Second Sight

I've been asked by several people whether it would be possible to mount a sensor on the gun bodies sold at Tagbits so I re-designed a sensor mount to fit onto the forestock section. When fitted with a 3 way milestag sensor this should allow for a low cost solution, but will allow body mounted sensors to be added later if required:

Here's a view looking down on the Milestag Gun

Here is the printed part fitted with an acrylic dome:

The underside has been modified to ensure the dome mounting screws and M3 nut are flush:

Here is the part on one of my Mk4 guns:

Looking at the height of the dome on the CAD model, I was concerned that the dome might obscure the optical red dot sight:

A rather poor camera shot down the sight confirms this. The bright dot is the 'red dot' of the sight:

I am going to have to re-engineer my picatinnny rail mount to be higher. A second sight.

2012 Spares

After my extruder mount failed the other week, I declared that I needed to stock up on spare parts for my RepRap. I've printed this set of bits which is all but one of the components that I have identified as critical.

After printing the missing part I'll have a full set of spares. I really need to have pairs of some of these fittings though, namely the bar and linear bearing clamps as it doesn't really make sense to replace one of these in isolation.

Axis of Evil:Fixed

Because it's Christmas Eve I was really sociable and retired to the workshop to create a new mounting bracket for my Wade extruder. Reprap is like a drug. You've got to print stuff, and when you can't you have to fix it. Anyhow, I found some 1.6mm steel sheet in my materials stash and made this:

To make it I printed a 1:1 2d plot of the piece, then glued this to the steel with 3M Spray Mount. I then use an optical centre punch to centre the holes, then opened them up with a 3mm spotting drill before drilling through with a 4MM HSS bit. The larger holes I drilled with a stepped drill bit. Here is it fitted to my RepRap bot:

Lesson: Identify critical parts on the RepRap and make sure you print spares!

(Z) Axis of Evil

I successfully completed another 8 hour print yesterday, but I caught the Wade extruder mount with my hand and this happened:

I've been printing spares for my machine on and off for months. Unfortunately I hadn't got around to this part:

I'll just have to make a metal version of it by hand.

Printing on Kapton Tape

Nophead lent me some Kapton tape and I tried an ABS print on it last night:

It is an 8 hour print of a large part, it came out really well:

Although the part was much more firmly attached to the kapton than I've seen with PET tape, it still managed to lift the tape slightly at the corners:

I'd really like to eliminate this lifting if I can. It has not spoiled the printed part because as a percentage of the overall part size it is negligible. I'm going to try again with a higher chamber temperature. The above was done with a chamber temp of 42-45C. The tape though is great. It is 150mm which is exactly the width of my heated bed, so applying it is easy when I used the technique described below.This helps to avoid the inevitable bubbles when dealing with large adhesive tapes:

Bunged Up

Here's a video of my RepRap behaving as it should:



But for the last month or so I've been having problems. At random times the extruder started chewing filament instead of pushing into the heater. This of course resulted in failed prints. The first symptoms are particles of ABS accumulating on the idler bearing of the Wade extruder:

If allowed to continue printing, the extruder simply stops pushing ABS into the heater. On dismantling the extruder the hobbed bolt looks like this:

After cleaning with acetone it's pristine once again:

But after cleaning, sometimes I mange to get 2 or three large parts before another failure, othertimes it fails at the first print. I've tried reducing the flow rate of the extruder but this hasn't had any effect. The only consistent thing is that the print always fails on the second or third layer, never the first.

I got the nozzle from Wolfgang at RepRap Fab and I've bought a new one to see if this will improve things.

Buy Demand

I've posted on several forums that I'm open to suggestions for parts and kits to be available at www.tagbits.co.uk . One suggestion was for a Milestag CORE gun kit to complement the existing
Milestag UMT kit.

As I already had a design for the CORE module, I've added a CORE kit to the shop here.