Flexibility, Automation in Small Metalcasting Facilities
Two case studies illustrate how automation can be implemented in a small metalcasting facility in order to react to today’s global manufacturing demands for quickly delivered customized parts.
Rhythm Wadhwa, Norwegian University of Scence & Technology-Valgrinda, Department of Production & Quality Engineering, Trondheim, Norway
(Click here to see the story as it appears in the October issue of Modern Casting.)
In recent years, flexibility has attracted significant attention from small to medium enterprises (SMEs) in metalcasting and academia due to varying customer demands and increasing competition. Changing operating conditions are forcing firms to be flexible in handling variations in demand and product and uncertainty and changes in the environment. Such factors have affected manufacturing companies for a long time, but their influence has escalated during the past 20 years as a result of advances in manufacturing technology and demand for mass customization.
Organizations, both large and small, require reconfigurable equipment to produce one-of-a-kind or small batch quantities of customized products. Client demand for small volumes of customizable product leads to a paradigm shift in how effectively an SME, with 10-25 employees on average, would operate to quickly and effectively deliver parts. Identifying best practices is a tricky process that is difficult to implement, which is more noticeable when the companies are SMEs. Typically, SMEs have limited resources and knowledge of automation methodologies. To address this, the Norwegian Research Council started a project to test the concept of a shared flexible manufacturing environment tailored to metalcasting SME requirements.
The participating metalcasting consortium in the project agreed to test part handling automation solutions at two metalcasting facilities in a living lab setting. Living labs began to emerge in early 2000, and the concept has since grown. A precondition in living lab activities is that they are used in a real-world context. During this living lab process, constant feedback for improvement was collected and transformed into a requirement list for the technology providers.
Case Study One: Flexible Robot Part Handling in an Iron Casting Facility
Preferring to remain anonymous, the iron metalcaster is a manufacturer of residential wood stoves. The company faces seasonal customer demand patterns and produces eight series of wood stoves, each with four variants. Two of the series have special coating processes after the individual assembly parts are cast, with special handling requirements. The metalcaster implemented a test automation cell between the cleaning and sorting processes as a potential test area for implementing a flexible automation solution for handling the varying part families. The company wanted to test an automation cell built around the range of products that they manufacture and choose the best way to integrate it into production. The company incorporated a used robot to implement cost effective, quick changeovers for fast, flexible part routing and handling.
The overall design concept of the material handling’s Ethernet communication handling system consisted of three subsystems: the robot manipulator, the material handling system and the vision system. In the cell, an overhead camera identified the orientation of the part lying on the conveyor belt, which was internally tracked by the robot (Fig. 1). The image captured by the camera was processed by the vision system and transferred via closed network connection to the robot. The robot gripper then moved the electromagnets accordingly to pick up the part.
Vision System Challenge: Picking from Conveyor vs. Bin
The vision module was to perform object recognition of a three-dimensional part and locate the coordinates. Markers were cast-in to aid in an accurate estimation of the part’s orientation for a pick-and-place operation from a conveyor belt and stationary bin. The stove components were flat with dimensions varying between 0.3 and 0.9 sq. in. (200 and 600 sq. mm) and thicknesses between 0.2 and 0.3 in. (5 and 8 mm). Picking from a conveyor belt when parts were lying separately at a distance was conveniently implemented for automation. But when parts were combined in random order in a bin, issues arose in identifying the part orientation. Two marking options were tested for this purpose: concentric circles and straight lines (Fig. 2).
The straight line markers were discovered to have a reflection limitation when the tilt angle of the vision system was greater than 30 degrees for iron castings. This made the concentric circles a better option for tracking because a part of the circle was identifiable even under the light of the vision cameras (reflection issues).
Handling the parts once they arrived at the machine was also important. Implementing machine flexibility with the use of robots with reconfigurable grippers and intelligent interfaces (flexible workspace, vision system etc.), automatic tool changers and multi-axis robots helped to enhance material handling flexibility at the most affordable price. Figures 3 and 4 show two gripper prototypes used in the iron facility. The yellow lines indicate the direction of travel of the electromagnet heads to enable part handling encompassing different workspaces.
Case Study Two: Modular Concept for Part Handling & Fixture Flexibility in an Aluminum Casting Facility
In the second case study, an aluminum casting facility wanted to analyze how and where it could use modular components for handling automation. It wanted to look into pallets and overhead conveyors for the internal transport of castings, which would require significant investment and maintenance costs because they would be specially tailored for each new product. During production, parts were transported around the facility on pallets that were linked to different assembly lines. For robotic grippers to handle the parts, they would have to be positioned securely.
Moreover, handling sand cores required additional constraints to ensure they were not worn or cracked during transport. The fixture blocks were adapted to the sand core shapes to ensure enough rest area was available and they would be fixed properly on the pallet.
In the tested automated pick-and-place cell, various manual and motor-propelled jigs and fixtures rotated parts and assemblies through several axes and adjusted to the needs of numerous assemblers. Flexibility in the pallet fixture determined the degree of freedom available to part loading schedules. This flexibility also had to be taken into account when dealing with the ability to accommodate different parts of different shapes and sizes.
As part of the Autocast Project, the aluminum casting facility implemented four modular solutions for handling aluminum parts and sand cores. One of those solutions is shown in Figs. 5 and 6. The same standard base plate was used to transport sand cores and aluminum parts. The aluminum parts were supported by three flexible points. Three arms were adjustable in X, Y and Z directions to ensure all parts within a product family (i.e., swing arms) can be added to the pallet. The implementation presents an integrated solution in which no part must be replaced when the pallet is converted. Aluminum part location pins were adjustable in the height (Z) and longitudinal direction (X). The arms also could be turned around the Z axis of the tubes and rotated independently. When arms were properly adjusted in all directions, they had to be fixed in this position.
ncountering a scenario in which you are forced to suddenly and immediately suspend melting operations for an extended period can be a death sentence for many metalcasting facilities. Small to mid-size businesses are the backbone of the industry, but many do not survive when forced into extended downtime. One disaster-stricken metalcaster, however, found resilience through its own perseverance and a circle of support from peers, friends, suppliers, teams from installation and repair providers, an original equipment manufacturer and even competitors.
Tonkawa Foundry, a third-generation, family-owned operation in Tonkawa, Okla., was entering its 65th year of operation this year when a significant technical failure ravaged the power supply and melting furnaces on January 17. Thanks to the textbook evacuation directed by Operations Manager Carrie Haley, no one was physically harmed during the incident, but the extent of emotional and financial damage, and just how long the event would take Tonkawa offline, was unclear.
Tonkawa’s power supply and two steel-shell furnaces would have to be rebuilt. No part of the reconstruction process could begin until the insurance company approved removal of the equipment from the site. The potential loss of Tonkawa’s employees and customers to competing metalcasters seemed inevitable.
Within two days of the incident, repair, installation and equipment representatives were on site at Tonkawa to survey the damage. Once the insurance company issued approval to begin work, the installation team mobilized within 24 hours to remove the equipment and disassemble the melt deck.
Since the damaged equipment was installed in the 1980s and 1990s, Tonkawa and an equipment services and repair company quickly strategized a plan and identified ways to enhance the safety, efficiency and overall productivity of Tonkawa’s melt deck.
“The most critical issue was for our team to organize a response plan,” said Steve Otto, executive vice president for EMSCO’s New Jersey Installation Division. “We needed to arrive at Tonkawa ready to work as soon as possible and deliver quickly and thoroughly so they could get back to the business of melting and producing castings, and minimize their risk of closing.”
Several years after Tonkawa’s melt deck was originally installed, an elevation change was required to accommodate the use of a larger capacity ladle under the spout of the furnaces. Rather than raising the entire melt deck, only the area supporting the furnaces was elevated. As a result, the power supply and workstation were two steps down from the furnaces, creating a number of inconveniences and challenges that impacted overall work flow in the melt area. Additionally, the proximity of the power supply to the furnaces not only contributed to the limited workspace, but also increased the odds of the power supply facing damage.
The damage to the melt deck required it to be reconstructed. It was determined to be the ideal opportunity to raise the entire deck to the same elevation and arrange the power supply, workstation and furnaces onto one level. The furnace installation company provided the layout concepts, and with the aid of Rajesh Krishnamurthy, applications engineer, Oklahoma State Univ., Tonkawa used the concepts to generate blueprints for the new deck construction. The results yielded a modernized melt system with an even elevation, strategically placed power supply, enhanced worker safety and increased operator productivity.
“Eliminating the steps and relocating the power supply farther from the furnaces was a significant improvement to our melt deck,” Tonkawa Co-Owner Jim Salisbury said.
Within four days of insurance company approval, all damaged equipment had been removed and shipped for repair.
The insurance company required an autopsy on the damaged furnace before any repair work could begin. The forensic analysis was hosted by EMSCO in Anniston, Ala., in the presence of insurance company personnel, as well as an assembly of industry representatives from the companies who had received notices of potential subrogation from the insurance company.
Tonkawa’s furnace was completely disassembled while the insurance company’s forensic inspector directed, photographed, cataloged and analyzed every turn of every bolt on the furnace over a nine-hour workday. The coil was dissected, and lining samples were retained for future reference.
While the furnace sustained extensive damage, it did not have to be replaced entirely.
Structural reconstruction was performed to address run-out damage in the bottom of the furnace, a new coil was fabricated and the hydraulic cylinders were repacked and resealed. Fortunately, the major components were salvageable, and ultimately, the furnace was rebuilt for half the cost of a new furnace.
“The furnace experienced a significant technical failure,” said Jimmy Horton, vice president and general manager of southern operations, EMSCO. “However, not only was the unit rebuilt, it was rebuilt using minimal replacement parts.”
Though work was underway on the furnaces, Tonkawa was challenged with a projected lead time of 14 weeks on the power supply.
When accounting for the three weeks lost to insurance company holds and the time required for installation, Tonkawa was looking at a total production loss of 18-20 weeks. From the perspective of sibling co-owners Sandy Salisbury Linton and Jim Salisbury, Tonkawa could not survive such a long period of lost productivity. After putting their heads together with their furnace supplier, it was determined the reason for the long turnaround on the power supply could be traced to the manufacturer of the steel cabinet that housed the power supply.
The solution? The existing cabinet would be completely refurbished and Tonkawa would do the work rather than the initial manufacturer. This reduced the 14-week lead time to just five weeks.
Tonkawa is the single source for a number of its customers. Although lead-time had been significantly reduced, the Tonkawa team still needed a strategy to keep the single source customers in business as well as a plan to retain their larger customers.
Tonkawa pours many wear-resistant, high-chrome alloys for the agriculture and shot blast industries. Kansas Castings, Belle Plaine, Kan., which is a friendly competitor, is located 50 miles north of Tonkawa. Kansas Castings offered Tonkawa two to three heats every Friday for as long as it needed.
“We made molds, put them on a flatbed trailer, prayed it wasn’t going to rain in Oklahoma, and drove the molds to Kansas Castings. We were molding, shot blasting, cleaning, grinding and shipping every Friday,” Salisbury Linton said.
Others joined the circle of support that was quickly surrounding the Tonkawa Foundry family.
Modern Investment Casting Corporation (MICC) is located 12 miles east of Tonkawa in Ponca City, Okla. Though MICC is an investment shop and Tonkawa is a sand casting facility, MICC’s relationship with Tonkawa dates back years to when Sandy and Jim’s father, Gene Salisbury, was at the helm.
“Gene was always willing to help you out,” said MICC owner, Dave Cashon. “His advice was invaluable for us over the years, so when the opportunity arose to support Sandy and Jim, we volunteered our help.”
MICC offered to pour anything Tonkawa needed every Friday in its furnace. Tonkawa brought its alloy, furnace hand and molds, while MICC provided its furnace and a furnace hand for three heats. Many of the specialty parts Tonkawa produces were completed with MICC’s support.
When Salisbury Linton approached Cashon and asked him to issue her an invoice to cover the overhead Tonkawa was consuming, Cashon told her if she brought in six-dozen donuts every Friday morning they’d call it even.
“We’re all kind of like family,” Cashon said. “We’re all part of the same industry and though we may be friendly competitors at times, you don’t want to see anybody go through what they’ve gone through and it could have just as easily been our furnace that failed. While we all take the appropriate measures and perform maintenance to prevent these scenarios from occurring, they unfortunately still occur from time to time in our industry.”
Tonkawa had recently added steel work to its menu of services and Central Machine & Tool, Enid, Okla., was able to take Tonkawa’s patterns and fulfill its steel orders so it would not fall behind with those customers, while CFM Corporation, Blackwell, Okla., took three of Tonkawa’s employees on a temporary basis and kept them working during the downtime. Additionally, a couple of Tonkawa’s major suppliers extended their payables terms.
Thanks to Tonkawa’s suppliers, friends and its personnel’s own passion, persistence and dedication, the business is up, running and recovering—placing it among the few shops of its size to overcome the odds and remain in business after facing calamity.
Nearly eight months after that devastating Saturday evening in January, Salisbury Linton reflected on the people and events that helped Tonkawa rise from the ashes. “We certainly would not have the opportunity to see what the future holds for Tonkawa if it weren’t for all the kind-hearted people who cared about what happened to us. Everyone still checks in on us.”