|Different castings demand different sand for their cores and molds. Humtown Products used chromite sand in this sample, in order to ensure the casting chills faster in its mold. |
It’s hard to imagine a traditional foundry without a core room. Most foundries conclude that the best route to profitability is to produce highly engineered castings, and the designs that lead to the those castings typically feature some complex details, with internal cavities and passages that can only be achieved with reliable cores. Naturally, they further conclude that those cores have to be produced on site.
On the other hand, it’s possible that high operating costs, quality standards, and production difficulties will change these assumptions. Although most foundries continue to produce cores in-house, some already have concluded coremaking is no longer a necessary part of their operations. They realize they can outsource the process to specialists.
“For many foundries, in-house core production has been a sort of necessary evil that for several reasons is no longer practical,” according to Dick Holden with Advanced Sales Dynamics. “I think it’s fair to say that in-house core production is often a deterrent to productivity and profitability, and could be the source of considerable waste.”
Holden, an industrial consultant, explains that the foundries that are outsourcing coremaking have determined that their business is making and finishing castings — so that investing in, operating, and maintaining core rooms adds unnecessary overhead costs to their enterprises. For example, he points out that the core room consumes energy, compressed air, air scrubbers, and floor space. Coremaking also costs foundries in terms of raw materials, as well as periodic charges for capital equipment. Obviously, there are labor costs involved in operating a core room, too.
“If you want to learn the true costs of cores, you can get those from an outside core making specialist,” Holden adds. “Not only do they track overhead completely and accurately, but they also help to keep the outsourcing of cores competitive and affordable. Just considering the foundry’s unidentified overhead, it is highly possible for them to lower core costs by going outside to a core specialist.”
In addition to cost, consider the foundries’ quality concerns. While many of the operations that produce their own cores have experienced technicians (or even craftsmen) available, those production skills are among the many talents that metalcasters today find hard to develop and replace. Also, producing cores on site may be (for some operations) an area where qualitycontrol measures cannot keep up with cost-saving objectives. They may not realize the best way to source the optimal silica materials, for example.
In this context, Holden points to Humtown Products, a core and patternmaker in Columbiana, OH, that uses all virgin sand (lake sand, roundgrain silica sand, chromite sand, olivine sand, zircon sand, and others on request) for consistency in quality and composition.
“Many foundries recycle sand for use in making cores,” Holden explains. “So, there might be a mixture of fine and coarse materials in it, or it might be coarse this time and fine the next. Without consistency your core results, and possibly casting results, will vary all over the place.”
He adds that it is important to use different sands for certain types of castings, including the many grades of iron and steel, steel alloys, copper, brass, zinc. For example, manganese steel castings call for an olivine sand with the right pH properties.
“If you want the casting to chill faster in the mold, you should use a chromite sand, which comes from Africa,” advises Don Covert, Humtown’s Technical Sales Representative. “Zircon sand is more for steel castings, and much of that material comes from Florida. Not only do the sand types and quality make a difference, but also the types of powder additives. If you want to capture nitrogen out of a certain kind of steel, you should add the black iron oxide, spherox, or an appropriate powder additive to the sand and blend,” says Covert.
Time considerations — By definition, cores must be accurate to the finished casting design. For example, oil pump passages for jet engines have very fine and small passages throughout the casting. If the core is not prepared properly, including the right sand mixture, flaws such as “burn in” can result.
“It can be very challenging to correct that kind of problem,” Covert reports. “The effect of burn-in is like metal spikes protruding into the casting passages. These will restrict the flow of the pump, and when they do a flow test on the casting, it will fail the test. Or, if you get something with too high of a resin, you can have gas pockets in the casting, which can result in leakage. If you have those types of defects in an internal passage, it can be difficult to remedy them.”
Holden adds that many cores produce castings with excessive stock that require unnecessary machine time. On the other hand, cores that produce castings with too little clean-up stock for machining usually end up wasting valuable machine time and the castings ultimately have to be re-melted.
“If those castings are tested after machining and the flaws are undetected, then both the machine time and testing are wasted, plus delivery may be thrown off schedule,” Holden says.
According to Covert, Humtown checks the quality of its cores very carefully, and because the firm also has longtime pattern design and fabrication capabilities, worn or out-of- spec tooling can be quickly and accurately corrected, a significant value-added service to foundry and OEM customers.
Leveraging capacity — One of the main reasons metalcasters choose to contract their coremaking is faster turnaround time. While some may outsource cores with difficult configurations, Covert says they may be holding back their throughput inadvertently by continuing to make simpler cores in-house.
“Some foundries struggle to make 10 sets of cores per day,” Covert says, “where an outside core specialist like Humtown can produce 100 sets of those same cores every hour.” He says that turnaround time for an core specialist may be a matter of days to two or three weeks, compared to several weeks or even months for the in-house core room.
The outside specialist are accustomed to earning foundries’ business for large-volume coremaking, but Holden says there are instances when a metalcaster should assign even smaller order to a contractor. As a consultant, he points out that the space occupied by a core room can be put to more profitable use, making more castings for example, or installing finishing equipment to increase their value-adding potential.
Compliance issues — A final consideration is environmental regulation. All coremaking operations are subject to EPA requirements, including some that are very stringent about clearing the air within the department or building because the catalysts used to cure the cores are considered hazardous. Some specialty coremakers may be required to seal the entire building in order to recycle the air. Foundries that produce cores cannot seal the building, so they may be required to have air scrubbers dedicated to each core machine. Even with this investment in equipment, cores will emit gas for periods up to 24 hours, exposing the area to the catalyst, and subjecting the operation to EPA-compliance issues.
“Foundries already have enough air quality issues to deal with,” says Holden. “When you consider the capital investment required for air scrubbing equipment, the many months it takes to get those systems installed, approved, and permitted, plus the tasks of dealing with continual monitoring, the already marginal benefits of having an in-house core production facility become all the more problematic.”
Laempe Buys Hottinger Sales/Service
Laempe & Mssner offers planning, construction, assembly, and manufacturing of metalcasting technology, including core shooters, gassing systems, and sand preparation equipment. The group’s North American equipment sales, parts, and service support are coordinated by Laempe Reich.
“With these steps, we will charge existing capacity more efficiently and achieve advantages in Research & Development and Purchasing, as well as in Production,” explained Werner Mssner, the group’s principal shareholder. “Furthermore, we will optimize our worldwide distribution network to boost our position as global market leader.”
At the same time, Laempe & Mssner has formed a strategic alliance with Rperwerk RW-Giessereimaschinen GmbH, to develop, manufacture, and distribute of core-related equipment. Rperwerk supplies casting machinery as well as core shooters. In August, Mssner Vermgens- und Beteiligungsgesellschaft GmbH, the principle shareholder of Laempe Mssner, purchased Rperwerk.
“Above all, Laempe & Mssner and Rperwerk will collaborate in developing new machines and systems, but also in purchasing and sales. Furthermore, Laempe & Mssner gets access to valuable know-how in the field of low-pressure gravity diecasting,” according to Mssner.