Canadian Plastics

Lightning-speed lasers

The use of laser technology in the precision metal cutting industry is becoming more common. State-of-the-art laser machines were featured at this year's IMTS show in Chicago with applications seeming...

December 1, 2000   Canadian Plastics



The use of laser technology in the precision metal cutting industry is becoming more common. State-of-the-art laser machines were featured at this year’s IMTS show in Chicago with applications seemingly limited only by the manufacturer’s and end-user’s imaginations.

One of the highlights of my career was the opportunity to apply the technology of laser digitizing to the fabrication of electrodes. Laser digitizing is a three-dimensional process in which a laser beam is used to take measurements of a part, master, die, etc. to generate a database of geometric surface information. In comparison to conventional methods, laser measurement is more flexible and accurate; the data it generates can be used to reverse engineer, transfer information to a CAD/CAM system or obtain product intelligence. The more complex the detail on the model the greater the value of the process.

Preparation crucial

The process has four main steps. The first step is model preparation. The model is cleaned, located on a CNC, jig, fixture or some other device so that it cannot be moved during the digitizing process. Once the model is fixed, any deep holes in the part should be filled with plasticine so that the model’s surface is intact.

The next step is the registration of the data. At this point the digitizer is set up to identify a zero point in the X, Y and Z-axis, as well as the perimeter of the area digitized. At this stage, the operator needs to decide the density of the number of points taken, the direction of digitizing, and degree of detail needed. Once all the variables have been established the digitizer can then begin collecting the surface data through unattended operation.

The third step involves the processing of the collected surface data. In this stage the raw information may be converted to an IGES file and sent to a CAD/CAM system for reverse engineering, scaled for shrink, expanded, rotated, plotted, mirrored, translated, male to female conversion or vice versa, compensated to create a tool path and/or any combination of these required to achieve the end results.

The fourth step is the creation of tool paths and the milling of the die, electrode, part or mold. It can often be run unattended depending on the material you’re cutting, the depth you have to go, and the type of machine you have. The operator can create roughing tool paths, semi-finish, and finishing in a variety of patterns across the electrode, die or part

What advantage is a laser digitizer to your company? The table at left compares the time it took to make electrodes or cores and cavities from models using conventional and laser-based technology. The parts were rich with intricate detail and scrolling. In both cases laser digitizing helped reduce mold lead-time, and freed manpower. Once the part database gets generated and processed for tool path creation, apprentices can often be assigned to support the project saving on the cost of labor.

In comparison to a conventional CMM, laser digitizing is superior when working with soft material that could easily be distorted by a touch probe. Because the laser uses a beam of light to make measurements, no direct contact is made with the object being measured. Any material could be used provided it did not react to the power of the laser.

Set up tips

When working with a laser, set up the model in such a way that a datum point or surface can be established. Shiny surfaces may cause the beam to be reflected so it is recommended that the surfaces that are to be digitized be painted white. Clean the part or model to remove fibers, dust and grains. (The laser’s accuracy is in the millionths). Fill all deep holes with plasticine that would allow the beam to disappear. (Note: I found Crown FaultFinder Developer works great to coat the digitized surface with a white non-damaging layer that can easily be removed after.)CPL

Mark is the chair of manufacturing and transportation at St. Clair College in Windsor, Ont.

Part (electrode) Conventional Time to make Laser technology Time to make
technology electrode or cut electrode or cut
core and cavity core and cavity
Antique door Make model 110 hours Laser digitize 50 hours
handle Manual Deckel CNC machine
Hand work to Min. bench work
finish
Action figure Make model 155 hours Laser digitize 65 hours
(wax) Manual deckel CNC machine
Hand work to Min. bench Work
finish


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