Saturday, July 30, 2011

Calibration, here we come!

Hot end mounted

Mounting detail

With a new X carriage that actually has room for the heatsink (courtesy of Auzze), it's now time to start calibration!

It's been a long road getting here, and would have been quite a bit longer without the generosity of the reprap community. My first post in this blog was November 3, 2009! So, almost 21 months later, I'm just about to start :D

Friday, July 29, 2011

Hobbed Bolts

Here's the bolt I've been using in my latest round of experiments:

Home-made Bolt

Home-made Bolt

As you can see, the teeth are crudely effective. This bolt was made with a hand-held cordless drill and an M6 tap, and it shows! Also, due to the short shank, I had to insert them backwards, with the nylock in my wade's gear and the bolt head on the back- a less than ideal arrangement. If I had a lathe I could perhaps have cut the teeth straight into the threads, but that's almost impossible with a hand drill.

Auzze generously decided to send me a preview of some hobbed bolts he's going to sell via his online shop (still under construction), pictured below:

Auzze's Bolt

Auzze's Bolt

I think these will be far more effective, and at the very least more uniform! Unlike my dishevelled creation, these actually have a groove for the filament to ride in. The position of the hob is slightly different to mine, but some washer swapping had it lined up perfectly

Between Auzze, GregFrost and the various RUGs, it looks like Australia is really starting to get its reprap on!

Thursday, July 28, 2011

Experimental MakerGear Hot End

The amazing and lovely folk at MakerGear sent me an experimental 1.75mm barrel (2mm bore) for my experiments with nylon.

WARNING: when heated, nylon can emit hydrogen cyanide, a gas that's deadly even in low concentrations. lists MAXIMUM EXPOSURE to a mere 10ppm over 8 hours! Nylon also emits a number of other noxious gases such as Carbon Monoxide. Please see a MSDS before switching your printer to nylon, and install adequate ventilation!

Having said that, this barrel should work beautifully for anyone needing higher temperatures to print at speed, or experiencing jamming issues. Read on!

Experimental SS Barrel

It's stainless steel, which has 7.5x lower thermal conductivity than brass. The notch in the middle is a thermal break, to give us a very short thermal transition from <Tglass to >Tmelt, which should help massively with the jamming I've been experiencing with the regular brass barrel conducting heat far up into the insulator, as well as my hot-end having difficult achieving target temperature.

I have also added some felt insulation to my heater to help it reach target temperatures of 260°C and above:

With Insulated Heater

Even with this excellent barrel material and carefully cut thermal break, we can help sharpen the thermal transition even more by adding a heatsink just above the break.

Heatsink All put together

And does it work?

New Possibilities

So far my experiments have simply been pushing some filament through, then leaving it for a while, coming back and pushing more through. This was impossible with the brass barrel, the heat travelling up would cause the nylon to swell, and jam in the barrel without melting. With some wider testing, this barrel could be a contender for the title of "jam-proof"!

Here I am holding the heatsink while the nozzle is at 260°C! That's over 200°C dropped across a distance of about 2.5mm!

Thermal Break Is Effective

My only complaint is that it's not long enough at the top- there's no room between mounting plate and heatsink for M4 nuts, let alone a carriage. Rick informs me that they will be made longer before appearing in the shop.

As soon as my new X carriage (with room for the heatsink) arrives, I could be printing!

Update: After almost exactly an hour, the felt turned black and started smoking. Apparently it's great at 110°C but can't take 260°C, or maybe my felt isn't pure wool felt. I may just keep heating it until it's all carbonised and see if it settles down or falls apart.