Compressed Air Nozzles with TPU 95A

[arktape 2]

In the manufacturing process for tape we make a shaft is aired up to 90 psi to expand the shaft. This allows the spools of product to slide off when the air is released. We have been using store bought air gun nozzles (Picture 1 circled in red). We are burning through these every 2-3 days per machine, multiplied by 4-5 machines running 24/7 at $3.50 a piece it adds up. I was tasked with 3-d printing a replacement that was cheaper and lasted longer. I started with just ABS (pictures next to store bought). I realized that ABS won't seal the shaft and therefore won't inflate the shaft. I bought some Black UM TPU 95A to make a flexible tip to seal. I used White ABS on the bottom and made some "zig zags" to transition from ABS to TPU. I originally had a cone with a hole in it to make up the nozzle (#1). This was way to stiff to seal. I then made a hollow cone with a wall thickness of 0.03 inches (#2). This provided a lot more flexibility but the "Z" (up) direction was still really stiff. The "Z" is the part that needs to seal and it would be nice if it was softer. The design may need to be changed to achieve this. The issue with my first and second successful print was there was a under-extruded part 1/3 of the way up which when pushed side to side it expanded and looks to leak or fail there and did when I pushed to hard on #1. I then changed the flow settings to 130% instead of 106% (#3). I also changed the retraction to 20-30 mm?? because the TPU was leaking out and caused blobs and possibly some "under-extrusion" layers where material wouldn't stick on #1 and #2. This provided a smooth finish and no under-extrusion but is very stiff and may not seal. I am waiting for them to go on the machines but need to find some time when we are less busy in case they fail fast. I thought it would be helpful to document this process and also ask for help with making a flexible air tight part. I am cutting 1/8" NPT  threads into the ABS. Some parts I have yet to cut the threads in yet.

[Torgeir 248]

Hi @arktape,

 

Interesting project..

I would print the nozzle using nylon, it's very strong and will handle the pressure.

For the sealing, I would use a heath shrink tube, of the "soft" type and using special glue for good attachment.

The grooves after 3d printing the nozzle will provide good adhesion for glue

Google Raychem heat shrink tube..

So, when a sealing is done, remove the old tube and install a "new" sealing into the nylon nozzle.

 

Another option is to just print another sleeve with TPU 95A, which can be threaded over the nylon nozzle.

The option is yours.  🙂

 

 

Thanks

Torgeir

 

 

[UbuntuBirdy 56]

52 minutes ago, Torgeir said:

Hi @arktape,

 

Interesting project..

I would print the nozzle using nylon, it's very strong and will handle the pressure.

For the sealing, I would use a heath shrink tube, of the "soft" type and using special glue for good attachment.

The grooves after 3d printing the nozzle will provide good adhesion for glue

Google Raychem heat shrink tube..

So, when a sealing is done, remove the old tube and install a "new" sealing into the nylon nozzle.

 

Another option is to just print another sleeve with TPU 95A, which can be threaded over the nylon nozzle.

The option is yours.  🙂

 

 

Thanks

Torgeir

 

 

If he has to buy additional parts and has to do additional work, the 3d printed solution will cost dramatically more than the ones they can buy...

[GregValiant 1,318]

I think the ones I've used were compression molded.  Have you considered making a multi-cavity mold and pouring them out of 80-90 durometer urethane?  

[Torgeir 248]

Well, there's an option for that..

Isn't the issue to make something that's last?

Hmm, -maybe I misunderstood this thing..

[arktape 2]

1 hour ago, Torgeir said:

Hi @arktape,

 

Interesting project..

I would print the nozzle using nylon, it's very strong and will handle the pressure.

For the sealing, I would use a heath shrink tube, of the "soft" type and using special glue for good attachment.

The grooves after 3d printing the nozzle will provide good adhesion for glue

Google Raychem heat shrink tube..

So, when a sealing is done, remove the old tube and install a "new" sealing into the nylon nozzle.

 

Another option is to just print another sleeve with TPU 95A, which can be threaded over the nylon nozzle.

The option is yours.  🙂

 

 

Thanks

Torgeir

 

 

I think you understood it well. I appreciate the ideas. I may try this with the only ABS ones I have printed (I didn't have nylon when I made them but just got nylon yesterday). I need to understand how the old ones are failing because the heat shrink tube may fail sooner than the current nozzles and still require the machine to be down to fix. 

[arktape 2]

25 minutes ago, GregValiant said:

I think the ones I've used were compression molded.  Have you considered making a multi-cavity mold and pouring them out of 80-90 durometer urethane?  

No, I haven't thought about this. It seems like a good idea. The current nozzles are around 50 duro and the maintenance people did say that they used to be harder back in the day. I will look into this. I was hoping to make it with the 3-D printer but this may be a better option. 

[GregValiant 1,318]

Urethane needs 100 to 200°C to cure.  Hotter cures faster.  The ones I was involved with (cutting CNC paths) were aluminum molds and cured on heated tables.  Come to think of it some used urethane molds poured around a "hob" (a part machined to pre-shrink dimensions) so a mold printed in ABS might work.

 

Actually, a phone call to a rubber and plastics outfit and "Hey, how much for a thousand of these" might go a long way.  You could pick the material specs too.  I'm pretty sure you could beat the $3.50/pc. price all to hell since you don't need the brass.

[Torgeir 248]

1 hour ago, arktape said:

I think you understood it well. I appreciate the ideas. I may try this with the only ABS ones I have printed (I didn't have nylon when I made them but just got nylon yesterday). I need to understand how the old ones are failing because the heat shrink tube may fail sooner than the current nozzles and still require the machine to be down to fix. 

Hi @arktape,

 

Thanks.

 

Whats materials selected here matter, I'll think. As this is a bleeding nozzle, -the temperature decrease and the whole thing will bee very cold.. So maybe ABS become very brittle and just snap at times.

The nylon is the strongest filament I've been printing ever.. -And also take "some" lo temperatures, -but how this work for your project, I cannot tell.

So I'll think all this depend of the physics involved, and to find a perfect match that's make this setup last.

 

Anyway, good luck.

Torgeir

 

 

[geert_2 558]

I just read this now. An option might be to print it in nylon, but a bit too small, and then using a vice press it on the brass element with brute force? So it will seal well and won't fall off? Nylon may be able to handle this brute force.