Understanding Modulator Wear and Repair

What is the Modulator?

It’s the heart of your system.

It’s the engine running the machine.

It’s the thing that turns your blaster from a simple dirt-chucker to a sophisticated surface-refinement tool.

All Comco micro-abrasive blasters feature our patented modulator. This modulator forces air into the abrasive tank, a pressure vessel, which fluidizes the abrasive, and then draws that fluidized mixture back out of the tank and into the mixing chamber before sending the abrasive stream out toward the nozzle. This pressurization/ fluidization process happens at a rate of 60 times per second and is integral to delivering a consistently-mixed and evenly-metered abrasive stream.

How Does the Modulator Work?

There are three primary components in the Comco modulator housing assembly: the body, the core, and the nose. The body is connected to the tank; the nose is connected to the regulator. Air flows from the nose, pushing the core against the far seat, which opens the valve and allows air to flow through.

There is an electromagnet surrounding the modulator. When this magnet engages, it pulls the core up against the nose, creating a tight seal and temporarily impeding air flow. This, in turn, causes a low-pressure region to form in the mixing chamber, forcing the fluidized air and abrasive mixture from the tank into the chamber below.

As long as the core and the nose form a tight seal, then the system keeps a good rhythm of alternating pressure: high pressure when the core releases and low pressure when the core seals. This pressure fluctuation in the tank causes the metered fluidization and feeding of the abrasive.

Below: badly worn core exposed to abrasive.

Grooves Form & the Seal Breaks

As grooves form on the body and the core’s edges dull, the core begins to shift off-track and fails to seat tightly against the nose. When this crucial seal is broken, the fluctuation in pressure decreases (ex: decrease from a 5-2 psi). When the pressure decreases, the abrasive fails to fluidize consistently.

3 Ways to Identify a Worn Modulator

Rattle vs. Hum

A good modulator hums. A worn modulator rattles. The gradual shift from one sound to the other over time may be hard to notice, so we usually recommend tracking blast hours and abrasive flow.

Blast Hours

If you are into preventive maintenance, we recommend tracking blast hours to schedule a replacement. The AccuFlo modulator has a lifespan of 5,000 blast hours; MicroBlaster, Powerflo and DirectFlo modulators should be replaced every 2,000 blast hours.

Low Flow

It is time to replace the modulator when you no longer get strong pulses of air into the tank. You will see the outward manifestation in your abrasive flow. When a modulator is too worn to seal, your abrasive flow starts out strong, but within 3-5 seconds drops off to almost nothing.

The AccuFlo® has a Better Modulator

We significantly improved the design of the modulator in our latest MicroBlaster, the AccuFlo. These improvements dramatically increase the modulator’s lifespan to 5,000 blast hours. (The modulator on our standard MicroBlaster should be replaced every 2,000 blast hours.)

Why is it better?

1. Location: the modulator sits further away from the tank to reduce the potential for abrasive contamination.
2. Orientation: the vertical orientation reduces the potential for uneven wear that forms on the core and the body when the modulator lies horizontally like it does in our other blasters.
3. Easy Replacement: the whole unit can be removed with 2 Philips screws and push-connect fittings. All hoses on the AccuFlo are color-coded to improve confidence in assembly.

Modulator Housing Assembly Part Numbers

It’s a good idea to have a backup on-hand and avoid production interruption. To order a replacement modulator assembly for your blaster, contact Customer Service via email or call 1-800-796-6626.

• AccuFlo® modulator assembly (Part No. MB2250)
• MicroBlaster® modulator housing assembly (Part No. MB1301-2)*
• DirectFlo™ / PowerFlo® modulator housing assembly (Part No. PF2040)*

*Typically the cylindrical housing assembly within the coil needs to be replaced on the MicroBlaster, PowerFlo and DirectFlo; not the coil itself.

Dig Deeper

Questions about Blaster Maintenance?

Email me or give me a call at 1-818-841-5500.