Monthly Archives: November 2012

Tinkeriffic Snack Mill

mill_full

All of the pieces necessary to build this structure can be found in the Tinkertoy Classic Jumbo Set.

You will need:

Print the sawmill. Be sure to print the foot twice. The guide bar is optional.

First wrap a piece of tape around an orange rod to create a tight fit for the blade– you don’t want the saw to bind up or slip when cutting something hard like an apple or carrot.

tape

Slide the blade onto the rod. It should be very snug.

blade

Put one spool onto the peg on one side of the bed.

wheel

Slide the orange rod through the spool’s center bore and secure it with a clip.

lock

Do the same on the other side. Be sure that the saw blade can spin freely in the bed’s center groove.

two_locks

Make a crank handle by sticking the yellow rod into the round-edged spool. Add the coupling to one end of the orange rod.

Put two clips in the top bores of the spools. Connect these clips with a blue rod. This adds stability to the sawmill.

brace

Insert the feet into one of the edge bores on two spools.

feet

Connect the footed spools with a blue rod, and connect the footed assembly to the bed assembly with two red rods.

back_end

You’re ready to go! Start cutting. You can snap the guide bar into the hexagonal holes on the bed if you want straight cuts.

Unless you have a prehensile tail or have epoxied the bed and feet to a cutting board, milling a snack is a two-person job.

Hang the crank over a countertop edge so it doesn’t strike your work surface while turning. Hold down the rest of the assembly with your free hand.

Crank the saw up to speed before feeding it a snack. A child should easily be able to produce 60 RPM, which is enough to cut a carrot. Feed the snack through the mill and continue cranking until the snack has passed the blade.

apple

Once More, With Rigor

This is a follow-up to yesterday’s post on printing with PLA, where I claimed that the orientation of the painter’s tape on the build platform is important to the stick-to-it-ive-ness of a PLA print.

But is it? Really?

A comment from CymonsGames (who’s doing some great stuff on Thingiverse, BTW) got me thinking. Is this 3d-printing feng shui, or is this a real effect? Does the grain of the painter’s tape matter? It worked once yesterday.

But anecdotes ain’t data, people. Imma test this.

I’ll try and remove as many variables as possible from the experiment, but since my basement clean room is currently occupied by an eldritch horror I’m stitching together from abattoir scraps, I’ve got my Replicator in the living room and ambient temperature control isn’t really possible. It’ll be somewhere between 64° and 69°F.

I made a special model for this print test: it’s just a 30x30x2mm solid with a raised zheng on it.

And some skeuomorphic rivets. Because, rivets.

Most importantly, this model is thin, so I can run this print a bunch of times quickly.

ReplicatorG Settings:
10% infill
.22 layer height
print 240° on first layer, 210° afterwards
HBP: 35°C

I used fresh tape before every print, all from the same roll. The first three prints were with front-to-back tape, the next three were with side-to-side tape. All tape was the same stuff, 3M Scotch 2090-1A ScotchBlue Painter’s Tape.

Minor tip: Make sure you have tape everywhere that you plan to lay down PLA, especially the homing line from the corner of the build platform to the start of the print. If you miss that little detail, your print head may end up dragging a blob of plastic all over your first surface and mess with the print.

Here are the results:

In summary: these tests don’t show much difference in stickiness with different orientations of painter’s tape.

I even mixed up the orientations just to see if I could mess up the print. No good. Every print looked more or less the same except for a little curling on front-to-back #1.

The information contained in that last post is no longer operative. Put your tape on side-to-side, front-to-back, whatever gets you through the day.

Scientific method. For great justice.

Printing on Painters’ Tape

Here’s a little tip that would have saved me some grief and troubleshooting when printing with PLA on painters’ tape with my MakerBot Replicator 1.

The orientation of the tape matters.

Lay your tape front-to-back on your build platform, not side-to-side.

Look at this photo (of blue PLA on blue painters’ tape, so click to embiggen):

See where the front-to-back tape ends, and the side-to-side tape creates a rats’ nest of tangled PLA filaments?

Now look at the same print, but with front-to-back tape covering the print surface:

Much, much better adhesion. Fun new model coming soon, so watch this space.

How does my toaster work?

TL;DR summary: I fixed a busted toaster in 16 minutes without burning or electrocuting myself. HUGE WIN. Also: toasters are more complicated than you’d think.

WARNING: Grody photo of a crumb-crusted toaster follows.

Our toaster stopped working a week ago, sending ripples of calamity through our breakfast routine. Then the family went away for Thanksgiving and upon our return I noticed that the toaster had failed to heal itself in our absence.

The toast wouldn’t stay down. Push the plunger, the bread pops right back up. I supposed maybe a spring had come loose, so I popped the cover off and took a look at the mechanism.

As I worked I was half-hoping that I’d screw it up badly enough that I’d need to buy a new toaster and use this one as the body for a toasterbot or something.

No springs seem to be out of place, and nothing looks bent, broken, or obviously amiss. No butter or fried mice gumming up the works, although there’s about half a pound of toast particles rattling around in there.

Ho ho, what’s this? This seems like an awful lot of electronics for something as simple as a toaster. Bears further investigation, obviously.

When the plunger’s down, the little plastic lever to the right drops a metal strip across the two contacts, completing a circuit.

And what’s up with that coil? Electricity flowing through that coil creates a magnetic field, which will keep the metal strip and in turn, the plunger, stuck in the down position.

A timer elsewhere in the unit must turn off the electromagnet when the toaster thinks the toast is ready, releasing the spring-loaded lever.

So. If the circuit were to fail, the electromagnet wouldn’t keep the plunger in the down position.

Sure enough, there was a crumb shorting out the electromagnet. A quick puff of air and she’s working again.

Twenty bucks saved.

Repairing a Toy with 3D Printing

My daughter bought an inexpensive headlamp recently, and like many inexpensive toys, it broke within hours of purchase. She can’t wear it anymore because part of the buckle assembly snapped off and we managed to lose the broken piece before she could glue it back together.

Here’s the damage.

This is a perfect opportunity to fire up the MakerBot Replicator.

If you look carefully in the back of the photo you’ll see an AppleCore earbud wrap, which I highly recommend if you’ve got a bazillion small cables in your life. AppleCores are great stocking stuffers for geeks, BTW, and the holiday shopping season is nigh.

Moving on: let’s test one of my expectations about Living In The Future: in The Future, one will be able to repair broken household items quickly and easily using a 3D printer.

TL;DR version: we don’t live in The Future yet. But we’re getting there. This whole process took about an hour and a half of human-time.

The first step is to get a scan of the broken part. Scanning it with 123DCatch is probably too much hassle for what’s basically a flat object, so I put the headlamp down on a flatbed scanner and covered it with a few sheets of office paper and a black piece of cloth to keep too much light from getting in.

And then a little levels adjustment in Photoshop to bring out the contour I need for tracing. I’m going to add an entirely new backing to the headlamp instead of trying to replace just the broken bit.

I brought the photo into Maya, and traced the edges with NURBS curves. Next, extruded the poly surface, made sure the dimensions were correct, and exported to ReplicatorG. After 45 minutes of vertex wrangling I had this shape:

The slice and print went quickly. I glued the 3D printed part to the original with JB Weld.

(JB Weld also makes a great stocking stuffer for geeks. I once owned a ’92 Toyota Corolla [R.I.P. Felipe] that was 30% JB Weld by weight, not including the zip ties and the fuel door I machined out of an old PC case.)

Wait 24 hours to cure, and we’re done.

Totally functional, if not the most beautiful repair ever. I debated putting the STL for this up on Thingiverse, but this model is useful to exactly one person in the world so there’s not a lot of point in sharing it. If you must have one, email me or DM me.

Why We Don’t Live in The Future Just Yet: The barrier to entry on doing this at home is still pretty high for most people– computers and software are cheap, but the 3D printer required to do this hasn’t hit the sub-$300 range yet. Five years, maybe?

The technical skills for working in 3D aren’t too common yet either, but the easy availability of apps like SketchUp and TinkerCAD will take care of that in time.

BUT. I could see a service like this being offered at your local hardware store in The Future. Bring in your busted genechtagazoink and an eager nerdling will drop the part in a yellow, overbuilt scanner made by DeWalt, flop the geometry around in some yet-to-be-announced Autodesk product, and then print you a replacement part while you wait, sort of like the way house keys are copied now.

(If you ever meet me in person and want to start a good rant about legacy technology, ask me how I feel about house keys.)

Naturally, I found the broken-off piece this morning. Next to the fridge. Feh.