Six common quality control problems in shoes and how to fix them

Just as with any manufactured product, shoes can suffer from problems stemming from their manufacturing. However, with proper actions, you can minimize or eliminate these problems altogether.

Here we look at six of the most common quality problems that occur during footwear manufacturing and the steps you can take to prevent poor quality goods from reaching the marketplace.

It’s important to note, too, that while the defects outlined in this article are important, other testing—to check for hazardous material components, color fastness, and adherence to safety standards—should continue to be a part of your overall approach to quality control. A comprehensive supply chain partner will be able to recommend and deliver the tests and inspections necessary to ensure your products are safe, meet all local and federal regulations, and look and function the way your customer expects.

Issue 1 - Metal contamination and sharp points

The manufacturing of shoes often requires stitching, as well as the use of nails and tacks. Needles can break and remain in the shoe, while nails and tacks may be improperly flattened, leaving sharp points in the shoe. Any such foreign metal objects can cause serious injury to the customer.

If the shoe contains no metal parts by design, you can use a metal detector to detect any foreign metal objects.

However, if the shoes do contain metal by design, then regular quality control inspection must be carried out to ensure that the shoes are made correctly, with no sharp protruding points that could harm the customer.

Clearly, this is among the most dangerous of defects. Metal contamination can result in consumer injury, which could have devasting effects on the victim, and the companies responsible for the product’s manufacture could face lawsuits.

Many of the ISO testing protocols would prevent metal- and point-contaminated products from reaching the marketplace, but only if you’ve partnered with an expert quality control company that knows which tests and inspections are required.

Issue 2 - Excessive glue

The various parts of shoes are generally stitched and/or bonded with glue. If the glue is applied sloppily or excessively, it will flow out of the joint, making an ugly defect that’s visible to the client.

If appearing in a noticeable area, this type of defect can ruin the shoe’s appearance, and your customer is very likely to return the footwear for a refund.

However, this defect is easy to eliminate because:

• You can modify your manufacturing process to ensure that glue is applied correctly, and in the right amount.
• It is possible to fix the issue at later steps of the production process.
• The right quality control program ensures this defect doesn’t reoccur.

Strong quality control protocols can ensure excessive glue isn’t a problem for your footwear. The International Organization for Standards’ ISO/CD 20537.2 establishes the language necessary to visually inspect footwear for this sort of cosmetic quality problem. Your lab and quality control partners should be familiar with these guidelines.

Issue 3 - Weak bonds

Weak bonds occur when two bonded or glued surfaces, usually the sole and the upper, either come apart after a short period of use or aren’t bonded when the product leaves the factory. It can be caused by:

• Insufficient or incorrectly applied glue.
• Wrong type of glue being used.

This type of defect will also prompt your customer to return the shoe.

Fixing this defect is usually as simple as inspecting and adjusting the manufacturing process to make sure the correct glue and application technique are used, but only proper testing will reveal this defect’s presence. Unlike excessive glue defect, weak glue bonds are unlikely to be noticed during visual inspection.

Several ISO standards dictate testing practices for the strength of the glue used to bond different pieces of footwear, including ISO 17708:2018 and ISO 24266:2020. Your quality control expert will know which standards and tests apply to the specific kind of footwear you’re manufacturing.

Issue 4 - Size

All shoes are manufactured to standard sizes, and the customer expects the physical dimensions of their shoe to correspond to the stated sizing. A shoe can be incorrectly sized for two reasons:

• The tooling is worn out and no longer has the correct tolerances.
• Mistakes in handling and packaging.

The second reason is far more common than the first. To ensure that your sizing is accurate, you must inspect your shoes prior to shipping, and if any issues are found, you should investigate your packaging and shipping areas to find the source of the problem.

Comparing goods to the golden sample, again, will help maintain consistent production and sizing. Adherence to your manufacturing standards can only be expected through regular inspections by third-party experts with access to the necessary testing facilities.

Issue 5 - Asymmetry

When parts of a shoe are assembled into a whole, all parts must line up correctly. In a typical shoe, the left and right halves are joined in a seam that should follow a perfectly straight centerline running the length of the shoe.

Any seam that is crooked or runs parallel to this line is a defect that may result in the customer returning the shoe.

While small discrepancies might not come to the attention of a lot of everyday shoe buyers, so-called “sneaker heads” (collectors of athletic shoes) will be looking carefully to ensure their shoes are perfect. They have a powerful presence on the internet, and their complaints could damage the brand’s reputation. The same holds true for the other cosmetic defects you might encounter with your footwear manufacturing.

The easiest way to detect these defects is to compare the shoe to the perfect sample of the same shoe model (the so-called “golden sample”) and to its corresponding left/right partner. Your third-party quality control partner will develop procedures—checklists and “what to watch for” guidelines, for example—that help ensure your manufactured products look like the matched pair your customers expect.

Issue 6 - Scuff marks

Scuff marks are the marks left on shoes, particularly leather or glossy footwear, after they have been handled carelessly or improperly packaged for transportation.

Once you discover scuff defects in your products, you will need to investigate which stage of the production process created them and correct the problem accordingly.

ISO standards outline the sort of abrasion resistance manufacturers should require, and third-party inspectors can ensure that the production processes are taking the correct steps to avoid the rough handling that often causes scuff and abrasion defects.

Eliminate defects with testing and continuous quality inspections

None of the defects listed above can be fixed unless they have first been spotted, which can only be done with a thorough testing and quality inspection process.

The reverse is true: if no one is inspecting your product, they will almost certainly leave the factory with a number of defects, resulting in product returns or even costly recalls.

Here at QIMA we provide best-in-class physical and chemical laboratory testing for footwear. We test the physical characteristics and chemical composition of your shoes to make sure they match the quality you demand and pass all required product safety regulations.

We can also provide a continuous inspection service for your entire production process: from initial batch to packaging and shipping. After all, your carefully designed production processes are useless unless you make sure your workers are actually following them.

With offices in over 85 countries, we can have a qualified QC inspector onsite anywhere in the world within 48 hours.

Get in contact with QIMA today and find out how we can help you manufacture perfect shoes.