Getting more from your cleaning room: cleaning and finishing operations in low- and high-volume facilities have their problems, from automation to expenses. Although there is no immediate solution, there are several remedies for improvement.

In an era of tighter process controls and lean manufacturing techniques, metalcasting facilities continuously are looking to enhance their overall operation from design to shipment. This includes both revamping the facility layout and investing in new technology. While the first area of concern often is in pre-pouring operations, such as molding and coremaking, the cleaning room tends to be left out of focus.

However, no casting can be shipped unless it is processed through the cleaning and finishing operations, which generally consume half of a facility's workload in terms of man hours. By taking a full observation of the cleaning side of things, a company can improve its facility's total production and throughput.

The top priority for the cleaning half of the facility should be to minimize the expenses involved when finishing castings. This includes using the fewest amounts of resources possible while maintaining a safe and ergonomically correct facility to ship the components on time.

Cleaning and finishing operations can be defined as any task after shakeout. That includes removing the gating systems, removing sand and scale (shot blasting), grinding parting lines, welding and gauging (if necessary), inspection and shipping. Although most castings, large or small, will be cleaned and finished, both low- to medium-production facilities ([+ or -] 200 molds/day) and high-production facilities ([+ or -] 200 molds/hr.) endure individual burdens in their cleaning operations. There are no complete solutions, but there are ways to alleviate the problems.

Low-Volume Automation

When it comes to dilemmas faced by lower-volume production facilities, one of the toughest problems is automating and increasing throughput in the cleaning room. This is generally due to the lack of available technology for short-run castings. Most machines available for automating and streamlining finishing operations are designed for higher runs, thus limiting the choices of lower-volume plants. Further, tooling costs for automated systems can be at such a high price that a low- to medium-volume facility cannot justify the expense.

There is, however, a recent development in the form of automated grinding machines available for lower-volume facilities. These flexible automation cells for the grinding of castings can be reprogrammed to clean different families of components.

The controlling factor for justifying such a machine is the time the facility spends on grinding, and thus, the total savings. The least-expensive machines are manually loaded units ranging from $35,000-$40,000. Tooling can range from basic push-through operations for $5,000 to sophisticated tooling of $60,000. Higher-priced grinding machines range up to $400,000 and include multiple stations, but they have tooling costs of $110,000 per set. Contrarily, these units can process up to 900 parts/ hr. whereas the smaller single-station units are limited to 80 parts/hr.

Automated grinding machines can require a relatively low investment, but the tooling costs can be prohibitive if too many sets are needed. The payback on such machines can greatly benefit a company, but this depends on what the manual rate is for finishing each casting.

Another reason to consider automation is with employee difficulties. Numerous facilities have struggled to build a stable workforce in the cleaning room because few people desire to work near the machinery intrinsic with the cleaning operations, such as grinding machines.

Other employee problems being addressed more frequently are repetitive stress injuries (RSIs), better known as carpal tunnel syndrome. Any person with repeated constant movement or operation is at a higher risk for an RSI, which can lead to lost-time injuries and inhibit production. This is not new to the industry, but many facilities are looking into methods to avoid RSIs.

One of the largest benefits offered in automation is the repetition and quality of finished castings. Automated finishing processes can lead to consistent production because they can ensure a higher level of repetitive quality.

If a casting company wants to gain this quality and upgrade automation without investing any extra capital, there are incremental opportunities to improving operations. Labor-assist devices, such as balancers or manipulators, will help the operator in his/her handling of the parts. They can be used for cutting gates, grinding gate pads and even parting-line flash with large and heavy castings. These devices improve throughput and quality because they can relieve some of the fatigue factors found in manual operations. This concept can be regarded as semi-automation, but the price range varies depending on what device is needed.

High-Volume Automation

With their larger plants and elevated throughput rates, high-volume production facilities are more willing to put their capital into automation. By doing so, there often have been positive paybacks for the company.

Although management teams at a high-volume facility may be hesitant to invest in automation due to costs, they must know that if a facility maintains steady production with machines, the company will profit in the long run.

Despite the lucrative paybacks with cleaning automation, many high-volume facilities will invest more in pre-shakeout machines than post-shakeout. Although sufficient sand and core maintenance and proper pouring techniques may decrease the need for cleaning and finishing, facilities still utilize their cleaning practices. Thus, the cleaning room is left with finding a unit that is justifiable in cost that can perform at the required production rates. An alternative is to find less expensive units that can be used in multiples to achieve the same rates.

Other problems faced in high-volume facilities involve maintenance of the cleaning machines. Constantly running, high-throughput units will require more preventative maintenance solely because of the duty cycle they endure. This cannot be overlooked because most of these units are inline, and if they go down, the whole cleaning line can be affected. To keep the facility working if the unit fails, provisions need to be made with careful planning and layout work to maintain the flow of castings.

If a facility uses multiple units, the layout needs to provide for easy access between the units and the main line. For example, if four units are required, two can be put on each side of the line so operators can remove castings from the line, finish and return them easily to the main material flow path. Another method to maintain speed with multiple units is having an extra machine. This machine can be used as an emergency backup or for lower-production castings.

Continuous or Cell?

When castings come through shakeout, they generally will encounter one of two types of cleaning lines, cellular or continuous. These methods vary on volume, quality and speed.

Continuous cleaning lines incorporating high speed are best suited, but not limited to, a high-volume facility. Continuous lines run castings through stations of cooling, processing, shot blasting, grinding and shipping all inline.

The idea is to move the castings from station to station as fast as possible. If a product mix is consistent in size, shape, pouring and degree of cleanliness, then continuous is beneficial.

For blast machines on a continuous system, the throughput is controlled by the most difficult casting to clean. They move castings based on gravity and incline. However, despite virtue of design, some castings will remain in the machine for longer or shorter periods of time because they will go to the bottom of the pile and receive more tumbling time while some stay up near the top or skip across the top and out. This can lead to the overcleaning of certain castings. Further, if a facility needs to maintain segregation by heats or mold lines, the continuous line will run them all together.

If segregation is necessary, the best solution is with automated batch (cellular) processing. This is comprised of multiple batch units that are fed via an automatic load conveyor/shuttle that receives the castings from the shakeout line and will automatically shuttle them to the different cleaning units. These batch units have the ability to be completely purging so no castings are mixed. When unloading, the unload conveyor can be controlled in terms of where the castings are discharged either through direction changes or gates.

Automated cellular operations can keep better segregation and will provide more consistent cleaning. The castings are maintained at one station that will incorporate all the cutting, grinding, etc., as opposed to multiple stations on a continuous line.

Automated cellular cleaning lines involve the castings coming from shakeout and going to another conveyor where they will be taken manually (with the use of crates and forklifts) or by shuttle cars that go back and forth. Those shuttle cars will fill and go to the available blast machine, where the casting can be cleaned in one spot. A major advantage for a facility with cellular layout is that there is less opportunity for quality problems to go unnoticed. But the logistics of that are a little more complicated than a strand like continuous.

For instance, each cell has to have enough flexibility to accommodate any product day by day. Also, the volume that goes through each cell needs to be closely examined so there is no over or underflow of castings per cell. Automatic cellular manufacturing is gaining popularity, though many facilities still focus on continuous or manually operated cell lines. The choice of continuous or cellular is driven mostly from volume and costs. Typically, lower-volume facilities will more easily justify cellular handling.

Know the System

Even though using a cellular automation layout often can be advantageous to the facility, it is not mandatory for an efficient cleaning room. An improved layout will not be beneficial for a company that has a poor manufacturing system that includes tooling problems, no method for systematically correcting problems, excess work-in-process and poor employee training.

To prevent this, facility staffs should have a strong focus on creating a valuable management system. This includes keeping their processes defined, reworking of castings under control and not overloading one station or another.

One of the first steps in any system-improvement activity should be to create a flow chart that shows how the castings are actually processed, not how management thinks they are being processed. In addition to the processing steps, the flow chart also should include the handling, inspection and delays. Thus, when something becomes a problem, the staff will recognize it because of the valuable system. This can successfully be done at low-volume facilities because the majority of the castings can be grouped by those having same or similar process plans despite differences in shape. Although low-volume facilities might think to improve their operations by readjusting the layout (relocating conveyors, eliminating individual cleaning stations), there is a chance the system will not be fixed if the staff is not managing the process.

One method to improve process management in cleaning operations is bringing inspection stations right to the roller conveyor after castings come from the line, whether it is manual or automatic. This saves handling time and costs because if there are any castings with problems, they will be noticed immediately and sent back to the previous station. Also, the inspectors and the cleaning stations can better communicate what needs to be fixed to prevent further errors. The castings can be shipped faster because they would not be held in bins for days while waiting for inspection. Further, castings likely would encounter the cleaning operations only once instead of being recleaned multiple times.

Keep a Buffer Zone 

Molding processes can impact the entire cleaning operation in the flow-of-castings analysis because certain molds are made at certain rates. In order to coordinate the entire casting flow from start to finish, facilities will focus on unit costs and payback, such as the process itself, material handling and material flow. But sometimes the investment in capital required to maintain a perfect uniform flow is too excessive to justify. As such, several facilities will spend only one shift molding and two shifts cleaning. However, this might not be the best option available because the payback still can be lower than if automated equipment were used.

But some work-in-process is necessary to help level out the varying processing requirements of the castings produced. For metalcasting facilities, particularly lower-volume operations, it often is logical to have a buffer of inventory near shakeout, which is between a batch operation (pouring) and individual piece operations (grinding). A buffer is a strategic amount of inventory necessary to allow variability in the process steps for cleaning rooms that produce a wide range of parts. It helps ensure that the cleaning room has enough, but not too many, castings on which to work and can be simply managed by observing the designated area.

Buffers differ from having a set inventory of finished castings because buffers are part of work-in-process methods. The castings will remain mobile on the shop floor, which can help the staff catch quality errors easier. Further, the strategic management of work-in-process will reduce storage and labor costs because there would not be a large inventory of finished castings to move around the facility. This would free up more space and reduce holding costs, material-handling costs, the chance of quality problems going unnoticed and the amount of capital invested in the inventory.

The number of castings that should be placed in a buffer depends on variability caused by the product types, product quality and employees. For instance, if there is a wide variance in processing times, a certain casting needs more time for cleaning, and the buffer may need to be larger.

When properly managed, the buffer will provide assurance that the cleaning room will have enough parts to work on, but parts should not sit there for more than a day or two. The cleaning room should be managed so that when castings are released from the buffer, the cleaning room can handle the work without delay. If it cannot, then there is no reason to release more parts into the cleaning area, and if the buffer is full, resources should be shifted from the molding/pouring area to the cleaning room. If the buffer is emptying out, however, the molding and pouring lines will need more assistance.

For this system to work, especially for lower-volume operations, which have a wide variety of parts with many processing requirements, there needs to be flexibility in the facility's personnel to gain a smooth flow of operations. Cross-training employees in both the pre- and post-shakeout operations would allow the company to shift people from molding to the cleaning room and vise versa.

Buffers can be used for either high- or low-volume production facilities. If a buffer is never emptied, then its size can be reduced to further minimize inventory. But buffers have to be larger for low-volume facilities because some castings need more work than others. Buffers also can lighten burdens caused by rash jobs, which can dealy other jobs. Future rash jobs can be avoided if the facility keeps a number of castings in the buffer area to maintain the product output and not wait for parts to be cast.

Paid in Full

Regardless of the methods to improve a cleaning facility, the main focus should spin back to using the facility's full capabilities. It is a matter of observing the complete process layout to maximize space and labor utilization. If a cleaning operation does not need a complete overhaul, but still looks for some improvement, the use of conveyors could be the most useful. A one-time revamp is not necessary, but if conveyors can be gradually phased in, the former capabilities (such as forklifts) can be phased out. And as with the other forms of automation, payback is a driving factor in creating the right system. The fewer stops castings experience will lead to higher cost savings and quicker production.

Dan Spinner is the vice president of Sinto Surface Preparation, Roberts Sinto Corp., Lansing, Mich.

Frank Peters is an associate professor in the Industrial & Manufacturing Systems Engineering Dept. at Iowa State Univ., Ames, Iowa. He also serves as a member of the AFS 1E Industrial Engineering Committee.

Kevin O'Shaughnessy, Assistant Editor

For More Information

"Opening Up to Robotic Change," R. Anaparti, MODERN CASTING, January 2004, p. 40-42.

"Considerations for a More Efficient Cleaning Operation," N. Luther, MODERN CASTING, January 2001, p. 29-31.