Maintaining the level of quality engineered into the casting process is the key to obtaining high levels of casting quality. When you visit your casting supplier, make sure you have the chance to look at how your pattern equipment is maintained. Your pattern and coreboxes all require upkeep to ensure they continue producing high quality castings that meet your specifications. Wear due to sand abrasion, handling damage, and even humidity levels in the foundry can adversely affect pattern equipment. To help you understand what needs to be done, let’s walk through the steps.

Addressing wear. When you order sample castings from your new pattern, the foundry will take measurements of the castings to ensure they meet your specifications. Often, there are slight pattern adjustments that need to be made, such as removing or adding a bit of material on the pattern to bring the dimensions into tolerance. This process may be repeated several times and is very common in the casting industry. However, there is a very important step that should be taken at this point: 3D scanning of the pattern equipment, which is the industry’s best practice.

Over time, the abrasive nature of sand-casting processes will erode the materials used in pattern construction. To make sure they can tell when the pattern is beginning to wear to the point that dimensional conformance may be an issue, the foundry should make a 3D scan of the pattern, its gating system, and all coreboxes. The pattern can then be rescanned on a regular basis to determine the amount of wear that has taken place. Checks are performed after a pre-determined number of molds or cores have been made. The buyer should work closely with the foundry engineering team to determine the correct inspection interval. 
Remember that sand abrasion will cause patterns to become smaller, affecting external dimension surfaces of the casting, while abrasion in a corebox will make the core larger, affecting internal passageways. Often, cores that are larger due to corebox wear will not fit correctly into the corresponding core prints, which will drive core location issues. Common sense tells us that wooden patterns will wear quicker than metal equipment. 

Pattern and corebox damage. Take a close look at your patterns and core equipment; you’ll notice they are heavy, and depending on their physical size, they can be cumbersome to move and store. Obviously, damage from handling can occur, and this needs to be repaired before the next run of castings. 

Most foundries perform a damage check before each production run of castings. This is normally performed by the foundry’s internal pattern shop, where skilled tradesmen review and repair the tooling as required. In cases where the pattern or corebox is severely damaged, the foundry may choose to send the equipment out to a commercial pattern shop for repair or replacement.
Common types of damage include scrapes and nicks to the pattern, cracks or breaks to risers–– which are often made from wood and therefore more susceptible to damage––and worn or broken corebox pins. What you should look for and what is considered an industry best practice is the use of a documented ready-to-run tagging and sign-off system that indicates when the equipment has been reviewed and is ready for use. 

How patterns are stored is another essential part of keeping your tooling in good condition. When you review the pattern storage area there are several key items to look for. A primary priority is that they should be stored in an enclosed area that has sprinkler system coverage in case of fire. Tooling should be stored on shelves or a rack system and should not contact each other. There should be a computerized inventory system (or manual card system) that clearly marks the storage location for each pattern and corebox. 

Costs associated with maintenance. The question you probably have at this point is, “Who pays for repairs?” There are several possible scenarios here. The cost for normal day-to-day tooling repair and upkeep is covered by the foundry. The cost to repair or replace severely damaged patterns or coreboxes are often negotiated between the OEM and foundry, depending upon the cause of the damage. And last, worn out tools would be replaced by the OEM.