The Hell Ya Beller Fun with hot, pointy, sharp, and caustic stuff.

19Jul/150

Dogfooding with FreeCAD Path

"Eating your own dog food, also called dogfooding, is a slang term used to reference a scenario in which a company uses its own product to validate the quality and capabilities of the product"

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.

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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.

Selection_013

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.

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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.

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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:

IMG_1547

 

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.

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17Jul/150

Bending & Gluing

About a year ago I bought a standing desk.  The desks are really nice but the options for surfaces are either very basic or expensive. I wanted to do something custom so I bought it without a top.  I had an old top (actually a door) to use in the meantime and started thinking about what I wanted.

Time has gone by and my big ideas kept getting pushed down the stack  - until recently.  A friend owed me a favor and volunteered to help me move the project ahead.  I had access to a some remnant strips of walnut and decided to make a "butcher block" surface by gluing them together.  After thinking it through, we decided to make the whole surface curved by bending the strips around a form.  The finished desk will be about seven feet wide and 24 inches deep.  The rough idea:

Selection_037

 

First we made the form from a couple layers of plywood.  The arc has a 110" radius and was cut with a router attached to a board pivoting around a screw.  Sorry I didn't get any pics of that process.

Next we ripped and planed strips of walnut and maple.  The walnut is 5/8" thick and the maple is about 1/4".  There will be a strip of maple about ever three inches of walnut.

Then it's just a process of applying glue, clamping to the form and letting it dry over night.  Repeat.  I was hoping to be able to glue multiple strips at once, but in the end we could only do that with one strip of walnut and one strip of maple.

Heres a picture after about eleven strips.  The form is on the right side.

 

IMG_20150417_122613

About this time, we got smart and mounted the whole thing vertically.  This way, it's easier to keep the strips in alignment and we don't have to fight with the glue oozing out the back and gluing the desk to the table below.

 

 

IMG_20150423_143135

At one or two strips per day, it took over three weeks to build up the full width of 24"  Below, you can see the full piece wiith the form leaning against the wall.  A lot of time was spent cleaning up glue and planing the layers flat.

IMG_20150513_105634

We added one more strip to the front and back edges.  These strips are 1.5" thick to give a 'skirt'.  This makes the whole desk look thicker and helps hide the attachment to the frame. We started working out details for how to finish the ends.  We marked the ends as shown.

IMG_20150626_142805

And cut them even.  You can see the front and back skirt boards on the edge.

 

IMG_20150626_144516

To finish the ends, we cut larger blocks of walnut that will be mounted perpendicular to the arc.  They'll be attached with screws but otherwise not glued.  This will allow the strips to expand and contract with humidity without breaking glue joints.  We marked the curve to continue through the sides.

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And cut them off to match.

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Final planing and touch up (sides removed)

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Then sanding and finishing!

IMG_20150707_135514 IMG_20150707_135525

After installing on the Uplift frame and mounting monitors.  I'm really thrilled with how the whole thing came out.  \

Big thanks to my friend Dan for all the help with this project.

IMG_20150717_132247

16Apr/150

FreeCAD Path Workbench – Big Vision and Baby Steps.

Selection_105
MyNameIs_Bobimage

Smooth sailing? Not quite yet.

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.

Big Vision:

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
  • Fast

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?

Time

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?

babystepsRather 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.

8Dec/140

Maker Redux

For the last eighteen months I've been working with a group building a way for people with ideas to get things made by people with tools.  Here's the big idea:

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20Nov/130

A nifty work-around for HeeksCNC Kurve offset error

HeeksCNC can be finicky about profiles.  Often I've found that a sketch which should be easily profiled won't generate any gcode at all.  When I look in the console, I find an error like this

  File "/usr/lib/heekscnc/kurve_funcs.py", line 247, in profile
    raise Exception, "couldn't offset kurve " + str(offset_curve)
Exception: couldn't offset kurve <area.Curve object at 0xb6f4bf2c>
It most often happens when profiling inside a closed sketch where the radii is close to the diameter of the cutter.  Sometimes I can get around it by changing from climb to conventional milling or vice versa.
Recently I was profiling several cutouts that were exact copies of one another just rotated around a central point.  Some of the cutouts would profile fine and others wouldn't  I emailed Dan Heeks the author of the software and he clued me in to a work-around.
It seems that the error is coming from the entry point.  By simply setting a new start point for the profile close to the middle of the longest span, the error magically disappears.
This won't work in every case, especially if the pocket is very close to the size of the cutter or made up of tight curves but for the most common cases it should work fine.  Thanks Dan!
8Oct/132

CAD Is Hard!

cadishardI 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.

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14Apr/131

FreeCAD WebGL Export.

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

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Select objects in the tree

 

Export the objects (File -> Export) and select WebGL

Selection_14-04-2013-002

 

 

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.)

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18Mar/132

Vendor provided CAD data.

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

milltableextrusion

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.

mcmastercarr

 

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.

misumi

 

I wish all vendors provided this, along with detailed specs, schematics, and illustrated parts lists.  If you know other noteworthy vendors, drop a comment.

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28Nov/120

Fun in the shop

I spent the Thanksgiving holiday at my brother's place.  It was a very relaxing weekend spent eating too much and shooting stuff.  (I'm not very into guns but this stuff is fun!)

My brother recently bought a jealousy inducing lathe like this:

lathe1

This thing was barely out of the crate.  The DRO hadn't even been installed yet and and he was just getting familiar with it.  So, of course, we decided we needed to make something  -- preferably a piece of high-precision technology.

 

Armed with a healthy disregard for prior planning, a can-do attitude, and the proper fluids:

fluids

 

we started making chips.

chips

 

Two days (and late nights) later, the world's first tactical yo-yo.  Heavy enough to take your head clean off.

yo

 

The first field test was less than impressive

brokenstring

So, back to the drawing board:

drawingboard

In the end, the device functioned within specification.  It's a bit heavy for normal use but there's plenty of material that can still be removed to improve it.

All joking aside, I really enjoyed this project. Too often we think through a project and, figuring that we could do it, we declare it done.  Actually DOING it unearths all kinds of tricky problems but that's where real experience is developed.  I know my meager skills on the lathe were improved greatly.   And I had a blast.

 

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14Nov/122

Keeping Good Company.

A reader on my Magic Clock site made me aware of this TED talk by Massimo Banzi, Co-inventor of the Arduino.  He lists some really cool projects ranging from the important to the silly.  I might be closer to the Farting Chair end of the scale, but hey, I made the list.  Fast forward to 10:25 to skip all that nonsense about 14 year old kids changing the world by detecting earthquakes.