Finite Cleaning of Assemblies

DAIMLER CHRYSLER awarded a contract to TECH-TRANS for the development of an automated system for the removal of chips and extraneous debris being found in the internal worm trails and spool areas of assembled transmission valve bodies.

ABSTRACT

Achieving the production rates of high quality transmissions was also being hampered by contamination fouling the precision testing equipment, creating production down-time. Based upon the experience gained in similar applications, TECH-TRANS applied it's proprietary and "patented" PULSED-CLEANING process, along with the systems and controls integration to meet the challenge. The expected results could be summarized and confirmed as well as demonstrated prior to order placement for systems proof of concept prior to order.

Part to part cycle is 11 seconds which provides an actual vacuum contact time of less than 4 seconds. As compressed air was not available in sufficient volumes for this application area, TECH-TRANS proposed a closed-loop regenerative system. Within this proprietary process, filtered exhaust gases from the back side of the vacuum generating turbine are controlled within the contact tooling to provide the cross flow air volumes required to agitate the debris for simultaneous removal by the vacuum ports supplied within the same tooling. Floor space is always an area of concern and while the system could be located up to 100 feet away from the actual work station, the system design was sized to "drop-in" directly over the existing transfer line.

THE PROBLEM

Transmissions rely upon the "valve-body" to control functionality such as shift points and gear selection. Being the most critical component requires a precise assembly and test procedure to achieve the high quality standards required of this part. During the assembly of tight tolerance components, small chips broken from sharp edges, along with other debris generated during the assembly process were entering the valve body areas and had to be removed. The important testing stations, also experienced considerable down-time due to debris from the valve bodies blocking screens and cutting seals. This is a critical quality step and when the test stands become clogged due to debris jamming, then production rates can not be maintained. Additional labor and down-time were becoming associated with this phase of the assembly operation. A temporary fix of air nozzles used over the line proved ineffective at solving the problem and further consumed large quantities of compressed air and generated a housekeeping problem. As compressed air was considered at a premium, any possibility of using further quantities for any system would not be acceptable. On occasion, some parts were able to get through the system only to necessitate further re-work and additional , non-productive labor being expended. From a warranty and customer satisfaction standpoint, the high incident of the problem was not acceptable and exceeded warranty cost expectations. It was determined that the existing washer systems were not extracting the chips and debris from these deep grooves and in some cases may have deposited them from other areas being washed. Debris also entered the valve body during handling either from gloves or the dunnage racks used for transfer. Hanging chips were generated during the assembly stages, such as when the spools and retaining clips were inserted into the valve body. The manufacturing process dictates that every valve body must be cleaned to assure conformance to high quality standards.

SOLUTION

This particular plant had two previous TECH-TRANS systems in place generating positive results in in a similar application. As a result, TECH-TRANS was contacted to determine if it's proven capability could be developed to overcome this particular problem. It was decided that an existing station area would accommodate both the main vacuum collection system as well as the proposed automation. The "PULSED-CLEANING" process was incorporated utilizing the exhaust gases generated from the back side of the turbine – vacuum generator. This met the plants requirement to minimize plant generated compressed air. The proprietary process is developed around the principle of high volumes of air flows generated as part of the vacuum and discharge of the turbine. These air flows are directed to the part via a cast urethane tool which has internal ports for the delivery of air flows to critical areas of the valve body. A discriminator assembly "pulse-generator" is used to alternate and control the air flows. The reversing rate, or "pulse" rate, and air flow volumes were tested and confirmed at TECH- TRANS. The station lift and associated tooling was built as part of the sub-assembly used for the final systems run-off and installation.

Labor costs have been reduced by building a higher quality part that requires less re-work, thus increasing the overall line efficiencies and part quality. Warranty issues also merit a reduction which should to improved customer satisfaction. TECH-TRANS designed and built the vacuum equipment, tooled vacuum head, lift station and related automation, systems integration and provided on site installation supervision. Preliminary engineering included full 3-D CAD design as well as simulation of the proposed motions to verify the proposed automation design.

The documented improvements provided by this first system have led to a second system being purchased and installed for another product line in the same facility.

BENEFITS:

FULLY AUTOMATED , IN--STATION CHIP REMOVAL / CLEANING
IMPROVED LINE EFFICIENCIES – REDUCED RE-WORK & SCRAP
IMPROVED PART QUALITY – WARRANTY COST REDUCTION

See video
shadow