This is a short introduction. I am a (professional) Industrial Designer. I know, it is kind of irrelevant, but it is important for my further explanations as I am well trained at analyzing problems and offering thoughts. For all Issues described further on, I will use a machine everyone knows as metaphorical comparison, just to emphasize the story. The coffee-machine. But now for the facts: I am running an Ultimaker Original with very few modifications, and recently chose to replace the original printhead with the acclaimed E3D-V6 Hotend that promised "no more clogs - more materials" which sounded awesome, as I am also selling prints for prototypes and presentation models and I could bring my UMO back into this business. In the original printhead there was a nylon-glassfibre-part behind the heatbreak that gets worn out every other month, so I chose an all metal hotend instead, with the promise of better reliability and less maintenance. So I placed my order for the bowden-set with fan, added a couple of nozzles and extras that quickly added up to about 150€. So i printed a couple of different mounts for the E3D before changing, to tryout which is good and to be on the safe side for printing happily away after implementation. I looked at the design when it arrived, and it was very reassuring, its heavy, its metal, its thoroughly machined. Looks good, feels good. Everything a consumer wants. After putting everything together on my saturday morning, I was eager to start printing. But, as always, calibration, readjusting the end stops, drilling holes for new screws etc. got in the way. Finally i could start a first small job - and oh joy, only 20 minutes in, a clogged hotend. First i could not figure out where, how and why. I ran the print with 210°C on PLA instead of the usual 195, as I figured the melting distance of the filament to be smaller, thus less contact with hot metal and higher temps for quicker melting. After disassembly I realized that the filament blobbed on top of the heat break within the heatsink - right between the bowden tube and the entry into the heat sink. How could that happen? How did the heat get there, when there was so much heatsink in between the heaterblock and the bowden? I restarted, and this time I got a clog somewhere in the heat break, which is a lot harder to get out. Great! So I started analyzing the whole thing with the question in mind: "Where is the heat, how does it move?", and realized some things. Problems and Solutions (a: for the user; b: for the manufacturer) 1. The heat break screws into the heat sink very, very loosely. If you unscrew it a tiny bit, it wobbles. This is either a sign for lousy machining, or intentional gaps. This leads to a very bad heat transmission between the heat break and the heat sink. What you would want is a direct, ideally one part solution there. It is a bad idea to thermically disconnect the heat break from the heat sink, as the heat rather travels up the break to the top within the metal, than to cross an insulating gap of air into another metal. Furthermore you create a chimney effect within the heat sink: The heated air on the bottom moves up along the threading and ends up in the little chamber between bowden and heat sink. Solution 1 a): Use a generous amount of thermic paste - usually used to connect processors to heat sinks - in the threading. It is not ideal, but helps. You want to avoid enclosed air or any kind of air flow within the threading. Remove surplus paste on the bottom of the heat sink and the top of heat break within the heat sink by pushing some filament through until it comes out clean. Solution 1 b): Machine the heat break and the heat sink either in one part or as a push in conus where the heat break is low heat conductive while the sink is high conductive. That gives you a large surface for heat transmission between the break and the sink. 2. The heat sink has a thicker metal centre on the bottom than on the top. This means that more heat is stored within the material than transported to the surface, where the air flow takes it away from the critical parts. What you would want is a large surface without a lot of mass. Mass stores heat. Guess why you have a heater block, and not a wire. The thicker bottom end just means that there is more heat inside to soften the filament way before its time in the heater block / nozzle. Solution 2 a): Forget it if you do not have a lathe. Lay down and cry out of frustration. Then look for a professional who has one. If you have one, mill out some of the metal between the disks until you have only a little left. Be careful! Solution 2 b): Do not create a heat storage on the bottom of the sink. Rather aim to distribute the heat as quickly as possible into the surface of the heat sink so the air flow will have a maximized effect. Look at CPU-coolers. The best ones have very thin copper lamella to have a high surface to airflow ratio. 3. The heat break does not have a very smooth (ideally polished) inside surface. That is in fact a huge problem. If the filament goes in, it suddenly faces a large drag on the heat break surface. This means that your extruder could fail or grind. Additionaly this means more surface to transmit heat to the filament, if the heat break is warm. Solution 3 a): Hard to tell. I heard using oil as lubricant. Some use a drill to widen the opening a little, some use fine sand paper to polish it. None sounds to safe, or easy to use. Oil can mess up a print, drilling can destroy the part. Sanding may deform the inside and leave uneven surfaces. Solution 3 b): Get your shit together. Its not so hard to machine a straight hole into an aluminium block. Have proper tools. Have quality control. Steal from other heat break designs! Look at the ultimaker original heat break. It has a large plate before the heat sink and gives off a lot of heat to the lowest lamella of the heat sink. Its just too short to go all the way up into the E3D-heat sink, otherwise i would use it. 4. The heat break has a long threaded part in the heater block. This leads to more than necessary heat transmission into a part that should stay cool right outside the heater block. Here it is an advantage that it is wobbly, as there is not much surface to pick up heat. But it connects to the hot nozzle with a flat surface, so it picks up a lot of heat there. It is unavoidable i guess, but still a problem. Solution 4 a): I used a special heat stopping paste from the jewelry equipment shop. It reduces heat transmission up to 800°C, so we should be fine. Apply on the threading of the heat break, use a toothpick or something to rub it into the threading of the heater block close to the surface. Be careful not to get this stuff into the threading of the nozzle. There you want a maximum of heat transmission. I used the thermic paste for CPU cooling as well. It might be good to have a tiny layer of heat stop between nozzle and heat break. Solution 4 b): You could make the nozzle threading longer, and the heat break threading shorter. It should still tighten hard enough without risk of breaking. You could use a material to coat the heat breaks threading that has very low heat conductivity and resists heat up to 300°C. Would PEEK work? 5. The heat break tends to have slightly different diameters on the inside. This can only be caused by bad material, bending while machining or a slightly eccentric drill or lathe, maybe a partially blunt drill. It leads to filament clogs when it gets warm because of all previously mentioned reasons, as the filament expands, fills the slightly larger diameters, creates more drag than the extruder can handle and then clogs. Solution 5 a): See 2 a). Get a lathe, carefully drill it open without destroying it. Solution 5 b): See 3 b). Get your shit together, drill straight holes. Have QC. Now imagine, you bought a complex coffee-machine for about 1500€, that you have to disassemble every other month just to get coffee out of it. And if you do not put another hour into calibrating it afterwards, all coffee tastes like a trolls armpit. If you calibrate it, it will only be every fifth coffee. Finally you find a solution for your trolls armpit problem, for only a tenth of the price, and order it. After installing the solution, you realize that the coffee does not taste like armpit anymore, but comes out as syrup - And half of the time nothing comes out, and you have to dissassemble the whole thing while it is running hot, burn your fingers while doing so, just to get some ground coffee out of the system. You have to do this once a day, if you want two coffees. Not really an improvement. After reading up on your strange problem you realize that its not uncommom, but rather everywhere. The solutions offered vary between going at your coffee machine with a power drill or doing strange shamanistic dances around it at the right time just after it started heating up. You wonder why you should pay this amount of money for a machine and an addon that is actually pretty simple, but makes it so complicated. How can it be that such a flawed system is being sold so often? To sum up with some of my thoughts about consumer 3D-Printing: I am amazed about something. There is no other industry that is able to sell really expensive consumer machines which need so much maintenance and effort just to make them do what they should once in a while. Thats why they are called consumer machines. You want to consume the possibility of manufacturing some stuff, even if its dollar store items. But you are not able to, unless you spend a whole lot of time with your toy. Imagine any, really ANY other product category having the same issues as consumer 3D-Printing, would you buy one? Would they even be on the market? Its a miracle. The fact that there is a whole sub-industry developing to compensate for the flaws of the main industry, and everybody accepts it, is sensational.