Design and Construction of an Optimum Mold Cooling System
Size, number and position of cooling channels
The rule is simple
The Mold Cooling System is a heat-exchanger. The faster the heat is removed from the mold (i.e. from the injected polymer) the faster the molding will solidify and get ready for ejection.
So, the best cooling system obtains the minimum allowed -by the polymer- temperature, as possible even in all mold surfaces. It sounds easy, but it is not. We face a dynamic system and not a static one. Neither the heating rate (from the melt to the mold surfaces), nor the cooling rate (from the mold surfaces to the cooling system) is homogenious. So, although, the rule is simple,
the solution is complex!
Optimization criteria
- Channels diameter (determined by Reynolds Number)
- Channels Distribution (by max temperature deviation on mold surface)
- Cooling System of different mold halfes (controls warpage. Sometimes a predetermined deviation is needed)
- Total number of channels and diameters (related to cooling fluid supply system)
Improving cooling system
Deal with 'hard-to-cool' areas in simple geometries
Internal corners are mold areas 'surrounded' be molten polymer during injection. One critical point is the implementation of cooling channels at these areas to improve the heat removal rate.
In simple geometries, like the displayed 'L' shaped profile, both identification of 'hard-to-cool' areas and corresponding remedies are almost obvious.
Implementing an additional channel close the internal corner, improves drastically the cool time and the part warpage.
Conformal Cooling Channels
Cooling of 'real' complex shapes
In this case, a difficult computational analysis is needed, in order to design an optimum cooling system.
Unfortunately, this is only half the problem. Traditional methods for machining cooling channels are limited to drilling or in special cases, by machining complex shaped channels on mating surfaces of different subinserts. The latter, with the cost of an elevated mold construction complexity, introduce quasi-conformal channels, again with the strong limitation to place all cooling channels in a single plane. So, even if computational analysis systems have been since years in the market (flow simulations and cooling/warpage analysis), the 'ideal' cooling channels that 'follow' the shape of the inserts, the so-called conformal cooling channels were for years beyond the manufacturing technologies.
Today, metal 3D printing offers the possibility of the construction of any shape of conformal cooling channels.
Metal3D SA, is able to print in H13 mold insert workpieces with incorporated the conformal cooling channels.
Metal3D SA, may either deliver the printed insert for finishing by the customer (as 'enhanced' workpieces) or provide a finished cavity insert ready to be fitted into the mold, according to customers specifications.
Conformal Cooling Channels on 'Standard' mold Components
We can also deliver several special components that incorporate conformal cooling channels:
- Cold-Runner Sprues for Thermosetting Processing
- Special Sprue Bushings
- Special Sub-inserts for 'hard-to-cool' areas