Cavity mold continues to wear, product quality soon follows

The glass mold cavity was scanned on the Surveyor WS-2030, a dual-purpose Wenzel CMM with Laser Design 3-D laser scanning technology

A leading North American manufacturer of glass tableware noticed a decline in the quality of a glass mug it produced because of wear in its cavity mold. The mugs were no longer to spec with the design model and the company wanted to inspect the cavity mold to determine where the errors were occurring in the as-built product compared to the as-designed model so corrections could be made. 

The company needed to have the mold scanned and an investigation performed as quickly as possible to avoid lengthy delays in their production line schedule. The cavity mold was sent to GKS Inspection Services in Minneapolis, MN to perform the inspection. 

Scanning For Cavities

At GKS, the cavity mold was scanned on the Surveyor WS-2030 (20” x 30” x 20” work volume), a dual-purpose Wenzel CMM with Laser Design 3-D laser scanning technology. The laser was mounted on the CMM’s programmable Renishaw PH-10 (CNC) indexing head, which positioned the laser probe around the heavy mold to capture the geometry from several different orientations.

The Renishaw PH-10 head is used to scan a part or tool from a variety of orientations without having to move the part. The scanning program takes only a couple of minutes to set up and runs automatically unattended.

Typically, laser scanning is ten times faster than the most advanced touch probe speed, because lasers are able to collect over 75,000 3-D coordinates per second. Laser scanning is ideal for improving part quality because the whole surface of an object is scanned, not just landmark dimensions, so free-form surfaces and irregular shapes are easily captured.

The mold was scanned completely in a few minutes outputting millions of coordinates defining the complete shape of the mold cavity.

The mold was scanned completely in a few minutes outputting millions of coordinates defining the complete shape of the mold cavity. The scanner accuracy was 0.001” and Geomagic Qualify inspection software was used for processing the data.

For fast turnaround inspections like this mold project, the inspection report can be set up to yield the desired information during the scan process. The data is processed for the customized inspection report while the laser is still scanning so the report is ready less than one minute after scanning is complete. The total time from start of scan to final report with 3-D color error map and all the desired dimensions reported was less than 12 minutes.

Filling Cavities

After the cavity mold was scanned, the error report was generated in Geomagic Qualify, clearly showing the discrepancies in the as-built/as-designed versions. The out-of-spec worm surfaces on the mold were very apparent in the scan data.

The glassmaker then used the point cloud data to quickly rebuild the surfaces to their original surface area and volume conditions using Geomagic Studio reverse engineering software.  They added material where the abrasive glass molding process had worn down the metal, changing the shape of the molded product.

The cavity shape information was registered to the mold’s tooling holes within 0.0001”.

The cavity shape information was registered to the mold’s tooling holes within 0.0001” using the ultra-accurate touch probe measuring capabilities within the same coordinate system as the laser scan data. The ultra-precise touch probe measuring capability combined with the high-speed laser scanning technology make this process fast, automated, and user-friendly.

Methods previously used to accomplish the same results were manual and labor intensive, time consuming, operator-dependent, and difficult to repeat from operator to operator. The complexity and difficulty of the process usually led manufacturers to completely remanufacture molds instead of reworking them, which is much less expensive. By using the 3-D laser scanning process described above, reworking the molds can be completed in a fraction of the time.
  
Laser Design’s integration of the SLP laser scanning probe technology with the high mechanical accuracy of the Wenzel CMM touch probe brings the best of both worlds to one measuring system. Existing Wenzel CMM users will be amazed at the time and cost savings and the superb accuracies of using non-contact 3-D laser measurement with Wenzel’s laser scanning partner, Laser Design, Inc.