have you ever seen ?

[machinedude]

i just need to come up with a way to test what 3.5 Nm of torque feels like to spin and get a feel for it and find out if that is breakaway torque or running torque? the manufacturer was not clear on that in the documentation. if it feels a lot better than what i was testing then buying these might make sense but not pleasant since the cost of one is more than the whole budget of what i started.

[adbuch]

OK. Thanks! I get it. Good luck.
David

[machinedude]

when it comes to rotary joints if you have a lot of breakaway torque need you can find yourself in a bunch of other problems down the road. it does not matter if it is a hydraulic or pneumatic system the stationary part of the joint need to be restrained. this article explains it pretty well.
https://uea-inc.com/blog/feature-articl ... c-swivels/

[Deezl Smoke]

I'm going to butcher this I know, but let me try to write this for clarification.
Using the standard 3 axis's of X, Y, and Z. Z being the tube clamping, X being the rotation of the tube while cutting, and Y being the length wise movement of the tube being cut.
Your hope is to hold air pressure to Z while X is in motion, correct? And the issue is the torque required to overcome the sealing materials and design, correct?

So let me just ask this and see if you have already kaboshed the idea or whether it makes sense. Even if you have never been near a semi truck, you have heard them in movies and videos etc., when the park, there is a loud instant release of air. That is setting the park brake. Now would it work for you to pressurize Z clamping the tube, then with a one way check valve in the line with a small accumulator, release the air to the X? The Z would be held per requirements, but the pressure is released from the X rotary.
Then,....using a sequencing valve that is plumbed between the X and the check valve, release the air to Z for placing the next part.
I can go into more detail, but no need to if this concept is in no way what you are wanting to do.

[machinedude]

i did a quick and dirty test with a torque wrench and the ones i found are probably 3 times better than what i started with. if this old torque wrench is accurate? i have no clue where it came from but it's the kind with a metal pointer against a scale and not the breaking action type. so 3.5 Nm seems like a fix for everything but i'm going to test a few more times to be sure.

[machinedude]

interesting response from this rotary union manufacturer. i did not ask this question but got some extra information on drive motor requirements and was told 2kw with reduction to drive one of these. this idea of mine has to drive two of these. Wow so if this is the case i would be looking at a 4kw servo with reduction. it seems to me that this rotary union lacks efficiency, or they are off somewhere?

[machinedude]

I have been thinking hard about my situation and think i will try a version 2.0 of a union. i am going to try making my own seals for this so i have control over sizes to fit my needs. i can make use of some of the parts from the first stab at this thing by doing it this way. The problem i have hit is cost of material and cost of seals for something this big. so when you find a way to reduce material costs finding a seal design the right size becomes a problem. So i find myself forced to try and take matters into my own hands So if i can get the seals right the rest should be downhill from there.

So i guess i will find out at some point if my stubbornness pays off and i beat this thing I'm not ready to toss in the towel just yet

[Deezl Smoke]

Keep us updated as you progress please.
I still think if you can start with allowing a small amount of air escape, you might find the rotation power consumption low enough, then start working more on reducing the air escape, might be a consideration.

[machinedude]

i think the big problem with these types of joints are power requirements to get them moving. so when you have a small extrusion gap between the shaft and the housing you create a pinch point for the seal to get caught up in when you add pressure to the mix. what i am planning removes that part of it with the pressure issues causing problems with rotation. all my sealing should be done with compression so air pressure should not matter as long as 90 psi can be held. if it works then a in-line oiler will need added. these types of seals ride on a thin film of oil and without that the heat builds up on the sealing lip and will make the seal fail eventually.

[machinedude]

i got a mold made so i can cast my own seals so yesterday was productive at least. i have never seen anything like this before so i will have to see how it goes. the idea is to have the housing be sealed mechanically and be 100% static and let the sealing lip do the sealing mechanically controlled by the shaft diameter. this approach should remove the air pressure pit fall all together, i hope. things like this have a pretty small cross section so casing could be a project in itself.

this type of seal is a little bit more forgiving with the extrusion gap between the shaft and housing, so you get a little more play on the runout between the two.

seal 2.jpg

[Joe Jones]

Have you ever seen the BIG BANG THEORY episode where the guys try to assemble a wood entertainment center for Penny? They take a simple task and incorporate the most convoluted, complicated, mechanically involved method they can imagine.

If you want to cut a length of tube or pipe, and you can get that pipe beneath the torch on the table's gantry, why not K.I.S.S.? Why bother with hydraulics and synchronized chucks, etc.?

Create round templates for the various shapes. Attach a few of them along the length, and roll them on a set of rollers. It doesn't seem to be that complicated. Yes, you would manually advance the tube or extrusion the machine's cut length, but beyond that, you would just be cutting tube the same way a pipe cutter works. You would need THC to keep the torch above non-round shapes.

The templates can be made from steel, or aluminum, or even plywood for that matter.

I will try to draw something up to illustrate this concept, but right now I have too many things that are demanding my time.

Here is the basic concept ...

Joe

EXTRUSION CUTTER JPG.jpg

[machinedude]

well to put it short nothing is stupid simple with automation. Sadly, times are changing. robotics are becoming more common than ever these days. For me this has been something i have taken an interest in since i was a kid. most would be like why bother but for me i see potential in this application for lots of things. it keeps me thinking and that keeps me out of trouble

[weldguy]

Joe has a good point but I can certainly appreciate what your trying to do and applaud your ingenuity. I will be following this topic in hopes of seeing more of your progress on this.

[machinedude]

i did a cast to see what kind of hang up points i might run into. i have to tweak some things and refine my process some but for the most part it worked well. i actually think this will work pretty well once I sort some little stuff out. i got enough from it to test some fit and function aspects. i can't test any pressure aspects until i build one but i think i am on the right track.

the whole template idea joe pointed out is basically the same concept as what i am doing just i want to use soft jaws as my template to hold and center things.

[machinedude]

i put some more time into making some modifications to my mold and now have things coming out nice. they are a bit of a pain in the butt to mold and on a large scale i would not want to do them this way. But for my needs i will make do with what i have. i actually learned something new doing this. it turns out if you bake you casting at 150 degrees for about 4 hours you get a stiffer rubber. not to mention you save a ton of time on curing as well. i never knew you could enhance the rubber by baking it but knew about the reduced cure time. So i learned something new

i have some new material coming for the housings so once i get that i can start getting some progress made hopefully.

[Deezl Smoke]

I love learning new things. It's what keeps life so interesting.

[plasmanewbie]

Me too, learning new things is worth the extra time, especially if you are enjoying the process. Well done.