An Investigation into the Use of Control Technology in the Car Industry
The Mustang’s body area encompasses 355,000 square feet. It also utilizes 145 robots to perform welding for structural integrity, material handling for assembly, and sealer application for water leak prevention.
Six major assembly/welding lines, along with three subassembly and buildup areas, are required to complete a Mustang body. There are three subassembly buildup areas: front structure framing and respot where a front end is created, rear pan assembly and respot, and the bodyside subassembly. The six major assembly/welding lines are:
1) The press line which joins the rear pan, center pan and front end to create an underbody.
2) The underbody respot and clamp line which joins the bodysides to the underbody.
3) The welding bucks which provide dimensional and weld integrity.
4) The roof line
5) The IBM respot line
6) And the closure line which assembles the doors, hood and rear deck lid to the vehicle.
A perception vision system is also used to verify dimensional quality.
The last process before a unit leaves the body area is metal finishing, where metal surface imperfections are removed before delivering a body to paint.
The paint department provides four functions to the finished product. The four functions are: the application of the phosphate/e-coat coatings, body sealer, primer coating, and color coatings. The following is a brief description of each of these functions:
The phosphate coating is the primary safeguard against rust. In addition, the phosphate coating provides an excellent surface that paint will adhere to. The application process causes nonferrous crystals to grow directly onto the metal. Because the phosphate is crystalline, the finished product is rough when viewed under a microscope.
The next process is an application of a water based primer using electricity to cause the primer to migrate to any uncoated metal surface of the unit. This process requires the unit to be dipped into a tank holding 90,000 gallons of the electro-coat primer; an electric current is applied to the paint and the unit is connected to the opposite electrical polarity. This creates an attraction which causes the paint to flow deep into all the joints and interior surfaces of the unit.
Sealers are applied to all the welded seams on the unit to eliminate the possibility of water leaking into the unit from the exterior. Robots apply sealer to the interior floor pan, the fire wall, the left and right wheel house, and the back panel of the unit. This equals approximately 70% of the sealer that is applied in the paint shop. There are minimal sealer operations before and after the robots, to reach areas of the unit that the robots can’t reach. In addition, hot metal patches are applied to certain areas of the unit to provide sound deadening, and wide noise reduction.
This is a workable layer of paint that is smoothed and dressed so that the color coats can be applied over a perfect base. Mustang primer is color compatible; that means that a chip to the color coat will be less noticeable because the color underneath is close to the same color as the exterior of the car. Most of the prime coat is applied with robots called “Bells”, which use the principles of electrical attraction to apply the paint. A bell doesn’t spray paint using pressurized air, rather the bells spin at very high speed which atomizes the paint into very small particles. The side to side motion of the bell ensures that an even coating of paint is applied.
The first step is applying a perfect color coat is to prepare a perfect surface to apply the color coat onto. Thus, the first operations in the enamel area are: sanding operations that remove surface imperfections and smooth the previously applied primer, then the unit is wiped and blown clean. Next, the color coats are applied using robot bells and a type of robot called a reciprocator. A reciprocator used air to supply the final metallic color coats. The reciprocator doesn’t influence the orientation of the metallic particles within the layer of paint.
After color coating, the unit is coated with a clearcoat paint which provides shine. Red units are coated with a tinted clearcoat. In this case, the clearcoat paint is tinted with a red tint, which makes the shine appear a mile deep.
At the present time the Mustang plant uses six different primers, five exterior primers, ten exterior color coats, and two clearcoats, tinted and clear.
The attention to quality within the paint shop has resulted in reduction in customer concerns of 32% based on the average number of customer concerns reported by NVQ for the 1994 model compared to the first quarter NVQ for the 1997 model.
Future Quality Actions
Dearborn Assembly Plant has just been authorized to construct a new paint facility to be located on the east side of the plant. This shop will be a separated, stand alone facility utilizing the latest technology to produce the best painted surface on the market. The new paint shop will be constructed employing clean room principles, those operations that create dirt will be on the first floor of the new building, while the clean activities will be on the second floor. Access to the second floor will be limited to individuals passing through clean rooms and dressed in approved garments. The paint will be water based in contrast to the current solvent based paint. The water based paint is environmentally safer. This facility will be launched with the 2000 model year Mustang.
Due to the unframed door glass system on the Mustang, unique door glass setting fixtures have been installed to fit and adjust the door glass. the installation of convertible tops is integrated within the production system, instead of being installed off line in a subassembly area. Four synchronous carriers (also known as people movers) have been installed within the trim department that allow the operators and their work station to move with each unit, eliminating unnecessary walk time. Various overhead conveyor systems are used to transport components such as instrument panels, door panels, “A” and “C” appliquï¿½s from subassembly and select areas to on line operations. An automated windshield and backlite decking robot system has also been incorporated within the trim department.
The chassis department also has several overhead conveyor systems that are used to transport components such as: front and rear bumpers, taillights, rocker panels and engines from subassembly and select areas to on line operations. Automatic crossmember and front engine mount secure facilities are also installed within the chassis department. Semiautomatic engine decking, front spring press and rear axle decking sleds are incorporated within the chassis department. Within the area known as the loop, an overhead power and free clam shell conveyor system is used for installation of underbody suspension components. Two overhead synchronous carriers are also installed for the front gear box and detent secure process. State of the art brake fill and hydroboost/brake stroke equipment, with panel view trouble shooting screens, are installed. Semi automated gas fill system and unique FORI and ANZEN toe in facilities that use laser technology are also installed within the chassis department.
The final area has installed over 48 unique articulating arms. All these facilities within the final assembly area have been installed in our continuing our efforts to improve quality, ergonomics, safety and productivity.
Vehicles entering pre delivery are subjected to a variety of inspection, test, surveillance and audit functions in line with the plants quality operating system (QOS). Every vehicle must pass exterior, interior, underbody, electrical function, water test, road test and underhood examination prior to being released to transportation. Audits are taken on released vehicles to verify the effectiveness of the QOS. Representing the “voice of the customer”, Pre delivery continues to review and analyze customer data to improve the QOS, inspection methodology and the quality of released vehicles.
Plant engineering operations consists of three departments: Maintenance, Plant Services, and Plant Engineering. These departments work closely together in maintaining and improving Dearborn Assembly’s appearance and overall performance.
Maintenance and plant services perform non production activities which consist of skilled trades who maintain the facilities required for the assembly process. Their responsibilities vary from daily clean up operations to the maintenance of miles of conveyors which exist in Dearborn Assembly.
Plant Engineering is a non production department consisting of engineers who assist Dearborn Assembly in solving their electrical, mechanical and environmental problems. Their work involves new project implementation, equipment design improvements and constant compliance with local, state, and federal regulations.