Troubleshooting for Painting process -Butsu example-

Introduction

Defects due to particles tend to be more serious due to paint-induced particles, dust, fiber scraps, insects, other minute materials and also due to electrostatic adsorption due to static electricity. Therefore, it is necessary to grasp and observe the conditions of the surrounding environment in order to solve these problems.

Paint and paint can

1. Inclusion of dust deposited on the top plate of the paint can into the paint.
2. The top plate of the paint can was released with a can-cutter, and an agitator blade scraped the inner wall of the paint can.
3. The required amount was taken from the hardener can of the two-component urethane paint and some of the hardener cured in the can because the lid was closed without purging nitrogen.

Compounding tanks and their surrounding facilities

1. Water condensed in a local exhaust duct connected to a paint supply tank for preparing a two-component urethane paint mixed into the supply tank and reacted with a curing agent (isocyanate) to form particles.
2. The coagulated paint remaining on the mesh was dropped and mixed when the paint filtration mesh was replaced.

Paint supply route

1. Paint is deposited and cured on the dead space between the ball of the ball valve and the housing in the paint piping. (Selection of a valve without dead space or cleaning in a valve half-open state is recommended)
2. Potential difference caused by different metal bonding occurred at the joint part of brass ball valve and the stainless steel piping, and water-based paint agglomerated.
3. Paint sedimentation are generated in the piping due to long-term use without cleaning of the paint supply piping. If cleaning is insufficient even after cleaning of the paint piping, the deposited paint particles fall off and discharge. It is necessary to continue thorough cleaning of long-standing deposited paints over several days using powerful paint piping cleaners.
4. Paint sedimentation are generated in the dead space (near the entrance and exit) inside the diaphragm pump for feeding paint.
5. The water-based paint was washed with water after high-pressure air extrusion, but the water-based paint was not redissolved in water after drying. Brush using water-based paint is immersed in water immediately, and can be reused well by repeating leaving for ten minutes and washing with water."
6. At the static mixer for two-part urethane paint, gels and particles are always generated. (Observation)

Painting booths and their surrounding environment

1. The spray air used to remove dust causes the resin parts to take more static, resulting in electrostatic adsorption of dust.
2. Humidity in the painting booth was not controlled. Painting was carried out under a low humidity atmosphere, and dust was electrostatically adsorbed.
3. The dust accumulated on the electrode of the static electricity removal device came off.
4. Particles of paint adhering to the top plate of the painting booth drops off due to the howling (periodic vibration) of the painting booth.
5. Powdery paint was scattered by the wind blown off toward the gratings and painting jigs, on which paint that easily pulverized adhered and accumulated.
6. Dust deposited between the door and the door frame used to enter and exit the paint booth came off.
7. The BOX tissue and roll paper were brought into the paint booth and paint preparation room. (Nonwoven fabric with dustproof cut surface is good.)
8. Painting with reduced capacity of the exhaust fan in order to suppress foaming of painting booth water, painting mist during painting scattered through the booth.
9. The amount of air supplied to the painting booth was small. When the door of the building was opened, dust in the room and from the outside scattered toward the painting booth.

Others

1. Mosquitoes that occur in a pool of water, such as a gutter. (Pesticides that prevent flies and mosquitoes from emerging from maggots to feathers are on the market.)
2. The insects gathered in the street lighting around the painting room. (It is necessary to use UV cut lighting and UV lighting separately.)
3. The electrostatic clothes were dried outdoors in the sun or washed and dried together with the gloves. Therefore, the electrostatic clothes were covered with waste thread and dust.