What is the Modulator?

It’s the heart of your system; the engine running the machine; 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.


 

signs of modulator wear

Why Does the Modulator Need Maintenance?

Rapid Motion Wears

The core moves back and forth inside the modulator body about 60 times per second. This rapid motion wears the edges of the core and carves corresponding grooves inside the body.

Abrasive Wears

The body attaches to the mixing chamber of the tank. This means that abrasive particles occasionally sneak back into the modulator during operation. Abrasive particles like to stick to the modulator’s core. So, add abrasive to the core’s rapid motion, and boom, you’ve made an excellent environment for wear and tear on your modulator.

Grooves Form and 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.

Body grooves on Modulator

Above:  grooves formed on a modulator body.

Below: badly worn core exposed to abrasive.

Badly worn modulator core

How 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.

Good v. Bad modulator output

Blue line charts the output of a good modulator; Red the output of a worn modulator.

Note the initial surge of abrasive charted by the red line followed by a rapidly weakening stream that never recovers. This is a typical indication a modulator is worn and needs to be replaced.

Not recognizing this sign quickly can lead to further damage. An operator may start pumping the footswitch to get that initial surge of abrasive at the beginning of the cycle. Pedal pumping may work in the short run, but more often than not, it results in inconsistent blaster performance and causes wear throughout the machine.


The AccuFlo® Features 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 the modulator better on the AccuFlo?

  1. Location- the modulator sits further away from the tank to reduce the potential for abrasive contamination.
  2. Orientation-  its 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 at sales@comcoinc.com or 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.


Rob in Tech Support

Questions about modulator or blaster maintenance?

Email me or give us a call at 1-800-796-6626.