M6 Version of MakerBeam

8 Jan


A small experiment in 3d printing something like “MakerBeam”, an aluminium extrusion based construction technique, itself derived from 80/20 extrusion (which, by the way, is silly expensive here in New Zealand).

I have lots of sizes of M6 hex head bolts so I scaled it up a bit to fit the heads of those bolts, rather than special headed bolts or special nuts. There’s an M6 thread down the hole in the centre.


The four diagonal slits in the design are an attempt to be tricky. They’re only 0.1mm wide so they should get melted together when printed. However, they trigger the slicer software to add a full set of perimeters around them, greatly strengthening the weakest point of the shape. Not sure how well it will work, but worth a try. I could achieve the same effect by fiddling with the slicer and defining extra volumes to print with higher infill or solid, but I’d rather define it in the model, not the slicer.

sliced makerbeam

In the slicer (I use “Slic3r”) preview window, you can see how diagonal slits have added a lot of extra strength.


Cosplay Experiment (3D Print + Cloth Mache) Spiral Horn

7 Jan

steps of spiral horn

Papier mache (and the related “cloth mache”) techniques has some excellent features. It’s extremely cheap, and can make strong and light weight objects. However – at least when I do it – it can end up rather lumpy and irregular.

I love 3D printing, but making large structures with a normal printer gets expensive fast, and also takes a long time. The longest print I’ve done took 16 hours, but some people routinely print 50 to 100 hour prints. The shapes should be exactly what you planned (except when something goes wrong) but laying down all those layers takes time.

I’m not the first person to think of combining these two techniques. I got the idea from 3d-print-and-papier-mache and I’m sure others have done it as well.

I was playing around with “vase mode” on my printer the other day. This is a special way of 3d printing where, rather than laying down a series of layers, the printer lays down molten filament in one continuous SPIRAL layer. The resulting object has to be hollow, with thin walls only one layer thick. However, since the extruder doesn’t stop and start but just keeps looping around while slowly rising, the results tend to be very smooth and are surprisingly strong for their weight. It’s also much faster as only the outside skin is being printed

horn render

I drew up this horn shape in Fusion 360. (For those interested, it’s a loft between two circles, with a coil edge as the guide rail).


Here it is printing. It came out very nicely, with lovely smooth curves that felt very nice to the touch.


My first attempt wasn’t so good. In vase mode, each line of filament must partially overlap the one below, since there’s no interior. If it moves too far horizontally from the previous layer, it ends up splodging in mid-air. I need to do some more experimenting to find the shallowest angles I can print.


I cut some strips of cloth from the rag pile, and wrapped my 3d printed “horn”. I worked in a spiral pattern from the bottom, dipping the cloth in heavily diluted white pva glue (probably 50/50 water to glue). It took a couple of tries but was surprisingly easy.


The very wet mix took a long time to dry. I left it sitting for a couple of days. Since the armature was 3d printed, I didn’t need to worry about it getting damaged or mouldy.

I need to do a bit of trimming and sculpting at the ends, where the cloth ended, but only minor stuff.

Here it is on the turntable, ready for painting. My turntable is built from a car wheel bearing, with a cordless drill motor for rotation. Using spray paint, this gives me a much more even coating.


This is after a very quick paint job. I just grabbed the first couple of cans that came to hand (which happened to be blue and gold). However, it does look a lot nicer than the plain white.

It looks, and is, pretty rough. I’m sure I’ll do more experimenting with this, though. One big advantage of this technique is that I can simply mirror image the model, and hence the 3d print. Compared to trying to make two parts look the same by hand, that should be a big improvement.

Storage for Boot (Trunk) of Toyota Caldina

7 Jan


The boot of our family car is usually full of ‘stuff’. Jackets and blankets in case of a breakdown, tow rope, leather gloves, etc. These tend to get shoved to and fro to make room but flop around and spread out. This annoyed me more than usual the other day, when I had to clear everything out to get access to the floor.


I didn’t take a photo of the mess in the boot, but this is the sort of junk that was in there, hurled over into the back seat.


Looking at the boot, there’s an area just behind the back seat where things could be stored vertically if there was a suitable container.

I took some measurements and used Fusion 360 to work out the angles. I could have drawn up a cad diagram of the unit but it was just as easy to lay it out on paper.

boot storage

This is what I came up with. It’s a simple box with two partitions. One side is angled to match the slope of the back of the back seat. The other is dropped down a bit to make access easier. Cardboard was the material of choice for this. (The rendering above was done after the fact, while experimenting with Fusion 360’s new sheet metal workspace, which can also be used for cardboard boxes).


I found a suitable chunk of cardboard from our huge collection in the shed and we marked out the main shape and cut it out. Folded up and held with clamps, it looked pretty reasonable, and fitted firmly into the space I’d planned.


When I put it down on the floor, it was immediately inspected.


The weak point will probably be the back (front as you look at it) wall. It’s already got two layers of cardboard over much of it, so I filled in the gap, then covered it with another complete layer. Probably overkill, but cardboard is cheap and light. We slathered it with pva glue and weighted the sandwich of layers down with exercise weights and wood.

I flipped it the next morning, and glued the angled face. The partitions were added with more pva and some tricky clamping. I added a rim of clear tape just for looks


This is what it looks like in place for a test fit. I mucked up the measurements slightly and had to cut a notch for the handle which releases the sunshade fitting. A lot easier to change in cardboard than something harder.


And this is what it looks like full of stuff. It absorbs a heap of bits and pieces and still leaves most of the boot clear.


Christmas Lights Obelisk/Pyramid

9 Jan

Barbara wanted some pretty Christmas lights. It was a bit late for Christmas (i.e. it was January). So?


We started with some 100×25 Oregon, ripped in down to 50×25. Here I’ve chopped four 1600mm lengths to form the sides of the pyramid/obelisk. We found a nice looking christmas tree on Google Images then used a graphics package to measure the angle – turns out that 80°  from horizontal was the angle we thought looked good.


Some simple trigonometry gave us the size of the base (close enough to 500mm), to get the angle we wanted. Some more 50×25 oregon and various offcuts from the mitre saw gave us a base.


We braced it up for strength, since I planned on placing one or two concrete blocks onto the base to weight it down. (We get strong winds around our place).


Some 7mm holes and M6 bolts attached the ‘legs’ to the base. Forgot to allow for the 25mm offset from the ends of the pieces of wood, so our angle won’t be quite correct.


A very sophisticated (not) mechanism fastened the top together. One zip-tie.


Here’s the result so far, with a human for size comparison.


Chicken wire! Messy stuff to work with, but a compressed air stapler made it easy to pin it down. We only put wire over three sides, leaving the fourth side open to allow placing concrete blocks (for weight) and christmas tree lights (for pretty).


We put it up on an earth bank overnight, to check it wouldn’t blow down.


Barbara fitted the lights through the chicken mesh. Took quite a while. Here we ran a quick test in a darkened room. Looking good!

Come nightfall, it was very pretty.

Avoiding electrocution while testing 240v circuits

3 Jan


I needed to measure the output voltages on a bunch of unmarked transformers I’d accumulated. (No, I’m not a hoarder. I can stop any time I want to. Perhaps.)

I’ve done this before, with just a bunch of alligator clips, a mains cord, and a multi-meter. It’s very simple, but it’s *dangerous*. Reaching over live 240v wires to take measurements isn’t a good idea. Worse is that a bunch of wires in mid-air have a tendency to move around, generally shorting something wires together.


I recently made up a number of little test boards to hold test circuits in place without having to worry about wires getting loose. Here, for example, is a test with an arduino (on a solderless breadboard), an L298 motor driver, and a worm geared motor. The boards are 85mm long, with two rows of M4 holes 10mm apart. The rows are 75mm apart. They’re mounted to a laser cut piece of 6mm mdf, with two long rows of M4 tapped holes. (MDF taps quite well with a tap in a cordless drill).

I really don’t know, yet, whether these ‘boards mounted on boards’ are a good idea or not. However, they’re cheap and worth trying. In particular, they hold wires securely for testing which was exactly what I wanted for testing my transformers.


Here’s a test victim hooked up to a test setup. I grabbed a spare chunk of 12mm MDF (I didn’t even bother cutting it square). I marked a grid of cross marks at 10mm x 25mm spacing using the laser cutter, then drilled and tapped just the few holes I wanted to hold things down. Chocolate blocks, hot melt glued down, gave me a secure but adjustable fixing for wires.

Note that I used a female EAN mains plug rather than a standard power cord to supply power. I physically unplugged it every time I changed the circuit, which I probably wouldn’t have done if it was a plug into a wall socket.

This particular transformer made me glad I’d gone to the trouble, as it was very easy to power it off when I plugged it in and it started to hiss and smoke. Looks like I picked up a 110V primary transformer somewhere along the line and it *really* didn’t like running on 240V.


Even when I ended up using crocodile clips, they were much more secure when clipped into the immobile terminal blocks.

A quick test of a crude opto-coupled triac circuit felt a lot safer when wired up like this as well. I wouldn’t trust a solderless breadboard at 240V.

Laser cut numbered pegs for workmen

7 Nov


We had a tradesman coming out to do some “stump munching” of some of our (large) supply of stumps. We only want a few done, and some of them are in the deep grass. So, laser cutter to the rescue.


Here’s the laser cutter chopping out some mdf numbers – about 80mm wide x 140mm high. Mdf is 3mm thick, but I should have used 6mm.


For a quick job, they came out ok. The bright yellow plastic would be really good for this but it’s PVC. Cutting pvc on the laser will rot your lungs from the hydrochloric acid vapour. Worse, it damages the optics of the laser!


A very quick spray paint with flourescent pink from a rattle can.


Some cheap bits of wood. Once again, a box of kindling from the supermarket.


Bits of wood pointed on the mitre saw, and pink numbers stapled on with the air nailer.


These did the job. You can see them from some distance. Next time I’ll use thicker material as the staples pulled right through on a couple when I hammered the stake into the ground.



Quick laser-cut carpentry clamp storage

30 Oct


There’s a saying in carpentry “You can never have too many clamps.” This is true until you need to store them. I’ve got a bunch of these cheap “F” clamps which make a messy pile. I knocked this holder together out of 3mm mdf. The slots are 5mm wide and go back 70mm.



As usual, I used the very handy “BoxMaker” extension for Inkscape, though I drew the slots in DesignSpark Mechanical. Note that the top layer (with slots) is doubled up with an extra layer to make it stronger. It might have been OK like that but I later added some simple braces. After that it was plenty strong enough.



Here it is attached to the wall. (It’s actually attached with a French Cleat so I can move it around if I want to).


And here it is fully populated. I screwed another piece of wood to the bottom of the back, a bit thicker than the cleat at the top, so the top now slopes towards the back by a few degrees.

Very quick. Very cheap.