Clean, Safe, Productive Steel Finishing
American Foundry Group’s finishing department renovation greatly improved operations.
Nathan P. Vanbecelaere, Manufacturing Engineer, and Sergio Chavez, General Manager, American Foundry Group, Muskogee, Oklahoma
(Click here to see the story as it appears in the January 2015 issue of Modern Casting.)
Oklahoma-based American Foundry Group’s Muskogee Division produces up to 2,200 tons in steel castings each year, primarily supplying the pump and valve industry. The work ranges in size from 40 to 6,000 lbs. During the late summer and fall of 2012, the time was right to invest in a complete renovation of the cleaning and finishing department in Muskogee. The ultimate goal of this conversion was to construct a facility that was clean, safe and productive, to aid in maximizing throughput in the finishing department while reducing lead times. The approach also would support developing a more efficient workflow, as well as improving air quality, lighting and emissions removal to make for a more suitable work environment.
American Foundry Group found it necessary to overhaul this department because it was a source of poor quality, and it was negatively impacting delivery dates due to inefficiencies. It also was becoming an unsafe environment in terms of injuries and air quality.
The department was dealing with compiled clusters of dissimilar castings due to the lack of space and material flow. Many of these castings were stored in baskets outside of the cleaning room, leaving them outdoors. This could require castings to return to shot blast multiple times before finishing. Also, there were too few cranes, which made it more difficult to maneuver castings about each station and to and from the work booths. These were air hoists that had a tendency to leak hydraulic oil over time. Quality was becoming a concern due to the lack of lighting and dissimilar alloys being grouped together.
Figure 1 shows images of the previous working conditions and setup of the cleaning and finishing department. Images 1A and 1C display the condition of the old arc/weld booths. These pictures reveal some of the air quality and lighting conditions of this department, as well. Image 1B shows the old grind booths. Image 1D is a look at the large floor grinding booths.
Each booth was designed keeping in mind the balance between spacious and space efficient. The weld and arc booths will see a wide variety of shapes and sizes of castings funnel through each day. To ensure the booths were designed to suppress emissions to their full potential, they needed to be upgraded in a way that would exceed air quality standards to meet that of the Department of Environmental Quality (DEQ) for the state of Oklahoma. Improving air quality also makes for a much more appropriate work environment for the employees in and around this department.
The initial engineering design of each weld/arc booth is shown in Fig. 2A, excluding the curtain enclosures that protect from arc and weld flash. This booth was fabricated primarily out of 12-gage sheet metal walls and hood. The overhead covers on these booths are notched to allow the hoists to have space to safely maneuver castings in and out of each work table. The tables consist of steel castings, manufactured in-house to be able to nest in each booth properly. The air handler initially sat about 32 inches from the front of the table. These are rated at 4,500 CFM and can absorb a large amount of emissions and smoke. They have four fire-retardant cartridges with a manual air pulse cleaning system.
An analysis of the initial prototype for the weld/arc booth quickly revealed all of the debris from the arc/welders was being drawn through the shield and into the filters, making them susceptible to fire. This called for a buffer section of 36 inches, which was added between the work area and air handler. The wall separating these were louvered to aid in deflecting sparks from entering the filter chamber. Lastly, removable trays were placed beneath the filters, which are emptied after filters have been replaced or cleaned.
The primary focus for this improvement was geared toward everything that follows the removal or “cut off” of the risers and gating. This leaves the blast, arc, grind, and weld procedures. It has always been a practice at American Foundry to segregate the castings based on weight. The large floor will normally consist of castings weighing more than 200 lbs. The small floor takes ease in maneuvering most castings below 200 lbs.
The original workflow design for the small floor setup placed the “green line,” the first position to touch the castings, before or in front of the arc/weld booth. After shakeout, the castings went straight to cut off risers and contacts. After heat treat, the green line would get a portion of the grinding on the contacts, then continue down the line. If there was too much material for the grinder to remove, the welder was in position to arc remaining material. The finish line grinders would do the final touches to the castings. This was creating a large amount of work for the grinders and causing the cleaning room to consume more abrasives than we found necessary.
The group was fortunate to have inherited a much larger space to begin the design of the new finishing department. Although this is a benefit, a larger footprint can decrease efficiency quickly by increasing walking space between each station. This made the layout of the workflow very important to increasing efficiencies. Travel time for each casting needed to be reduced tremendously. A study done in April 2012 had discovered how far a casting traveled around the cleaning room before finally being transported to the shipping dock. It revealed that a batch of castings could travel as far as 960 ft. from heat treat to shipping. This was not only a slow process for cleaning but gave each fork lift a workout to do the moving.
One important part of the new room design is the segregation of specific materials. Separation of materials was much more difficult with the previous setup, because it would delay the progress of certain heats and impact on-time delivery. It is not a good practice to obtain and store multiple types of weld rod within the same weld booth. This meant that if multiple material types would move down the line, welders would have to leave the booth and walk down to the supply room to obtain the correct weld rod.
In the newly developed cleaning and finishing department, the green line that had been the first position to touch the castings was moved. Now, an arc booth has been placed at the front of this line. This position is to remove a majority of the excess material (contacts, flashing, etc.) before the casting reaches a grinding wheel.
A case study was completed to analyze how much of an improvement was made by the placement of the arc booth in front of the green line. Currently, three different types of abrasive wheels are used in the cleaning department. They will be called Type A, B, and C. The most accurate way to derive the usage was based on the total amount of weight cleaned through all departments against the number of wheels used. Table 1 displays the success the department now has in reducing abrasive usage. Table 2 displays an idea of the amount of reduction made in abrasive use over the course of the last year.
The facility’s total usage of abrasive dropped from $30,971/year to $18,680/year. These numbers do not include the last quarter of 2013 and can be slightly skewed due to the decrease in orders over the course of the year.
A few modifications made to the finishing department resulted in an injury reduction. Before, a large majority of castings were being transported in large bins or baskets. At times, operators would attempt to do much of the lifting to and from baskets without the use of a hoist, to accelerate production. The improved design of the grind booths also allowed for a separate enclosure to capture all of the debris. This eliminated the possibility of grinding being done toward one another, reducing various other injuries (see Table 3).
Throughout 2012, the cleaning room was operating with a lead time of nearly 16 weeks. With the improved facility, American Foundry Group has been able to eliminate overtime while reducing lead times down to nearly five weeks, which is much closer to its overall goal of three weeks.
The 16-week lead time existed while running an average 267 hours of overtime each week in the cleaning department. This was a gross pay of $202,342 in 2012. Over time, that figure has been reduced to an average 21.5 hours without increasing the work force. The projected overtime pay for 2013 is $16,304.
The total cost savings can be summed up with the success of the primary goals, which focused on abrasive and overtime reduction.