Sunday, 5 July 2009

Time for a new Blog/Website

This Blog has been fine so far but now I have a quantity of work that needs to be documented in an instructional format instead of blogged.

A lot of my online work over the last year or two has been in the form of contributions to the RepRap Project so it has mostly been documented there and blogged here.

Whilst I will be still continuing to contribute to that very worthwhile project there are some things I have done that I need to document that fit more properly in a number of other projects.

Being at a cross roads I have taken the decision to consolidate my efforts using a single CMS/Blog that will allow me to mix blogging style updates with structured, instructional, static documents.

This will be done on my homepages hosted by ADSL24 and made available under a Creative Commons, Attribution-Noncommercial-Share Alike 3.0 Unported License.

My aim is to transfer some of the contents of this blog to the new AKA47 Blog in the form of collated documents as time allows.

For further reading etc please surf onwards to :-

AKA47, The Palace of Glittering Technological Delights.

Thursday, 9 April 2009

Broken Lathe Fixed Again

My mini lathe has been out of action for a little while because I broke it but it is again in working order. (I have been short of time too)

I smashed the plastic head stock gears cutting aluminium heat sinks using a parting tool. It all came to a sudden stop accompanied by the sound of gear teeth falling off inside the head stock.

I replaced these plastic gears with metal gears bought in as one for one replacements and also replaced the deep groove ball bearings with taper roller bearings.

All in all much better. the surface finishing is now much better particularly on facing cuts. Using preloaded taper roller bearings reduced the end float that was the cause of the poor finish. The gears that go now when it comes to a dead stop are the ones that can be accessed without tearing down the entire lathe and head stock.

Work can resume now on the plastic extruder, barrel components.

Monday, 26 January 2009

Worm Gear Filament Feed Test Bed

Here's the Worm Gear Filament Feed test bed. Constructed from laser cut acrylic.

The bracket on the right is a spare and the one on the left shows the test bed with gears, axles, O ring springs and an M3 machine screw to test the operation.

The O rings are used in place of springs and are common 16mm ID by 2.5mm. They provide the worm gears with more grip than springs and are both readily available and cheaper. They ideally need to be fitted to pulley wheels or at least collars that keep the axles square to the brackets.

This is something to be sorted that wasn't apparent until I assembled it all. I guess this is why prototyping and testing is useful.

Saturday, 10 January 2009

Feeding ABS with Worm Gears and Threaded Rod

Here's a method (inspired by all the other folk experimenting with alternative filament feeds) of feeding filament using Worm Gears and 3mm Studding.

Next job is to design the holder to mount it all to a RepRap extruder and a feed motor assembly.

The pitch of the M3 is 0.5mm per turn giving a feed rate of 0.5mm per turn of the drive shaft.

The tooth pattern cut into the gears is aprox 1mm deep so 0.33 of the diameter of a nominal 3mm plastic filament.

Whilst it all feels to grip prety well I will need to actually make an assembly and do some measurements to see how well it works really.

Worm Gear, Blank, Filament and drive shaft

Here's a picture of a worm gear, a gear blank, the drive shaft (a piece of M3 studding) and a piece of the 3mm plastic welding rod/filament that the assembly is expected to feed.

Cutting worm gears on a Lathe

Here is the finished worm gear holder with a worm gear blank in the holder and a finished worm gear on top for comparison. The cutter is a standard M3 Tap.

Note the 1.5mm PTFE disk under the worm gear blank (3mm thick) this is to centre the blank to the cutter and to support the gear during cutting whilst helping the gear to turn on the pin.

The pin is just a piece of axle with a coupling sleeve on to stop it falling through the gear holder.

I marked a line on each blank to show when it had done a full turn and with the RPM of the lathe set to about 200, advanced the gear holder into the cutter 0.05 mm per turn of the gear.

It could probably have been done quicker but I was'nt in a rush, the job worked perfectly and the cutter never broke.

Milling a Worm Gear Holder on a Lathe

I needed to mill out a slot on a holder that I was making to hold worm gear blanks whilst I cut the worm pattern into the gear. Not having a milling machine I used my mini lathe to mill a slot into the holder whilst it was mounted in the lathes tool post.

The picture above shows the milling bit in the lathe's chuck and the milled gear holder.

The milling bit was 6mm diameter and the worm gear blanks were 3mm thick. Milling the holder in the lathe it would be used in ensured that the slot was centred to the axis of the chuck.