Category Archives: Polargraph

No Bots Left Working

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MK7 Fan Shroud

What you see above is the final print from my Thing-o-Matic for a while. I finally finished off the last of the filament I own. In fact, just like when I ran out of my original natural color filament I had to switch colors mid-print (using Jetty’s excellent firmware‘s pause feature) just to avoid running out of plastic.

That’s a MK7 fan holder/print cooler. Right before that I printed a MK7 ball bearing extruder drive. I had wanted to upgrade to a MK7 extruder and start using 1.75mm filament, but there was no point in reconfiguring my machine while I still had 3mm plastic. I’ve ordered new plastic (white PLA and blue ABS), and it should arrive tomorrow. Unfortunately it looks like it will be at least two weeks before I’ll get my new extruder, so my Makerbot is getting a rest.

For extra fun, I broke my Polargraph last week. After printing out the new case, I hooked things back up in a hurry. Well I should have thought harder about that because I got wires crossed on the pen lift servo and fried it. Dang. I got a new servo in today, so I should be back in business. I’ll have to play with it tomorrow. I think I need to adjust the position the servo uses to lift the pen up, I’m not sure it’s far enough at the default with the new servo.

Building and Running My Polargraph SD

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Complex print (better picture)

Once I received the kit, it didn’t take me too long to build. I used RJ-11 jacks and cables to connect the motors and gondola to the controller board. I started to print out the Polargraph SD’s case after it was posted to Thingiverse this morning. It’s going to take some time, the bottom of the case is just a little too big for my Thing-o-Matic, so I had to slice it into two pieces.

It certainly takes a long time to print, so I’m glad I waited to get a version that could run without a computer attached (although I suppose that could have been my Raspberry Pi’s job). Since nothing is being heated over 220° C, I don’t worry about leaving it alone. I’ve been starting prints before I leave for work in the morning, so they’re ready when I get home. That didn’t work out perfectly today, when this happened:

Solid square GameBoy

It had been going for about 7 hours. I’ve been trying the different printing styles, and this was called “solid square wave”. That seems to mean that every pixel that isn’t blank is solid black. Since it wasn’t turning out to be much of a drawing, I stopped the print.

Polargraph brownout

I’ve had other adventures too. We had a summer storm last week that caused two very short brownouts. They were long enough to trigger the alarm on my UPS, but not long enough to cause problems with my TV, XBox 360 or other electronics. The capacitor’s in the Arduino’s power supply kept it running, it never missed a step.

On the other hand, the steppers didn’t fare as well. It looks like when the brownouts occurred, there wasn’t enough current to keep the stepper motor’s locked in position, the pen fell down the paper. That caused the neat little mistake above. I’m using a giant linear wall-wart for a power supply, and I guess it doesn’t have enough output filtering to be able to supply the motors during those fractions of a second.

I’ve had a few other adventures. At one point I accidentally changed the pen width to be much too wide. This caused drawings to look too sparse (first attempt), instead of having the contrast it should.

I also had a positioning problem caused by running firmware that was too bleeding-edge out of the SVN tree. It meant I got to help debug the problem, which Sandy quickly fixed. When I tried the Norwegian drawing style, I ran into an issue with the way The Gimp made the headers on PGM files, which I fixed myself. That meant I wrote and submitted my first patch to an open source project.

I Bought A Polargraph SD

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First drawing

A couple of years ago I saw a link to a robot called Hektor. The robot draws with a spray paint can, moved around by two stepper motors which dangle the can from a gondola. I thought it was great, but I never thought I’d have something like that.

In the last two years, I have learned about Arduino based drawing robots such as the Drawbot and the Polargraph. I got even more interested earlier this year following MakerBlock’s Drawbot adventures. I was busier at the time tinkering with my Makerbot, but I was also worried about another aspect: I didn’t want to have to leave my laptop connected to the machine for hours. One of my favorite features of my Thing-o-Matic is that I can operate it from the LCD interface and print from an SD card, so my laptop remains available.

Sandy Noble showed pictures in April of a prototype of the Polargraph SD. I watched that but when it was released I decided not to do anything because at £255 (after shipping) it was just too expensive. Earlier this month I got the itch again, and I was going to send an email asking if there would be a cheaper kit version when I noticed the vitamin kit. I can’t help but wonder if it was available the whole time and I just missed it every time I checked.

But it was there, and I had the time, so I bought one and started using it.