I had referred to CTQ or critical to quality dimensions in one of my last blogs. These are the dimensions of a manufactured component that absolutely must meet the desired specifications. At Sourcing Allies, we work with your factory in China to ensure that they do.
In this blog, I will briefly talk about the extent we go to ensure that the critical dimensions are met. One of the ways we do this is by designing custom test equipment.
Take this recent example. We were working with a Chinese factory to manufacture a little steel shaft – an inch long and 2 mm in diameter– which fits inside a gearbox. This pin had a tiny slot at one end, and it was critical that it was the right shape because the component would have been useless otherwise. Each one of these pins had to be checked to see if it had the right structure – with the little slot at the end. But the challenge, from a quality control standpoint, was that the pins were being sent to our client in batches of 105,000.
Regardless of the AQL (Acceptable Quality Limit) used, manual checks (especially on such a small part ) are never 100% effective because no matter how many times you perform the check there is always the possibility of a proportion of bad parts getting through due to general eye fatigue and possible misses. This really bothered me and pushed me to start playing with designs of an electronic box that could do the job instead.
Simply put, it is a box containing sensors and supporting electronics. The idea was that if you pushed the pin into the box one by one, the light on the box would indicate whether the pin had the required structure or not. When the green light came on, it meant that the pin was good to go, while a red light meant the pin had to be discarded. This not only helped us to remove the possibility of human error, it sped up the quality control process considerably too.
Other custom tests
This isn’t the first custom test equipment we designed. We have done simpler ones in the past. For instance, we have manufactured products that are essentially pieces of cast iron with holes in them. To test that these parts were uniform across all batches, we designed little insertable test jigs that could be pushed into the holes. The jig would slot straight in if the holes in the metal part aligned correctly. But if the holes were not right, they would not go in.
We make these little test jigs and gauges all the time for our clients. Often, it is in collaboration with the factory where we design the equipment and work with them to incorporate it in their quality control process.
Do we use these tests on all parts?
It depends on the complexity of the part, the batch volume, and the manufacturing process used among other things. Often, custom test equipment and jigs are very helpful and needed. In those cases, we apply it in collaboration with the customer and the factory.
Test equipment and quality checks are important components of manufacturing. However, we focus most on the manufacturing process itself, meaning that it is always best to make the part correctly right from the beginning. That said, quality checks are always needed for verifying that quality expectations are met
