Modern manufacturing is global. One company’s product—like a sedan, a tractor, or an airliner—may be made of materials from dozens of countries and assembled in dozens more. No matter how many smaller contract manufacturers are involved in creating a final product—whether one or two hundred—only one company is ultimately responsible for the final project.
The original company—the one that commissioned the product design and contracted the smaller manufacturers—must guarantee the safety and efficacy of the final project. So, when subcontracting the assembly of product components out to third-party or contract manufacturers, you must follow effective procedures to ensure product quality. Companies should provide their contract manufacturers with torque specifications for all critical fasteners and confirm that their torque values have been adhered to upon receipt of the components.
Specifying Torque Values for Contract Manufacturers
Every fastener has an ideal torque range, which depends on the load it must carry and its fastening materials. Torque is radial force, or force applied in a circular motion. Applying torque to a threaded fastener, like a screw or a bolt, compresses its threads, thereby creating tension that holds the fastener and substrate materials together. Too much torque and the fastener or substrates can warp or deform and will be more likely to strip or tear loose. Not enough torque and the fastener won’t have enough tension to hold or might shear. This means it could work itself loose under stress.
When critical fasteners fail, they can cause product damage or failure and can create dangerous situations. Non-critical fasteners, while not as directly dangerous, still increase the stress on all the other components in a product when they fail, creating the potential for product degradation and cascading failures. So, in manufacturing, it’s essential to know how much torque a fastener needs and to use a tool that can apply precisely that amount.
When subcontracting the assembly of various product components, the company that designed the product is responsible for knowing and communicating product specifications, including torque values. The product’s design team should identify the torque ranges for all critical and non-critical fasteners and communicate them to the contract manufacturer.
There can be issues when working with foreign companies, which typically use one or several foreign languages. Proper translation, preferably by a native speaker, is essential for clear communication. In addition, foreign companies are more likely to use metric measurements than standard American measurements. So, companies must use one of the following strategies:
- Design their products using metric measurements.
- Convert their measurements to metric for the contract manufacturer.
- Require the contract manufacturer to work with American standard measurements.
Regardless of your chosen method, specifying the torque values contract manufacturers must follow is not enough. It’s also essential to verify that they have been adhered to upon delivery before installing their components in the final product.
Verifying Torque Values from Contract Manufacturers
It’s irresponsible for a company to install third-party components in their products without verifying that product specifications, including torque specifications, have been followed. At the same time, it’s burdensome and inefficient to test every single screw and bolt in every component delivered.
Instead, companies can verify torque using a two-tiered approach. The first tier involves reviewing manufacturing data produced by the contract manufacturer. The second consists of testing a statistically significant amount of fasteners upon receipt of the finished component.
The first tier requires good communication between the parent company and the contract manufacturer. The contract should contain a clause concerning how to collect and report fastening data. The contract manufacturer can collect data about torque delivered during production using a screw counter, DC control system, or another automated data collection system.
If the contractor lacks these capabilities, they can still provide quality assurance verification torque analyzers and sensors to verify and record torque values. Quality assurance engineers should designate the percentage of products they must test, and guidelines for data reporting should be specified and communicated. Your contract should require proper reporting measures.
Once the product component has been delivered, it’s up to the original company’s quality assurance team to verify that torque standards have been met. This should include assessing the contractor’s reports and physically verifying torque values for critical fasteners. Physical verification can be accomplished using torque measurement instruments. If discrepancies arise between the torque values reported and those observed by quality assurance personnel, you should complete further testing before installation.
No matter how many contract manufacturers contribute components, only one company owns the final product. It’s up to that company to do everything possible to ensure its products are safe and reliable. To ensure fasteners are correctly installed, the original manufacturer must specify and verify their contract manufacturers’ torque values. Clear communication and proper diagnostic tools can prevent accidents, and revenues can rise.
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