Heater Block with Screw-On Thermistor
by rp_one_labs, published
1. Use of M3 stud screw-on thermistor. It is easy to install and remove, makes assembly and maintanance of hot end really simple.
2. Another useful feature is ability of heater block assembly to be secured on barrel with M3 x 6 set screw. This will prevent block from twist during nozzle changes. This feature is similar to one found in updated budaschnozzle 1.2 heater block design, it was implemented in response to requests from users of previous version. Thank you for your feedback!
Drawings and instructions are provided, or you can get completed, manufactured parts here:
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.32mm ID PTFE will be perfectly fine, I think. You can make a google or ebay search for 0.3mm ID tubing and find a lot of sources. M3 Brass hex stud is commonly used item for PC motherboard mounting. There are also #6-32 studs available, they are tiny bit larger, aside of different thread size, but this is Ok for DIY. Same here: search and find a lot of sources. I did not supply part numbers because it makes not much sense to buy M3 brass studs from mcmaster, they were too expensive last time I checked.
Where can you source the parts for the thermistor? I haven't been able to find the .3 PTFE tubing, I found .32 PTFE Tubing or the fasteners.
Thank you. GB Weld, according their own packaging, rated up to 550F / 287C when fully cured. I de-rated this number a little, to be completely safe. It was already used under 240 C for long time, no problems at all. According to other source, temperature of 600F / 316C is possible for 10 minutes. This stuff is used to fix engine blocks.
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Guidelines for aluminum blocks are basically the same as for previous version:
I.) For CNC machining: This thing to be machined from 3/8" x 3/4" 6061-T6 extruded bar, then tapped M3 & M6 according to drawing. Machining strategy is up to you. Use STL / STEP files and drawing to create G-code.
II.) You can make it manually from 3/8" x 3/4" 6061-T6 extruded bar stock:
- Cut 18.5mm long piece of extruded bar preferably with band saw.
Manual hack saw gives less straight cut, you might need to file
rough side for better appearance.
- Mark hole centers according to drawing.
- Drill necessary holes using drill press (not manual drill),
consult with drawing for drill bit diameters. Make small pilot holes
prior to drill holes for M6 and heater, for better centering.
- Tap M6 hole preferably on the drill press, for straigtness.
- M3 holes can be tapped manually.
Making of M3 stud thermistor is straigth forward. See drawing for details. You will need:
- NTC EPCOS thermistor.
- M3 x 4 brass standoff.
- 0.3mm ID PTFE tubing.
- JST crimp-on connector male & female. Similar to one used for small rc aircraft batteries.
- JB Weld steel epoxy resin.
Sequence of operations:
- Put 55-57mm long pieces of PTFE tubing on thermistor leads.
- Crimp female contacts on thermistor leads.
- Prepare epoxy mix and put small portion of epoxy inside M3 hex standoff.
- Secure brass standoff and insert thermistor with PTFE tubing and conector.
- Keep thermistor leads straigth until epoxy cured. You might need to develop some kind of fixture to hold parts together.
Hex thermistor safely rated up to 500F / 260C for prolonged period of time because it uses JB Weld steel epoxy to fix thermistor in hex stud housing.
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