2.Sealer – Paint Shop

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2. Sealer

2.1. Removing slave tools after PT/ED and installation of jigs for paint.

The process consists of 2 stages where 2 operators usually work.

  1. The body is going to working area and operator reinstallation jigs  doors, hood, trunk and then stacked in special numbered containers.
  2. Next, the body is moving to conveyor and other operators install jigs, door retainer “upper” layer of a subsequent secondary primer, base and clearcoat.

Jigs for paint is like “L-shaped” guides, they are installed in place of the seal,  doors do not touch doorway.Jigs must lock the doors in a closed position, so that there is no arbitrary opening on the turntable of the conveyor line.

On the hood is installed a technological spacer, on the trunk of the limiter to the place of the staff lock.

Paint jigs is designed and manufactured in such a way that it is not allowed to touch the front surface of the body, while providing a clearance on the assembled car, the gaps between the elements should not be more than 5 mm.

2.2. Underbody

The process consists of 3 stages:

  1. Preparation of the body for the application of the underbody without air. It includes isolation (masking) all technological holes in the floor to prevent falling and overspray mastic inside the body.

Used material for insulation:

  • Painting tape with a resistance of 60 ° С + wrapping paper (the cheapest method)
  • Correx is a thin plastic sheet on which various stubs are stamped and used for insulation on the body (more modern and expensive method)
  1. Applying process for underbody – Underbody.

It is applied by without air method with stationary stations (the main supplier of Graco).

Body rises and passes over the head painter at the height of an arm and a painter produces mastic application on all underbody and thresholds, it is the most common type of conveyor and the method of application to plants the Russian Federation. Essential requirement for this method is the use of a water wall, the water is fed to the walls and floor, removes excess mastic which hit the wall when applied.

On European plants, a conveyor is used, where the body in an inverted position passes sideways near the painter (in this case the operator) sideways, at an angle of 90 degrees.

Plus the European method is the production culture “cleanliness of the workplace”, does not require a water wall, material saving, operator’s PPE and harmfulness is much lower than that of “overhead” technology. Does not require body insulation and waste disposal.

The operation of applying mastic can be automated by means of robots. Application can be as horizontal (robots are installed from below), and vertical (robots are installed sideways). Automation allows to minimize material consumption, as well as accuracy during application.

  

Material:

Mastic plastisol is designed to protect the bottom and thresholds of car bodies from corrosion, abrasion and improve noise insulation of the cabin during operation in all macroclimatic ranges (usually +/- 50 ° C), including conditions B5 in accordance with GOST 15150.

Mastic plastisol is a dispersion of polyvinyl chloride resins in a plasticizer with the addition of heat stabilizers, viscosity stabilizers, fillers, adhesive / thixotropic and other components. In the system, the material is under high pressure, of the order of 200 Bar.

For Russian Federation territory of the car manufacturers “lay” the film thickness from 800 to 1500 microns, often covering from 2000 to 2500 microns.

The thickness of the coating is checked only on the wet layer by means of a “comb”.

There are concerns that do not use underbody for their models, while the class of the car is not cheap. Explanations in this case there and remains on the conscience of the brand.

  1. Dropping the body onto the floor conveyor and unmasking all the insulating materials on the body, recycling of waste (paper, foil, tape, etc.).

2.3. Sealer.

Mastic is designed for sealing internal and external welded joints of bodies and joints of metal panels

     The process consists of 2 stages:

  1. Application of sealer on the non-face surface (slang “invisible zone”) of the interior space of the body. The sealer is applied with a thin nozzle on the gun, then the compaction and leveling with the brush is performed, in other words, the mastic is “hammered” into the slots and joints of the panels. This process is very fast and does not require an aesthetic appearance, because in the subsequent assembly of the body is made and all elements are closed (ie, invisible).
  2. Application of sealer on the front surface (specific zones) of the body, such as flanging doors, hood, trunk, engine compartment, i.e. where the consumer sees in the process of operating the car.

Sealer is applied using specially designed nozzles, each nozzle is designed for its element.

At European factories, automatic application, robots or a conveyor with the principle of “Stop-Go” (Manipulation by hand) are often used.

 

Conveyor START-STOP – bodies in the amount of 10 or more pieces go into the mastic coating chamber and stop for a given cycle (the time is calculated from the calculation of the designed capacity of the shop) at this moment the robots or operators apply their section on the body, after the time (cycle) in the oven (drying chamber). But, not always car manufacturers use the furnace, it is also possible to use an intermediate infrared drying lamp to harden the top layer of mastic (creating a “crust”), and complete drying of the coating will be carried out in a secondary chamber (Primer).

In Russian plants, this process is applied only by painters manually and with a constantly moving conveyor. In this process it is very important and right to carry out balancing between painters, and also to install equipment and to stretch hoses so that painters do not get confused and do not interfere with performing operations to each other.

When buying a car, the suture mastic can also serve as an indicator of the integrity of the car. In the event that there are obvious differences in the thickness of the seam, or the uniformity of the application differs from other seams, it is very likely that the body repair was performed, especially if the application was made by robots.

2.4 Laying / installation of noise-vibro gaskets

The material is used as vibration damping coatings in cars to reduce vibration of vehicles.

The material can be mounted on horizontal, vertical and inclined surfaces. The main component in the manufacture of noise-vibro strip is Bitumen with various fillers and additives, it is divided into 3 different processes and technologies, depending on the chosen type of material that is used in the production of strip.

  1. Strip without protective paper, i.e. with low adhesive properties (or its absence). Strip fall into the shop from the warehouse and they must be kept at the shop temperature for 24 hours, then the painter makes a re-packing of the strip, i.e. the aged strip are piled under the IR-lamp in stacks and, if necessary, they are replenished in order to heat the gaskets and melt the top layer for gluing to the surface of the body.
  2. Strip with glue composition.Strip fall into the shop from the warehouse and they must be kept at a temperature of 8 hours, then the painter makes a re-packing of the strip, i.e. aged gaskets are piled in stacks and, if necessary, they are replenished, but before laying the strip on the body surface, a protective paper is removed.

    The body is suitable for the stowage station and in the first and second versions the painter takes the required quantity and puts it on the surface of the body, positions, then each rolls out with a roller.

  3. On European and especially American concerns use automatic application by robots. This process is identical completely to the process of application of underbody, the only difference is the material itself, because during polymerization (drying), this material foams and increases in volume approximately 2-2.5 times.

Of all the proposed options, the cheapest method is No. 3, because the material for production is cheaper, but it necessarily requires serious investments for the purchase and installation of robots, so the factories that produce cars on the territory of the Russian Federation do not apply this method.

2.5 Drying for sealer

It consists of 2 stages. The number of stages is calculated at the design stage and depends on the speed of the body through the furnace, the “polymerization window”, the metal capacity of the body (mass and dimensions). Each stage is a unit in which there is a separate (independent) burner operating on gas fuel, heats the air to a predetermined temperature and is supplied by fans to its stage, before that hot air passes through 2 stages of purification with the help of heat resistant filters.

Example of temperatures in each stage:

1 -100 °С

2 -120 °С

2.6 Sanding of the KTL coating

It is a pass-through type booth (input / output) and is divided into technological operations:

  • Completion of the roof, painters are on a special trestle and only the roof element is modified.
  • Racks, hood, trunk, door elements to the middle part (50%) + internal openings
  • Wings, thresholds, door elements from the middle to the bottom + internal apertures.
  • Inspection

Material, i.e. abrasive and tools.

90% sanding of the defects, dirt, KTL runs, plastisol on the front surface is carried out with the help of a hand holder with a diameter of 77 mm (slang “tit”), in the center there is a niche with foam rubber for wetting the disc and a surface with a DI water.

To eliminate the defect, abrasive is used with the P-320 cell, in the case of bigs P-280 defects.

This booth necessarily requires a centralized supply of demineralized water.

Lighting – according to the RF LC, these operations require an illumination of 800 lux

Process

Operator in spray booth performs an inspection of the surface of the elements and tactile hand, if a defect is detected, removes it with a hand holder or a machine from 77 to 125 mm in diameter, then wipes the surface of the stripped area with a microfibre cloth from water or cut. dust. Basically, all the work is done point-by-point and manually using a demo. water, thereby ensuring a minimum removal of soil and the formation of a thin section. dust, otherwise there may be additional defects in coloring, for example, rub, risks, polishing to metal.

Conveyor repair in case of damage to the KTL coating or in the case of stripping to metal use 2K universal epoxy primer light gray (white).

2K Primers provides good corrosion protection when applied to bare metal, and also has excellent adhesion to many surfaces and layers. The recommended coating thickness is 5-10 μm. It is recommended for painting parts on the system “wet on wet”. Can be used as a first primer, i.e. cataphoresis with subsequent application of the filler, and in the version of the equalizer soil, with subsequent application of any decorative coatings of the base + clearcoat.

This repair primer + base and clearcoat provides protection in the saline mist chamber as a substitute for cataphoretic soil up to 1000 hours.