I decided not to clutter up Chris Hurds thread and just start my own. Here I will document the prototyping process of the vacuum gripper. Chris did a great job of testing the system of using a small cylinder as a vacuum source. He stated in his thread that it could hold for up to 5 minutes. I estimated the cylinder to be about 5ml or less. I figured the best way to improve this is to use a larger cylinder. My testing held a heavy cell phone for over 3 hours. His solution was expensive. The cylinder by itself was ~$15.00. We’re using inexpensive 10ml syringes instead. They are only a couple bucks. I have located sources for the fittings, cups and tubing. You would not believe how many hours I looked for these simple parts. I will have the parts for the mechanical assembly for the servo and syringe cut from 1/4" PVC.
Here is the video…
Here are some images… Note the last image shows how to make the cup rotate.
Would a small fan provide enough ‘suction’ for these purposes? It would compensate for any leakage, possibly allowing semi-porous materials to be held for long periods, and shutting off the fan would mean almost instant loss of suction thereby facilitating release. Also, a mini motor and fan would probably be more forgiving, and simple On-Off operation is easy to implement with any controller.
In simple terms no, a small fan would not be able to provide enough suction.
Fans are very inefficient at creating a suction, common Fans are designed to move a lot of air with relatively low pressure. Computer fans for example.
You would need to create an air pump, which is different, and air pump similar to a water pump, if sealed properly, would create much more suction. This is actually how vacuum cleaners work.
A vacuum fan. It uses a centrifuge to move air outwards away from the center input. Or at least i think that’s how it works.
A centrifuge creates negative pressure from the center, fans create positive pressure. http://ecx.images-amazon.com/images/I/41oLWZRo2%2BL.SS500.jpg
Now then, if you scale this down, you could possibly make one that would work, but it would need to use a high torque, high RPM motor in a properly sealed housing. This is why those little usb powered keyboard vacuums don’t work very well, they are not properly sealed, and doing so would require much more torque.
Though a high powered motor from lets say… an RC airplane or helicopter would be more than sufficient. But would also be noisy, and would have a heavy power drain. Though it can be triggered using a nice beefy relay.
In simple terms, a syringe sucker is just cheaper, quieter and more efficient.
But don’t let this deter you from coming up with more ideas. Even if they won’t work, you should still voice your ideas. For one who fails, succeeds at learning.
On the subject, it would be possible to create a continuous pump. using 1 way valves and a release actuator.
If you create a syringe that has 1 way valves on both ends. you could pump it multiple times to create even more suction, or to even maintain suction over time. Then using a simple release valve, similar to those on those medical blood pressure devices that strap around your arm, to release air back into the channel.
Using this technique you could create some serious negative pressure, probably enough that if you used it on your arm, it would look like a mosquito bite.
Edit:
Added some Check Valves should anyone want to give it a try. usplastic.com/catalog/item.a … &catid=489
I would if i had some money or funding to put into the project.
If you can combine it with a negative pressure sensor, you could make it maintain a specified negative pressure. Essentially, as long as it’s powered, it’ll hold an item indefinitely.
Only problem i see you facing, is without a sensor, you have to calculate how many pumps is enough… To many and you’ll overwork your servo.
PS you could probably use a Turn Open/close release valve, as opposed to a button press. Just attach the valve directly to the servo.
Edit:
This could easily be combined with the universal robot gripper. viewtopic.php?f=17&t=6823
It’s all about using a fast servo on the syringe. Possibly even 2 syringe pumps working together for a faster uninterrupted suction.
as one syringe is moving in, the other is moving out. (i can’t think of the word for when they take turns. it’s like on the tip of my tongue.)
