How DMLS Enables Efficient Injection Mold Inserts
with Conformal Cooling Channel

3D printing metal parts opens up new design possibilities that can solve problems for a variety of industries. A case in point: injection mold inserts, which help to cool plastic parts just after they’ve been formed. Conformal cooling channels, which aren’t possible to build using conventional machining methods, can be built into 3D-printed core inserts using DMLS to significantly improve cooling performance.

Quickly cooling injection-molded parts has always been a challenge. Conventional drilling and milling can only produce straight-line holes in mold inserts. During molding, water is pumped into these channels, which cools the core and draws heat away from the molded part.

As part geometry becomes more complex, it gets harder to keep cooling channels uniformly close to the tool walls. That leads to uneven cooling, longer cycle times and thermal stresses, which can cause defects like warpage, sink marks and weld lines.

To solve this problem, Fathom can 3D print a new core insert out of tool steel using Direct Metal Laser Sintering (DMLS) at a near net shape. DMLS produces solid 3D-printed parts by melting metal powder with a laser beam, layer-by-layer, out of powdered metal. Parts printed with DMLS are 100% dense and require minimal post-processing. The 3D-printed metal insert can then be machined to meet the customer’s exact tolerance requirements.

Cooling lines can be incorporated into the 3D-printed core insert’s design, running just below its surface. Because they are so close to the molten resin, they can remove residual heat quickly from the molded parts. Conformal cooling 3D printing can cool parts quickly and uniformly, resulting in:

• Reduced part failure
• Reduced part cost
• Increased throughput
• Fewer assembly and fit issues with other parts

Inserts designed with conformal cooling channels can increase injection molding productivity by 30-60%.

Fathom engineers can help you redesign your injection mold core inserts for optimal performance using conformal cooling 3D printing.

A customer was having problems with plastic closures warping as they cooled because the tool contained a deep draw cavity. Fathom designed a core insert made using DMLS that contained conformal cooling channels. They drew heat away from the closures, enabling them to cool faster without warping.

Read the case study

Design recommendations for the layout of heating/cooling channels with DMLS are the same as the ones given for conventionally designed channels as both are based on the plastic recrystallization and heat conductivity theories. In order to achieve a constant temperature level, the channel diameter should be chosen depending on the distance between the heating/cooling channel and cavity.

Depending on the design of the product, the optimal diameter should be chosen between 4-12 mm. Some inserts, such as closely placed ejector pins or parts with thin walls, make it difficult to adhere to this rule. DMLS can build channels down to 1 mm when using specially treated fluids to avoid clogging. Simulation software can be an especially useful resource to prepare your part for printing. If you have any design questions, talk to a Fathom expert before submitting your CAD file.