Here they are! I think this is the most requested product we’ve released, since the reddit thread where the enterprising amaurer3210 created his own and we showed off the first early prototypes of these we’ve had people clamouring for them. It took us by surprise! They took longer than expected, we had to learn an entirely new class of materials and manufacturing methods, which were surprisingly different to what we’re used to.
We’re making them available as a pack of 3 socks for £3.50, and because these are shaped to fit the newer cartridge style heater block we’ve made a convenient pack that includes everything you need to upgrade to cartridge based thermistors and silicone socks in a single product.
We’re now shipping one of these with every HotEnd full kit we send out, with no price increase. (This obviously excludes Cyclops, and Volcano, onto which these will not fit.)
The first and most obvious advantage to these is it rids us of the horrible blackened smear of burnt on plastic that we’ve come to know, hate, but accept as an inevitability. Instead you have a clean, attractive blue cover. It’s not just about keeping things pretty though, these add some significant functional benefits.
The socks are made from a silicone rubber, the same sort of stuff that flexible rubber-like bakeware is made from. Except we don’t have to conform to food standards, so we could test a wide range of engineering grade silicone resins, optimising for temperature resistance and not adhering to molten plastic.
A few others have done sock type things before, but because we’re using extra fancy compression moulding we can get the cover right down the nozzle, with just the final sub-millimetre tip of the nozzle poking out. They are optimised for 0.40mm nozzles but as silicone is flexible these will fit nozzles from 0.25mm to 0.80mm without issues.
The underside of the sock is heavily filleted in order to avoid any nooks or crannies into which plastic loves to build up. Together with a fine surface finish on the underside they are very resilient to goop building up on them. For the most part they remain close to spotless with zero build up. Extended printing with very sticky materials can result in some minor build up, however once the hotend cools any material can easily be peeled off the non-stick surface. Keeping the hot parts clean generally makes things much nicer, screws and cartridges can be more easily changed, and nozzles more easily identified.
If material isn’t building up on the hotend then it also can’t form a blob which drops off halfway through a print. This is particularly relevant to intentionally stickier materials like Edge, and filled materials which love to blob up and drop onto prints at random points. It helps with pretty prints too, the occasional black fleck of carbonised material getting dropped onto a pristine white print is most annoying. These work exceptionally well when used in conjunction with a wipe and dump area on dual extrusion systems, really making for exceptionally clean dual extrusion prints.
The most significant functional advantage is that they keep heat inside the hotend where it belongs, and not out causing trouble where it shouldn’t. This means you can have a powerful unducted blower fan pointing right at the tip of the nozzle giving extremely effective print cooling without causing a drop in nozzle temperatures.
This means you can get really crazy good overhangs and bridges with materials that really like fan cooling like PLA. It also means you can use simpler, less flow restrictive duct designs, which have been shown to give better results https://www.desiquintans.com/coolingtests, as well as cranking up fan speeds to the max without causing temperature fluctuations.
Further improving matters the layer of silicone stops heat radiating from the heater block onto the area being printed. This and a lot of air really make a big difference for tall thin prints that usually suffer from getting melty due to not cooling in time for the next layer.
Generally the reduction in lost heat from both airflow and radiation give a more consistent and stable system to control. This means tighter, more easily tuned PID loops, and faster heat up times.
You should always let your machine cool down completely before you put your hands into the build area. Let us not pretend however that we all follow this rule with 100% obedience. If you’ve been reprappin’ since before it was cool, you probably have a few battle scars on your hands. The socks don’t make it safe to touch the hotend, but should you make a mistake it’s not actually at all painful.
We’re using a non-stick silicone resin with a particularly high temperature resilience. You can run these at a constant temperature of 300C without degradation. Going hotter than 300C is beyond the rated specs, but only results in slow aging and eventually weakness and splitting, they won’t melt into a horrible mess. Surprisingly they are pretty usable up to 400C, but with reduced life.
In normal use the socks don’t have infinite life, it depends a lot on the materials, temperatures, and how much you’re doing things that apply stress like dragging them over a wiper, but you should expect to easily get 100+ hours of use, in even the quite abusive conditions. Normally it’s some sort of print failure where a part curls up into the path of the hotend or becomes detached from the bed that causes the damage. We’ve been able to keep them pretty cheap too, at £3.50 for 3x new replacements.
The socks just push on from the bottom, no reassembly needed - there are cutouts for the wiring, on both sides so you can have your wires coming out whichever direction is most convenient to your set up. They fit rather snugly onto the hotend, and have retaining hooks around the top that hold onto the heater block. Silicone is a material with an exceptionally high thermal expansion coefficient, so they get quite a bit bigger as the hotend warms up. This is why they might seem too tight or small when first pushed onto the hotend. Fear not, they grow to a perfect fit when the hotend reaches printing temperatures, and the retaining hooks resist dislodging from actions like wiping and the occasional drag by a curling overhang etc.
They are designed to fit most optimally when using the most popular 0.40mm nozzle size, but they’ve been carefully designed to still fully wrap around and cover the full range of nozzle sizes from 0.25mm up to 0.80mm - the silicone stretches to conform to each. You do have to have assembled the hotend as-per the instructions, with the prescribed half-turn of the nozzle back out from the heater block in order to get things to line up optimally.
And yes, we’re nearly there on the Volcano version - some tweaks needed, but expect these to land in the next few weeks and be included in Volcano packs by default, and for separate purchase too.