Vacuum Pressure Impregnation (VPI) is a method to insulate wound electro-mechanical parts thoroughly with a resin or varnish. VPI is a critical process to insulate and seal the porosity of the parts. VPI is essential to ensure that parts function correctly and improve the longevity of the equipment (Image 1). This blog is a guide that will explain the process, advantages and applications of VPI.
The Albert Handtmann Metallgusswerk GmbH is the largest lightweight (aluminum) foundry in Germany. The family-owned company has continually endeavored to improve its casting and machining processes to benefit its customers worldwide.
Thus, when Daimler AG awarded Handtmann a contract to cast and machine one third of the entire worldwide production of transmission cases and clutch housings for the Mercedes A-Class, B-Class, CLA-Class, and GLA-Class vehicles, the managing directors and board at Handtmann saw an opportunity. It was an opportunity to build a world-class production facility fully dedicated to automated one-piece flow in the complete machining and post-machining processes of these Mercedes cases and housings.
As a company, Handtmann was expert in almost all of the production processes required as part of this new facility. However, in order to achieve true one-piece flow, Handtmann had to bring inside a critical aspect of quality control that the company had previously hired out, vacuum impregnation.
In the past after machining, Handtmann had always sent out its transmission cases and clutch housings to vendors to be vacuum impregnated. The company’s experience here was not always pleasant. At external points parts have been damaged during transport or contaminated. To avoid additional handling and costly washing-process, they decided to integrate this process into the (manufacturing) line.
For Handtmann, the challenge was to quickly educate its executives on the detailed aspects of vacuum impregnation, then chose the proper vacuum impregnation equipment to install. This equipment would have to meet Handtmann’s demands to seal casting porosity effectively and to meet production volumes, to do so in a 96-second per piece TAKT time, to fit into a confined space on the facility’s floor, and to fully integrate within the automated processes that would govern the entirety of the plant.
Since several of Handtmann’s vacuum impregnation service providers also build impregnation equipment, the company began by soliciting bids from these traditional sources. However, it was apparent immediately on receipt of these bids that the equipment proposed could not possibly be installed as part of a one-piece flow manufacturing line. The big batch systems that were recommended require parts to be manually loaded and unloaded and they carry a high risk for damage and contamination to the machined parts. They require significantly more TAKT time to complete the impregnation process. They also require a tremendous amount of floor space, for both the equipment itself as well as for loading and unloading areas. Hence, the big batch systems proposed early on were completely disqualified. Handtmann needed more advanced technology. Enter Godfrey & Wing.
By chance, a Handtmann engineering executive came across an article about a different process of vacuum impregnation called Continuous Flow Impregnation written by Ralf Versmold, Godfrey & Wing’s sales and service director for Europe based in Germany. As the name itself indicates, Continuous Flow technology was developed by Godfrey & Wing to answer the demand for the vacuum impregnation process to be fast, efficient, and capable of being installed as part of a machining line where floor space is limited.
After visiting several CFi installations in 2012 and learning firsthand from Godfrey & Wing customers about the effectiveness and efficiency of these CFi systems, Handtmann purchased a multi-station CFi from Godfrey & Wing in early 2013. The system was installed in Handtmann’s new Mercedes one-piece flow manufacturing facility in Biberach, Germany in late 2013 where it operates alongside machining centers, parts cleaning equipment, and pressure test benches in a fully automated environment. This CFi includes a compact impregnation pressure vessel, a high-speed centrifuge, a wash tank, and three cure stations, all serviced by a robotic arm and automated conveyors. Six days per week, 24 hours per day, this CFi vacuum impregnates every transmission case and clutch housing that fails its initial pressure test.
Considering the four demands required of it– speed, efficiency, and total automation within a small footprint, Godfrey & Wing’s Continuous Flow Impregnation system has proved to be the perfect solution for Handtmann Metallgusswerk in its dedicated Mercedes machining facility. Today, this CFi plays an integral role in the manufacture of these transmission cases and clutch housings and it does so in one of the most advanced manufacturing facilities in the world.
Production manager Heiko Pfeiffer sees a huge cost/handling and thus competitive advantage due to the direct automatic integration of the CFi-technology. He confirms, that the CFi-technology is actually the only possibility to integrate the impregnation-process into the manufacturing-process within a modern production-environment.
The Continuous Flow Impregnation (CFi) System is a lean, front loading vacuum impregnation system that uses a robot for part handling and transfers between modules. This impregnation system has a cycle times of less than 95 seconds. Individual part handling leads to many process improvements, such as shorter cycle times, better rinse results without risk of contamination, damage or discoloration. Furthermore, each part passes through an identical process, and process parameters can be directly associated with a particular part (tracking).
Continuous flow is the most recent technology in vacuum impregnation. Continuous flow vacuum impregnation systems are cellular or lean in design, focused on conserving valuable resources including labor, power and floor space while being more ergonomic than batch systems. The individual modules are loaded from the front, eliminating the need for overhead hoists and cranes. These systems impregnate smaller size batches or single components per impregnation cycle. This allows for reduction of individual module cycle times as well as increased mechanical manipulation assisting in the accomplishment of the four basic tasks of the impregnation process.
In general, lean, front loading continuous flow vacuum impregnation equipment uses smaller modules with little or no supporting infrastructure. Front loading systems can occupy as little as 86 ft2 of floor space and utilize conventional basket dimensions (e.g.: 600 x 450 x 350 mm), which can be adapted to meet specific part dimensions, if required.
Advantages of continuous flow vacuum impregnation systems:
Disadvantages of continuous flow vacuum impregnation systems:
The CFi technology is fully self-contained for quality with the robot and PLC working together to ensure that parts do not leave the cell if they have not met all of the pre-determined process parameters. Likewise, the use of robotics shortens cycle times, improving overall TAKT time and production volumes. At the same time robotic handling provides for repeatable processing while controlling handling damage.
The Continuous Flow Vacuum Impregnation technology offers manufacturers and OEMs the opportunity to completely integrate the impregnation process into their overall production line eliminating labor, reducing WIP and controlling costs. Existing cells deliver over 240,000 cycles per year operating 24/7. They are ideally suited for larger powertrain installations where uniformity and repeatability are essential to part quality and delivery is paramount. Higher volumes, expansion or ramping production can be met by integrating duplicate cells. The Continuous Flow Vacuum Impregnation technology enables continuous production through lean manufacturing.
| System | Workload Size | Process | Cycle Time | Use | Labor | Floor Space Requirement |
|---|---|---|---|---|---|---|
| Top loading batch system | 24-96 inches in diameter; working depths of 12-120 inches | DVP, DV or W | 20-40 minutes | Jobbing and processing hundreds of unique parts, large and small | High | 1.000 to 10.000 square feet, including storage and support equipment |
| Front loading system | Rectangular tote size of 300 mm x 400 mm x 800 mm | DVP or DV | 240-540 seconds | Specialized, similar parts, large and small | Low | Low |
| Continuous flow system | Rectangular tote size of 300 mm x 400 mm x 800 mm or direct part handling | DVP or DV | 90 seconds | Specialized, similar parts, large and small | Low to None | Low - less than 600 square feet |
