Creation of the Perfect Mold

One of our prestigious customers, a mold-making company, had a small dilemma. Their customer, who is a plastic chair molder/manufacturer, wanted a special mold for a plastic chair that included the Texas map on it as well as a series of patterns and a rose shape. But, since the cost of such a mold is substantial, they wanted to build just one insert which could be changed in the mold, so that the mold could become multitasking and produce more than one kind of chair. Furthermore, they had just provided a handmade sketch for the mold insert. Thus, an ideal art-to-part strategy was employed to handle the situation.

Following this, the sketch was used as a basis by an experienced patternmaker to make a full-scale clay model that represented the actual mold insert with the proper dimensions to fit in the mold.

First Steps

Applications 3D was hired to reverse engineer the clay model into a high-quality, workable CAD file. Firstly, an accurate 3d Scanning or digitizing of the model is needed for reverse engineering. This was achieved using state of an art Steinbichler Comet 75 white light scanning system. Since this model contained some very fine features, the Comet 75 was an ideal machine to digitize it. Furthermore, the Comet 75 measures 420,000 XYZ points in a 2-inch by 3-inch area. That meant a lot of points were to be collected over the whole model during the process.

Lastly, after the scanning was completed, the scan data was processed to form into an STL file, which essentially is a large mesh of 3-sided polygons or triangles.

During this process, the data was optimally reduced or “decimated “ to intelligently reduce the number of points on the planar areas and keep a high number of points in the areas of high curvature or small features. Thus, this whole process was done on Polyworks, a state-of-the-art point processing software.

Creation of the Mold

The STL file was then used to manually convert each feature and shape into a high-quality, high-accuracy surface. This engineering-grade surfacing was then performed on Imageware, one of the world’s best freeform surface modeling tools.

Then, not only did the surface model look good, but it also conformed to the stringent accuracy and continuity requirements of the downstream mold designing and machining software.

The IGES surface model was used to program the cutter paths for the CNC machines and was eventually used to machine the insert successfully by our customer. Finally, it fits well in the mold and is now mass-producing the custom chairs!