To make the color consistency an acceptable standard, the key is to break down the spray surface treatment into "batch comparison+process recording+sampling judgment", so that color difference, film thickness, and curing status can be traced and reviewed.

In batch delivery, color consistency is not about "looking similar", but about writing the color difference requirements of the sprayed surface treatment into the inspection caliber and being able to reproduce them. We usually use samples from the same batch for comparison, combined with film thickness point inspection and furnace temperature curve recording, to avoid color drift caused by fluctuations in curing energy; Taking a batch of electric control cabinet shells as an example, the color difference of the first piece was relatively large after wire replacement, which was traced back to changes in the load of the curing furnace. After adjustment, the batch stabilized.

However, relying solely on final inspection is difficult to mitigate risks. Consistent color requires incorporating pre-treatment, spray room cleaning, and color changing and cleaning into the process control. We will make the substrate batch, fixture grounding status, spraying parameters (gun cycle/voltage), and dust management fixed inspection items, and bind the "batch comparison first piece confirmation process sampling" rhythm on the work order; This type of approach can move the color difference issue from "rework after the fact" to "process warning", but there is currently no authoritative data on the unified data caliber publicly available in the industry.

High frequency trigger points for color difference: coupling relationship between substrate batch, pre-treatment residue, spray film thickness fluctuation, and insufficient curing

Further examination of the root cause of color difference often reveals that it is not a single point of abnormality, but rather a combination of "substrate condition+pre-treatment residue+film thickness fluctuation+insufficient curing". For example, the difference in surface tension and roughness between galvanized sheet and cold-rolled sheet can alter the spreading of powder/paint film; If ion residues are carried in by water washing, and combined with thin and thick edges of the cornea, insufficient solidification energy can easily lead to local graying or discoloration. The key here is to trace the material batch and pre-treatment parameters together, rather than just focusing on the spraying section.

Process control points for color consistency: sample/retention, batch comparison, color change and cleaning, spray room cleanliness and dust management

In order to ensure consistent and controllable colors, we will establish a "control system" for spray surface treatment: a sample and a retention sample will be created for each color, and the first piece of the batch must be confirmed under the same light source conditions; When changing colors, clear the line and empty the recycling system to avoid color deviation caused by the mixing of old powder/paint; Spray room filtration and airflow organization are checked periodically, and dust deposition directly affects the uniformity of appearance particles and color. For large components such as cabinets and energy storage cabinets, the consistency of the spraying path must also be written into the process card.

How to implement the acceptance criteria: expression of color difference tolerance, inspection frequency, and traceability fields (work order/fixture/furnace temperature curve)

When the acceptance criteria are implemented, we tend to write "color consistency" as an executable clause: the color difference tolerance (such as expressed in Δ E) corresponds to the detection position and light source conditions, and the film thickness sampling point position and frequency are synchronized; The traceability field should at least include the work order number, substrate batch, fixture number/grounding record, spray parameters, and furnace temperature curve screenshots or data. In this way, once color deviation occurs, it can be traced back to the specific stages of pre-treatment, spraying, and curing on the same traceability chain, reducing repeated trial and error and expanding rework.