Chinese Conundrum

I've been buying IS1790 playback chips from AliExpress. These are about 1/3rd the price of the 'official' chips from DigiKey. Lately though I have been experiencing failures of around 50% of the chips that have been delivered.

The supplied chips are obviously copies, and when they work they work 100% of the original. However, the only way to check if they function or not is to solder a 28 pin SOIC down and hope for the best. A bit inconvenient if it proves faulty.

So to allow me to check the chips before sticking them down I came up with this:

It's a Tagbits UMT board wired into a 28 pin SOIC ZIF (Zero Insertion Force) socket. This lets me plug in a chip and test it without requiring me to solder it to a PCB.

Punch Drunk

I started work on my CNC router over the weekend. It's a moving bed design with an aluminium frame fitted to a 25mm base of MDF.
To get the holes for mounting the linear rails and extrusion I printed a huge 1500x600mm 1:1 print of the CAD drawing of the base onto vellum. This was then stuck to the MDF with spray mount.

I used my optical centre punch to get the holes centred. These are fantastic. Here is a 1:1 print of the mounting holes at the end of one on the linear rails. The holes are M4.

And looking through the centre punch:

It's easy to see how accurately the holes can be positioned when using a tool like this. The one I use is from Dankroy Ltd.

Here is the base made up with a piece of MDF used for the moving bed. Once I'm happy with the layout I'm going to drill some 15mm aluminium plate for the bed itself.

Ivor Biggun

Now I've acquired an A0 printer, I've been able to start on my CNC router. It's a moving bed design as I believe this kind is better suited to milling metals. It's a bit big at around 1500mm x 600mm and I need to drill some accurately positioned holes.

So I've printed a 1:1 scale diagram of the SBR20 linear rails and the machine bed so I can start drilling some holes.

I got several different kinds of paper when I got the printer. I'm using HP Vellum paper for the engineering prints as this is a dimensionally stable paper which is translucent. This will allow me to overlay it onto the parts I wish to drill and align the outline of the part with the real thing.

Here is the print for the linear rails:

The holes each have a cross-hair which I will use in conjunction with my optical centre punch to get precise hole positioning.

Hot Rocks

Found a video of a prototype project I worked on a few years ago:

A bonus feature for a 3 player gaming machine we were doing. All the machines are linked with a proprietary bus which allows them to synchronise the effects, and the volcano has an Ethernet connection to all 3 machines so any one can start the bonus. The lighting effects are all written in Pawn scripting language, and uploaded to the lighting controller at the start of each session. Looked good, but we never put it into production.

Milestag sniper rifle

Visit Tagbits to see the full range of tagger products described in this blog.

Finally got around to trying out my Milestag sniper rifle at Steve's (Operation Lasertag) site in Wakefield. Fantastic day out with son Joshua as usual. Rifle performed well in situations where enemy was attacking from a distance. Useless close up though! All 3D printed as usual.

Need to learn...

I really....really need to learn to say no when work offers me things that they are throwing away...

HP Designjet 500 with about £300 of paper. Coincidentally I am in need of a large format printer as I'm starting on my CNC router.

More rolling my own..part 2

I've had some great results with my Filastruder and ABS pellets from CraigRK

The temperature and nozzle diameter are critical. With the standard nozzle supplied by Filastruder I got filament I was not happy with. It was brittle when extruded at 220C, and had a rough outer texture. Anything much below this suffered from too much die swell and I was getting filament of 3.2MM which jammed one of my extruders. I found this was the case with pellets from several sources, so this is obviously a result of the hardware.

Lower temperatures seemed to improve the filament quality, but there was a corresponding increase the die swell. I'm now running with a 2.5mm orifice on a filtered die. This was supplied at 1.75mm and drilled to 2.5mm, and with an extrusion temp. of 190C.

I found horizontal extrusion less than satisfactory with jams regularly occurring. I tried vertical extrusion but found that the hopper guides available on Thingiverse simply jammed after a few minutes extrusion.

So I got a hack saw to the vertical hopper feed, and hot aired the chute until I could screw in a cola bottle, and mounted the filastruder at 45 degrees:

This gave me reliable pellet feed and after a nights worth of extrusion I was presented with this:

About 0.8Kg of filament. It is of really good quality. Here is a 10x view under the microscope:

Nice and smooth. And it is not brittle. It turns white as it is bent around a small radius as you would expect HQ filament to do.

Here is one of my Lasertag parts printed wholly from home grown filament:

I'm now at the stage where my primary source of filament is myself. It's much cheaper! The only problem I have now is spooling it up, perhaps I should get a Filawinder.