Taking the “Error” out of Trial and Error

A Case Study by Shyamal Roy


Smart users realize that decisions made in the early stages of design have the maximum impact on the final performance of any product. Most-engineering design is non-deterministic. That means engineers do not have a formula where they can feed parameters and out pops the optimal design. Instead the trial and error method is used until the optimal design is established. In the prevalent design paradigm engineers are forced to use expensive “build-test-fix” method to arrive at the design that will perform as expected.


Simulation-driven mechanical design enables users to perform the trial and error in the early stages of design when conflicts are easy to detect and the least expensive to fix. GrafiCalc software enables users to conceptualize, analyze and validate critical engineering parameters before committing to the final design. GrafiCalc also includes geometry Goal Seek technology that enables users to automatically solve design challenges that benefit from optimization against desired shape, position, and fit criteria.

Case study

Here a user had defined the concept of a machine designed to punch dog food biscuits as shown in the following illustration. The challenge was to establish the equations for the servomotors so that the bottom end of the lapper arm moved at a constant velocity as the punch was lowered. The user estimated a design time of about one month using a mid-range CAD application, a motion simulation add-on and a data analysis application using the “build-test-fix” methodology.

In GrafiCalc the geometry was sketched and constrained to reflect the functional intents of the design as shown in the following figure. The geometry of the mechanism was back solved using inverse kinematics to establish constant velocity for the end of the lapper arm, point C.

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Next the transient value of the length of the actuators was collected in GrafiCalc and pasted into Excel to develop the equations for the servomotors as shown in the following figure.

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With GrafiCalc the optimal solution was obtained in an hour in the pre-modeling stage of the design.

Information about GrafiCalc is available at www.inventbetter.com