A Smooth-Surfaced Mold Without Hand Finishing Is Finally Possible

For most mold makers, hand polishing and post-production jobs are facts of life. A smooth surface in a mold is very important for its overall performance. Even after a couple of weeks of its production, a mold’s surface remains unpleasantly rough. Mold suppliers have to hire manual labor for giving a mold smooth, finished surface. Manual labor, however, eats a lot of time. In addition, with lack of qualified workers, the finishing job is becoming tougher with every passing day. Apart from lack of labor, the rising cost associated with the finishing work is frustrating and a significant profit killer.

As found in many instances of life, technology saved the day in this scenario too. The advances of Non-uniform Rational Basis Spline (NURBS) technology help a mold to be finished while in production. Thus, we can finally bid adieu to the age-old, laborious, profit-killer job of hand finishing. But has technology given an accurate solution? Read on to know…

What is NURBS?

Developed in 1950s, NURBS is a technique – a mathematical way – for regenerating freeform shapes and curves (ship’s hull, car’s body, etc.). The technology is used along with CAM systems and CAD packages. There is, however, a caveat with this technology. Regardless of the use of NURBS, hand finishing is required for attaining a specific amount of smooth finish.

When designing a complex curvature shape, CAM equipment outputs three points X, Y and Z. Such series of points uses linear movements that help in creating curve. Many such small-sized linear movements are required for generating a curve. When the CAM equipment is left in such a form, a control attempts to go to every individual point and solicit confirmation about its destination.

Such feedback loop can literally throttle the equipment’s actual speed of operation. The feedback loop has to crunch a lot of data; this results in slowing the equipment and affecting its accuracy. Both programmers and machinists fail to address such a problem even by using the NURBS. Owing to the inefficiency of both man and machine, labors will have to do a little bit of that frustrating finishing task. Wait there is more…

A new hope

Many advances are made in the overall functionality of NURBS. The most significant advancement in the technology has been the development of a tolerance band. The tolerance band is predetermined by programmers using points. Such a programmer-controlled band is used to create a spline. The spline is apt to eliminate repetitive points existing on the spline path. Because many points have already been eliminated, the feedback loop does not have to do the exhaustive data-crunching work.

Benefits of the approach include:

• Faster, smoother tool path

• High-speed feed rates

• Elimination of redundant points

• Faster speed of control loops

• High-speed cycle times

• Molds having smooth surface and dimensional accuracy

With fewer redundant points on the path, a smooth-surfaced mold is expected to be manufactured by the machine.


Post time: 02-08-2017