What is scientific molding? Moving the setup from "feel" to data
The core steps of an approach that takes the process out of the operator's hands and makes it measurable, repeatable and transferable to another machine.
Do you get different results running the same mold with the same raw material on two machines? Or do part dimensions change between shifts? This is usually because the process is defined by "the values on the setup screen" rather than by what the material actually experiences in the mold.
Scientific molding is a method that defines the process through what the material experiences in the cavity, instead of through machine values.
The core idea: decoupled molding (separating fill and hold)
It splits the cycle into two separate jobs:
- Fill: Fill the cavity to 95–99% under velocity control. The goal here is for the material to flow at a stable speed.
- Hold and cooling: Complete the remaining volume with pressure, hold until the gate freezes, then cool the part.
Optimizing both separately makes the question "what changed when I turned this one setting?" answerable.
The sequence
- Viscosity curve test: Find the injection speed at which viscosity is insensitive to speed. (See the details in our separate article.)
- Pressure drop test: See how much of the machine pressure during filling is spent on the nozzle, runner, gate and cavity. If you're close to the machine limit, the setup window is narrow.
- Gate-freeze study: Increase holding time until weight stabilizes.
- Cooling time study: Find the cooling time that's sufficient for part dimensions and warpage.
- Cycle time and process window: Vary settings within certain ranges and show within which limits the part stays good.
Why does it work?
- Transferable to another machine: Instead of "this speed, this changeover, this pressure," you describe "changeover at this cavity fill ratio, this holding time."
- Repeatability improves: Lot-to-lot differences, seasonal changes and shift differences become easier to notice.
- Lower quality cost: Knowing the process window reduces scrap and setup time.
A practical starting point
Keep a process sheet (set sheet) for every new mold: record the results of every trial, the machine used, the material lot and the mold temperature. When the same mold moves to another machine, this sheet is the starting point.
Note: Scientific molding isn't software or a device, it's a working discipline. It's much more powerful with a cavity pressure sensor, but it can also be applied without one.
The "machine setup starting values" our calculation tool provides are the starting point for this work; as you validate the results, you build your own mold's own dataset. Go to the tool.
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