Designing Axle Stubs for 3D printing

The crank-in-a-box that I’m working on needs an axle stub to locate it in the box. I designed the parts that I needed in Fusion 360 and printed them out.

The first version is on the left below. As a by-product of the printing process you can see that the top, and to a lesser degree, the bottom of the part are slightly flaired out. As a result the parts won’t fit in the matching hole without being filed down.

The part on the right is my attempt to get round the problem. axleStub-a02

I’ve gone into Fusion 360 and added a 0.5m chamfer to the top and bottom edge.axleStub-a01

It works a treat and the parts now fit together very nicely. (Just to mention, I’m making the hole 0.25mm larger than the part resulting in a nice tight fit)

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3D Printed Geneva Drive

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The Geneva Drive is an elegant mechanism used to convert rotary motion into intermittent motion.  Click on the image above to view a video of the drive in action on my Instagram feed.geneva-a15 I’ve designed the part for this project in Autodesk Fusion 360. If you have access to a 3D you can follow these construction instructions to make your own 3D printed Geneva Drive.

Download
Download the STL files from the link above. They should be suitable for most 3D printers.

I printed the parts out in a variety of colours of PLA from rigid.ink using an Ultimaker 2.

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Here are the five parts ready for assembly.You will also need some cyano glue a small screw and a washer.

geneva-a07A dot of cyano glue holds the handle and crank together.

geneva-a08Thread the crank through the hole in the base.

geneva-a09Fit the drive wheel to the crank. A dot of cyano holds the drive wheel onto place. Make sure that it turns freely.

geneva-a10Fit the Geneva wheel over the pin on the base so that it lines up with the drive wheel as shown.

geneva-a11A small screw and washer holds the Geneva wheel into place. Don’t over tighten it as the wheel needs to be able to turn freely.

geneva-a12That’s it! Your completed Geneva Drive.

 

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Hand-cranked Planetary Gear

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Make your own hand cranked planetary gearbox from laser cut parts.
Download the parts in pdf and dxf format here:
You will need:

3mm plywood.
12mm dowel: 15mm long x 1 | 55mm long x 1 | 30mm long x 1
6mm dowel: 15mm long x 6 | 36mm long x 1
optional 12mm wooden ball
12mm MDF baseboard 130mm x 100mm
6 small wood screw.

Start with the parts from the ringgear.pdf file. You will need to cut out two copies of the ring gears. Cut out the parts from 3mm plywood on your laser cutter. These make up the frame of the gear box.  Each of the two ring gears is made from three layers. The centre layer has a longer tongue than the two outer layers.planet-a01

Use cocktail sticks to help align the pieces as you glue them together.planet-a02

Glue the third layer into place and again line it up with cocktail sticks through the location holes.planet-a03

Notice how the longer tongue protrudes from the centre of the ring.planet-a04

Clamp the parts up and let the glue dry thoroughly. Repeat this process to make up the second ring.planet-a05

Glue together the three spacers.planet-a06

Fit the two rings into the base and glue them down. Thread the spacer into position glue it and clamp it into position at the top of the ring.planet-a07

Assembling the Parts from Planetary1

The larger gear has eighteen teeth. You will need a dowel 12mm diameter x 15mm long
Thread and glue the three gears to the dowel and centre them along the length of the dowel. Use the small arrow to help accurately line up the teeth.planet-a08

The two spacer pieces have a slightly larger centre hole than the holes in the gears. Glue them onto one side of the gear.planet-a09

Carefully clamp them up as the glue dries.planet-a10

Glue and clamp the spacer side of the gear to the spider lining it up carefully with the hole in the spider.planet-a12

The small gears have twelve teeth each. The dowel is 6mm diameter x 15mm long. Glue together the three gear pieces and centre them over the dowel. planet-a11

Assemble all three in the same way.planet-a13

Drop the three small gears into the spider.planet-a14

Glue in the three spacers.planet-a15

…and fit the cover piece into place gluing it to the spacers to complete the first planetary gear module.planet-a16

Planetary gear viewed from the other side.planet-a17

Assembling the stands.pdf parts

The main gear has eighteen teeth and is made from three layers. The dowel is 12mm diameter x 55mm long. Thread and glue together the three gears onto the dowel carefully lining up the teeth. The dowel should protrude just under 3mm from the top gear.planet-a18

You will need these four parts to make the handle stand.planet-a19

Glue and clamp them together.planet-a20

The completed handle stand.planet-a21

Thread the gear into place in the stand with the five spacers fitted as in the picture.planet-a22

These parts make up the output stand.planet-a30

Front and back views of the assembled output stand are shown here. Use glue to fit the parts together.planet-a31

Making up the parts from handle.pdf

You will need a 6mm diameter dowel 36mm long. A wooden ball finishes off the handle nicely. The ball in the illustration below is a 12mm diameter beech wooden ball with a 6mm hole drilled into it. The balls can be purchased from eBay – I’ve written a blog post on drilling  holes in wooden balls here.

The handle is made from two layers. Glue and clamp then together then fit the handle to the drive shaft as shown. The remaining parts (the star and spacer) will be fitted to the output shaft later.planet-a23

Assembling the parts for planetary2.pdf

You will need the final 12mm dowel for this part. 12mm diameter x 30mm long.

There are three circular spacers in this module. Two large outer diameter (27.5mm) and one with a smaller outside diameter (25mm). Starting with the smaller spacer, line it up with the hole in the spacer and glue it down.planet-a24

 

Fit and glue the two larger spacers to the end of the dowel so that they are a flush fit. Glue the spacers and dowel to the first spacer so that they are lined up as accurately as possible. planet-a26

Make up the three twelve tooth gears as before. Drop them into place on the spider.planet-a27

Glue the three spacers into position…planet-a28

…thread the ring into position and glue it to the spacers to complete the second planetary gear.planet-a29

Final Assembly of the Parts

Draw an alignment line 22.5mm from the centre of the board. Line up the edge of the ring gear base with your alignment line then screw the ring gear to the centre of the board.planet-a32

Fit the second gear assembly into the first ring gear.planet-a33

Fit the output stand over the output shaft. Screw the stand into place.planet-a34

Push fit the star onto the output shaft. This helps make the turn of the output shaft clear and visible.planet-a35

From the other side of the gear, fit the first planetary gear into place.planet-a36

Fit the input gear and handle into place in the first planetary gear…planet-a37

…and screw the stand into position.planet-a38

 

That’s it! Turn the handle and marvel as the wheels within wheels turn in beautifully harmonic synchrony!planet-a39

 

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Planetary Gearbox


The latest model in the Archive Project needs a slow turning shaft onto which I can fix some cams. There is limited space under the model so I looked for a reduction gear that was compact. This planetary reduction gear seems to fit the bill nicely!

On the input side the motor turns at around one hundred rpm.

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The output is roughly eleven rpm. One tune every five and a half seconds.planet-a02

There are two stages to the gear box, each reduces the speed by a third.planet-a03

One of the two planetary gears.

planet-a04

Exploded view. The parts are made from 3mm laser cut plywood. The gears are made from three identical layers bonded together.planet-a05

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Finished First Prototype

The final part of the posable maquette is the head. I’ve used a double ended ball joint for the neck. I’ve changed the design of the body section to accommodate this.`posable-c01

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Here’s the first completed prototype. I now need to go through the model and make the improvements that have come up as I put the parts together.

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Making Ball Joints

At each joint in the posable wooden maquette is a ball joint. This comprises a 12mm wooden ball fitted to a length of 6mm dowel. To this end, I need to be able to quickly and accurately drill a 6mm hole into a wooden ball.

Here’s the jig I’ve come up with.

I’ve drilled a 6mm hole into a piece of 2″ x 1″ and countersunk it. This will be where the ball sits. I’ve then cut out four pieces of 3mm ply on the laser cutter with the top piece over hanging. I’ve screwed them down to the 2″ x 1″ so that their edge is 40mm from the centre of the hole.posable-b02

Here is the jig with the ball sitting in place.posable-b03

The clamp piece is another rectangle of laser cut ply. It has a 10mm diameter hole cut 40mm from the edge.posable-b04

The clamp works with simple finger pressure to hold the ball as it is drilled.posable-b05

I’m using a pillar drill for accuracy. Step by step:

Lower the drill to line up the jig with the drill bit then clamp the jig into place. (Clamps aren’t shown on these pictures)posable-b06

Raise the drill, fit the ball and clamp piece.posable-b07

Drill down into the ball. Quick and accurate!posable-b08

Sample balls and dowels.posable-b09

Having worked out how to make accurate ball joints I’ve been working on the maquette. Latest step, I’ve added body, shoulders and neck. Looking good so far!posable-b11 posable-b10

As a quick try out, I’ve added a spare leg onto the shoulder, the actual arms will need to be smaller and thinner but you can see the effect.posable-b01

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Posable Progress

posable01I’ve had a brief hiatus while I waited for these lovely 12mm wooden balls to arrive from eBay. Now they are here I’m back in action!

posable02

First step (Ha! Step! Geddit? 🙂 was to redesign the ankle. I’ve fitted the ball to the foot rather than the leg. The result feels a lot more  solid.

posable03

With the ball on the foot the shin section has become a a double socket piece. There are some issues with lining up all four parts of the shin that I might have to address. Perhaps a couple of alignment holes through all four pieces?

I’ve also lengthened the shin a little to be a bit more anatomically accurate.

posable1000

I haven’t cheated this time, I’ve actually made two legs. This is the picture from my Instagram feed. You follow me on Instagram right?

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Laser-cut Posable Maquette

poseable-a09Is it pose-able, poseable or posable? I seem to have settled on the latter for now. Anyway, I’m working on a posable character made from laser-cut ply wood.

My starting point is a ball and socket design that I came up with a while back. The balls are 12mm (1/2″) wooden balls purchased from eBay. I drill a 6mm hole into the ball and glued in a short section of 6mm dowel. This is then glued into the laser cut parts. Friction holds the ball and socket together making a posable joint.
poseable-a01

I started with the legs: Here are the various parts for a leg unit. I cut a notch into the top of the socket section to make it easier to push the ball in later.poseable-a02

Trouble is, the finished part is weak. Of the three that I made, two cracked in the same place as the one in the picture. Obviously a design flaw.

poseable-a05

I did manage to make this foot and shin section for the part that hadn’t broken but obviously changes need to be made.poseable-a04

Rather than assembling the leg section then forcing in the ball I thought it might be better to assemble the leg around the ball. This means that it probably won’t be possible to pull the pieces apart once it is assembled but I don’t think that matters. I’m aiming at a posable character, not a 3D jigsaw.

In the next version I’ll make the inner sections slightly longer. That will keep the pressure on the ball and make the joint slightly stiffer so that it holds its pose better.poseable-a06

Here’s a completed leg. The design still needs some work. The thigh needs to be heavier and the shin lighter for example but I reckon it is a good start.poseable-a07

For the Instagram picture I took two photographs of the one leg, flipped one and photoshopped them together to show how they move and how they would fit together in a finished model.posable1000b

Next, I’ll make some improvements to the leg and foot then have a go at the body.

This might make me a nice Kickstarter project 🙂

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Battery Replacement.

I love my 5th gen iPod Nano. I use the voice-over feature to navigate through the menu to listen to podcasts in the small hours without disturbing #truelove. Recently the battery has began to loose its power, to the point now where the battery runs flat after no more than thirty minutes. The 5th gen ipod is no longer made so I decided to change the battery myself. And so to iFixIt!ipod-a05

The new battery on the right below, purchased from eBay for £3.99

The instructions on iFixIt are clear and comprehensive (there is an error in step 18 but it is corrected in the comments) I cursed Apple all the way through the fix, this device really isn’t designed to be mended. Glued parts, tight tolerances, awkward snap joins. Curse you Apple!ipod-a04

Fully apart and still working!ipod-a01

And here it is back together! The top of the bezel is slightly bent and I had to remove and reattach the screen as there was a cat hair under it (you can just about make out Ruby the cat in the background of the picture) but apart from that it works perfectly and hopefully the battery will be back to the full twenty four hour playback.ipod-a03

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Moon Rise

sceneCorrected

I made this picture in Illustrator. The stars in the background are created using Astute Graphics space fill tool which allows you to quickly fill an area with randomly scattered repeating shapes. I saved out the picture as a jpeg and dropped it into PhotoShop. On the layer below I pasted some paper texture clip art and I changed the blend model of the trees layer to multiply. Ta daa! To finish off a added a little vignette then posted it on my Instagram channel.

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