In the world of metal castings, few topics generate more confusion––and debate––than casting quality expectations. Over years of mentoring casting buyers, designers, and quality engineers, one question continues to surface: What truly constitutes a defect? Let’s review the nuances of casting quality requirements, look at how vague specifications lead to inconsistent inspections, and review tips on how to communicate effectively with foundries to ensure prompt, accurate resolutions. 

To begin, let’s start with a basic understanding: To be rejectable, the casting must exhibit some type of feature that violates or falls outside a specification requirement. A common example would be a cast feature that is dimensionally out of tolerance to a drawing specification. These are most often easily measured by hand-held measuring equipment, gages, or coordinate measuring machines and are always clearly understood by inspectors and quality personnel. The important point to remember with this is that the casting is being rejected against a known specification noncompliance. If the defect in question does not violate a specification requirement, is it still a defect? 

This can often be a thorny question and comes up quite regularly during production. A good example of this is casting surface finish. I’ve encountered situations where an inspector quarantined several castings from a production run for having a rough surface finish and wanted to reject them. However, the specification stated something to the effect that “the casting must be finished in a manner that exhibits good workmanship.” In this case, the inspection criteria is unclear and requires a level of judgment that will vary from one inspector to the next. The answer in this type of situation is that the specification requirement must be changed to provide clear direction as to what is rejectable.

In practice, this example is a good illustration of why OEMs should follow industry standards such as ASTM, ANSI, or MIL specs whenever possible to clearly define what is acceptable and what is not. 

COMMUNICATE CLEARLY

So, let’s assume you have a clear issue with a casting that is rejectable. It’s important for you to understand that how you communicate this to the foundry can either provide you with quick resolution or can lead to lengthy discussions and disagreements. 

If your defect description says “Diameter is oversize” or “Casting has a defect on Surface A,” then you can expect there to be numerous questions from the foundry quality team. Your defect description needs to be complete and specific, so for the examples listed above, the descriptions should read something like: “Diameter 2.00 in. +/- .09 in. measures 2.126 in.––see measurement report attached;” or “Casting has a 12mm-long crack on Surface A that violates specification X123 section 7.2.1.” 
It’s obvious that the more detail you can provide in a description, the better off you will be. But there are also a few additional points of information and documentation you can provide to the foundry that will help them respond quickly and concisely. If possible, provide clear photos of the defect in question. Remember, a picture is worth a thousand words. It’s always good practice to include something that indicates scale in your photo, such as a metal ruler next to the defect. In some cases, a video can be a better indicator of what you are encountering.

If the foundry is located close to your facility, you may want them to come in and physically see the questionable casting in person. This is always the best option, especially when the defect is difficult to describe or there is an urgency that demands a quick resolution to the issue. 

I would be remiss if I didn’t include a few thoughts on issuing a Corrective Action Request (CAR). The completion of a CAR is a powerful tool that the foundry can use to eliminate casting defects, but its use needs to be applied correctly. This tool’s power comes into play when there is an issue that is systemic or encountered repeatedly, and the quantity or cost of affected castings is significant. The CAR requires time and analysis to be completed and implemented successfully by the foundry team. If you ask for these to be completed for one-off types of issues, you will ultimately bog down their system and cause ineffective problem resolution. 

Whether you’re on the shop floor or in the office, having a solid handle on casting quality expectations can save you time, money, and a lot of back-and-forth.