Looking for small bore flexible air hose for print cooling

I am hoping to pick the minds of somebody on this forum who may know where to get small diameter reinforced flexible tubing. What I need is something with a bore of about 2mm which is able to deliver air at a pressure of about 10 bar (1.0MPa, 145psi) while being both flexible and lightweight.

The need for this is to deliver air for "near field" part cooling immediately after the nozzle on a 3D printer. This will be similar to the "Berd-Air" or Tusk type of cooler which directs cold air at a fairly low speed and only on freshly laid plastic. This ensures maximum fidelity of the fine details by preventing sag-back of the plastic. To get cold air I want to deliver the air at high pressure and allow it to expand through a small orifice into a chamber and then be directed near the printing nozzle.

So far I have found nothing that really fits the bill of ca. 2mm i.d., 10 bar, flexible and lightweight. Any suggestions?

Mike

... there are standard pneumatic hoses with 4mm outer diameter. 2.5mm inner (or even thinner with 2mm outer diam), what could fit your needs -- e.q. look at SMC pneumatics:

[www.smc.eu]

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

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leadinglights
I am hoping to pick the minds of somebody on this forum who may know where to get small diameter reinforced flexible tubing. What I need is something with a bore of about 2mm which is able to deliver air at a pressure of about 10 bar (1.0MPa, 145psi) while being both flexible and lightweight.

The need for this is to deliver air for "near field" part cooling immediately after the nozzle on a 3D printer. This will be similar to the "Berd-Air" or Tusk type of cooler which directs cold air at a fairly low speed and only on freshly laid plastic. This ensures maximum fidelity of the fine details by preventing sag-back of the plastic. To get cold air I want to deliver the air at high pressure and allow it to expand through a small orifice into a chamber and then be directed near the printing nozzle.

So far I have found nothing that really fits the bill of ca. 2mm i.d., 10 bar, flexible and lightweight. Any suggestions?

Mike

Years ago I used hollow "O" ring cord for a similar application. From memory it was 1mm bore and about 3mm OD. It handled 120 PSI without turning into a sausage. I don't recall the material, but probably Viton or Buna-N. Certainly not silicone. The medical industry also uses all kinds of tiny bore lumen tubing that has to handle pretty ferocious syringe injection pressures, without rupturing inside the patient.

For mad scientists like ourselves, the McMaster-Carr website is absolutely invaluable. I don't believe they ship internationally, but their website is one of the most useful resources on the web for generating ideas and further leads.

[www.mcmaster.com]

Just search on "tubing", plug in your size and pressure requirements, and watch the light-bulb go on. Plus, almost all of their hardware has directly downloadable CAD files, which I have sliced directly and used to print actual objects.

Here in the states, if I place an order by 8PM, the box is usually on my porch by 10AM the next day. I'm not sure how they do that. Must be some kind of teleportation device, since their shipping centers are in New Jersey and Chicago, and I'm in Maine. And they don't charge for over-night shipping either.

Edited 1 time(s). Last edit at 08/23/2021 04:23PM by rq3.

Thank you for the pointer to the McMaster-Carr website, like the Misumi and Accu websites it has many things for the mad scientist but often available if you are a registered business. As you point out though, if something can be found on their catalogues it can often be found elsewhere (eBay) at an inflated price.

I will probably use a polyurethane tube as suggested by VDX although it is more rigid than I would really like. Since similarly rigid PTFE tubing is used for Bowden tubes I guess it won’t be the end of the world if it is not as flexible as silicone.

I should mention that the first mention of using adiabatic cooling was by cozmicray in this forum back in 2016. Worth giving credit as he and I usually communicated with daggers drawn.

Mike

... the thinner tubes are more flexible, than you'll expect, compared to the thicker ones ... and check for "soft" vs. "rigid" - they have classified the for this too

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

You can't use teflon tubing of the type used for bowden tubes for extruders?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

For compressed air, 10 bar and really flexible, you will find PU tubing in any industrial supply store. Widely used in pneumatic automation systems (with 1/16" fittings, but also 1.8"). They are the best.

Festo, Legris, etc.

You will find these tubings on eBay or Ali if you have no industrial supply nearby.

Edited 1 time(s). Last edit at 08/24/2021 02:00PM by yet-another-average-joe.

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the_digital_dentist
You can't use teflon tubing of the type used for bowden tubes for extruders?

Standard Bowden tube is the fallback position but it would be nice to get as much flexibility in the various wires, conduits, and pipes going to the effector/carriage as possible.
In the case of the proposed cooling tube at 10 bar pressure, there will be an additional force straightening the tube. The magnitude of this force will depend on tube geometry and tube construction Received wisdom is that thin wall cross braided tube will have less force and remain more flexible - this, along with things like how much flow is needed? What size nozzle is needed? How much pressure is lost along the length of the tube? All remain to be determined by experiment.

Thank you yet-another-average-joe, I will check out Festo and Legris

Mike

... or you could just use the standard PTFE tube with the olives.

It's unlikely to be under 10 bar pressure it the end of the tube is open (maybe 1.1 bar absolute at the fan,) and heat resistant if it hits the nozzle by accident.

I might be wrong, however.

Regards.

Thank you Andrew_F.
PTFE has been explored but it is not as flexible as needed for this application although very thin-walled PTFE has been looked at. The end of the tube is not open but is restricted by a very small orifice so that the expansion of the air from high pressure, say 10 bar, to low will result in cooling of the air. To get this pressure a positive pressure pump such as a piston pump is needed.

There is no normal chance of the tubing accidentally coming in contact with the nozzle as it will be delivered to a chamber connected to and surrounding the nozzle. The purpose of this is to cool only the first say 20mm of filament after it has been deposited on the print.

The present status of this is that I will start with a 4mm bore 0.5mm wall Festo tube carrying air at 6 bar with a nozzle of 0.3mm and am hoping for the near-field cooling air to be delivered at about 15°C below ambient.

Mike

Cheers Mike,

Be interesting to see how it goes.

Speaking off the cuff without pulling out a copy of Perry's. The air will be heated by the compression needed to get it to 6 bar unless you are compressing off line and holding it in a reservoir (assume you are thinking this instead of a direct piston pump). If you are putting energy into compression, then immediately decompressing it, I have a suspicion that you may get more like 5°C cooler. However, the massive volume of air that the nozzle will induce through the venturi effect at the tip will definitely help with rapid cooling. (Venturi nozzle, even better.) I like the idea.

I've followed this post to see what the end result is.

Regards,

A

Edited 1 time(s). Last edit at 09/19/2021 07:04PM by Andrew_F.

The pipework from the compressor to the orifice will be something like 800mm of 6mm o.d. copper pipe and 400mm of the flexible tube while the high-pressure flow will be quite small. My guess is that almost all of the temperature rise from compression will have been lost through the plumbing: If this confidence is misplaced then some form of heat exchanger could be added.

At the moment I have little idea of how well - and even if the cooling of the air will improve print definition. Simply using low pressure (ca 80mb) air to a quite large nozzle or "Berd Ring" a flow of about 2000ml/min seems to be about right so I would hope for somewhat less than 300ml/min of air at 6 bar will be where to start.

I can't promise any great speed on this as it is one of several ongoing projects [reprap.org] [reprap.org] [reprap.org] and I am also a bit hors de combat at the moment.

Mike

No need to reply Mike.

I just saw those projects you're working on - reminds me of the research I used to do.

Intriguing. The z height sensor could be commercialised.

I like the way you think.

Regards,

A