Earn your finishing school diploma: to go to the head of the class in product flow, you've got to start at the back of your process--in the finishing room.
So it's no wonder that metalcasters looking to improve their workflow are inclined to shy away tom finishing and look first at their molding and coremaking. But that inclination can be misguided, s the assignments of tooling up and pouring a casting generally take less time than making the final adjustments--the adjustments that make the casting socially acceptable to the buyer.
"One of the main things that you run into is that molding machine with green sand can run, for example. 25 different castings." said Norris Luther, president of Luther and Associates, Tucson, Ariz. "But a finishing line lacks the flexibility to run seven or eight different castings on the same line."
That lagging work time and lack of flexibility generally add up to a casting bottleneck when solidified product reaches the finishing room. But by adjusting product flow and drawing from lean manufacturing principles, your finishing room can keep up with the rest of your metalcasting processes, and you can earn your finishing school diploma.
The Finishing Room Tradeoff
Streamlining the finishing room is a balancing act. On one hand, you need a fast, efficient system in place in order to handle the same casting repeatedly; you need lean, continuous product flow. On the other hand, you must be flexible enough to change your process when ;t new casting comes down the line; that usually means you need batched product flow.
Traditionally, short and medium-run shops have achieved flexibility by clumping identical castings together in batches. Because the metalcasting side might be running several different jobs in one day, the finishing room waits until a significant amount of one type of casting has solidified and then performs one cleaning operation over and over again (such as gate removal) before passing the batch on to the next operation (such as grinding).
In higher production facilities, where a single casting is run thousands of times per clay, the method of continuous product flow is preferable. Because the same casting is coming out of molds--through shakeout and the shot blast--all clay long, it can be placed on a conveyor belt behind another casting of the same type and shuttled past workers, each performing a different task and then repositioning it on the belt.
To achieve results from cleaning and finishing room improvements, you must divide your study time, applying general principles of lean manufacturing and using the best aspects of both continuous product flow and batched castings.
"You have to analyze each job, because each metalcasting facility has different sizes and different problems." Luther said.
The end game for streamlining the cleaning room, even for short and medium-run facilities, is to examine current operating procedure and institute some aspects of continuous process flow.
"In my survey of metalcasting facilities, the type of handling system that is most used is the batch type," Luther said. "Those facilities increase their handling by about 25%." Continuous loading of castings onto a conveyor belt will reduce the amount of handling that is performed by each worker.
"Every time someone picks up a casting, it's lost time," said Paul Barker Jr., primary consultant for Barker and Associates, Fort Wayne, Ind. "And 90%, of the time that you reduce tin]e, you reduce cost."
The first step is to move all of the cleaning and finishing equipment in your facility into close proximity. Next, Barker suggests a conveyor line start immediately after the castings come out of the shot blast. One worker should be there to inspect each casting before it goes down the line, and no defective casting should make it past that gatekeeper.
"Lean manufacturing is about eliminating waste," said Matt Sullivan, vice president of manufacturing at Buck Co., Quarryville, Pa. By going to continuous product flow through lean manufacturing, Buck Co. has reduced its ferrous finishing times from 14.5 to 5.5 days.
The worker at the start of the conveyor should place castings on the belt at regular intervals; it helps to have it sectioned off with white stripes approximately 18-in. apart. The first-line inspector can place one or multiple castings in each segment, depending on how many workers are on the conveyor belt down the line. With proper preparation, several different castings can be placed on the same conveyor, with different workers handling different castings.
When It's On the Line
Conveyor belts can be a cheap way to keep your product moving, but short of automating your finishing room, machines can't clean your product for you. Using personnel properly can make continuous product flow work for your plant, whatever its size.
For high and mid-production facilities, a few general rules govern all activities. First, workers should be assigned simple, focused tasks.
"You don't want to have someone doing three different operations," said Barker. "They should have one tool, two at the most. Each individual has a certain thing he does. If you have 60 castings to put through in an hour, and the process time is 10 minutes, how many people do you have on the line? Ten people. You divide the operation up into simple tasks."
Barker suggests developing a single, illustrated sheet that contains all of the instructions that a floor worker will need to complete his singular task. The sheet can easily be replaced by another if a new casting is conveyed down the belt.
Handling is of cardinal importance on the finishing line, and that goes for both casting and tool handling. Keeping tools in their proper place by mounting them on spring-loaded hangers can limit the latter, and Barker suggests dividing the casting into sections to decrease the former.
"Let's say your casting is a cube," he said. "It's easier to chip the three sides that are exposed than to chip the entire cube." The next person on the line will be responsible for performing the same job on the unexposed sides of the casting. Handling can be eliminated further if the worker downstream is considered in advance. The person who performs the operation on the exposed sides should reposition the part on the belt with the unfinished portions exposed. With smaller parts that must be removed from the belt for hand grinding, the part should be returned to the belt with the unfinished sides up. Barker also suggests the use of baffles, or deflectors, to tip the metalwork into position.
High and mid-production facilities also should plan ahead for periods of down time to keep the line running. A lack of one of three things can create downtime for a finishing line--manpower, machine power and product. The first can be accounted for by training each individual worker in multiple cleaning and finishing jobs. If your gate cutter is on break, there should be someone else who can pick up the slack.
The latter two deficiencies--machine power and castings--can be alleviated by keeping a small surplus of castings waiting in the wing. Essentially, the continuous flow, lean facility must implement some elements of batched flow. With those extra castings on hand, line workers can continue to produce even in the face of a down blast or a rash of defective castings.
Job Shopping Around
High production metalcasters have it easier than job shops when it comes to speeding up their finishing processes. But there are certain aspects of the lean, continuous flow mindset that can carry over and be effective.
Just as in a high production facility, job shops should have a gatekeeper at the exit of the blast that inspects each casting and sends only viable parts to the next man in the processing chain.
"If you have a defective casting in your hands already, why not get rid of it?" Barker asked. "Let the person whose job it is to grind just grind. Don't put it on the line."
Each man in the processing line also should have simple, printed instructions indicating the steps to be taken with each casting. The sheets, which should include a clear picture of the casting described, can be changed during the clay with little disruption. Included in the instructions should be a description of the required tools. Belt)re a finishing room employee begins work on a casting, he or she should have all of the necessary materials on hand, eliminating handling and downtime.
For job shops, it is perhaps more critical to hone the upstream metalcasting processes than in high production shops. Where continuous flow finishing can make up for lost time when the same casting comes through again and again, a near net shape casting often is required to shave time in a job shop.
"If you have, say, a 0.5-in. wall or a surface that is 2 in. high, can you take 0.06 in. off that surface?" asked Barker. "If you can reduce any amount of metal. do it. Saving metal not only saves you money on the raw materials, but it also eliminates finishing time."
The Balancing Act
High production outfits, medium run casters and job shops all can improve finishing by balancing task times and manpower For example, Barker presented a situation where three tasks are required to finish a casting. Task A requires 20 seconds of work. Task B takes 40 seconds, and task C requires a full minute. The work time is therefore 60 seconds, regardless of how many people are put on the line. Instead of using three floor personnel to perform one task per person, combine task A and B, and the full process can be completed in the same amount of time by only two workers.
"We no longer assign tasks to people per day," Sullivan said. "Instead, we balance the tasks among different people. We also balance the flow through."
In other words, use multitasking to eliminate bottlenecks. If one task seems to be causing a pileup, workers should be flexible enough to help out with that task rather than continuing their own and burying the downstream worker.
The result of continuous flow practices, for shops of all types, goes beyond simply speeding up the finishing operation. It also allows better quantification of your progress.
"It results in better visual compliance determination," Sullivan said. "There are more visual measures for our supervisors. [With hatched castings], you can't tell if" you get further ahead or further behind by the end of the day. [With continuous flow], the piles are smaller, so it is easier to tell if something's gotten done."
There are no quick fixes in the cleaning and finishing operations, just as there are none in the upstream processes. But by studying your operation and the principles of continuous product flow, you can gain the tools that will help you pass the test.
"Some people think you can improve without it, but to stay price competitive, you have to do some engineering," Luther said.
For More Information
"Considerations for a More Efficient Cleaning Operation," N. Luther, MODERN CASTING, January 2001, p. 29.
Shea Gibbs, Assistant Editor
Keys to a fine Finishing Room
Trim the fat
[check] Remove defective castings as soon as you spot them. It is best to have a gatekeeper at the front of a continuous processing line checking castings as they leave the shot blast.
[check] Pick up castings as little as possible. Every time a worker handles a casting, time is lost.
[check] Assign one simple task to each worker on the line. The task should be basic enough not only to complete quickly, but to be taught to several different workers.
[check] Anticipate the next person on the line. Upstream workers should reposition castings in the most convenient manner for the next worker downstream.
[check] Train workers in multiple finishing room tasks. This will enable them to help out with tasks that cause bottlenecks and to take over entirely when breaks are needed.
Have tools ready
[check] Use spring-loaded, hanging tools. The benefit of eliminated handling goes tot tools as well as castings, and a hanging tool doesn't need to be picked up.
Prepare for the worst
[check] Prepare for machine downtime and scrapped castings by keeping a small backlog of castings. If the line is running and there are no castings, you're closing money.
Cast well, finish fast
[check] Fix recurring defects in the casting process. "People say, 'it's only 2 to 3% scrap,' but that can build up," said Paul Barker Jr., primary consultant, Barker and Associates, Fort Wayne, Ind. "Correct the problem even if it's a small one."
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|Date:||Jan 1, 2007|
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