The perfect matchplate molding operation: before MODERN CASTING could name the three best matchplate molding operations, we had to figure out what exactly makes one ideal and the envy of all others.
In order to highlight the very best foundries in matchplate molding, MODERN CASTING asked molding suppliers to nominate plants that have implemented cutting edge technology and engineering to make their matchplate operation the model of efficiency. Suppliers considered several different aspects in their analysis, including physical layout, mold handling and versatility.
Three foundries--Acme Foundry/ Magic Circle, Inc., Coffeyville, Kansas; Littlestown Foundry, Inc., Littlestown, Pennsylvania; and Donsco, Inc., Belleville Div., Belleville, Pennsylvania--were deemed to be the best overall.
But what really makes a great matchplate molding operation? What do the three profiled foundries posses that others lack?
This article will discuss the capabilities of matchplate molding and the opportunities (such as cost and labor reduction) that it can lead to. For examples of top-of-the-line matchplate molding operations, see "The Best of Matchplate Molding" on p.27.
A Look Back
The matchplate molding approach to green sand molding is one of two principle types of machine molding in use today. In the process, the cope and drag mold impressions are each formed on a side of a single pattern plate. The major advantage to this is that a single machine can make both cope and drag molds from one pattern (in cope and drag molding, separate patterns, and possibly separate machines, are used to make the mold halves).
Matchplate molding first became popular in the U.S. as a way to replace small loose pattern work molding, where the low tooling cost for a single matchplate pattern could be justified for higher casting volumes. Because European adoption of this approach has yet to develop as extensively, the U.S. accounts for the majority of all matchplate molding production in the world.
Early matchplate molding involved the operator assembling a pair of removable "snap-flasks" together with the pattern, and then filling each side of the mold with sand, followed by a simple machine squeeze cycle to make the mold. Those early mold machines were generically called 'squeezer' machines (later equipment added a jolt action or simultaneous jolt and squeeze capability). After stripping the mold, the snap flasks remained at the machine for reuse and flaskless molds were delivered onto a mold handling system for pour-off and cooling prior to shakeout.
Since their introduction, automatic matchplate molding has continued to evolve to incorporate the newest technology and operational achievements. Following is a short timeline of events:
* The design of fully automatic matchplate molding machines was introduced in the early 1960s. It incorporated aspects of filling sand onto the pattern face (riddled or slinger approach) plus hydraulic squeeze action to make 14 x 18 in. size molds;
* As the system got its feet wet, many other new features were introduced, including the blow method of filling the mold halves, although this method was a departure from the conventional squeezer molding technique, and acceptance in the industry was slow. Ultimately the transition allowed foundries to increase mold production from an average of 200-300 molds/ shift up to 80-100 molds/hr;
* In 1978, a larger 30 x 32 in. mold size automatic flaskless molding machine first became available;
* Matchplate molding machines began to integrate more features, including one with a sequential blow-fill, squeeze, coreset and strip cycle. This machine achieved a molding rate of 240 molds/hr;
* A mold tilt-up with vertical blow was incorporated into the design of matchplate molding machines in 1995. This design approach was instrumental in replacing many manual and older matchplate squeeze-molding operations throughout the U.S.;
* An extensive list of optional equipment has been developed over recent years to complement these machines, including automatic lubrications systems, pattern heaters and vibrators, automatic pattern and mold blow-off devices, automatic core setters and automatic pattern changers.
Matchplate Molding Opportunities
Today, matchplate molding machines come equipped with operator-friendly controls, which can make the difference between achieving the output of, high-quality, high-volume mold production or low productivity from the foundry. Touch screen, graphic PLC control panels with manual and automatic modes, plus startup and diagnostic programs also are featured regularly.
Database information also is available to the machine operator. PLC memory storage of tooling records for all operating parameters allows the machine settings to automatically be entered when a bar code reader identifies occurrence of a pattern change.
Reliable production records generated by or at the machine, with online feedback to central computers can improve efficiency and lower operating costs. Future trends in this area can be expected to include full operating manual information retrievable at the operator station and direct machine telephone/modem connection to remote offsite maintenance centers for trouble-shooting and reprogramming in real time.
Automated matchplate molding systems also create the opportunity to correct one area of weakness in many foundries--a lack of complete integration between the molding units and the operating system (such as mold handling, pouring, sands system logistics and core-pattern scheduling). The optimum production system is engineered for balanced logistical and material flow at all times, with real time interaction when stoppages occur or job changes vary the sand-metal-core demand. Computer simulation of operating conditions and requirements, prior to designing new molding facilities, is considered a necessity for future foundries to compete in world markets.
While integration of complete system control between all operating units is required, it is difficult when different suppliers manufacture the matchptate machine and individual system units. One possible solution is a project 'design/build' engineering approach with responsibility for control systems.
Improved productivity also is considered a factor in today's competitive environment. A major element is molds per hour (ultimately higher quantities of good castings produced per unit of production cost). Newer machine uptimes are reported to be more than 90% by the better-run foundries, due in part to the specification of OEM built-in diagnostics and orders for maintenance training by the machine manufacturer. Unfortunately, ancillary support equipment often is found to be responsible for much of the measured down time.
Foundries that are able to achieve a 5% improvement in overall system uptime at typical molding rates of 160 molds per hour (equivalent to 60 molds per 7.5-hour shift), can readily calculate the payback at a known profit factor per mold.
Other competitive benefits afforded by the matchplate molding approach include:
* less required supporting equipment to be purchased and installed;
* generally less floor space than equivalent capacity tight flask system;
* lower energy costs due to less material handling required;
* reduced maintenance expenses.
Modern matchplate molding equipment is capable of better mold quality, less shift due to machine-mold mismatch (in some cases 0.15 mm or less), consistent dense molds for less grinding and improved parting line definition. In addition, the machines are enclosed for a cleaner, quieter working environment with reduced operator exposure to safety risks or service-related problems. Reduction in casting scrap rate and lower casting cleaning room costs are parts of most economic justification models when new foundry equipment is planned.
Due to the variation in casting product requirements and other factors involved to make a mold--sand specifications and control, pattern tooling configuration, etc.--every operation has different parameters for what constitutes a quality operation. While the side blow-fill method adopted by most automated matchplate machine manufacturers has been in use for several years, there is disagreement throughout the industry as to whether all jobs can be made on these types of machines.
Sand, when distributed across the pattern face during side blow-fill, often results in 'shadowing' if the sand flow is obstructed or deflected by high profile pattern shapes. Also, deep pockets are sometimes difficult to fill with side blow compared to top fill. Each operator has his own opinion of what is the best.
The mold compaction capabilities on all matchplate molding machines have hydraulic pressures, some with proportional valve control of hydraulic cylinders. This allows for mold squeeze pressures ranging from approximately 85-145 psi, depending on squeeze piston size.
Mold hardness (density) from 85-90 is stated to be achievable on any of these machines. However, a range of hardness is required to suit different specifications for ferrous or nonferrous casting applications. Squeeze pressure should not exceed the limits of sand spring-back or cause deterioration of clay-water layers and sand grain fracture. Flexibility of machine settings also is important to make adjustments to mold height, blow pressures, and pattern strip/draw rates etc.
New Installation Payback
After installing a matchplate molding line, how long does it take for a foundry to begin to see a return on investment? A competitive foundry operator generally looks for project payback in two years, about a 40% return on its investment depending on methods of depreciation and tax schedules. Return on investment for individual pieces of equipment can vary depending upon efficiency of replacement process, or opportunity for cost reduction due to previous high labor and material costs in the facility.
In a recent case study, the management of an efficiently run green sand aluminum foundry carried out an evaluation and ROI for a project to replace one older style automated matchplate molding system plus auxiliary equipment. The plan included installation of a new matchplate molding unit, a new melting furnace and an automatic pouring device. Changes to the sand system and improvements to casting cooling/transfer systems also were planned, with total new capital expenditures estimated to be several million dollars.
A major cost savings was identified as the newer molding was projected to reduce hourly labor by seven employees while still producing more castings than the lower rated older molding machine. Additional cost reductions in metal melting, material handling and projected scrap reductions were taken into consideration. In the overall plan, the individual cost of the molding unit and other new equipment, including engineering fees, was competitively bid to obtain least cost, and best possible return on investment.
In the final analysis the best green sand matchplate molding operation is one in which the user foundry is able to produce his specific product at the least cost, lowest scrap and highest safety with minimum headache to management and operating employees.
About the Author
John T. Nelson has spent his entire career in the foundry industry. He has held positions with major equipment manufacturers during the development period of automated matchplate molding machines and is now owner of an independent sales company, Equip/Tech Services, Inc., Barrington, Illinois.
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|Author:||Nelson, John T.|
|Date:||Aug 1, 2003|
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