Pneumatic cylinders are useful in actuating various devices whenever pressurized air is available. This customizer allows to generate cylinders with arbitrary bore sizes and stroke lengths and has many other adjustable parameters.
Two main options are available for tube sockets: M5 and 4 mm. The M5 type allows insertion of M5 pneumatic fittings, e.g. the RIKI 4 x M5. For the 4 mm type, three variants are available: a plain 4 mm socket, one with locking clamp and a locking clamp version with integrated support.
Compiling the scad file also generates output text (visible in OpenScad) which lists the required dimensions for additional parts, such as the rod, seals and fasteners. For convenience the STL files of the gold cylinder (bore 16 x 16 mm, stroke 30 mm) and red cylinder (bore 30 x 24 mm, stroke 50 mm) are provided, along with the seal cutter blocks. New parametric seal cutters can be created with Thing 3020690.
The customizer makes use of the ISO screw thread modules by RevK.
High infill is stronger and reduces leakage through the housing, but low infill also seems to works fine.
The 4mmLock version of the socket needs support. Integrated support is provided by the 4mmLockSupport version. When using automatic support, take care that the air vents do not get occluded.
The seal and rod geometries for a specific cylinder can be found in the output window of OpenSCAD. Here we need a 3 mm rod with length 56 mm, M3 threaded on both ends with thread lengths 10 mm and 9 mm, respectively.
The brass rod can be tapped using a M3 die. A drill in combination with the seal cutter block can be used to get the thread nicely straight.
Fully insert the 9 mm thread into the rod head. A drill and a beam may be useful here. It may be necessary to tap part of the head's inner thread if insertion is too difficult.
The silicone seals need to be cut to 16.3 x 16.3 mm with slanted edges and a 3 mm hole in the center. Use the seal cutting block customizer (thing:3020690) to make cutting blocks of different dimensions. First make the center hole using a suitable punch or wood drill.
Insert a M3 bolt through the cutting block and seal and then cut the seal's edges. For each edge cut, first fully insert the 9 mm blade knife and then press it all way down. Make sure that the seal stays in position. Afterwards examine each seal for squareness and dimension consistency.
Use the seal with the cleanest center hole (3 mm circular without burrs) for the rod seal (right) and the two remaining ones for the piston. The nuts can be used to keep the seals in place. The seals have a large and a small face due to the slanted edges. The smaller face must be in contact with the piston and the larger face is oriented towards the nut and air chamber. The orientation of the rightmost seal does not matter. The piston seals must be able to rotate and flex, so a tiny gap is left between each seal and nut.
Enlarge the 3 mm rod hole in the housing so that the rod can slide in and out, but do not make it larger than absolutely necessary to avoid jamming of the seal. Grind top surface smooth and also grind the sides of the piston. Insert rod and assemble piston.
Apply sealant such as blue silicone to the housing.
Mount top and bottom plates and fasten with M2 x 25 mm screws. Tap M5 sockets, I use a makeshift tap by cutting a M5 bolt for this.
Insert M5 x 4 mm sockets. The cylinder is now ready!
An alternative fitting type for 4 mm tubes with lock is also available. The integrated support (if used) can be removed using pliers. Drill the socket with size somewhere between 3.7 and 4.2 mm such that your 4 mm tubes can be pressed in with not too much force.
The clip itself can be snapped on the 4 mm tube. Leave around 4-5 mm of tube below the clip. Glue is optional but not necessary, the horizontally printed layers of the clip already provide a certain amount of strain relief.
Insert the tube and rotate the clip below the clamp for a secure attachment.