Robot Eliminates WIP, Improves Efficiency

To efficiently produce components for over-the-road cargo tanks, Betts Industries Inc. (Warren, Pennsylvania) needed to eliminate any redundancies or inefficiencies within the manufacturing processes. By incorporating two Mori Seiki lathes, a part wash/dry system and a FANUC robot from Automated Cells and Equipment Inc. (Painted Post, New York), the company was able to eliminate a secondary leak test process, reduce manual labor and eliminate work-in-process (WIP) inventory.

Betts Industries is a vertically-integrated production shop that designs, manufactures and assembles components used in the production of cargo tanks for the petroleum and chemical processing industries. The company is home to more than 280 employees and about 30 machine tools ranging in size from small Swiss-type machines to dual-spindle/dual-turret lathes and horizontal and vertical mills. The facility also includes robotic welding and a metal stamping department with 600-ton capability.

In addition to designing and manufacturing manhole lids, tank truck valves and lighting components, Betts Industries designs and manufactures normal vents, which relieve both pressure and vacuum in a cargo tank to maintain safe operating pressures. To produce the vents, the company lightly machined key areas of an aluminum die-cast housing with a single-spindle lathe and then performed an initial leak test on the housing to verify its proper operation. A dedicated operator loaded and unloaded the lathe and leak tested every machined housing.

This was a very demanding process for the operator. If the housing passed the initial leak test, the operator cleaned, dried and packed the housing into dunnage for storage in a WIP inventory area located within the facility. The housing was later taken out of the WIP inventory and transported to an assembly area, where it was assembled into a normal vent, final leak tested, packed and shipped to the end user for installation in a cargo tank.

Taking a look at the initial leak test, Scott Angove, engineering manufacturing manager, and Glenn Burt, manufacturing engineer, decided to see if the entire housing could be machined from an impact-forged aluminum blank. By controlling the entire process for making the housing and precisely machining all features into the final component, the men wanted to ensure 100-percent pass of the initial component leak test without ever having to leak test the machined housing. Of course, the final assembly would be thoroughly tested and validated before it was shipped to the customer.

After some dedicated research and testing, the men determined that this was entirely possible; however, they were concerned about maintaining the cost of the final product. Machining the entire housing would require more time, two newer and faster lathes, and automation to efficiently move the product to and from the machining process.

Betts Industries already used FANUC robots in both its welding cells and another machine tending cell, so the company knew that using a robot for moving the part throughout the process was the right answer. It would also help push the limits further with the normal vent project. For instance, instead of washing and drying parts by hand, Mr. Angove and Mr. Burt wanted to use a robot to move the parts into and out of the parts washing and drying system. Boldt Machinery Inc. (Mattydale, New York) and Automated Cells & Equipment were brought into the project to help define the final cell layout and its components. Once cycle times were established with the new lathes, the washer, robot and appropriate tooling could be defined.

Automated Cells model MT20D drawer-based robotic machine tender with a FANUC M-20iA robot was surrounded on two sides with Mori Seiki NLX1500 SY500 dual-spindle lathes, each with a vertical operating pneumatic auto door and integrated “hurricane” boxes for part chip removal. A part wash/dry system and sample part chute were also incorporated within the robot cell. The MT20D stores a total of 480 impact-forged housing blanks in four drawers (120 per drawer) prior to machining. The operator opens and loads raw forgings into each of the four drawers prior to starting the lathes. Once the cell is started, the robot automatically opens the first drawer from inside the robot cell, grips a raw housing and loads it into the first lathe. This process is repeated to load the second lathe. Both dual-spindle lathes machine the parts completely.

Machined parts are then placed back into the drawers for the operator to unload outside the robot cell. The robot end-of-arm tooling uses a single sealed gripper with fingers capable of gripping the raw parts longitudinally and the machined parts perpendicularly. The end-of-arm tooling is also designed to enable interfacing of the tool (with part) into the wash/dry system and includes a blow-off nozzle for part and chuck cleaning during part unload/load within the lathe.

The pneumatic auto doors provide quick access for the robot during machine unload/load cycles and maximize machine run time. The integrated hurricane boxes mounted to the machine doors enable remaining chips to be removed from the parts prior to entry into the wash/dry system. The boxes feature a coolant drain port with baffle to enable any remaining coolant to drain off the parts and back into the lathe automatically.

The parts cleaning system includes dual portholes—one for the wash cycle and one for the dry cycle. A thorough hot-water wash with high-pressure jets cleans each part, and a final rinse with deionized (DI) water prevents spotting of the aluminum housing. This is especially critical, as any remaining coolant on a sealing surface can affect its sealing performance, failing the final inspection and leak test. The robot manipulates the parts within the wash/dry system to increase both washing and drying performance. This is especially important for cleaning cross-drilled holes and the inside surface of the housing. The addition of the automated wash and dry process has eliminated all rework associated with cleaning of the housing and directly contributed to a 100-percent passing rate at the final testing phase, saving both time and labor.

A sample part chute is integrated within the robot cell to enable on-demand sampling of machined housings. The machined part is simply placed into the sample chute (instead of being loaded back into the drawer) and is conveyed outside the robot cell for inspection by the operator or the quality control department.

An auto-dialer is also integrated within the robot cell to call the quality control department for a part inspection after a predetermined number of pieces have been run. The robot will also call a maintenance technician (via cellphone) if a machine or robot fault occurs or the cell is in need of service, thus reducing downtime.

The last major improvement was the integration of the final assembly process at the robot cell. Instead of storing machined housings within WIP inventory, the assembly process was relocated to the robot cell. As drawers of parts are completed, the finished housings are then assembled into the final product, tested and packed for shipment. The assembly operator is now the same person who runs the robot cell producing the machined housings. The robot drawer system queue of 480 parts, coupled with the efficiency of both the FANUC robot and Mori Seiki lathes enabled a full day’s worth of production to be reduced from three shifts to just 11 hours.

As a direct result of the robot cell implementation and changing from a die-cast housing to a fully machined housing, the company saved 7,500 man hours in anticipated annual machine tending labor, and a 90-percent reduction in inventory was achieved. According to Mr. Angove, “The normal vent project was a tremendous success with even more benefits than we could have ever imagined. The drawer system has enabled us to adjust to changing laborer schedules and customer demand with no WIP inventory. The cell delivers completely machined parts, spotlessly cleaned, and untouched by human hands, enabling much more efficient assembly and testing.”