I'm proposing a new hot end design with a more flexible mount system. It can be lightweight and still mechanically very 'stiff'
The main design feature is a cylinder in which the heater and insulation are mounted.
The heater will be clamped in the centre of a cylinder using 3 screw that are running through threaded holes in the cylinder. The screws have pointed tips to increase grip and decrease heat transfer, the heater body has shallow pits where the screws touch to increase grip.
I've made a quick sketch up model to illustrate this. This sketch up drawing doesn't include the barrel yet.
The advantages of this design are:
- Easy adaptation to existing extruder-hotend mounting systems:
- A 16 mm rod could be clamped the same way as the copper head is clamped to allow legacy mounting to wade's extruder.
- cylinder can easily be fixed into an MDF disk, to allow easy use with an arcol.hu v3 style mounting system.
- Fix |_ profiles to the cylinder (inside or outside) using screws and threaded holes in the cylinder or pop rivets.
- Attach metal 6 sided rods directly using screws and threaded holes in the cylinder.
- The cylinder could be extended all the way up to the extruder and can be incorporated in the extruder design. Holes can be drilled/strips can be cut out to manipulate airflow, cooling and weight.
- Flexible mounting system to exchange hot ends:
- The heater& insulation can be easily exchanged by loosening the 3 screws while the cylinder can stay attached to the extruder.
- A wide variety of existing hot end designs can be easily adapted to fit into cylinder mount.
- Improved mechanical and thermodynamic properties:
- This type of hot end mount can be fairly lightweight and mechanically 'stiff'.
- This mount system takes away most mechanical stress from the barrel of the hot end. Because of this it is possible to redesign the barrel to improve on its thermodynamic properties.
proof of concept - prototype
I made a first prototype to experiment with this design.
For this I am using an aluminum cylinder, as it is lightweight, a good thermal conductor and easy to work with.
I'm using a cut to measure piece of aluminum tube. OD: 32 mm ID: 26 mm length: 26 mm
The cylinder has 3 M3 threaded holes, evenly spaces around the centre.
I do not have easy access to proper tools, so i need to do everything with hand tools and a powerdrill. I found a nice copper hose connector and a welding post copper nozzle in the local DIY market. The hose connector has a 3 mm inner diameter The nozzle has a 6mm outer and a 0.8 mm inner diameter that seems to runs through the whole length of it.
I drilled a 5.5mm hole in the top of the hose connector, made the welding nozzle (6mm) slightly conical and hammered it in. (hopefully it wont fall out during heat up..). because of the hammering the nozzle got a bit smaller. I opened it up with a 0.6 mm pin. I opened up the inside of the nozzle bit by drilling into the hose connector from the back with a 3mm drill. Nozzle channel length should be 2 mm now.
The hose connector bit that goes into the hose got cut to about 8 mm and filed down to 6mm OD.
I will use insulated nichrome wire and fire cement for the heater. I will insulate the cement with tape and heat resistant silicone. It should not touch the cylinder.
The heater has small pits drilled into it where the clamp screws touch.
The nichrome wire and thermistor are still underway.. so I'm stuck here for now.