How OEMs Benefit from State Line’s In-House Testing
State Line Foundries conducts a variety of tests internally on the iron castings it produces. For an operation of its size, this makes it unique. Many of its competitors outsource some or all their testing.
Why invest in providing these capabilities in-house? Because State Line is committed to providing its customers with exceptional outcomes, such as faster throughput and exceptionally high first-pass yield. Simply put, mediocre outcomes are NOT “good enough.”
“If we spot trouble or even a sign of trouble, we search until we identify the cause,” says Sean McGough, quality manager at State Line. “We are not shy about scrapping castings internally. We would rather scrap something here than roll the dice to see if the customer finds it. We’ll fix the problem. Not all foundries are willing to do that.”
It’s uncommon for a foundry of State Line’s size to handle so much testing internally. “When we have customers visit, they always mention that they like that we do so much in-house,” McGough explains.
State Line’s internal evaluations include chemical, mechanical and soundness verification, as well as internal dimensional layout.
Chemical checks are run while the iron is melting and afterward, to ensure the material recipe for each part is accurately followed.
With these analyses, all raw materials are placed in the furnace using induction melters. When the melt reaches 2500º F, a sample is run through a spectrometer – a tool that uses wavelengths to measure the elements contained in the iron.
Mechanical processes include checking whether a casting has the desired tensile strength and hardness. “We don’t want it too soft or too hard, so when the customers machine it, it has the qualities they need,” McGough clarifies.
State Line produces castings from gray and ductile iron. Gray iron mechanical assessments include tensile strength and hardness. Ductile iron parts receive those tests, plus evaluations of yield strength (how much force is needed to break the part) and elongation (how far the part will stretch without breaking).
During this test, a casting is cut with a bandsaw. “It gives us the ability to see, at a sub-surface level, what the issues are,” McGough states. “Soundness verification is a good option if there is a belief that shrink porosity may occur. It’s a way to confirm what the mold flow analyses may be showing us.”
Internal dimensional layouts
These reviews are used to determine if the customer’s tooling produces a casting that matches its print.
With internal dimensional layouts, State Line quality assurance workers use a coordinate measuring machine (CMM) to check specific points on the casting. Software overlays the dimensions of the actual casting with the customer’s print to identify areas where it may be out of spec.
A discrepancy is usually the result of old or flawed tooling. The customer can then opt to rebuild the tool or simply live with the discrepancy. “It’s an opportunity for the customer to make that decision early in the production process,” McGough offers.
McGough explains that the internal reviews – chemical, mechanical and other types of tests – have a variety of goals. The mechanical and chemical exams are “just making sure we’re meeting customers specs and requirements.”
“The additional tests help determine if there will be an issue with the casting – before it gets to the customer’s machine shop. These are preventive measures that stop a bad part from reaching a customer.”
The benefits of internal testing
State Line has found several key advantages to handling the majority of its casting tests internally.
Running tests in-house is often substantially faster than outside testing. That’s especially important for tight timeframe projects where every hour counts.
State Line also gets instant results with chemical checks. Compare that to shipping material to an outside lab and then waiting another day or two for results.
With mechanical analyses, the casting must cool for a day, but the internal exam can be conducted immediately after – usually within 24 hours. If the evaluation is conducted externally, the iron must cool for a full day before it can be shipped.
“By handling these verifications internally, we avoid having to pack and ship the part, then wait for it to be tested by an outside firm,” McGough details. “Because we do it right away, we can make any adjustments immediately. That helps us keep the process moving.”
State Line retains results from all its internal tests, which is a considerable amount of data.
“Having that internally gives us the ability to track trends,” McGough says. “We can take as many samples as we want. We’re not shy about it.”
These reviews can lead to minor adjustments that, if left unchecked, could evolve into something bigger. “If, for example, we see a steady reduction in elongation, if we’re meeting the spec, but it’s consistently lower, we can make adjustments to alloys so we stay perfectly on target,” McGough stresses.
Hardness and tensile strength trends can also be evaluated – and adjusted, if necessary.
Internal testing is a key reason why State Line maintains an exceptionally high pass yield.
“We verify that soundness and hardness are in the right range,” McGough asserts. “When the casting gets to the customer, there is less of a chance of a problem. We do everything we can to catch an issue that could lead to a part needing to be scrapped.”
When needed, State Line also expedites external assessments.
“Some casting tests require a great deal of expensive equipment and expertise that isn’t practical for us to acquire, given the lack of regular use,” McGough explains.
In those cases, State Line coordinates the external reviews, including X-rays that examine shrink porosity, voids and slag.
“Sometimes we’ll X-ray a part with a critical area that appears more susceptible to defects,” McGough summarizes. “For example, if a casting contains two heavy sections with a light section in between.”
External testing efforts also include mag-particle and fluid penetrant inspections, which use a dye to uncover cracks.
A more intense dimensional verification can also be conducted externally. It measures part dimensions with a laser instead of a CMM arm for greater accuracy.
The right team is key to casting success
State Line has the equipment and personnel necessary to run the internal tests. The “melt lab,” where chemical adjustments are made, is run by staff with decades of experience. That’s also the case in the finishing department, where hardness is analyzed.
Although the equipment is not particularly high-tech, State Line has been quick to modernize whenever possible.
“We use some modern technology, including a digital upgrade on the tensile machine,” McGough details. “There are new technologies, to a certain degree, but the basics of the sand iron industry haven’t changed for a century.”
To State Line, that means investing in technology when it can and employing personnel with the experience, knowledge and commitment needed to get the most out of it.
And, of course, it means using the data gathered by testing to ensure that State Line can provide customers with the best possible castings.
“You have to act on the data,” McGough stresses. “You have to be willing to scrap a casting – sometimes even when it’s within the requirements – to make sure the customer doesn’t have any problems down the road.”
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Tags: dimensional layout, First pass yield, hardness, mechanical assessment, tensile strength, Testing