Someone saw a cockroach up on twelve.....

Proton pack design is pretty well complete. tommyb345b has beaten me to completion with my own design. But my copy of it is coming along nicely:

All the files are available at: Thingiverse

Seeing things running through MY head.

In my quest to design a fully 3D printable Ghsotbusters' Proton Pack, I've had to make the part known as the 'Synch Generator'.

This is a large part, and it's the biggest thing I've ever made, weighing in at about 770g.

It's made of 6 paired copies, plus two other pairs, and is designed to be bolted together with M4 bolts. I printed it all in PLA to avoid ABS warping. Both my printers are in heated chambers, but even that struggles to prevent warping on such large parts.
All the proton pack parts can be downloaded here.

Busted

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I believe the technical term is 'a failed print'

In Tandem

Gunbot with Z Probe and Mendel 90 printing simultaneously.X Axis a bit noisy.....

Gunbot Broken

I've had my custom 250mm x 150mm 3D printer 'gunbot' for about 2 years now...and I've broke it. It uses the extruder controller that nophead developed some time ago and I went and plugged the extruder stepper motor where the hot end and thermistor should be connected. This connected 12V to the input of a 3.3V micro, and it is no more.....

The micro in this design is a 28 pin TSSOP package and this is a bit hard to remove without resorting to scalpels.

But my mate Dave has access to 22,000UKP worth of SMD rework station.

It's a nice piece of kit that heats the PCB from underneath and when near the re-flow temp, activates an infra red source to heat the targeted chip to the melting point of the solder. Here the IR beam can be seen targeting the faulty chip:

After the faulty chip is removed, a CCTV camera with a zoom lens is used to accurately apply solder paste to the pads:

The SMD rework machine has a CCTV camera and a prism to allow the chip and the PCB pads to be aligned. A light source can be faded upwards or downwards to illuminate the PCB or the underside of the chip to be placed. By fading between the chip and the PCB pads the chip can be accurately aligned. A vacuum holds the chip on a manipulator, and the chip is lowered onto the pads, and the vacuum released to free the chip.

Here is the PCB with the replaced MPU:

Further Filastruder Fun

I've been doing some empirical tests with my Filastruder in an attempt to optimise the Filament produced from the ABS pellets I bought. I decided to extrude 1m of Filament at a range of temperatures, and measure the diameter at 6 positions along each length.
This allows me to calculate an average diameter and a max-min deviation.
I extruded at temps. from 190C to 205C in 5C steps. With the following results:

I'm aiming for 0.1cm deviation with an average diameter of just under 3mm. The inlet manifold of my reprap extruder is 3.2mm and so I want to stay comfortably far away from this with a minimum deviation.

Looking at this rather small data set, it seems that 200C is the best temperature for the ABS pellets I have. Temperature less than this start to make the die swell a significant factor, increasing the filament diameter to over 3.0mm.

I also noticed that as the temperature increases, the surface of the produced filament become rougher.
I took some x10 magnification shots of filament with my trusty old stereo microscope:

First, 3mm ABS filament purchased from Reprapsource

Nice and smooth.

Second, Filatruder made 3mm ABS filament extruded at 190C:

Not bad, considering it is home made. Next, 3mm ABS filament extruded at 210C:

Noticably rougher. In the prints I have done, I do not see this as being an issue as the extruder hobbed bolt will average out the 'roughness'. So long as the filament is a reasonably consistent diameter, all should be well.

However, I found an unusual problem when using Filastruder filament, but in a wierd Z axis kinda way....

I've had great results with a couple of my Milestag Lasertag gun handgrips.

I decided to try a more complex print, this one is of my infra red focus tubes:

The print failed around Z=30mm, but seemed to recover at about Z=35mm. A second print of the same gcode failed in the same way. This is gcode I have been printing with reprapsource filament without issue for 2 years.

This image shows the failure on one of the tubes at approx. Z=30mm

A print of another of my Milestag gun parts failed twice, also around the 30mm mark:

I decided to try a simple 20mm square tube print to a height of 40mm, this also failed around the Z=30mm mark:

The only common factor here is Z. All the prints have massively varying X and Y deviations. Z is the only common factor.
Which is when I realised that some months ago I was having a problem with skipping on the X axis. Some prints would fail due to a loss of x motor steps as the layer changed to the new layer. It turned out to be a lack of current on the X axis stepper, but prior to this I changed the software to raise the extruder by 10mm at the start of a new layer.
The thought behind this was that the extruder was jammming on the previous layer as it homed to the start of the next one.
My 'gunbot' is in a heated chamber, with the ABS filament entering from the top:

Through a small hole:

My theory was that the roughness of the 210C extruded filament was catching on the walls of the heated chamber when the extruder raised itself by 10mm at the start of each new layer. This caused it to bend inside the chamber, and exert pressure on the extruder. This slight increase in pressure was enough to clog up the extruder after about 30mm of Z printing.

Here is the same breech part successfully printed on the left hand side with Z retraction removed, compared with its failed peer, which has the 10mm Z retraction:

Filastruder print results

I printed one of my Lasertag focus tubes with the Filastruder produced filament that I made yesterday. This is a tube designed to hold an infra red LED at the focal point of a lens, and allow the LED to be moved along the focal plane to allow it to be properly focussed. I was really pleased with the results:

The natural ABS supplied with the Filastruder kit has a slightly off white colouring as expected. But the final result is comparable the output from commercially produced filament.

The top surfaces of the flat objects were nicely filled and even:

And no blobs on the Z axis:

The issue I had was with the end of a 45 degree chamfer on the Z axis. It appears that the filament was forced along too tight a radius. I have increased the extrusion temperature, this was done at 230C, and I'm trying again. Fantastic results for first attempt!

Filastruder Build

I started building my Filastruder kit over the weekend. Stage one is to fasten the nipple (AKA pipe) to the flange.

Then slide the hopper body onto the nipple,(not shown in this pic), and fit the threaded coupling. The coupling is where the brass die screws into.

Stage three involves fitting the auger and assembling the thrust bearing. The thrust bearing is sandwiched between two washers which can be seen butted up against the thrust plate (the upper of the two plywood sheets).

The next stage is to fit the drive collar. This is a 3/8" socket which locks with a small pin against the flat on the output drive of the gearbox.

The pin is held in place with some tape.

The motor is fitted to a small sheet of plywood which is fastened to the base plate with a couple of wood screws. Don't do what I did and pre-drill the screw holes so that the screws clash with the bolts holding the motor in place.

Here it is all fixed together. The heater band and electrics need to be added next.

After fitting the heater band and doing a small test extrusion, I noticed a significant temperature drop from that dialled in on the temperature controller to the actual temperature. A difference of around 30C when the drive motor is running. This is to be expected as the molten ABS is taking heat away from the heated die. I added some extra insulation in the form of aluminium foil:

Here it is with 3D printed switch/ PID controller bracket from Thingiverse and the extended hopper fitted:

The output spooled up:

I've found that the best scenario is to have it reasonably high up. I used a height of about 1.7m for this run. Also, the landing zone needs to be as clear as possible so the filament does not build up as it rubs against (say) a wall, then jars as gravity frees it. I've been getting +/-0.1mm on the filament. I believe I can improve this by reducing the aforementioned jarring. Overall: HAPPY ;O)

Dome on the range part two.

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I make sensor domes for my Milestag guns using 2mm acrylic sheet heated in the oven and press formed over a mold using a 3d printed ring which is designed to fit over the mold. You can see the mold and the forming ring here:

The ring fits into an MDF sheet that allows me to push down enough force to deform the acrylic over the mold:

I wanted to experiment with polycarbonate sheet. It is cheaper and tougher than acrylic. However, it has a higher glass transition temperature (147C) than acrylic (107C) and this caused the ABS plastic of the forming ring to soften and leave deposits on the egde of the dome during the deformation process.

I decided to make a replacement forming ring from aluminium. I bought a billet from ebay for about £6.

I used a combination of drills and boring bars on the lathe to turn a replacement ring. It came out rather well:

It fits nicely into the MDF sheet and works slightly better than the ABS ring when forming the sheet as it has a narrower rim which allows me to apply more pressure to the sheet.

Safety Last

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My Milestag sniper rifle is coming along nicely. It has to be ready for the 22nd September when my son plans to use it at his lasertag party. The plan is to have two teams of 8 against a lone sniper.

I've added a couple of features to the rifle:

I've added a Barrett style muzzle brake:

And a mount for the RJ9 connector for the head sensors:

I've plumbed in the LS2020 laser module and this is working. This is going to be used at a commercial lasertag site, which uses Adventure Sports equipment. I have created a special version of my open source UMT code to be compatible with the AS protocol.

I've decided to play it safe with the LS2020 laser. Even though it is a class 1 device, I have modified the software to enable the PIC watchdog timer. The worst case Milestag packet length is around 27ms (all 1s). My software kicks the watchdog only in the 'turn the laser off' code which is called continuously unless a Milestag packet is being transmitted. The watchdog timeout is set to around 30ms and so if anything goes wrong and the laser is left on, the watchdog will reset the PIC and turn it off. So the laser will only ever be on for a maximum of 30ms.

The final step is to align the laser with the telescopic sight. To achieve this I've printed an adapter to allow me to attach a bullet camera to the telescopic sight:

And I've created a special version of the software that sends a Milestag packet every 500ms so I do not have to stand there pressing the trigger and reload buttons as I line up the sights.

Laser diode adjuster: Third time lucky

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After 3D printing my Mk2 LS2020 laser diode adjuster I decided that it could be improved. I managed to reduce the height by about 20mm and improve rigidity. Here is the new design:

Here it is fitted to the sniper rifle body, note that the wooden stock is now stained:

From the top it is noticeably slimmer than the previous version:

Laser Adjuster Fitted

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I fitted the LS2020 laser adjuster to my Milestag sniper rifle after printing and fitting a picatinny mounting clamp. It looks good, but it sticks out too far. I've had a few ideas for a Mk3.

Second Sight

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After designing a windage/elevation moubnt for the LS2020 laser diode, I realised that there would be too great a moment if the laser was twisted. So I redesigned the entire thing and came up with this:

It has an arm which rotates around an M4 screw. This is held in position by a long M4 bolt which engages in a 'V' indentation in the outer circumference of the arm. This screw acts as a worm drive and allows accurate positioning for the elevation.
The windage adjustment mounts on the arm, and uses a pair of hinged plates. These are moved together/apart by an M3 screw threaded into a brass bar embedded in the lower plate. This has some rotation as the angle of the M3 screw changes as adjustments are made.

Here it is in the real world, the LS2020 module is just visible.

The elevation adjustment screw can be seen in the centre of the plate with six screws: