Vacuum Levels

Timeismoney08

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Does having a bigger pocket of vacuum assist in picking objects?

I would have though it wasn't true, but it appears cups with more bellows at the same diameter have a much better hold on my items I'm picking.
 
In terms of pure force nope. Surface area controls force but the bellows allow the cups to conform and seal better. They also resist peeling off.
 
F = p x A

So, all other things being equal, yes, a larger pocket will produce more force. In this equation p = the pressure difference between the atmosphere and the pocket and A is the area of the pocket.
 
Are the objects you're lifting porous? I used to work on palletizing robots and had to come up with some methods to test gripper strength. I found that volume of the vacuum pump (blower) was very important and that the porosity of the cardboard boxes could vary dramatically from one lot number to the next. I made some polycarbonate (non-porous) jigs and used digital vacuum gauges to measure vacuum levels and set baselines for what should work. There were times when the techs would struggle for hours but when we would run the test, it would pass, proving nothing was wrong with the vacuum system...they'd tell production to switch to a new lot of case materials and the problems would magically go away. Other times, the test would show reduced vacuum strength and we could leave it in place while looking for leaks.
 
Are the objects you're lifting porous? I used to work on palletizing robots and had to come up with some methods to test gripper strength. I found that volume of the vacuum pump (blower) was very important and that the porosity of the cardboard boxes could vary dramatically from one lot number to the next. I made some polycarbonate (non-porous) jigs and used digital vacuum gauges to measure vacuum levels and set baselines for what should work. There were times when the techs would struggle for hours but when we would run the test, it would pass, proving nothing was wrong with the vacuum system...they'd tell production to switch to a new lot of case materials and the problems would magically go away. Other times, the test would show reduced vacuum strength and we could leave it in place while looking for leaks.

They're not porous, but they do have a rough texture to them that will cause some leakage to a small degree. I set it up for testing and can pick it up fine. It's just intermittent in production.


Thanks for answering!
 
F = p x A

So, all other things being equal, yes, a larger pocket will produce more force. In this equation p = the pressure difference between the atmosphere and the pocket and A is the area of the pocket.

Thanks for your answer.

I guess another way to pose the question would be, if the pocket had more empty space (vacuum), would it take longer to peel off our part if it leaked slightly but then regained the seal?

Does the vacuum act as a buffer like a reservoir tank would for compressed air? Or does a small leak automatically change the pressure difference within a very short period of time?
 
Seems that the larger the volume of the cup, the longer it will take a similarly sized leak to negate the vacuum compared to a smaller sized cup.
 
although, now that I think about it a bit more, I guess the flow speed of the air would remain faster for longer as well in a larger cup, so maybe they end up being fairly similar? I can check with my robotics guy and get back to you.
 
Force will be the same for the same diameter. However, I believe volume can matter.

Evaluate the two extremes:

1. A rubber hose with no bellows. You can make suction and pick something up, but as soon as you break the seal a little bit, air comes in, the cardboard starts to fall, and suction is lost immediately.

2. Multiple ribbed bellows . When you start to break the seal, the bellows expand. This does two things:
..... 1. The bellows expanding will suck in air (create vacuum).
..... 2. The bellows will push toward your cardboard - ie they chase after the cardboard and give you a chance of recapturing it.

So I believe that the larger volume (same diameter) will be more effective.
 
2. Multiple ribbed bellows . When you start to break the seal, the bellows expand. This does two things:
..... 1. The bellows expanding will suck in air (create vacuum).
..... 2. The bellows will push toward your cardboard - ie they chase after the cardboard and give you a chance of recapturing it.


This is a good point, though I believe it may have more to do with the ability to expand and retract vs the additional volume itself. So more bellows allows for more expansion and retraction, which can help with the grip of the cup. It wouldn't be the additional volume.

My robotics guy says that the larger volume may slow the rate at which the vacuum force degrades to a small extent, but it wouldn't be enough of an effect to purposely use a larger volume cup *for* that effect. The better solution is faster airflow to combat the leakage.
 
Force will be the same for the same diameter. However, I believe volume can matter.

Evaluate the two extremes:

1. A rubber hose with no bellows. You can make suction and pick something up, but as soon as you break the seal a little bit, air comes in, the cardboard starts to fall, and suction is lost immediately.

2. Multiple ribbed bellows . When you start to break the seal, the bellows expand. This does two things:
..... 1. The bellows expanding will suck in air (create vacuum).
..... 2. The bellows will push toward your cardboard - ie they chase after the cardboard and give you a chance of recapturing it.

So I believe that the larger volume (same diameter) will be more effective.


Wow, this is a great explanation. Thanks!
 
This is a good point, though I believe it may have more to do with the ability to expand and retract vs the additional volume itself. So more bellows allows for more expansion and retraction, which can help with the grip of the cup. It wouldn't be the additional volume.

My robotics guy says that the larger volume may slow the rate at which the vacuum force degrades to a small extent, but it wouldn't be enough of an effect to purposely use a larger volume cup *for* that effect. The better solution is faster airflow to combat the leakage.

We already have a really high flow generator on the system. The problem is some parts are smooth and some have a really rough texture.

Thanks for looking so much into it for me!
 
Loving this thread! sub'd
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