Know when to transition from sand casting to permanent mold
January 23, 2017

Sand casting is an ideal solution for producing low volumes at a low tooling or start-up cost. However, once your product volumes increase, permanent mold casting might be a better solution since sand casting requires a new mold for every casting.
Permanent mold casting applies a single mold made out of tool steel that can produce 100,000 pieces or more versus a brand new mold for every part when using the sand casting process. Permanent mold creates consistent parts and lowers your costs. If your part contains internal cavities and undercuts, permanent mold can also use sand cores to create them.

KEY SIGNALS TO MAKE THE SWITCH TO PERMANENT MOLD

  • Your quantities are on the rise (more than 500 pieces a year).
  • You’re looking for a better surface finish.
  • You want to produce a higher quality part that provides tighter tolerances and dimensional stability.

BENEFITS OF PERMANENT MOLD CASTINGS

REDUCE CASTING COST

As we previously said, sand casting needs a new mold for each part that is produced – increasing your costs and cycle time. Permanent mold counters this by employing molds that have a lifespan of 100,000+ parts. Reusing the same mold shortens cycle time and reduces cost. The tighter tolerances of permanent mold enable many features to be cast to size enhancing productivity by avoiding secondary machining and finishing costs.
BETTER SURFACE FINISH AND AESTHETICS
Due to sand’s coarse nature, sand casting generally produces a rougher surface finish versus permanent mold. We machine the mold cavities to a smooth finish and apply fine, talcum-like coatings that result in a finer more aesthetically pleasing casting.

IMPROVE QUALITY

SOLIDIFICATION RATES

Due to sand’s coarse nature, sand casting generally produces a rougher surface finish versus permanent mold. We machine the mold cavities to a smooth finish and apply fine, talcum-like coatings that result in a finer more aesthetically pleasing casting.

CONTROLLING SOLIDIFICATION

Castings generally have different part features that solidify at different rates. In permanent mold we can control the solidification rate of various part features by adjusting mold coatings (as seen to the left) as well as incorporating water or air to cool the mold in specific areas.

TOLERANCES

Permanent mold can achieve more accurate tolerances at +/- 0.015″ whereas sand casting only achieves +/- 0.030″. Our measurement technology ensures accuracy on tight tolerances.

DIMENSIONAL STABILITY

Permanent mold improves dimensional stability because it uses one mold to make every part. Sand casting results in more variability since every part is made with a different mold.

Permanent mold may not be the right solution for every part, but the most common reasons to switch are:

  • Increasing speed and volume of production.
  • Decreasing cost per piece.
  • Reducing lead times.
  • Enhancing surface finish.
  • Strengthening the casting.
  • Preventing defects.
  • Achieving tighter tolerances.
  • Improving dimensional stability.

For more information or to discuss the possibilities of switching to permanent mold casting, call or email us today.

Categories: Knowledge