The Mendel is Alive!

We have finally gotten the Makery Mendel to print properly!

So far we have printed a huge camera mount to connect Kevin’s camera and bike. Also, we have made a couple of new gears and linear bearing mounts to upgrade the ‘bot.

However, we are in need of funding for more plastic. The roll of PLA we are using is almost out, and a new spool will be about $65 plus shipping.

Here are some pics of stuff printed so far. :)

Happy Birthday Omaha Maker Group

Tuesday marked the 1 year anniversary of the Omaha Maker Group, known internally as Founding Day. It signifies the first [large] meeting of Makers at Upstream Brewery where the Omaha Maker Group name was chosen.  It wasn’t until later that we were legally organized, but that’s not the point.

In honor of the somewhat momentous occasion, we had a gathering at the Makery including cake and grilling, for around 20 people.  A good time was had by all, and it was a pretty good excuse to clean the place up a bit.

It occurs to me that the most valuable thing that the Omaha Maker Group has given us in the last year isn’t the physical workspace down at the Makery, nor any of the growing collection equipment there, but rather all of the people we’ve met.  We have really great bunch of  Makers, techies, artists and doers of all kinds; People willing to help when you get stuck on a project or to mock you into starting the project in the first place. For my part, I’ve made more than a few friends along the way.  Here’s to many more years of Making in Omaha.

Convert old 35mm film camera lenses to work with digital SLRs

Zach sez:

This week I took a simple camera lens from a $3 film camera I got from a thrift store and attached it to a cheap Canon body cap after drilling a hole in it. The result was a bit surprising once it was attached to the camera. Since the lens gets so close to the sensor, it made an inexpensive macro lens.


Nice going!

Print heads for the Makery Mendel

Tonight, I was on assignment for Brandon and the Makery Mendel again, this time drilling some really really tiny holes.

These acorn nuts will be used as print heads to extrude the molten plastic on the almost-done Makery Mendel 3D printer. I started the process by holding the piece of allthread (Which has a shallow hole in the end) in the lathe chuck and threading a nut onto the end.  I know that generally a bolt thread isn’t true enough to rely on for machining, but in this case, I want the operations all true to the bolt, as that’s how it’s going to be held in use.

Next, I faced off the rounded end of the nut, being careful not to get too deep (which is what happened on the rightmost unit). I then used a tiny drill bit in the tailstock chuck to ever-so-gently drill the hole.  On the 0.3mm unit, you can see where the drill bit had a slight bend in it, and wanted to drag around the part instead of start drilling in the center.  I was able to change the orientation of the bit in the chuck to correct this.

Finally, I cut a bit of an angle on the side of the nut, making it more conical than round.  Sort of like a cut-off funnel.  Hopefully it works well. One of the nuts turned out to be plated (which, sadly, is one of the sizes I didn’t make a duplicate for)

Doorbell Upgrade

Recently I discovered that my doorbell has become unreliable. The UPS guy never wants to wait around, and sometimes he takes the packages with him, so I had to do something about this problem. I picked up a new bell at the hardware store for a couple bucks, but it's a cheap plastic model, where the original is a nice heavy metal model with a light in it.

I took apart the old one to see if I could swap parts to reuse the nicer one, and found that the only part that was really a problem was the button, which has degraded on the side facing the afternoon sun.

Fortunately the new one is almost exactly the same size, so I swapped it in and had a like-new repair. Cool, 5 minutes and the job was done.

Of course, as soon as I reconnected the wires the little light bulb burned out. It's been running continuously for 5 years now, so I guess that isn't too bad a lifetime, but I'd like the button to be lit, so I'll need to get that little guy out of there and find a replacement.

I'd probably have to spend $15 on a new lighted switch to get one of those little 20VAC bulbs, so I'll be looking for something else. Twenty volts is a little low for neon bulbs and electroluminescent wire or film, so I guess it'll have to be an LED. Fortunately I've got a ton of those. Red would be neat, but maybe a little boring. I have a bunch of IR LED's and some luminescent powder, so I could coat the inside of the button and make it glow, but I'll probably have to replace it again in a few years, and I don't want to have to reapply the glow powder. So I think I'll go with one of the blue LEDs I had left over from my binary clock project.

The LED will need a diode to block half the AC voltage and a resistor to limit the current. I used 33mA for the clock, and that's plenty bright for this, so I found an ~800 ohm resistor for this.

There isn't much space in the doorbell, so I marked where the circuit board did not lay on top of the metal contacts, connected the resistor and diode and laid them out to see where I'd need new holes for the leads.

Looks like it will fit without much trouble. There is just enough room between the PCB and the wall to avoid squashing the resistor. I marked the trace where the new holes will go and drilled them out.

Then cut the trace between the new holes.

A little work with a needle file to make some new pads around the holes...

And I can solder in the new components.

Next the LED goes in, but first I lopped off the lens with the dremel to turn the end of the LED into a diffuser. There isn't enough room in the switch body to stand it up, and the beam is too narrow for that anyway.

Before I reassembled the switch I took the chance to bend the contacts into a higher arc so that the button only has to be pushed about 2mm to make contact. It was set for more like 3mm, which put the button almost inside the switch body, which was contributing to the difficulty of getting it to work.

I put it back together and hooked it up, and it's working as planned:

A neat improvement on this would be to replace the factory board with a custom board with an ATtiny13 and a couple SMT RGB LEDs so that the button could cycle through a set of colors. It would reset when the switch is pressed, so the startup code could do a neat flash of colors to indicate that it had been pressed before returning to the usual slow color cycle.

Motorized Potentiometer

I had a broken micro RC car that used a gearbox with a tiny potentiometer on it for controlling the steering angle. I thought it would be interesting to replace the little potentiometer with a regular sized version so I could set the position either manually or from a microcontroller by driving the motor.

I drilled a bit of brass rod to fit over the gearbox output and to fit the stub of shaft on the back of the pot. I used some loctite and epoxy to connect the shafts together, and ran it a bit to get it all concentric, then epoxied a bit of aluminum strap to both.

The next step is to come up with some code to read the pot and drive the motor to the commanded position. Since it holds position without power to the motor, the h-bridge can be left idle except when it is moving to a commanded position, so that a user can turn the knob to adjust a setting.

Stepping Up…

Tonight, I did some prep work on a new EasyDriver (on breadboard) that I ordered for an upcoming project. I mounted a 4-pin Molex Floppy connector for the motor output, and pin-headers reversed for breadboard mounting.

I also milled the gear off of a scrap stepper motor and built a coupler to a fancy leadscrew I had laying around. The leadscrew in question (pictured foreground) is about 9″ long, has 5 starts (5 parallel sets of threads) and has a twist-rate of 1 inch per turn (one TPI).  The screw is further teflon-coated and uses a (probably Delrin) plastic nut.

Brandon questions if “that wimpy stepper” can drive such an aggressive leadscrew, but I don’t think it’ll be a problem.  If it does become a problem, building a new coupler (or finding a motor that has the same shaft size) shouldn’t be hard.

Printer Parts – Heater Tube

Jason notes that I forgot to post a photo of the other Mendel parts I’ve been building for the MakeryMendel.  Below are photos of a stainless steel heater tube (the one that I didn’t ruin by welding a drillbit to the inside) as well as the “order form” that Brandon sent me. His drawings aren’t anything fancy, but we seem to have gotten the job done.  For scale, the bushing in the photo is 1″ OAL, and the threaded rod heater is 1.5″ OAL.  The picture with the fire is a prototype plaster bushing that we were testing.  It’d probably work, but we dried it a bit too fast and it developed a nasty crack.

BrandonSpec (Medium) Plaster Heater

Binding Books

This weekend some friends and I spent a few hours working on binding some books. We started with the paper from some drawing pads which we folded in half in sets of 4 to 6 to form signatures. We stacked between 5 and 8 of the signatures and stitched book tapes to them, then glued on the mull to form the book block.

I cut some 1/8th inch hardboard to make coverboards and the spine. To this we glued some card stock to make the hinge, and then to the coverboards we glued some fabrics.

The book block was then pasted into the cover along with end papers made from scrapbooking papers. This was then clamped to prevent the pages wrinkling while the paste dried.

The spines ended up being to wide IMO, I think I prefer them to be about 1/8 to a 1/4 inch narrower than we made these. On the other hand, we can put lots of stuff between the pages of these books and then the spine will be just right.

Zinc Casting

Did a quick zinc casting of a small knight figure. This was a sand casting demo for some friends who are interested in the skill. I was surprised that the shaft of the mace came out, since it is only about 2mm in diameter.

The casting ended up with a poor surface finish. I haven't worked out the main cause of this. It may be related to pouring temperature or venting.

For small things like this I think it would be interesting to try building a small electric furnace.