Extreme care, attention to detail needed to achieve quality control in the paint shop

Jan. 1, 2020
Follow these 12 steps to develop a zero-defect policy in the paint shop.
paint shop quality control Al Thomas

True quality control in the paint shop is a constant requirement. If a paint job is not checked and re-checked at every point, the consequences can be very costly in time and materials.

Quality guru W. Edwards Deming stressed years ago that quality and continuous improvement were the only way to assure continued success in manufacturing. He suggested building quality into products through statistical methods and preventing defects instead of trying to detect them. Worldwide manufacturing has since adopted his continuous improvement methods as its standard, with quality, efficiency and profit vastly improving as a result.

The collision repair industry has looked to manufacturing for methods to improve its operations. By preventing defects as its standard, it too will see improvements in production and quality, which will assure increased profits as well. So how does a shop go about developing a zero-defect policy?

STEP 1: Develop a SOP. It takes time to develop and revise a standard operating procedure (SOP), and it takes time to follow it. How can this help improve productivity? Once it is developed and in place, it helps keep repair procedures consistent. It also helps with supply purchasing. By standardizing a repair process, a simple standard supply list can be developed and maintained.

The SOP not only indicates the repair process, it also outlines quality verification at specific intervals, such as arrival, color retrieval, cleaning, initial prep, final prep, masking, booth prep, sealing, basecoat, clearcoat, detailing and final inspection. While you might choose to develop an SOP with different points, having a written document will help avoid costly mistakes.

Consider these SOP quality assurance points:

STEP 2: Upon arrival. The painter or paint team must inspect the vehicle as it arrives in the paint shop, making certain that all the work outlined in the work order (repair blueprint) has been completed to the shop's quality standard (see Fig. 2). The paint team should make a repair plan, which confirms the vehicle's position in the paint order, checks for needed supplies and notes any special requests, such as strips that may need to be ordered.
STEP 3: Color retrieval/verification. While it may seem that this step could come later in the process, the color verification may have significant impact on the vehicle's preparation. Many painters rely completely on their eye skill to verify a color match, but the sophistication of some colors makes it difficult to know all the needs of each color. Therefore a spray-out panel may need to be made (see Fig. 3). Not every color requires one, but many do, and by making a panel the paint technician will verify if a variance color will be needed, how many coats it will take for full coverage and how the vehicle preparation should proceed. A color that will reach full coverage with two coats will have a smaller color prep area than one that may take four coats.

STEP 4: Cleaning. Painters often skip this step because they think the vehicle already has been cleaned. But the cleaner a vehicle is as it is being prepared for paint, the less likely it will be to have defects. The degree of cleanliness required in the paint shop is much greater than what's required in the body shop. Something as simple as a helper eating at break and not washing his or her hands before masking a vehicle can cause contamination.

The entire vehicle should be soap and water washed (see Fig. 4) to remove water-soluble contaminants. Then the area to be refinished and the adjacent panels should be cleaned with a wax and grease remover to remove contaminants that are not water soluble. If sanding is begun before a vehicle is completely cleaned, it may drive the contaminants into the area being repaired instead of removing them.
STEP 5: Initial prep. Initial preparation is needed over a repair where the level of the repair needs to be raised to the level of the finish coat. Feathering and primer filler are used; then it is blocked (see Fig. 5), using a guide coat to visualize any defect that may need to be blocked out. This step will make the repair undetectable when refinished. A bright light such as a sun gun will help find small imperfections that can be repaired prior to final preparation.
STEP 6: Final prep. The area to be refinished, including the blend area, is prepared. Each paint manufacturer provides recommendations for the type of repair and the type of paint used. Solvent paint preparation often uses courser grit paper than a waterborne preparation, and the area to be blended must be prepared with a finer grit paper than the paint area. The paint manufacturer's recommendations should be followed, of course. But nearly as important is that this final prep gives the technician another opportunity to inspect the repaired area. While doing the final sanding or scuffing, inspect the area closely.
A good practice is to final-scuff and clean with a Scotch pad and scuffing paste (see Fig. 6), since this cleans and sands at the same time. The vehicle should be cleaned again after preparation and before masking. Inside the door jams, in the wheel openings – every part of the vehicle where dust from prep may have collected needs to be cleaned. You may be surprised how dirty these areas have again become (see Fig. 7).

After the vehicle is dried and inspected, it can be placed in front of the spray booth for masking.

STEP 7: Masking. Masking in the paint booth, can lead to dirt contamination. Though "bagging" the car must be done in the booth, all the rest of the masking should be done outside the booth, to eliminate as much dirt in the booth as possible (see Fig. 8).

Mask from the inside out – that is, open the doors, hatch, or hood in the area to be masked, and apply your mask in that area first. Then the openings can be closed and the paint area outlined with tape. A cut down used body filler shredder is an excellent tool to use to assure that the tape is pressed tight to those hard-to-reach areas. While applying tape, technicians should be constantly inspecting the vehicle for any possible defect as they proceed. The taped area can now have a small (12-inch) paper placed around the taped area, preparing it for bagging.

STEP 8: Booth prep. The cleaner the booth, the cleaner the final paint job will be (see Fig. 9). The booth should now be started, and all temperatures should be set correctly. It should be balanced to a slight positive air flow. If the booth cannot be balanced, it is likely that the filters are in need of changing. This should be done before the vehicle is painted. With the booth turned on, the booth interior should be blown off. Make sure the floor is clean and all needed tools are inside the booth, ready for use. Then the car and the parts that need to be painted are placed in the booth, the outer doors are closed, and all subsequent entries into the booth should be through the pedestrian door. Once the vehicle is in the booth and bagged, the masking should be inspected for loose areas, and if found they should be repaired before proceeding.
STEP 9: Sealing. Prior to sealing, the vehicle should be final cleaned with wax and grease remover, blown off and tacked. During this process, inspect it for any potential problems or defects, which if found should be repaired before proceeding. Often if any defects are discovered, a fine Scotch pad can be used to remove them (see Fig. 10).
Before spraying, clean the air hose with a used tack cloth (see Fig. 11). When placed on the booth floor, a hose can pick up dirt particles and deposit them into the paint job during painting, so a good tacking will go a long way to help eliminate dirt. After sealing (see Fig. 12), the area should be inspected for dirt nibs, and if any are found, they can be removed prior to basecoating.
STEP 10: Basecoat. Prior to basecoat application, the area should be blown and tacked to eliminate any dust/overspray that may have been deposited while spraying. The first coat of basecoat is applied and allowed to flash, then lightly tacked. Between coats of basecoat, a clean area of the tack cloth should be used each time the surface is tacked, since a surprising amount of overspray will have accumulated (see Fig. 13). Follow the paint maker's recommendations for flash time while preparing for clearcoating.

There is one last opportunity to inspect the vehicle before clearcoating. If any imperfections are found, they can be nib-sanded out. Then the area is re-sprayed with basecoat, preparing it for clearcoating.

STEP 11: Clearcoat. At this final step in refinishing, everything must be inspected and ready to go. If imperfections, dirt nibs, sand scratches or any other imperfections are found, they must be repaired now. Hopefully, if all the previous inspections have been performed correctly, none will be found. The vehicle should be blown off and tacked with a clean tack cloth (see Fig. 14). The hose should be cleaned then the clear is sprayed.
If a dirt speck is found during spraying of the clearcoat, it may be lifted with a tweezers or a piece of folded tape that can be used to lightly touch the dirt nib and lift it from the clear (see Fig. 15).
STEP 12: Detailing. Before the vehicle is removed from the booth, it should be inspected again. If there are no imperfections that cannot be repaired in detailing, the bag (plastic covering) can be removed and the vehicle taken to the detail area (see Fig. 16), where any nibs are removed. Overspray, if there is any, is also removed. Then the vehicle is stripped, washed and sent for reassembly.

If each step in this process is followed correctly, it will mean that the ones that come after each become another inspection, with little or no corrective action needed. Polishing can be kept to a minimum and cycle time will be reduced. By eliminating defects early, when they can be corrected more easily, final repair can be virtually eliminated. By finding and eliminating potential defects early in the paint shop, you "pay forward" in cycle time and profit.

About the Author

Al Thomas

Alfred Thomas is associate professor and department head of Collision Repair at Pennsylvania College of Technology. His technical experiences include 15 years in the collision industry as a technician and shop manager, 12 years as a secondary vocational instructor, and the past eight years as lead instructor at Penn College.

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