Help on designing a vacuum gripper

[frusciante89]

Hi guys, I have a UR10 in my workshop and I wanted to design a vacuum gripper, since their retail price is quite high. I was thinking of making something in this style:

https://gadgetron.online/add-ons/260-vacuum-suction-cup-robot-gripper.html

Basically, having a flange that attaches to the robot toolplate which also has a vacuum L shaped line inside. One end of this L will be on the side and it is where the vacuum enters. The other end of the L comes out perpendicular to the flange, and will be attached to a suction cup (I only need one cup, not 4 as shown in the picture).

I did some research and I figured I need:
- a venturi vacuum generator (6mm to 6mm)
- a solenoid valve
- a suction cup
- tubing (already have plenty of 6 mm piping)
- compressor (already have it)
- am I missing something?

In theory, this should be it. However, I've never worked with vacuum before, so I have some doubts:
- for the suction cup, do I directly connect it to a threaded hole on the flange? Do I need some kind of adaptor?
- regarding the threaded holes (one for the suction cup, and the other for the vacuum input tube), is a standard metric tapped hole ok? will it leak or does it need a particular threading?
- do you guys suggest any specific type of suction cup designs? Flats, bellows, etc.? Don't really know the difference.
My usecase is picking up polished wooden cubes (one at a time) that weigh around 600 grams

Thanks for your help,
Cheers from London

 

[itsmoked]

The pick-up force is just like all pressure related cases. Look at what your venturi will provide. Subtract that from the local atmospheric pressure to get you the difference. That difference over the area of the suction cup is the force available from that cup. Add up the cups to get the total force available. Once you have that all figured make sure you have at least 50% more than you need or better yet, 100% more than 600 grams.

Of course if you're moving that block fast then F = ma is going to be involved and the forces needed will be dictated by gravity AND F = ma so you will need more pick-up than just a slow dead-lift up from a table top.

If you end up needing lots of suction a venturi will put you in the poor-house as compressed air is expensive to make. Go to fleabay and buy any one of the bazillion little vacuum pumps and a little vacuum accumulator tank and a little filter to keep sawdust etc. from getting to the vacuum pump and it will save you a bunch of money over time.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LittleInch]

Lots of things are designed for positive pressure, not many for negative.

So your tubing needs to be metal not plastic and suitable for vacuum service.

I agree with it smoked - you really need to have a tank at negative pressure and something better than a venture to generate your positive pressure.

You'll need to provide some more info on the suction cup and this end flange L shaped pipe so we understand what it is you mean or are looking for.

you're only looking at max pressure of 1 bar so really any type of thread sealing should work.

The cups won't seal 100% on your wooden cube without some form of liquid seal so you need to have spare vacuum capacity. A bit of trial and error needed to see how the cup / item sealing goes and then what happens after the 50th and 100th time you try and pick it up.

And I agree with itsmoked - the real issue will be how fast you move or start / stop the robot arm. It could easily pick it up slowly but try anything else and the thing will fly off the end.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[btrueblood]

I third Keith's vacuum pump. Stiff plastic tubing (polypropylene, PFA, nylon...) can work for vacuum in small sizes like the 1/4" stuff you showed, but do take care that the stuff you buy is rated for vacuum as LittleInch suggests. The bigger the pump, and the bigger the tubes, the bigger the leak rate past the suction cups your pump can handle and still maintain a differential pressure at the suction cup, which produces the suction force that allows it to pick stuff up. FWIW, the best suction cups are molded to a metal piece that has the plumbing attachment and mechanical fastening means built into it. You might be able to prototype suction cups with a castable urethane resin, if you can't find one ready-made.

 

[Shrikantguthe]

Interesting Work.

Mr.Shrikant Guthe
Marketing Manager

http://www.gsourcedata.com

 

[Compositepro]

1/4" OD lines are capable only of very limited flow under vacuum conditions. Adequate flow is needed to get a suction cup to form an initial seal and to work when there is slight leakage. For this reason venturis (or eductors) are often located on the suction cup and supplied with compressed air.