Production Process Guidance of Leaf Springs - Leaf Springs Painting (Part 9)

Production Process Guidance of Leaf Springs

－Leaf Springs Painting (Part 9)

1. Definition:

Leaf springs painting is a process of spraying paint on the surface of the loose leaves or the leaf spring assemblies to prevent springs from rusting, and improve the service life of springs.

2. Application:

Loose spring leaves and leaf spring assemblies.

3. Operating procedure:

3.1. Preparation before spring painting

Before painting the leaf springs, the process card shall be checked first, spring painting is allowed only there are inspection qualification marks in the previous processes. Before painting, the spring assemblies or loose leaves must be shot blasted to achieve level SA2.5, to remove the oil stains, rusts and dusts on the surface of spring. Once the loose springs sprayed with primer, it is required to spray finish paint after the primer drying, otherwise the finish paint shall not be applied.

3.2. Paint mixing

Add special curing agent (weight ratio=8:1) into the paint, then add special diluent agent  about 30% of the paint weight to adjust the construction viscosity, filter with 120 mesh screen, mix evenly, adjust the construction viscosity of electrostatic painting to 13-17 seconds, adjust the construction viscosity of manual painting to 18-23 seconds, place it for about 15 minutes, and then use it.

The paint must be mixed according to necessary quantity. The mixed paint must be used up within 3 hours, otherwise it will be cemented and scrapped. Do not put the remaining used paint back into the original paint. The paint bucket containing the used residual paint shall be covered to avoid paint volatilization and cementation, resulting in waste.

3.3. Painting equipment adjustment

The temperatures in the combustion chamber and drying channel of the automatic painting line shall be set at 80 ℃, the chain speed shall be less than 4m / min, the leveling time shall be no less than 8 minutes, and the curing time shall be no less than 20 minutes. During manual painting, the painting shall be uniform without sagging, and the standing time shall not be less than 30 minutes until the paint is dry.

3.4. Requirements of painting

All products (conventional leaf springs and parabolic leaf springs) must be painted with two coats of paint. For leaf spring assemblies: loose leaves painted by primer first, and then apply the finish paint after leaf springs assembled (except the concave surface of the main leaf and the convex surface of the last leaf). For the loose leaves: primer at first, and then finish paint.

Pay special attention to the painting quality of the sides, ends, rolling eyes and wrapping eyes , bending positions and clamp sleeves of the leaf springs to ensure that the paint thicknesses of these parts meet the requirements.

The eye rolled leaves with bushes, the interior of the bushes shall not be painted.

The operation requirements of painting are that the best distance between the spray gun and the work pieces is 25-30cm, and the best painting angle is 90 °.

After painting, the surfaces of the leaf springs shall be bright, without pinholes, uniform, no missing spraying, no sagging, no orange peel ,with strong paint adhesion.

Requirements of screen printing:

The printing shall be carried out after the paint on the surface of the leaf springs  drying. The printing shall be clear, not skewed, and printed in order, and the printing templates shall be used. If there are requirements for camber height classification marks or action length classification marks, the process card shall be strictly followed.

3.5. Material Management

The painted leaf springs shall be neatly packed and warehoused. It is forbidden to place them at will, resulting in surface bruises.

4. Inspection standards of leaf spring painting (Refer to the standard: GB/T 19844-2018 / ISO 18137: 2015 MOD Leaf Spring - Technical Specifications):

The inspection standards of leaf spring painting are shown in Table 1 below.

Compiled by  WONDEE Autoparts

2022-5-12