(Mostly) 3D printed Air Compressor / Vacuum Pump

This is a working see through air compressor that can reach about 40psi. It is not completely 3D printed as you can imagine but the parts necessary are not that hard to find. 

Here is the video in which I describe how it works, the design and build process and some tests to see what it can do.

BILL OF MATERIALS

• 26-30mm acrylic tube cut to 60 to 62mm (It is hard to cut but around61mm should work the best.
• M3 screws and nuts.

1. 22x 12mm for the 4 connector, cap_single_oring and bottom_cap
2. 9x 15mm for 2 case_bearing_holder and piston_rod
3. 4x 8mm for 2 crank
4. 4x 5mm for lock_ring pieces.
5. 17x nuts

• 4x 80mm M3 threaded rods
• 2x 688 bearings 8x16x5
• 2x 608 bearings 8x22x7
• 1x 623 bearing 3x10x4
• Two lazercut pieces cut with the .dxf files. For the back I used 5mm mdf and for the front 3mm acrylic but polycarbonate would be better. Also it too can be 5mm. If you can't find a way to lazercut the pieces you can print case and case_front stl files instead.
• 2x 20mm inner diameter 2mm thickness O-rings (or similar size)
• 1x 24mm inner diameter 2.67 thickness O-ring(or similar size)
• 6mm by 6mm square rod can be any metal. You'll need to grind or sand the corners a bit to fit into the bearings.

1. 2x 50-60mm
2. 1x 40mm

• pneumatic fittings

1. G1/8-6mm check valve
2. 6mm-6mm check valve
3. 6mm hose
4. G1/8-6mm fitting

• 3D printed parts

1. crank x 2
2. bottom_cap
3. connector x 4
4. coke_cap (if you want to use a soda bottle as an air tank)
5. drill_bit_6x6_adaptor (to attach a drill bit to the crankshaft)
6. case_bearing_holder x 2
7. piston_rod
8. cap_single_oring (you'll also need another O-ring 11.11 x 1.78 or similar size should work fine)
9. piston
10. lock_ring x4
11. cap

PRINT SETTINGS

I used PLA and it works fine but if you have the chance a material with a higher melting point will be better. The parts that are writtenin bold are subjected to pressure and use 4-6 wall layers, high temperatures and thick layers to improve air-tightness.

The piston rod is a failure point so use 6 wall layers and print it laying flat with supports.

ASSEMBLY

Before the assembly I suggest watching the assembly part of the video. I shot a stop motion scene for the build. You can follow along there.

You need to sand the top of the acrylic tube so there is no sharp corners. 

The cap_single_oring needs to be tapped with g1/8-28 tap. You should tap it from the bottom so the teeth on the top are better since the fitting will be screwed from the top.

Few tips don't overtighten screws into the plastics. When attaching the piston rod to the piston you don't have to use a nut. The screw is self-tapping itself to the plastic. But if you use a nut don't overtighten it. 

In general using locktite is a good idea. For the pneumatic fittings use thin teflon tape.

Oil the O-rings and the cylinder.

I didn' had a way to drill and tap the square rod but if you can, the crankshaft will be much better when the screws go in to the metal. Currently it can slip a bit.

OPERATION

This is a working model but after all air gets hot when compressed so don't run for too long. Allow it to cool-down. You can use it pump up to 40 psi so a ball or a bicycle tire can be pumped up (you'll need to find correct pneumatic adapters for 6mm hose). But a car tire is too much it would take hours with cooling brakes and I didn't test the compressor for hours. Above 20 psi it's not super happy don't forget these things are normally metal and the one you built is not.

HAVE FUN