Material for hot end insulator not listed on WIKI page
Posted by jakowisp
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Material for hot end insulator not listed on WIKI page March 26, 2012 05:41PM |
Registered: 12 years ago Posts: 77 |
The hot end that came with my kit, used a brass hot end and screwed directly into a PTFE insulator. As has been mentioned in previous posts, the PTFE properties make it a poor mehacnical connector. After 3 full small part prints the hotend got wobbly and eventually became worthless. Blew out the threads.
A lot of post mention using a PEEK/PTFE combination.
I have been assembling an aluminum foundary and have a bunch of Rutland Furnace Cement around. You can get this furance cement at ACE Hardware in 8 oz pacakges for ~$2. Which is enough to make 9 16mm by 45mm insulating cylinders or more.(Guestimate based on how little cement was used) The thermal coeficeint is similar to PTFE. Depending on the brand you use it may be slightly lower or high than PTFE. 0.25 +/- .10 Once cured the cement has a working temperature up to 2700F. More than sufficient for our insulation needs.
I made a mold from my old PTFE Insulator using polymer clay I had around the house.
Using a 50mm M6 bolt, I threaded a m6 mudwasher and a nut to hold the washer tight.
Two more nuts were thread onto the bolt to become captured nuts.
Another mud washer was secured to the end of the bolt with tow more nuts.
The furnace cement was pressed around the screw and nuts between the washers. The mold pieces were zip tied around the cylinder to pressing the cement into the shape.
Once the cement was cured, the bolt and washers were removed leaving 4 nuts traped in the cement. (One of the five nuts was not incased in cement and was removed as well)
During the curing process the mold halves were removed at 220 F. The material for the mold can only go to 270F.
This was sufficient for the cement to keep its form.
Like the fisrt hot end the Brass end will screw into the insulator. This time the threads are a combination of cement and zync alloy nuts. The preasure won't blow out the threads. I will be following the PTFE/PEEK example, and insert a M6 threaded PTFE rod into the insulator.
I will need to break out my scale and take some weight measurements but currently it only adds a little bit to the weight.
A lot of post mention using a PEEK/PTFE combination.
I have been assembling an aluminum foundary and have a bunch of Rutland Furnace Cement around. You can get this furance cement at ACE Hardware in 8 oz pacakges for ~$2. Which is enough to make 9 16mm by 45mm insulating cylinders or more.(Guestimate based on how little cement was used) The thermal coeficeint is similar to PTFE. Depending on the brand you use it may be slightly lower or high than PTFE. 0.25 +/- .10 Once cured the cement has a working temperature up to 2700F. More than sufficient for our insulation needs.
I made a mold from my old PTFE Insulator using polymer clay I had around the house.
Using a 50mm M6 bolt, I threaded a m6 mudwasher and a nut to hold the washer tight.
Two more nuts were thread onto the bolt to become captured nuts.
Another mud washer was secured to the end of the bolt with tow more nuts.
The furnace cement was pressed around the screw and nuts between the washers. The mold pieces were zip tied around the cylinder to pressing the cement into the shape.
Once the cement was cured, the bolt and washers were removed leaving 4 nuts traped in the cement. (One of the five nuts was not incased in cement and was removed as well)
During the curing process the mold halves were removed at 220 F. The material for the mold can only go to 270F.
This was sufficient for the cement to keep its form.
Like the fisrt hot end the Brass end will screw into the insulator. This time the threads are a combination of cement and zync alloy nuts. The preasure won't blow out the threads. I will be following the PTFE/PEEK example, and insert a M6 threaded PTFE rod into the insulator.
I will need to break out my scale and take some weight measurements but currently it only adds a little bit to the weight.
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Re: Material for hot end insulator not listed on WIKI page March 27, 2012 12:29PM |
Registered: 15 years ago Posts: 123 |
I've found that if you just clamp the hot end brass tube to the PTFE insulator with like a piece of sheet metal and a couple of screws holding it to the extruder mount, all issues with "PTFE being a poor material" are eliminated. This is because the sheet metal and screws bear the weight of extrusion, not the PTFE tube itself. Even if the threads in the PTFE tube are totally stripped this method has still prevented all leaks for me. I haven't had any problems with heat transfer either, but that may be because I'm using an extruder made of wood and not ABS.
One problem i could see with the fire cement is its not as slippery as PTFE and so could increase extrusion forces. But if you put a ptfe tube inside the cement then it might be fine...
One problem i could see with the fire cement is its not as slippery as PTFE and so could increase extrusion forces. But if you put a ptfe tube inside the cement then it might be fine...
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