Tech Focus: Quality Control

Building perfect parts

| Author / Editor: Jérôme-Alexandre Lavoie / Steffen Donath

The reverse-engineering of a tooling.
The reverse-engineering of a tooling. (Source: Creaform)

Different phenomena can occur, causing a finished product to divert from the original model. Iterative processes of quality control are used to make sure that the parts live up to the standards.

At the beginning of a manufacturing process, a mould, dye or jig is engineered according to the theoretical CAD model. The aim of this tooling, made in the exact form of the nominal model, is to produce parts that correspond to the technical requirements. Different phenomena can interfere with the tooling, however, causing problems and imperfections on the parts. Adjustments and iterations are therefore required to ensure that the tools and moulds, even if they correspond exactly to their nominal models, produce good parts that meet quality controls and customer demands.

The reality of an industrial environment differs from the theory illustrated by CAD models. During the manufacturing process, several phenomena that are difficult to predict can occur. Spring-backs when stamping a dye, shrinkage when building a mould made of composite material, or interference from thermal forces when welding two elements together are all good examples of phenomena that can impact tooling precision. Nevertheless, modelling the removal of a composite resin, the spring-back of a dye, or the impact of a weld remains difficult, complex, and expensive.

Initially, the tooling is built according to the theoretical model, which is developed to create manufactured parts that meet production requirements. However, industrial reality is that the aforementioned phenomena often interfere with the moulded or stamped parts. As a result, the parts do not meet the technical demands and must be adjusted, corrected or altered in order to pass quality controls. Starting with nominal models is, of course, a good first step, but let’s not forget that what manufacturers want is not so much a perfect tooling, but good parts that meet technical requirements and customer needs.

Iterative process

When unpredictable phenomena alter manufactured parts, an iterative process of quality control commences. The most commonly used method is to work on the part before adjusting the tooling. More specifically, this method involves producing a part, measuring it, and analysing deviations between the part and the CAD model. If there are some missing (or extra) millimetres in one place or another, the corresponding surface on the mould, dye or jig must be worked on in order to grind or add material. Thus, the iteration is performed on the tooling after measuring the manufactured part. Once this operation has been completed, the manufacturing process is restarted in order to produce a new part that is then measured to determine whether there are any remaining deviations. This iterative process continues on a loop until the desired part is obtained (i.e., when the manufactured part corresponds to its CAD model).

This iterative process of quality control requires a fast measuring tool for producing the next part without delay. Additionally, the measurement technology must have the capability to be used directly on the shop floor and the capacity to measure all types of sizes, surface finishes and geometries. 3D scanning technology, with its speed, portability and versatility, enables production teams to make the required corrections to the tooling quickly and effectively.

CMM Report

It is not unusual for purchasers of manufactured parts to request a CMM report from the tooling manufacturers. Thus, having a second measurement tool that reduces the CMM workflow is an important benefit for manufacturing companies. With a portable 3D scanner, they can measure the majority of the entities and multiply the intermediate inspections, preserving the CMM for the final inspection and report generation.

Once a tooling for which the CMM has certified the manufactured parts exists, the mould, dye or jig is scanned for reverse engineering. This way, if the tooling wears out and a new one is needed, a new nominal model is not required for the next manufacturing process. Instead, the model that has proven to create fitting parts can be worked with. The original iteration time is thus saved for future productions.

Instead of measuring a part out of 50 or 100 with the CMM, 3D scanning technology makes it possible to conduct periodic quality controls. Fact is, a portable 3D scanner is beneficial for the mould and tool industry because it increases inspection sampling and saves time by measuring parts directly on the shop floor of the production site without having to bring them to the CMM. Thus, periodic quality controls ensure that the production remains in control and delivers parts on time.

If manufactured parts suddenly do not match the technical requirements, the manufacturing company falls into investigation mode, which will cause a lot of stress and uncertainty. With a portable 3D scanner, quality assurance is able to intervene without further delays and find the root cause by acquiring a lot of data quickly and investigating directly on the shop floor.

Conclusion

Several phenomena specific to an industrial environment regularly occur on the production floor, causing unexpected spring-backs or shrinkage. Necessary adjustments are required to ensure that the tooling, even if it matches its nominal model precisely, produces good parts that meet quality controls and customer requirements. These iterations are facilitated by 3D scanning, which, thanks to its speed, portability and versatility, is an effective alternative to the CMM, which thus remains free for final inspections.

What’s more, 3D scanning offers the possibility of reverse-engineering the tooling that produces the good parts, performing periodic quality controls and quickly resolving unexpected issues that may occur at any time.

Creaform will also be at Formnext. The company can be found in Hall 12.1, Booth E110.

Scanning for the metalworking industry

EMO 2019 / Creaform

Scanning for the metalworking industry

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