I work in a factory that uses extensive automation. Most of our end-of-arm tooling is suction-based... suction cups, grippers, discs and other shapes. The cost of these items add up over the year, we would like investigate the possibility of developing the technology to print replacements on demand. This also opens up the ability to make new non-stock-shape cups and grippers to enhance production too. What I am looking for is information on rubber or rubber-like materials (silicone, elastomer, soft-PVC and so forth) and general design considerations for such. Especially minimum thicknesses! I don't want to design a knife-edge part only to find that it can't be printed. Can anyone advise or point me in the right direction?
Queue up the cheesy music: This might be a job for Elasto Plastic The rest of the Shapeways materials are too rigid/brittle to make suction cups.
I would disregard the watertight statement and give it a try. From my experiences with the material it is watertight and would work for your application. It's not a solid, like say, cast silicone would be, it's more like, ummm... think sugar cube. It has porosity, but in thicker walls, say beyond 3 mm, it is solid enough to do what you want to do. Maybe it wouldn't work 100% of the time in a leak down test situation, given the random nature of the porosity, but in pick and place type applications it would work perfectly I feel. If it were my problem, I'd order up some samples and try it out. Shapeways will have the cheapest price as far as rapid prototyping services bureaus go. Everyone else is going to be too expensive.
Water is a liquid, air is a gas = it'll leak air even if water doesn't flow through. There is no way that the surface of a 3D printed model no matter the material is ever going to be airtight against a flush, smooth & flat surface without lots of post production finishing - you need a flat surface against a flat surface along with a relative vacuum for something to work as a suction cup. For pick & place operations, forget about any material Shapeways has to offer unless the cost of failure is an associated cost of prototyping a product that can be made via means other that 3D printing. fwiw a single suction failure on lifting a pallet layer of glass bottles for a productrion line can cause the entire load to be dropped and upwards of 3 hours for the cleanup... line down, N'0000's productivity down, 3 to 20 people getting paid to sweep up (been there, done that and got paid very well for cleaning up broken glass for half a day) Paul [hr]stop4stuff Modeller for hireShapeways Shop - Controller PendantTwitterYouTube[hr]
Actually we are looking at about a half hour to stop the line swap out a single cup, start up and go. If it doesn't grip the lightweight plastic product (30 grams) then we stop, and swap back. Only an idiot would trust an unknown quantity (such as a prototype gripper) in full-speed production -- this is why we have evaluation periods, tests, trials and engineering experts (me!) to test things before Production flips the switch. There seems to be a lack of experience printing elastomers and silicone rubbers at the moment and this is holding me up. I may have to bite the big one and buy my own printer and have at it.
I think you're thinking of a static suction cup design, like to attach something to a glass window or something like that for long periods of time. For that one would need a very good seal, a nearly perfect seal. In this case no Shapeways material would work. For pick and place automation equipment though, vacuum motors pull a continuous vacuum that continuously compensate for losses. There is only a failure when a large leak has developed, such as if an entire cup were to break off on a multi cup end effector. Consequently, a perfect seal is not necessary. This is why I feel Shapeways lasto-Plastic would work perfectly. It does have porosity, but not enough to be of concern with 3 mm walls when applied to pick and place equipment where a continuous vacuum is being pulled. By the way, check out Duann's introductory demonstration video for Elasto-Plastic. In particular, take a look at about 5:39.
Yep - transcript. 'The pores of the material seem to absorb moisture, so if you're making a planter or something, that's perfect, but its not exactly watertight' Water molecules are huge compared to air, if it doesn't hold water, it won't hold air and if it won't hold air it won't hold a vacuum relative to natural air pressure. Saying that a machine is constantly pulling that vacuum for the likes of suction cup useage means that the machine would be working to excess with higher running costs. I therefore stand by my statement that currently there is no 3D printable material suitable. Paul [hr]stop4stuff Modeller for hireShapeways Shop - Controller PendantTwitterYouTube[hr]
Unless these suction cups are huge it can't possibly cost a lot just to make a few and experiment in the final applications. There must be a way to infuse the elastomer with some kind of thermally activated rubber to seal up the voids and make them slicker. Perhaps such compounds could be diluted with an appropriate solvent to better penetrate the elasto before curing.