Maintenance & Troubleshooting

FAQ MicroBlaster

by Comco Sales and Support | December 20, 2023

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Understanding Modulator Wear and Repair

Comco’s MicroBlasters are built to last, and we do our best to make sure that every blaster is ready to go after installation. However, each abrasive environment and application are unique. So, from time to time, an issue may arise.

A list of Frequently Asked Questions and potential solutions are loosely organized below. Click on the question to see its answer in the drop-down box. Please use this page as a guide to perform simple maintenance and to better understand your blasting system.

If you need further assistance, please call us at 1-818-841-5500 or contact our Technical Support Team.

Click on the MicroBlaster model below to access its equipment manual.

If you do not see the manual for your model MicroBlaster above, please call 1-818-841-5500 or contact our Technical Support Team.

MB1440 MICROBLASTER TUNE-UP KIT INCLUDES:

MB1440 MicroBlaster Tune-up Kit

5 ST4020 1/4″ ferrules
2 MB1455 hose connectors with Quicknut
2 ST4019 brass nuts with sleeve
25 feet of MB1233 1/4″ abrasive hose
3 feet ST4012 1/4″ nylon tube
1 MB1230-1 nozzle nose
1 MB1301-2 modulator housing assembly
1 ST5022 O-ring
1 ST5624 O-ring
Instructions

Note: If you have an older tank cover assembly (MB1068), you also need to purchase the MB1450 MicroBlaster O-ring kit.

Note: Dual tank MicroBlasters require two tune-up kits.

THE MB1274-3 MICROBLASTER REPLACEMENT PARTS KIT INCLUDES:

1 MB1230-1 nozzle nose
1 MB1455 hose connector with Quicknut
2 ST4019 brass nuts with sleeve
25 feet of MB1233 1/4″ abrasive hose

THE MB1450 MICROBLASTER® TANK COVER O-RING KIT INCLUDES:

2 ST5022 O-rings
2 ST5023 O-rings
¼ oz. tube of adhesive
Thread gauge
O-ring replacement instructions

Note: For use on older MicroBlaster models equipped with the MB1068 tank cover assembly.

Use the following chart to determine the problem:

Items to Check	Solution
Is any abrasive flowing?	NOTE: If no air is flowing out of the nozzle either, then skip down to the next FAQ: Why are neither air nor abrasive exiting the nozzle? Verify the quality of abrasive flow by holding a piece of glass or shiny metal in front of the nozzle and depress the footswitch. If the tank is full and no abrasive flows through the air stream, then the tank orifice is more than likely clogged. Follow the instructions in the next step. If abrasive flows through the air stream but the flow is erratic, then skip the next step and proceed with the remainder of this checklist.
Is the tank orifice plugged?	Have you recently started using a different abrasive powder? The powder may be too large for the tank orifice. Try using a larger orifice or a smaller powder. Check out our Tank Orifice Selection Guide if you aren’t sure. If the tank orifice is properly sized for the powder, clogging may be due to some foreign particulate in the powder. Remove and replace the powder in the tank. (Check your blaster manual for this procedure). If neither of these options seem likely, remove the orifice and hold it up to the light. If blocked, clean with high-pressure air or run a fine wire through it. Sodium bicarbonate plates out inside the system frequently. If using sodium bicarbonate, inspect lines frequently, clean and and replace as needed. If clogging continues, proceed to the next step.
Is the tank orifice too small for the powder?	The orifice should be at least 4x larger than the average particle size. Check out our Tank Orifice Selection Guide.
Is moisture contaminating the abrasive?	Determine the type of gas that is connected to the system (compressed air, nitrogen or carbon dioxide). Compressed air can cause moisture in the line. The compressed air line is the most common source of moisture. GAS NOTE: Never connect to pure oxygen. It will cause an explosion. Turn the unit off. Carefully remove the tank cover without disturbing the abrasive in the tank. Note if there are obvious holes or cracks in the abrasive leading down to the orifice. If there are obvious clumps, cracks or holes in the abrasive, moisture is more than likely in your air line. Read our post on Moisture Issues and compare it with your air supply and the powder storage conditions. STORAGE NOTE: Abrasive must be stored in a cool and dry environment. No bags or bottles should be left open. Abrasive should not be left in the tank over the weekend or during downtime. When the system is not on, the tank is not pressurized and the flapper is not sealed. Moisture laden air can enter through the flapper, contaminating any remaining abrasive in the tank. Is a desiccant or a membrane dryer installed on the line? If a desiccant dryer in use, the desiccant may need to be replaced. DRYER NOTE: Our process requires a dew point of -25°F. Refrigerant dryers provide a dewpoint of +35°F. A refrigerant dryer alone is not sufficient, and your system require an accompanying desiccant or membrane dryer. If a desiccant or a membrane dryer are NOT installed, it is time to do so. See Air Dryers.
Is the modulator functioning?	Does the modulator audibly hum when the footswitch is actuated? If not, or if it rattles noisily, the modulator should be checked and probably replaced. The average life of a modulator is 500 hours or 6-12 months. About the modulator: The modulator creates pulses of air by alternating between an open position that allows free flow of air to the mixing chamber and a closed position that stops the flow of air to the tank. As the modulator wears, the core no longer closes tightly and air pulses no longer pulses properly. Abrasive may flow initially thanks to pressure pulses generated from the open pinch valve, but after that, only gravity pulls abrasive into the system. Learn more in our post: Modulator Maintenance.
Are you using abrasive from a manufacturer other than Comco?	Not all abrasive is designed for MicroBlasting. Industrial abrasives commonly have a greater percentage of fine and coarse particles, which impacts and interrupts a unit’s performance. Consider switching to Comco abrasives. We use proprietary systems and tools to maintain the purity of all our abrasives, ensuring optimum performance. Learn more about the importance of quality abrasive.

Use the following chart to determine the problem:

Items to Check	Solution
Is the electrical power ON?	Verify that the power switch is on. The power light should be illuminated. If it is not illuminated but the switch appears to be in the on position, then the power switch may be defective. Call our Technical Support team at 1-818-841-5500 if you suspect that is so. Examine the power cord. Is it connected? Is it damaged? If it is connected and does not appear damaged, then call our Technical Support team at the number above. Check the fuse located above the power supply on the back of the machine. Replace if necessary.
Does the pressure gage indicate pressure in the system?	If the needle on the gage is pointing to 0, turn the regulator knob clockwise until it registers pressure. Set the regulator to desired blast pressure. The regulator on the MicroBlaster should be set to at least 10psi lower than the house air.
Is the inlet valve working properly?	Periodically desiccant may pass through the dryer and stick in the inlet air valve. Remove the coil and body from the valve to check and clear trapped foreign particulate. If no foreign particulate appears to be trapped, check the valve to make sure the coil is not damaged. Replace if necessary.
Is the nozzle plugged?	Remove the nozzle and look through it. You should see light shining through the hole on the tip. Keep in mind that you may see light through glass bead. If plugged, run a small wire through the nozzle hole to clear. If plugging continues despite changing out the nozzle, either the tank is releasing too much abrasive or the nozzle is too small to flow the type of abrasive you are using. Check out our Nozzle Selection Guide.
Is the abrasive hose pinch valve (on the rear panel) opening?	When the footswitch is activated, the abrasive hose should slide freely through the hose pinch and the modulator should hum. If the pinch does not open, and you can hear the modulator humming, then the pinch assembly is not functioning properly. If you do not hear the modulator humming, then the footswitch may be defective. Either way, contact our Technical Support Specialists at 818-841-5500 / techsupport@comcoinc.com.
Is there a problem with the abrasive line?	Disconnect the abrasive line and check the fitting to see if it is clogged or crimped. Remove the clog or straighten the crimp. CLEAN: Sodium bicarbonate will plate at the output fitting over time. Remove and soak the fitting in a mild acid like vinegar. Dry the fitting completely before reinstalling. (Failure to dry completely will cause it to plate out again quickly.) REPLACE: Cutting abrasive will gradually wear away at this fitting. When the fitting grows too thin, the walls will collapse and close the opening. If cleaning did not solve your issue and/ or the fitting is thin, replace the output fitting.
Is the tank pressurizing?	When the machine is on, the tank should be pressurized. Tap on the flapper valve (located on the cover of the thank) to test pressurization. If the tank is pressurized, then the problem is between the tank and the nozzle. (Read and follow directions in boxes above.) If the tank is NOT pressurized, the problem is between the regulator and the tank. (Read and follow directions in boxes below.)
Is the check valve/ filter plugged with abrasive?	This simply requires a visual inspection. If it appears plugged, it may be time to order replacements. Call our Customer Service Specialists at 818-841-5500 to place your order.
Is the modulator working properly?	The modulator can become plugged with abrasive, prohibiting air from passing through. Remove the modulator and slide the core back and forth inside the body. If it does not slide easily, then the modulator is plugged and may require replacement. Call our Technical Support Specialists at 818-841-5500 / techsupport@comcoinc.com to inquire about next steps.

Verify that the appropriate abrasive hose is in use. We recommend only using our brand of abrasive hose with our equipment. If unsure, call our Customer Service Specialists at 818-841-5500.
Verify that the hose has not been pulled tight from the output fitting to the pinch valve.
Inspect the hose for sharp bends. Any sharp bend creates a wear point.
Not all wear is completely visible. Do not cut off short sections of the hose as those sections wear quickly. Replace the entire hose instead.
Inspect the output fitting for wear. If worn, it can crush the abrasive hose, creating excessive wear. Replace the fitting if necessary.
Inspect the pinch valve assembly. Any sharp edges on the plunger or pinch tube will cause hose to wear faster.

Make sure the tank has not been overfilled above the top of the vent tube. The stream will run rich with abrasive until the level drops below that point.
Check the bypass tube that is pressed into the bottom of the tank. Has it developed a hole through which abrasive is being drawn? If so, then replace.
Make sure that orifice is properly screwed in. If it is not, then it may allow air and abrasive to travel around the threads.
Inspect the orifice for wear. If worn, the opening will grow too large. Replace the orifice if necessary.
The orifice should be no larger than .005 its stamped size. Use a pin gauge to inspect.
If changing out of the orifice, vacuum all abrasive in the bottom of the tank. Leftover abrasive will cause the orifice to cross-thread and not seal properly.

Check for abrasive contamination. This happens when the check valves fail.
Check the breather port on the side of the cylinder. Is it plugged and preventing air from passing through? If yes, then unscrew it, tap out the clog and restore.
If neither of these options increase pinch valve speed, then contact our Technical Support Specialists at 818-841-5500 / techsupport@comcoinc.com.

Use the following chart to determine the problem:

Items to check	Solution
Is the air supply to the unit suffiicient?	Turn the regulator completely counter-clockwise before turning on the unit. This allows the pinches to close off pressure before the tank starts filling. Then, turn the machine “On”. After 5 seconds, increase the blast pressure to the desired level. Your blaster should have 2-3 SCFM of supply air coming into the back of the blaster.
Are the pinch valves closing properly?	Check both pinch valves. One is located on the vent and one on the abrasive tank. Slide the hoses back and forth. If the hoses slide easily, then the pinch valves are malfunctioning.
Is the O-ring in the tank cover worn? Is the tank cover worn?	If the O-ring is worn, then air will escape from the tank and prevent the system from reaching optimal pressurization. Check the O-ring on the tank cover for wear. Remove the cover and inspect for flat sections. Inspect the tank for grooves. If the O-ring has flat sections, or wear, replace the O-ring. If the tank has grooves or other signs of wear, replace the tank, too. NOTE: An air leak in the tank will cause the abrasive to eat through the sealing surface of the tank. The O-ring should be inspected and replaced as soon as signs of wear appear to prevent expensive tank replacement.

Also, view this video post on how to pressurize your system and achieve flow.

WARNING: The upper limit for air pressure is dictated by the house line pressure. There should be a 10psi buffer between blast pressure and line pressure. Turning the regulator knob clockwise beyond the line pressure will not increase blast pressure and potentially damage the regulator diaphragm.

Use the following chart to determine the problem:

Items to Check	Solution
Does your regulator hold the proper pressure?	As the unit sits idle, does the pressure gradually creep up to line pressure, only to drop back down the normal pressure once blasting begins? IF YES: there could be a problem with the diaphragm on the regulator. If the spring is not properly centered and air is leaking around it, pressure will increase to line pressure. Inspect the diaphragm and regulator assembly. Replace if necessary. IF NO: Contact our Technical Support Specialists at 818-841-5500 / techsupport@comcoinc.com.
Does the regulator stay at the desired blast pressure when idle only to drop significantly once blasting starts?	It is normal for the gauge to drop to 5-10 psi. For example, restrictions in the line may cause a drop of 5-10 psi between idle and blasting states. If the drop is greater than 10 psi, then there may be an insufficient air flow or line pressure and volume are too insufficient to support the current flow at the nozzle, and so pressure drops until it reaches equilibrium. Check the inlet air valve and regulator for a clog that could be restricting the air flow to the mixing chamber and nozzle. Check for leaks in the abrasive line going out of the nozzle. Check to make sure the nozzle has not been removed. If it has not been removed, check the nozzle size. The nozzle may be too large for the system. Check the inlet air supply to make sure it can deliver sufficient air volume. A 10 psi buffer should be maintained between blast pressure and supply pressure. Check the supply line from the compressor to the blaster. There could be a restriction, like a small diameter line, a partially open valve, etc.
Does the regulator drop less than 5 psi, but the air flow out of the nozzle is too weak?	Inspect the check valve and filter assembly for a clog. Check for plating in the mixing chamber, the output fitting, hose and nozzle. Clean these areas, if needed, or replace those parts. Inspect the nozzle for clogs. Clean with a fine wire, if needed. Inspect the pinch valve to make sure it opens completely. If it is not opening completely, there is likely abrasive contamination on the clean air side of the system and the cylinder is no longer working properly. In this case, the unit should be sent it for repair. Contact our Technical Support Specialists at 818-841-5500 / techsupport@comcoinc.com to inquire about next steps.

Also, view this video post on how to pressurize your system and achieve flow.

Diminished media flow after the first 5-10 seconds of blasting is a good indicator that the modulator is wearing out. The modulator is a precision electromagnetic valve that operates 50-60 times per second. This creates a pulsed air stream, fluidizing abrasive and drawing it from the tank to the mixing chamber.

Learn more in our post Understanding Modulator Wear and Repair.

Oil contamination causes clumps and clogs of abrasive at the orifice in the abrasive tank and in the nozzle. These clogs disrupt air flow and worse, may cause check-valve failure. Oil contamination prevents the check-valve from sealing properly, allowing abrasive to pass back through the system. The aggressive nature of abrasive quickly erodes the O-rings and seals on these components, resulting in costly repairs.

If you suspect that your MicroBlaster is contaminated with oil, there are a few signs you can look for to confirm this. New air lines that run clean air through the MicroBlaster are a milky white color. Exposure to oil causes these lines to turn a shade of orange or yellow.

To check for oil contamination:

Unscrew the black plastic bonnet inside the regulator to check for oil pools: oil tends to pool in the regulator assembly of the MicroBlaster.
Open the assembly to expose the filter element. Large clumps of abrasive stuck to the filter element indicate oil contamination.

Please read our post on Oil Contamination.

The top of the new style tank cover looks like this

The new style tank cover introduced in 2003 are designed for longer life and easier maintenance. If your tank has a label on the top like the one pictured here, then your MicroBlaster has the new style square Acme threads. Please order the Replacement Tank Cover Assembly, part number MB1568.

If your blaster does not have a label on top like the one pictured, then your MicroBlaster will not fit the new style tank cover unless you replace the tank as well as the cover. Tank replacement must be done at the factory. Please contact Technical Support at 818-841-5500 or techsupport@comcoinc.com for an RMA number before sending in your machine. Learn the advantages of the new tank cover design.

Our nozzles come in an array of shapes and sizes for a wide range of applications. The straight, round style nozzle with openings ranging from 0.015″ to 0.060″ meets most application requirements. Rectangular nozzles are available for applications that require a wide sweep or fan of abrasive.

Comco’s offers long-lasting Hi/Performance nozzles in addition to standard nozzles. Hi/Performance nozzles deliver an accelerated abrasive flow with a tighter focus, resulting in less over spray. The lifespan of these nozzles is 3-5x longer than most standard nozzles.

Items to Check	Solution
Is an O-ring in place?	The nozzle screws into the handpiece nose, a stainless steel component designed to endure abrasive wear. If the O-ring is not in place, or if it is not tightened properly; the nozzle, the threads of the nozzle will wear out quickly. If abrasive flows through the air stream but the flow is erratic, then skip the next step and proceed with the remainder of this checklist.
Does the hose have a sharp bend?	A sharp bend in the hose just upstream from the handpiece will push all abrasive to the outside of the bend, wearing down the side that sees the most abrasive quickly.
Are you using rectangular nozzles?	Due to their size, rectangular nozzles commonly wear faster than round nozzles. Once a wear characteristic starts to form in a nozzle, the characteristic will channel the abrasive through the location, accelerating the wear-rate. Two common wear patterns are the “football” and the “dogbone.” The football wear pattern occurs when the center of the rectangle wears faster than the edges. In this wear scenario, the center of the nozzle will start blow out quickly. The dogbone wear scenario occurs when the edges of the nozzle wear out much faster than the center.

Questions about MicroBlasting?

If you have questions about setting up, optimizing your blaster, or keeping it running smoothly, contact me:

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Understanding Modulator Wear and Repair

How can I obtain a copy of my MicroBlaster’s manual?

What’s in the MicroBlaster maintenance kits?

MB1440 MICROBLASTER TUNE-UP KIT INCLUDES:

THE MB1274-3 MICROBLASTER REPLACEMENT PARTS KIT INCLUDES:

THE MB1450 MICROBLASTER® TANK COVER O-RING KIT INCLUDES:

Why isn’t abrasive flowing out of the nozzle (but air is)?

Why are neither air nor abrasive exiting the nozzle?

Why is the abrasive hose wearing out so quickly?

Why is there too much abrasive in my air stream?

Why are the pinch cylinders unresponsive or moving slowly?

Why won’t my machine pressurize properly?

Why does my system have trouble maintaining consistent air pressure?

WARNING: The upper limit for air pressure is dictated by the house line pressure. There should be a 10psi buffer between blast pressure and line pressure. Turning the regulator knob clockwise beyond the line pressure will not increase blast pressure and potentially damage the regulator diaphragm.

What happens when my modulator wears out?

How does oil contamination affect my blaster? How do I know if oil is contaminating my Microblaster?

What is the difference between the old style and the new style tank covers, and how do I replace my tank cover?

What range of nozzles are available?

Why is my nozzle wearing out so quickly?

What parts comprise the handpiece assembly?

Questions about MicroBlasting?

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