Heated Nozzle

This instructable is about building a heated nozzle that is made with a food safe material that is compatible with cartridges extruders. I wanted to explore the difference between working with aluminum and stainless steel. There is a lot of internet talk about the good and the bad about aluminum cookware. Still is considered as a food safe material but obviously with poorer characteristics compared to stainless steel (in terms of corrosion).

For me, having no previous machining experience, aluminum was the first obvious choice to start learning. So I did.

Having a heated nozzle allow me to work and print a wider range of material that transform their properties with heat; for example chocolate, eggs or hydrocolloids.

Lets have some fun with the mill and the lathe!

The requirements are pretty straight forward. One end with a standard 1/4" NPT male connector (to cartridges). And the other one with a nozzle between 0.5 to 1.5mm (20 to 60 thousands) threaded. The nozzle end thread (1/2") screws into a heating block. The heating block has a heating cartridge and a thermistor to control the temperature.

Material list:

• Aluminum rod 0.65" (to learn how to build the nozzle)
• Stainless steel rod 0.65"
• Aluminum block
• 1 heated cartridge 12V 40W
• 1 thermistor

This was my first project machining ever. Along the process there has been a lot of lessons learn (many more to come too). It took me 12 tries to get the design where I wanted. Lessons learned along the way.

1. Use the lathe to align the threading die with the part to avoid misalignment.
2. Be patient.
3. Secure the part properly to the lathe chuck, it will slip!
4. Secure the part properly to the mill lathe, it will slip!
5. Small holes, require speed and coolant.
6. Small holes require short travel. Think about the ratio thickness/hole height.
7. Be patient.
8. Breaking small bits is too easy, be careful.
9. Cutting tools are tough, BUT they do break if you mess up cutting thickness and speed. WATCH OUT
10. Drilling with the lathe is easy. Drilling precisely too, but requires proper measure and focus while thrilling.
11. Threading a hole is easier that threading a rod. At least for me.
12. Be patient.

And finally here it is my first working prototype! Funny that all the designs were made by hand on a paper. Half way through the process I realized I had not touched my computer for a week. That made me smile.

The heating block was easier to make. The only consideration to keep in mind is to avoid the nozzle thread to collide with the heating cartridge hole. A part from that, I eye balled both the sensor hole and the holding sensor screw hole. A headless M3 bolt was added to secure the heating cartridge.

Both the sensor and the cartridge have a connector that hooks up a cable to the Smoothieboard. This allows to easily thread and unthread the heating block to the nozzle. Obviously inspiration came from E3D heating blocks.

I choose machinable 316L stainless steel.

There is a DIFFERENCE working with aluminum and stainless steel.

Turning the part did not feel harder. Required coolant running all the time, and doing smaller cuts (longer time). It did not feel "its was more difficult". Although chips are waaaaaaaaaaaaay harder. So I was really careful after reading horrible stories of people cutting their hands with the long stainless steel chips.

For me the hardest part was drilling holes. There was a major effort just to get the inner holes done, and specially taking care to get the right length for them.

To test the nozzles with Pinya 3. I design a simple support to hold the cartridges to the printer end effector. It is important to notice that the heated block needs to be screwed in after the capsule and the support are attached to the end effector. The heated block is bigger than the cartridge neck holder.

I like the idea of natural 3d printed stuff. Well, we could consider that everything is 3d printed. But... lets not go that way. To test the heated nozzles I wanted to mimic the way stalactites are build in real life, but using food and speeding up the process.

How? Dripping drops of agar agar to grow an Stalactite! The heated nozzle is used to make sure that the agar agar does not sets, thus clogging the nozzle. We keep the temperature above 40 degrees to about that.

To prepare the agar agar I was using 2gr of it and 100gr of water. Stir and bring to a boil make sure all the agar agar is properly dissolved.

My first approach was trying to set really slow speeds on Pronterface interface and extrude. 0.01mm/min and extrude 10 mm. The agar droplets rate was around 3.5 seconds. This turned out to be a short time for the previous droplets to set. So instead of a stalactite I had something that look like a fried egg. Trying to keep it simple, I tried to build the stalactite within a frozen icecream maker pot. That did not make a big different either.

It felt obvious that the problem was the setting times between each droplet. And the shortcut of using pronterface at its lowest rate was not good enough.

To overcome that I wrote a small webapp. This app generates a GCode that controls the printer to drop droplets at a desired time ratio. The parameters are number of droplets, size of the droplets (extrusion length), droplet rate (time between droplets) and starting and ending height for the nozzle.

Using this applications I was able to get my first stalactite!!! An more important... Test that I was able to control the heated nozzle with a new type of materials!

Hopefully more heated experiments coming soon.

Aluminum safety resources

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