Mini “More Extensible” Pneumatic Artificial Muscle with Bellows

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The original McKibben type pneumatic muscle can contract like muscles. We can also make an extensible pneumatic artificial muscle with same materials. A difference is using a braided sleeve with shorten state.

Video

https://youtu.be/ZgiZtd0dn6U
Process time: 60 min

Materials

  • Expandable braided cable sleeving (adaptive size from 6mm – 1/4″ to 13mm – 1/2″)
    MacMaster-Carr, Expandable Polyester Sleeving, 9284K2
  • Soft Latex rubber tubing (outer diameter: 6mm – 1/4″, inner diameter: 4mm – 5/32″)
    McMaster-Carr, Super-Soft Latex Rubber Semi-Clear Tubing, 5234K962
  • Barbed tube fittings
    • a reducer connector (for 1/8″ – 1/16″ tube inner diameter)
      McMaster-Carr, Barbed Tube Fitting, 5121K221
    • a plug (for 1/8″ tube inner diameter)
      McMaster-Carr, Barbed Tube Fitting, 5463K75
  • Cable ties (zip ties) (width: 2.5mm)

Tools and Equipments

  • Metal rod (diameter: 6mm, length: about 150mm)
  • Air tube (outer diameter: 3.2mm – 1/8″, inner diameter: 2mm – 5/64″)
    SMC, Polyurethane Tubing, TIUB01
  • Scissors
  • Ruler
  • Syringe
  • Cable tie gun (optional)

 

Directions

Prepare sleeving

Cut the braided sleeve in the four times the length of the desired muscle length, for example 320mm (=80m x 4).

Make the bellows

Insert a metal rod into the braided sleeve. Tie up the end of the rod and sleeve together with a cable tie. Push the sleeve along the rod and make bellows until no more shortening.

Tie up

Then tie up the other end of the sleeve.

Bake the sleeving

Bake in an oven at 120°C (248°F) for 20 minutes to fix the shorten state.

Prepare the sleeving

Put marks with tapes on the shortened sleeve with rod in the desired length, for example 80mm. Release the sleeve from the rod and cut the sleeve according to the marks.

Prepare the rubber tube

Cut the rubber tube in the same length.

Insert plug

Insert the barbed plug into the end of rubber tube.

Bundle

Insert the rubber tube into the braided sleeve.

Tie up

Tie up the end of the tube and sleeve together with a cable tie over the barbed plug. Tighten the cable tie to prevent air from leaking. Cut off the excess strap of the cable tie.

Insert connector

Insert the barbed connector into the other end of the rubber tube.

Finishing

Tie up the end of tube and sleeve together with a cable tie over the barbed connector. Tighten the tie to prevent the tubes from slipping off. Cut off the excess strap of the cable tie.

Test

Connect the air tube and syringe to inflate the rubber tube and contract the artificial muscle.

Test other muscles

Test other recipes, too.

Bon Appétit! (but don’t eat)

 

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