Foreign Matter Countermeasures in Cationic Electrodeposition Coating | Quality Stabilization Technology Managed from the Source

At Ohashi Tekko Vietnam, for foreign matter defects in cationic electrodeposition coating, we implement not only generation suppression, intrusion prevention, capture, and cleaning, but also component analysis at our Japan head office. We investigate the true nature and sources of foreign matter to prevent recurrence.

■ Overview

In cationic electrodeposition coating, foreign matter adhesion to the coated surface is one of the critical control items that affect appearance quality.

At Ohashi Tekko Vietnam, our foreign matter countermeasures do not end with mere cleaning or removal. We investigate each aspect—"where does foreign matter originate?", "how can we prevent its intrusion into products and paint tanks?", and "what is the foreign matter that has occurred?"—and implement countermeasures by combining equipment improvement, daily management, and component analysis at our Japan head office.

Through multi-stage foreign matter management, which includes "do not generate, do not allow to enter, do not drop, do not accumulate, capture, and analyze," we ensure stable quality in cationic electrodeposition coating.

■ Features

Regularly inspect and manage the angle of the current collector to stabilize its contact with the busbar.

Added a function to the equipment to adjust the voltage at the moment the current collector makes contact, reducing abnormal sparks.

Installed a dedicated cover near the current collector to reduce the risk of metallic foreign matter falling into or intruding into the paint tank.

Changed the paint tank's circulation filter from 30μm to 10μm to enhance the capture of fine foreign matter.

Installed a foreign matter fall prevention tray on the upper part of the hanger to prevent foreign matter from falling onto products or into various treatment tanks.

Regularly clean the tray with a vacuum cleaner to prevent re-scattering of accumulated matter.

For foreign matter whose cause cannot be identified locally, component analysis is conducted using the analytical equipment at the Japan head office.

■ Suppressing metallic foreign matter from its "source"

In electrodeposition coating, the current collector on the upper part of the hanger makes contact with the busbar, allowing electricity to flow to the product. If the angle or contact state of the current collector is not appropriate, abnormal sparks may occur during contact, potentially leading to the generation of fine metallic foreign matter.

Therefore, at Ohashi Tekko Vietnam, we regularly check and manage the angle of the current collector to maintain a stable contact state. Furthermore, we have added a function to the equipment to adjust the voltage at the moment the current collector makes contact, implementing measures to reduce the sparks themselves, which are a source of foreign matter.

■ "Do not allow generated foreign matter to enter the paint tank and capture it"

In addition to suppressing the generation of sparks, we also anticipate cases where metallic powder might be generated. A dedicated foreign matter fall prevention cover is installed near the current collector, reducing the risk of metallic foreign matter falling into or intruding into the paint tank below.

Furthermore, the paint tank's circulation filter has been upgraded from 30μm to 10μm to enhance filtration precision, strengthening measures to capture fine foreign matter within the tank. By combining multiple countermeasures—generation suppression, prevention of intrusion into the tank, and capture by filters—we aim to reduce foreign matter risk.

■ "Do not drop or accumulate foreign matter from above"

In the coating line, iron powder, rust, oil stains, etc., may fall from parts such as the conveyor chain. To prevent foreign matter from falling onto products or into various treatment tanks, a foreign matter fall prevention tray is installed on the upper part of the hanger.

Furthermore, if foreign matter remains accumulated in the tray, it may be re-scattered by vibration or airflow inside the drying oven. Therefore, regular cleaning using a vacuum cleaner is performed, implementing management not only to "catch" but also to "prevent accumulation."

■ "Do not just 'find' foreign matter" | Investigating the source through component analysis

If foreign matter is found on the coated surface, we classify it by checking its color, shape, adhesion location, etc., and investigate which process it might have adhered in.

In past improvement activities, we hypothesized the sources for fibrous foreign matter, iron/rust, metallic foreign matter, etc., and investigated and improved drying oven filters, ducts, conveyors, and hangers. Furthermore, there are cases where we even adjusted the airflow and damper conditions of the drying oven, leading to a reduction in foreign matter.

■ Investigating the source through component analysis in cooperation with the Japan head office

For foreign matter whose cause cannot be identified locally, it is possible to send the foreign matter to Ohashi Tekko's Japan head office and conduct component analysis using their analytical equipment. The analysis results are cross-referenced with investigation results of equipment, jigs, materials, and the work environment to narrow down the process and source of occurrence.

Connecting **Foreign matter collection → Component analysis at head office → Process/cause separation → Source narrowing → Recurrence prevention** is Ohashi Tekko Vietnam's approach to foreign matter management.

At Ohashi Tekko Vietnam, foreign matter countermeasures do not end with mere cleaning; they extend to source suppression, prevention of intrusion into the paint tank, capture, prevention of falling and accumulation, cause investigation, and even component analysis at the Japan head office.

Through multi-stage management of **"do not generate, do not allow to enter, do not drop, do not accumulate, capture, and analyze,"** we are preventing the recurrence of foreign matter in cationic electrodeposition coating.

■ For details, please download the PDF or feel free to contact us.