you can Ctrl-click individual faces in the object and then set different colors for them.
FreeCAD's assembly module is still in development. By all reports, this is going to be an amazing feature just dripping with awesome sauce. Alas, it's not here yet.
In the meantime, if you want to design anything with multiple parts, your options are pretty limited. Here's a technique I've been using on the OpenROV project:
1) Design each of the parts in a separate FreeCAD project file.
2) Export the part as a STEP 214 file (.stp)
3) Import all the step files into a new FreeCAD file just for the assembly.
4) Duplicate any parts you need multiple instance of.
5) Use the placement dialog to rotate and position the parts together.
Step 1 - Design each of the parts in a separate FreeCAD project file.
You can certainly design multiple parts in the same file but this causes problems if you need two instance of a part for the assembly. You can select a pad object and duplicate it, but the duplicated part will not be linked to the sketch so any downstream changes will not be incorporated into the duplicates. I use my FreeCAD designs in other software like HeeksCNC for generating gcode and I find that the .step files are more portable.
In the image below, I have three FreeCAD files open. bulkhead, ductingbracemount, and a new empty assembly file.
Step 2 - Export the part as a STEP 214 file (.stp)
Step files are widely supported by different CAD/CAM applications. FreeCAD is no exception. Both import and export have worked flawlessly for me. Simply select the solid in the project tree and click the menu item File->Export... Then, when the dialog appears, select STEP 214 from the file type and give it a name. Repeat for the other parts too.
Note: I use the same name as the file and the extension .stp. If you don't include the extension, FreeCAD won't write the file. I think that's a bug.
Now in my project directory I have bulkhead.fcstd bulkhead.stp ductingbracemount.fcstd, and ductingbracemount.stp. If I make changes to the part, I have to export again.
Step 3 - Import all the step files into a new FreeCAD file just for the assembly.
Switch to the empty assembly file and import the .stp files. This is just the reverse of the previous step. File->import. The import dialog will let you select multiple files at once and import them all. This is nice.
One thing to note about the import export: STEP files preserve the position and orientation of the parts in the global coordinate system. Once the parts are imported, you can adjust these properties. It's really helpful, though if you at least get your parts drawn in the right plane before exporting them. I find adjusting position to be relatively painless but getting the rotation correct is more frustrating. Once imported, the step files will behave like other objects. You can run boolean operations on them, adjust colors, make them invisible, etc.
4) Duplicate any parts you need multiple instance of.
In my example, I need two ductingbracemounts. Select the part in the tree and use Edit -> Duplicate selection. The duplicate will be in the same position as the original so it will be invisible until moved.
5) Use the placement dialog to rotate and position the parts together.
Select each part in the tree and use the placement dialog Edit->Placement...
to fine tune to rotation and location of the part. Most users will fine the Euler angles (Yaw, Pitch, and Roll) more comfortable than the default "Rotation axis with angle" for setting the rotation of the part.
Bonus step - Make pretty output.
Actually this is more of a teaser since it isn't in master branch yet but mrlukeparry has been doing some really cool stuff with the raytracing workbench and soon we'll be able to generate nice pictures like this:
Here's some things that would make this a lot easier
- FreeCAD should be able to import from other FreeCAD files. It would be nice to import a solid, sketch, or part from one file into another without having to export to step. Step is useful for going to other applications, but it would be nice to stay native whenever possible.
- When exporting, FreeCAD should give some help with the filename. Default the extension based on the type selected and default the filename to the current part name.
- Can anyone calculate the rotaton with angle in their head? I know it's superior to avoid gimble lock, but it's not very human friendly. Maybe I'm wrong.