Computer thinks it's a molding machine.

A unique new training tool allows your employees to learn how to run an injection machine on a desktop PC. They can learn to set up and run a part, eliminate part defects, and optimize cycle time, using all the controls available on a real press. As they tweak the on-screen controls, the "virtual machine" responds with realistic changes in process conditions and part quality.

The SimTech-1 injection machine simulator becomes available this month from Paulson Training Programs, Inc., Chester, Conn. (A prototype version was shown at NPE in Chicago in June.) The simulator gives a realistic molding experience even to the sound of the press, says general manager Craig Paulson. "Personnel get a chance to work on real molding problems without wasting precious machine time and material or risk of damaging the machine or mold," he notes. While other firms have simulated what happens once the material is injected into the mold, this is the first complete model for the entire molding process, including plastication, according to president Don Paulson.

The simulator comes as Windows 95 software on CD-ROM for under $10,000. It requires a PC with 120-MHz Pentium processor, amplified sound system, and 50 MB hard-disk space.

START UP & OPTIMIZE

The simulator is designed to mimic the behavior of a 100-ton press (90-ton metric). To begin a training session the user selects one of eight predefined parts and one of five generic resins (PE, PP, PS, ABS, or polycarbonate). There are also three levels of molding precision to choose from. The user then sets up the machine cycle using the onscreen control panel with three barrel-zone temperatures, mold core and cavity temperatures, screw rpm and backpressure, shot size, clamp force, injection and holding pressures and times, five segments of filling speed, mold-open and closed times, and velocity-to-pressure transfer point.

Using a combination of mathematic formulas and empirically based rules, the simulator calculates the effect of the selected settings on melt temperature, flow rate during filling, pressure in the mold, and cooling rate. This requires over 20 million calculations, which the software performs in about 10 sec. The simulator then shows the predicted filling time, overall cycle time, cushion size, melt temperature, and part weight and dimensions. If the software predicts the occurrence of any of 11 part defects (e.g., short shot, burn marks, sinks, flash, voids, distortion, or off-spec part dimensions), the screen displays a 3D solid image of the part with the defect present in the appropriate location.

The operator must decide what corrective action to take, while the computer responds to each action and offers helpful hints. The post-cycle summary screen shows the last five shots with a bar graph indicating the relative severity of each defect, so that the user can gauge his/her progress. Once the part is on spec, the user can then focus on changing conditions to achieve minimum cycle time. At the end of a session, the user is given a score based on the time it took to solve all problems and the final cycle time achieved. During the exercise, the simulator actuates alarms if the operator makes a mistake in set-up and offers hints if the molder needs help. For example, alarms warn if the melt temperature is set too low or if the filling speed calls for an injection pressure higher than is available. The user is also notified if the screw backpressure is too low to allow recovery in time for the next shot or if the screw would bottom out because there is insufficient cushion.

FIX MOLDING PROBLEMS

For the future, the Paulsons envision a more generalized tool that allows you to input a description of any part you want to mold and to "premold" the part in the computer instead of an actual press. The simulator would allow you to define a process set-up sheet, debug any problems, and optimize cycle time and quality. Additional screw designs and machine sizes may be included in the software database.