3D Systems’ metal additive manufacturing process and Cimatron mold design software enable significantly reduced cooling cycles for mold inserts

If the temperature changes during the injection molding cooling cycle are large, the risk of parts warping will be greatly increased. Testing of conventionally designed and manufactured injection molded automotive ducts resulted in temperature fluctuations of 132˚C throughout the test, leading B&J Specialty to recommend to its customers the use of conformal cooling injection molded inserts to achieve more even cooling. .

To achieve this goal, B&J Specialty engineers used 3D Systems' Cimatron® software to design the mold, and the internal cooling water circuits were designed to conform to the surface of the component. In order to produce the complex and precise internal cooling water circuits, they used 3D Systems’ metal additive manufacturing equipment ProX® DMP 300 for printing.

The new conformal cooling mold insert reduces the temperature change during the cooling process to 18˚C, and reduces the mold shrink cycle time from 1 minute to 40 seconds, increasing overall production efficiency by 30%.

According to Jarod Rauch, ProX® DMP 300 can control tolerances between 1/3000ths and 1/4000ths of an inch

Sub-optimal cooling water path results in large temperature changes

Conformally cooled molds use modern technology to solve a long-standing problem. Many injection molded parts have curved surfaces, but the holes used to create cooling channels can only be drilled in straight lines. In most cases, this means that the cooling circuit cannot match the geometric features of the component. Traditionally manufactured cooling lines must go around the outermost layer of the part to avoid interference with the mold cavity, which means that parts closer to the center of the part are usually farther away from the nearest cooling water path. This often results in significant temperature changes on the component at the very beginning of the cooling process.

B&J Specialty redesigned automotive ducting to increase cooling efficiency and features multiple irregular curved surfaces. During the original mold design process, cooling lines were drilled through a center and stator block in order to adjust the mold geometry to allow for a certain degree of warpage. For irregularly shaped pipes, several important features of the pipe have nothing to do with the cooling water path because there are restrictions on straight channels. The resulting temperature changes create residual stresses that cause parts to buckle as they cool.

In the past, part manufacturers have often addressed this issue by extending the cooling cycle to ensure the part is fully cured before removing it from the mold, and by adjusting the insert to allow for a certain amount of warpage. The problem with this method is that extending the cooling cycle will reduce production efficiency and increase parts manufacturing costs.

Compared with traditional linear cooling waterways, metal 3D printed conformal cooling waterways reduce temperature changes by 86%

Improve molds with conformal cooling channels

According to Jarod Rauch, information technology and 3D printing manager at B&J Specialty, automotive ducts are a good example of an improved conformal cooling design that can improve part quality, reduce scrap rates, and shorten cooling cycles. .

B&J Specialty proposed this solution to a customer, an automotive supplier, who agreed to test the new approach. After obtaining the CAD file of the original geometric data, B&J Specialty engineers began the design work using 3D Systems' Cimatron mold design software.

Rauch said B&J Specialty came into contact with Cimatron software while researching the application of conformal cooling on metal 3D printers. “We saw that 3D Systems provided a complete end-to-end solution, including mold design software, 3D printing modeling preparation software and 3D printer, which is what made me very happy with this solution,” said Rauch.

After working with Cimatron, B&J Specialty engineers abandoned the original straight-line cooling water path and replaced it with a conformal cooling water path that maintains a constant distance from the surface of the component. The use of metal 3D printing technology for final mold production allowed engineers to design complex cooling water circuits, while the quality of cross-sections and interface surfaces was improved.

Such features ensure turbulent flow, further increasing the heat transfer from the mold to the coolant, making cooling more efficient. Being able to cool the mold more efficiently reduces the defect rate of parts (such as warpage and sink marks) and ensures the quality of parts. This approach reduces correction, trial-and-error and sampling rates, produces higher-quality parts, and saves moldmakers and operators significant time and money.

Set expectations with accurate simulation

B&J Specialty engineers then imported the mold files from Cimatron software into Moldex3D (injection molding simulation software) for overall cooling simulation. “Cimatron is fully compatible with Moldex3D, allowing us to easily simulate the entire injection molding process, map the temperature changes of the mold and parts, identify hot spots and cooling points, and simulate the effects of different cooling times. " Rauch said.

The simulation process also pointed out some key areas for improvement, and the cooling strategy for such key areas can be redesigned before actual production. A simulation comparison between the original mold design and the new conformal cooling waterway design shows that the temperature distribution of the new parts has been greatly improved, with the temperature change reduced by 86%.

Cimatron is fully compatible with Moldex3D, allowing us to easily simulate the injection molding process to evaluate the design digitally.

3D printed mold inserts with conformal cooling channels

B&J Specialty engineers then used 3D Systems 3DXpert™ metal additive manufacturing software to design the mold inserts in preparation for production. They imported the part data, optimized the geometric feature data, calculated scan paths, laid out the 3D printing build platform, and sent the data directly from the 3DXpert software to the 3D Systems ProX DMP 300 metal 3D printer.

The ProX DMP 300 uses a high-precision laser head using 3D Systems LaserForm® material. For automotive pipe molds, B&J Specialty uses maraging steel.

B&J Specialty uses conformal cooling water channels to increase production efficiency by 30% with direct 3D metal printing

“The ProX DMP 300 is great for creating conformal cooling channels because it’s so precise,” Rauch said. “We can allow for tolerances of one part in three thousand to one part in four thousand.” 3D Systems’ patented Direct Metal Printing (DMP) technology allows us to create the finest details and thinnest walls using smaller particles of material thick. The final surface roughness of the parts can be 5μm (200Ra micro-inches) without much post-processing.

Production efficiency is greatly improved

After the printing was completed, B&J Specialty used a blue light 3D scanner to scan the insert into 3D Systems Geomagic® Control X™ inspection and metrology software, overlay the grid on the designed geometry, and verify the metal 3D printed mold insert. The inserts are then sent to the automotive supplier, who then installs them on the molding machine.

Rauch said: "Bechmark test results show that the conformal water path makes the cooling process more balanced, thus shortening the cooling cycle time, increasing production efficiency by 30%. Because conformal cooling shortens the cooling cycle time, it reduces the injection pressure, resulting in Mold life is greatly improved, which in turn reduces wear on the parting line and reduces the intricate details of the mold.”