Good Morning from my Robotics Lab! This is Shadow_8472, and today, I am ordering materials for the artificial muscle I’m going to be working with for a while. Let’s get started!
The McKibben Artificial Muscle
In my research this week, I learned the pneumatic muscle I’ve chosen to start prototyping with is in fact called a McKibben Muscle. An inner sleeve is typically made out of rubber. A fluid –usually air– is pumped in through an endcap. The sleeve expands radially, a woven outer casing translates that outwards expansion to a lengthwise contraction.
I’ve seen several tutorials on how to make these muscles online. The greatest design freedom is in the endcaps. They can be as simple as a clamp or complex enough to need a 3D printer. Their functions are to hold the inner sleeve and outer casing together, seal them off while still allowing air in and out within the greater pneumatic system, and provide mounting points to work on.
Materials Shopping
The most important part is the outer casing. I will be using cable management sleeving like what protects the cords coming off the power supply in my main computer tower. Squish them, and they expand: same principle in reverse of the muscle. I remember at least a couple sources saying to use nylon, but a little shopping yielded a selection of tubes made from polyethylene terephthalate (PET).
Tubing is almost as important as the casing. As long as it keeps air inside the muscle, it should work for all I know right now. I talked about it with my father while walking the dogs, and we figure longer-term durability will be best served by a rubber tube a bit thicker than a balloon, but not so thick it’s near difficult to inflate.
We’ve talked about an air source. Compressors are loud and bulky. Lower end models lack a tank for storing pressure, which I will need for anything resembling a decent response time. We also briefly considered getting a SCUBA tank, but those run more than a compressor and most certainly cost to refill. Whichever option we end up buying, this will be the most expensive part.
We’ve only baerly started brainstorming endcaps. My father proposed using a nut and a pipe clamp for one end, but I’m having trouble imagining how that will look while trying to attach a mount point. Perhaps some PVC piping will be involved after a trip to a hardware store. I can have a T pipe with a plug for a mount point across from the muscle and an adapter to the air supply coming off the tail.
Takeaway
The main consideration for buying parts at my stage is matching size. It won’t do to have an inner tube that barely fits in the expanded profile of the sleeve.
As noted above, it would seem everyone showing off their air-powered muscles has a slightly different design depending on his or her available tools. I don’t have access to a machine shop, so I won’t be modifying any metal parts. Neither is my 3D printer working right now: printed parts will need to wait.
I’m excited to start testing.
Final Question
What variables do you expect will affect the quality of my McKibben muscle design?