Air Compressor Troubleshooting Guide

Allevi bioprinters use pneumatic extrusion to push bioinks from syringes onto build surfaces. The compressed air that provides the pressure for this extrusion is therefore a key component of the printing mechanism. Below we discuss troubleshooting steps for some common issues with air compressors.

The air compressor is a bit noisy.

• Unfortunately, this is the nature of air compressors. There are some steps you can take to improve the noise in your work environment.
• The air hose included with your printer may be long enough to reach a separate room where you can set up the air compressor.
• You can reduce the frequency of tank refills which cause the rumbling noise by ensuring your air supply connections are all complete and firm.
• If you have compressed air as a utility in your lab space, you may be able to substitute this in for the air compressor. We have recommendations for this process detailed in the issue below.

I want to use my own compressed air source.

• It should be fine to substitute if your compressed air source meets the following criteria:
  • Can reach 120 + PSI max pressure
  • Ensures maintenance of pressure at requested level (may be referred to as kick-on threshold)
  • Works with compressed air rather than other compressed gases
  • Can be prevented from supplying 150 + PSI to the printer (if not, this can damage the printer)
• If your source does not have an output gauge, this may indicate that the output level is not very high. Also, we highly recommend that you only use pressure sources you can measure with a gauge.

The air compressor has been building pressure for several minutes, but the tank pressure gauge shows a pressure below 90 PSI.

• This is usually because the release valve in the outlet mechanism (this piece looks a bit like a brass whistle) has become ajar. Quickly open the valve and re-seal it. Note that this will make a loud noise as some air rushes out of the tank.
• If the compressor is still failing to fill completely, follow the steps for the slight hissing noise issue (immediately below this one).

The air compressor is making a slight hissing noise.

• First, turn off your air compressor.
• Next, use the release valve in the outlet mechanism (this piece looks a bit like a brass whistle) to empty the tank.
• With the tank emptied, ensure that the release valve is firmly back in the sealed position.
• Check each connection between the air compressor and the air supply junction in the back of the printer.
• After verifying firm connections between the compressor, air hose, air hose converter, and air supply junction, feel free to restart the air compressor.
• If the hissing noise persists, check the extruder air supply hoses.
• If the hissing persists, contact the Allevi Support Team.

I’m turning the main dial to increase the outlet pressure, but the pressure output isn’t increasing.

• First, make sure the compressor is plugged in and the power switch is set to “on” (happens to the best of us!)
• Next, ensure that you’re looking at the outlet gauge. The gauge directly connected to the tank measures the pressure in the tank. The gauge higher up on the outlet valve system measures the pressure exiting the tank through the outlet valve.
• If you are looking at the correct gauge and the power is on but it still isn’t working, you may be stuck below the refill threshold. In this case, the compressor may take a few minutes to sense it is not putting out enough pressure. Try waiting two minutes for the compressor to catch up.
• If the compressor still isn’t reaching the desired pressure, you can drop the current pressure below the previous refill threshold. This will trigger a refill at the desired pressure value. To do this, briefly pull on the air release valve in the outlet mechanism (this piece looks a bit like a brass whistle). This will make a loud noise as some air will rush out. Once some air has been let out, ensure that the outlet valve is closed and allow the compressor to refill.

I’m not used to working in pounds per square inch (PSI).

• 1 PSI = 0.00689 MPa = 0.06895 barr = 0.06805 atm