2.12 gripper design prototype number two [2.12 Design Notebook]
So today... we're going to spend some time putting together a second prototype of the gripper, hopefully properly this time. We're going to try to follow the assembly instructions for the gripper here: https://hackaday.io/project/158551/instructions
We won't use their pneumatic system yet we're just borrowing the mechanical design at the moment. But if we find that it is the air pressure regulation that's really making the prototypes fail then we will have to rig something together.
Here we go...
So we printed all the STL files, it's time to fill the balloon we are using with a funnel. Last time I think we definitely added too many coffee grounds. We're going to still eyeball it but make sure the balloon isn't much bigger than the funnel we 3D printed from the parts these guys made. We're using course coffee grounds.
That's a much better size - sorry I tend to over-do/overfill things. Don't over do things! We're going to be creating the gripper on hackaday with a few modifications because of lack of parts.
So that's it - there's the gripper. What I'm going to try to do is blow air in, pick up a nut, and suck air out and see how well its works. So it successfully grabs the nut when I do it with my mouth - but it does drop it if the thing shakes too much which means there's probably too much coffee in it still. We need to not overfill the membrane because doing so stretches it and stretching the membrane is NOT what we want (according to Ed from the maker space).
Let's try with less filling, even less. Or, just get a bigger balloon - and that's what we did (30cm balloon this time).
So this time we have less coffee in it and a much larger balloon. Hopefully it can better conform to shapes and do things.
This kind of works! I also noticed it works BETTER without tape around the edges like in the picture above, it works better like this:
I think that's because it doesn't constrain the balloon too much. I'm also generating the vacuum with my mouth instead of anything else that could be a factor. It still seems very hard to inflate the balloon. I want to try this again with some different material that isn't a balloon - some sort of flexible fabric that's air-tight but won't expand or contract so I can't accidentally fill it up too much, fill it with LESS coffee grounds and see how that conforms to objects.
The other problem I noticed is that this thing needs some sort of an edge to wrap around and grab - it does NOT do well on smooth surfaces and it wouldn't it would be relying on the friction of the balloon only not much grip. So that's something to account for in the design itself. We might want to try a pneumatic gripper of a different design entirely. Or maybe the same idea - but change the shape of the gripper so it can conform to smoother objects.
We just need to find the right ratio between the balloon size and the number of granules inside. We also need to find a better shape for this thing I think - otherwise it will be very hard to get this thing to work with smooth round bottles, it will pick up crushed fine. We need to find something that smushes very easily and we can just draw the air out. This doesn't smoosh as easily as we thought initially.
I'm going to do some more research tomorrow and see what our options are.
Maybe we want to look at something like a starfish gripper or something...
There's also things like this to look at: