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Polargraph Experiment #1

Motor Mounts

I needed a few motor mounts for a project and since I was at Milwaukee Makerspace it seemed quicker/faster to just laser cut a few since I had files on my laptop. (I could have 3D printed them as well.)

Polargraph

I assembled a quick and dirty polargraph, and while I attempted to use an Adafruit Motor Shield I had on hand, it did not work. The steppers were not moving, just humming and stuttering.

I then grabbed the CNC Shield I’ve been testing and put that in place. The steppers worked fine with a test sketch, but the firmware I wanted to load (Dan’s Makelangelo code) expects either an Adafruit Motor Shield or a RUMBA board. I thought about trying to rewrite things to work with the Pololu motor drivers, but it was also after 11pm.

(I later realized that I should have looked at the RUMBA firmware, as that supposedly works with RAMPS. And yes, while I do have a spare RAMPS board, it’s across town at my studio. I decided to punt and see what I could do with what was in my workshop.)

Shapes

I figured I’d throw Grbl on it and see what happened. I used Grbl Controller to connect to the board and loaded some G-code to run. I knew it would not work (as expected) but I tried anyway.

Drawing

Grbl supports machines that use Cartesian coordinates, but not those that use polar coordinates, like a polargraph. Still, I was surprised at what I got. It basically worked, except for flipping the image and running it diagonally up to the left.

Grbl Controller

I then took my original vector file and flipped it, and skewed it up and to the left, to match (somewhat) how it was drawn by the machine.

Shapes skewed

It actually sort of worked! I think it was after midnight by now so I gave up on it. My lack of math skills prevent me from converting between coordinate systems, but I think there’s a few things to explore here, and if I get time (uhhh) it may be something I play with a bit in the future. Also, if anyone wants to add polar coordinate support to Grbl that would be lovely. :)

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Spring Break 2015!

Being back in school means that I get something I didn’t get in the working world… SPRING BREAK!!!

Wikipedia defines Spring Break as “a vacational period in early spring at universities and schools in various countries in the northern hemisphere”.

Google’s image search shows us… uhh, never mind.

I thought I’d share some of the exciting highlights from my Spring Break. It got a little crazy!!!

Next week it’s back to school, which will basically be 8 weeks of total madness.

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3D Printer Malfunction

It has been __ days since the 3D printer had malfunctioned

I had a few responses to the new sign I made for the workshop. I cut some black vinyl to stick onto a piece of scrap white acrylic I had lying around.

It has been __ days since the 3D printer had malfunctioned

Of course more than one person joked that I could just permanently write a zero in place, or perhaps change the “days” to “hours” or even “minutes”.

If you want your own version, you can grab a file and have at it. Download an SVG, PDF, or DXF.

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Prusa i3 Progress

RepRap Prusa i3

We’re making good progress on our RepRap Prusa i3 in our Machines that Make class at UWM.

We cut the Lexan frames on the large CNC router after we wrote the G-code in RhinoCam. There was an engraving, and then one inside cut, one outside cut, and some center drill spots we marked before drilling the holes on the drill press and then tapping them for 3mm screws.

We also cut all the threaded and smooth rods on the horizontal bandsaw and then cleaned them all up on the belt sander. I learned a few new tricks for cutting threaded rod as well.

I’m a bit tempted to rebuild my Prusa i2 as a (laser-cut) Prusa i3, or maybe just build a second printer. I’d like to have a 1.75mm machine at some point instead of just 3mm so I can experiment with more filaments.

I’ve also been working on a few new machine design ideas, one will be a drawing machine, and another is a platform for building CNC machines that trade in precision for low-cost. More on those in future posts.

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CAM Workflow

DCRL

A big part of the work I do is the process, and trying to find tools that fit the way I work, and are also available. “Available” may mean open source, or free (as it beer) or multi-platform, or some other criteria I come up with.

In my Digital Craft class we’ve used RhinoCAM to generate the G-code needed to run the 4×8 CNC router in the DCRL. RhinoCAM has a lot of options, as it should for a full-on commercial package. Meanwhile, I’ve been working on a Shapeoko2, which is a small and affordable hobby-level CNC machine. For a machine like this, I’d like to use a workflow that doesn’t require expensive commercial software, because at some point I may not have access to Rhino and I’ll need tools I can afford.

(I should note that I have used CamBam in the past, but being commercial software that is Windows-only doesn’t entice me to want to use it again.)

I’ve played a little bit with Easel from our friends at Inventables, but I’m also not a fan of hosted solutions that can disappear, or start charging for access, etc. At this point I start to sound extremely picky, but really, I’m just looking for tools I can rely on, that are not expensive, and run on the platforms I use. (Easel is actually really nice, and while it’s easy to use, I think that comes at the price of hiding some of the complexity and advanced features I want to learn. Still, if you just want to cut/carve/engrave, check it out.)

I stumbled up MakerCAM, and there’s a bunch more info about it on the Shapeoko wiki. Basically it’s a Flash application (!) that you can use online, or download and run offline, which provides all the basic needs of a CAM application. And it actually works.

Inkscape

I started as I often do, drawing a 2D vector file in Inkscape. (Oh, I should mention there is an extension for Inkscape called Gcodetools, but we’ll skip that for now.) Once I had my Inkscape file I saved it as an SVG, as you normally would with Inkscape.

MakerCAM

I then loaded the SVG into MakerCAM. Note that if you load an SVG from Inkscape you need to set the px/inch to 90 in the preferences. Once in MakerCAM it’s fairly easy to create the toolpaths and generate the G-code. If in doubt, check out the help page and the tutorial page for all the info.

GrblController

After exporting my G-code file I was able to load it into the Grbl Controller and run it on the Shapeoko. Now, Grbl Controller is no Mach3, but it’s also open source, and multi-platform, so there’s that. (Yes, I know the image above does not match the first two images, that’s because I went crazy with the hatch fill from the Egg-Bot extension for Inkscape. Just pretend you know what I’m talking about.)

Oh, if you want to “run” your G-code before you run your G-code to make sure it’s doing what you think it’s doing, check out OpenSCAM, which is a nice little simulator.

(And yes, I know of Chilipeppr for Grbl, but I’ve not dug into it yet.)