Metrology

HOW TO ENSURE TOOLS AND MOLDS BUILD PERFECT PARTS

3D scanners enable reverse engineering, digital archiving and spot inspection of molds, tools and dies.

At the beginning of a manufacturing process, a mold, die or jig is engineered according to a theoretical CAD model. The aim of this tooling, made precisely from the nominal model, is to produce parts that correspond to the technical requirements.

It turns out, however, that there are often differences between the theoretical model and the reality. Different phenomena interfere with the tooling, causing imperfections on the parts.

Adjustments and iterations are required to ensure the tools and molds, even if they correspond exactly to their nominal models, produce good parts that meet quality controls and customer demands. These adjustments and iterations can be simplified and accelerated thanks to 3D scanning and 3D scanning inspections.

A handheld 3D laser scanner, such as this blue light HandySCAN 3D BLACK Series, enables high resolution accuracy for digital archiving of tooling, jigs and dies as well as reverse engineering of automotive parts. Non-predictable phenomena

The reality of an industrial environment differs from the theory illustrated in CAD models. During the manufacturing process, several phenomena that are difficult to predict can occur. Spring backs when stamping a die, shrinkage when building a mold made of composite material, or thermal forces when welding two elements together are all good examples of phenomena that impact tooling precision. Nevertheless, modeling the removal of a composite resin, the spring back of a die, 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 the production requirements. But, in the reality of the industry, the aforementioned phenomena interfere with the molded or stamped parts. As a result, the parts do not meet the technical demands and must be adjusted, corrected and altered to pass the 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.

An iterative inspection process

The most commonly used method is to work on the part before adjusting the tooling. More precisely, this method involves producing a part, measuring it and analyzing deviations between the part and the CAD model. Hence, if we notice that there are some missing (or extra) millimeters in one place, we will go to the corresponding surface on the mold, die or jig to grind or add material. Thus, the iteration is performed on the

tooling after measuring the manufactured part.

Once this operation is completed, we restart the manufacturing process in order to produce a new part that will be measured to verify if there are any remaining deviations. This iterative process will continue on a loop until we obtain the desired part (i.e., when the manufactured part corresponds to its CAD model).

This iterative process of quality control requires a fast measuring tool to produce the next part without delay. In addition, 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.

The customer who buys the manufactured parts may also require a CMM report from the tooling manufacturers. Thus, a second measurement tool that will reduce 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.

Digital Archiving

Once we have a tooling that produces a certified part, the mold, die or jig can be scanned as part of the reverse engineering process to create a 3D model. All initial iterations then can

Metrology tools, like this portable MetraSCAN 3D CMM, allows for periodic quality control checks since parts can be measured directly on the production floor.

be saved for future productions. This means that if the tooling wears out and a new one is required, we can work directly from the 3D model that is known to build good parts. All initial iteration time is saved for future productions.

A mold, die or jig can also be reverse engineered using a 3D scanner. Depending on the application and scanning environment, one type of 3D scanner may be preferred over another. For example, a portable 3D scanner may be used to acquire the 3D measurements of a mold right on the production floor.

Once the measurements are taken, a post-treatment process must be carried out to finalize and prepare the 3D scan data to be used in CAD software. This post-treatment process, which involves segmentation, alignment and positioning the part in space, is normally done using specialized software. The result is a “clean” STL file. Once ready, the clean file can then be exported directly to CAD software, like SolidWorks, AutoCAD or Inventor, or into reverse engineering software and then CAD software.

A reverse engineering expert or industrial designer will remodel the part either “as is,” meaning with potential imperfections, or based on the original design intent (parametric reverse engineering). Modifications can also be made to the 3D model, depending on the application or need.

Once the 3D model has been generated and improved upon, if required, many reverse engineering teams produce a prototype using additive manufacturing techniques. The watertight CAD file is sent to a 3D printer for the prototype to be made. Experts can then assess if the 3D model is accurate or if additional changes and prototypes are required. Once the final 3D model is approved, it is sent for official tooling.

Periodic quality control

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

If the manufactured parts suddenly do not match the technical requirements, the manufacturing company will fall into an investigation mode, which will cause a lot of stress and uncertainty. With a portable 3D scanner, quality assurance will be 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.

Several phenomena specific to an industrial environment regularly occur on the production floor. They cause unexpected spring backs or shrinkage. Necessary adjustments are required to ensure that the tooling, even if it exactly matches its nominal model, produces good parts that meet quality controls and customer requirements.

These iterations are facilitated by 3D scanning, which, due to its speed, portability and versatility, is an effective alternative to a CMM that can remain free for final inspections. In addition, 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. |DE

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This article was provided by Creaform