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Building a hot end from scratch

Posted by nojam 
Building a hot end from scratch
April 24, 2015 06:48PM
Here's a hot end I designed and built from scratch. I wanted to experiment with using hypodermic tubing as the barrel/nozzle. It doesn't use any active cooling right now, but the heat break is too long and is prone to jamming. I'm working on a heat sink that will change that. Let me know what you think!smiling smiley

Some pictures
Blog post I wrote about it.
Re: Building a hot end from scratch
April 24, 2015 10:47PM
Very interesting! What was you technique for forming the tip?
Re: Building a hot end from scratch
April 25, 2015 12:07PM
I form the tip with a tungsten carbide die. It's surprising easy, all you need is the die and a drill press.
Re: Building a hot end from scratch
April 25, 2015 02:09PM
Hi nojam, thanks for sharing this. I like the approach. In your reddit thread you stated that you use a jeweler's draw plate with tungsten carbide inserts. Is it something like shown in the picture? So if I understand this right, the tubing is chucked in the drill press, which is spinning, and then the tube is "drilled" into one of the draw plate dies as though you were trying to drill a hole in it... Do I have that right? I think this process is known as swaging.

Also, North90 made some interesting hot ends a while ago using a similar process - swaging stainless steel tubes onto welding tips. You might be interested in those. See North90s_hot-end and North90s_hot-end-v2. If you have time, please feel free to add your hot end design to the wiki too.

Re: Building a hot end from scratch
April 25, 2015 06:33PM
Hey Matt,

You could call it swaging, but I think that refers more to a special process of using rotating/clamping dies. The drawing plate in the picture looks like it will work. I actually tried making my own dies out of steel and heat treating them before finding out about the drawing plate!

Here's a picture of my drawing plate. You can buy it here.

The tubing is thin and the drill chuck will crush it without a mandrel. I just used a drill bit that fit snugly inside. After it's mounted and you add some oil to the dies. Start from the biggest die and work your way down. You want to be consistent with how far you push it into the die. It's definitely a "feel" thing, takes a few trys before getting it right.

I'll add it to the wiki if you think I should.
Re: Building a hot end from scratch
April 25, 2015 11:10PM
Very cool! I started something similar, but didn't get past forming the tip. I (unsuccessfully) tried using a pair of tilted bearings to roll down the tip, but the wall cracked. Plan B was to braze in a small tip, which also allows the end to have a shoulder surface to squish with. (Have the 50N solder and milk of magnesia, but haven't gotten to it yet.) Did you need to anneal the tip along the way to counter work hardening?

I'd planned to braze on a copper sheet cut to fins for cooling. - Maybe that would help your heat creep? (You don't really need hard solder here, sonce the temps aren't that high)

My starting point was a little different - a dispensing needle. These come with a luer lock at one end for easy mounting. I expected to also probably need to braze on the luer lock, since they come friction fit. I'll get to it sometime, but finishing the rest of the printer comes first. Even so, I'm excited to hear the tubing is up to the task.
Re: Building a hot end from scratch
April 26, 2015 12:47AM
I wonder if you couldn't heat the tubing with a torch to red hot then pull it to form the nozzle, similar to the way glass tubing is manipulated.
Re: Building a hot end from scratch
April 26, 2015 12:54AM
I tried something similar too! At first, I tried welding the tube shut and drilling a hole into the tip... Lot's of broken 0.5mm drill bits haha. Then my next attempt was brazing clock bushings into the tip.Cross section of bushing and tube. I really wish this would have worked because it seemed like such an elegant solution. Maybe I just suck at brazing.

You don't need to anneal the tip while working with it. The key is in the progressive dies, which slowly works the diameter down.

Edited 2 time(s). Last edit at 04/26/2015 01:15AM by nojam.
Re: Building a hot end from scratch
April 26, 2015 06:19PM
I tried also similar things, silver brazing a copper tip on a gauge 13 stainless steel needle, then drilling it. The copper tip was punched in hemisphere shape with a 2mm steel ball as a punch, before brazing.

I brazed also a copper heater block, and a simple copper sheet 0.5 mm thick, ~10 cm², as a heatsink, with a small fan blowing on it. The copper sheet was brazed perpendicular to the needle. The gap between the heater block and the copper sheet was about 1.5 mm.

It's a tedious and meticulous work, but the result works beautifully, and it is quite light weight. It seems that brazing a copper sheet is an order of magnitude more efficient, than running the needle trough an aluminium heatsink, even with thermal grease.

Thanks for the tip of the tip ! (formed through progressive dies)
Re: Building a hot end from scratch
April 27, 2015 06:48AM
... I have some "pneumatic resistors", what's a small brass tube with an inserted ruby-orifice, which are available with different bore diameters ... have some with 0.1, 0.2 and 0.3mm bores.

They are pretty easy to braze, but didn't test them for FDM ...

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Re: Building a hot end from scratch
April 27, 2015 09:51PM
I've never heard of pneumatic resistors before, sounds interesting
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