Mendel Custom Hot End (using some makerbot Mk5 hotend parts)

thingiverse

I had been using a variant on the original mendel hot end ( http://www.thingiverse.com/thing:2018 ) and was constantly getting heat transfer up to my (sadly) PLA printed extruder parts. These parts were actually deforming a little under the heat. So I redesigned to fit my needs. This is a new hotend design borrowing from from makerbot's MK5 extruder (see http://www.thingiverse.com/thing:3290 ). It has a nicrome wrapper cylindrical solid aluminum core and fits into a PTFE sleeve at the top which allows it to be used with the original mendel X carriage. Additionally it can be used with the MOSFETs on the mendel extruder controller board and doesn't require large clicky relays. ;) It makes use of the MK5 nozzle and thermal barrier tube that you can get easily from Makerbot Industries storefront. Instructions This design doesn't include any printed parts (unless you include my extruder bottom piece which is included for reference). Being in the states it wasn't easy to obtain metrics quantities. But the sizes don't need to be exact as most parts are machined to fit. Parts list: -Some old Reprap Mendel extruder parts -- http://reprap.org/wiki/Mendel_extruder -- nicrome on wires to wrap heater core -- thermistor on wires what to for the sensing -- PTFE tube 2024-T3 bare aluminum sheet/plate 0.75"x2"x0.125"(chosen as it is the cheapest) 6262-T6511 extruded aluminum round rod, dia 0.75",len 0.625"(chosen for slightly better machine-ability) Makerbot Industries Mk5 nozzlehttp://store.makerbot.com/toolheads/plastruder-mk5-1/mk5-nozzle.html MBI Mk5 thermal barrier tubehttp://store.makerbot.com/toolheads/plastruder-mk5-1/mk5-thermal-tube.html MBI Mk5 PTFE core tubehttp://store.makerbot.com/toolheads/plastruder-mk5-1/mk5-ptfe-coretube.html TO-5 heatsink (may not be necessary, also obtained many places)http://store.makerbot.com/toolheads/plastruder-mk5-1/to-5-heatsink.html Some long and short M3 bolts and nuts (optional) Thermal fudge/epoxy or the like (optional) Latex furnace/Vent appliance sealant (optional) Some kind of exterior insulation, ceramic, etc. Basic instructions below. Generally, you just need to drill holes in the various aluminum and tap threads into the heater core. I'm no pro fab'er so follow my instructions at your own risk. I'm sorry I don't remember the exact drill bit sizes I used for center holes, basically I was going for just larger than the thermal barrier tube. read note about drilling small holes in bottom plate where you can probably improve upon my process Drill out center holes on both aluminum plates (drill press) Drill out outer connector holes on both plates Drill inner connector holes for bottom plate -- After marking the holes, visually verify that they will fall inside the diameter of the heater core you are using -- Note, I had issues drilling this as I had drilled the large hole in the center first and the connector holes on the bottom abut it and this the drill bit deflects into the larger hole. It might be better to drill the smaller holes first for the bottom plate. YMMV Drill inner connector holes for top plate Drill out heater core center hole one (or two) sizes smaller than 3.8" Mark and Drill M2 holes (or something small) into heater core using bottom plate as a template. Tap heater core center hole to 3/8"-24 thread pitch as per Mk5 bits Tap heater core outer connector holes to M3 (or whatever your connector bolts are) (optional) mark and then cut a spiral groove around the aluminum Wrap and kapton tape nicrome wire (optional) cover wrapped nicrome with thermal fudge and allow to harden/slow heat to set (optional) cover horizontal periphery of heater with latex sealant assemble nozzle and barrier into heater core Affix thermistor (in reprap style) to mk5 nozzle using Kapton tape Finish assembly of plates and heat-sink as per diagram -- Note that you can vary the length of the bolts to adjust the distances between the plates and heater core. My original design had the bottom plate abutting the core, but i ended up having it be slightly offset. This helps reduce heat transfer and removed the need for the PTFE sheet insulation. Insert PTFE core tube and cut to length. Fab the PTFE upper cap. (I just cut short an old reprap PTFE insulator tube and drilled out the threaded side to 3/8") (optional) wrap the heater element in some kind of insulation to stop radiant heat loss. Use it and enjoy.