Why plastic injection molded part development can turn into a nightmare for management?
Plastic injection molding manufacturing process is a combination of science and art. For every component development Design engineers, tooling engineers and process engineers are required. Each set of design, tooling and process engineers have different but unique challenges. Each of the design, tooling and process engineering work like silos. The difficulties and challenges of each team of engineering are not shared by other engineering teams. Without having someone to connect these three engineering teams together can turn any simple part into a nightmare for the management.
Let’s understand the role and responsibilities of each engineering team involved.
Design engineering is considered specialization, defining products from concepts. Product design may involve assembly of components from various different manufacturing process. Primary function of design engineering is to convert industrial design requirements to engineering requirements. The design engineering defines all the components in the product and selects the manufacturing process for each component. Defining component includes material selection, shape, size, fit, finish and structural integrity. Knowledge of several manufacturing processes is essential in design engineering. For plastic components design engineering relies heavily on design guidelines published by plastic manufacturer. A design engineer collaborates with mold/tooling engineer to design the component, but design engineer is responsible for the structural integrity, tolerances, shape and material selection.
The challenges and responsibility for design engineering are
Structural integrity (structural analysis)
Design For Manufacturability (DFM)
Design For Manufacturability and Assembly (DFMA)
Selecting secondary processes
Converting industrial design requirements to engineering requirements
Generating 3D and 2D geometries
The design of component sets the direction of tooling requirements.
Tooling engineering is considered specialization in designing and constructing the mold/tool for plastic components. Tooling engineering designs and constructs following systems:
- Molten plastic flow path- sprue, runner, gate and cavities
- Cooling circuits- water lines
- Ejection system- ejector pins, blades, slides, lifters
- Core and cavity blocks
- Mold base
Each system needs to be designed and constructed with machining tool steel. Tooling engineering is working with high carbon steel (tool steel) using conventional manufacturing processes. The tooling engineering uses the conventional manufacturing processes in series of sequences to construct and assemble the full mold.
Tooling engineering has following challenges and responsibilities
- Selecting machining processes
- Scheduling and sequencing the machining processes
- Designing all the systems involved
- Assembly and working of moving parts
The tool design sets the limits of process windows.
Process engineering is specialization in setting the controls for heating, injecting and cooling the plastics. Heating, injecting and cooling needs to be set according to material specification. The process settings are dependent on material properties, part design, tool design, colorants and any other additives to the material.
Process Engineering has following challenges and responsibilities
- Plastic heating by compression and friction by adjusting back pressure and speed of the screw
- Holding molten plastic in heated barrel
- Controlling speed and pressure of molten plastic during injection
- Controlling cooling of molten plastic in the mold/tool
- Reduce/eliminate injection molding defects by adjusting process settings
- Recommend part and tool design modifications
- Adjust the process setting to achieve quality and cycle time targets
Process engineering can reduce injection molding defects by adjusting heating, injection and cooling of plastic. Process engineering is usually first to discover defects on the components. Process engineering have limited options as the processing limits are controlled by part and mold/tool design. But often asked to resolve the defects or deficiencies.
A comprehensive engineering approach, combined with plastics expert's help, will help...
Most often, part and tool modifications are expensive and time consuming. The part and tool modifications can lead to different injection molding defects. Most often an expert with knowledge with design, tooling and processing background can reduce the design and tooling modifications or number of iterations of modifications.
As Design engineering is responsible for product design, tooling engineering for machining, and assembly of the tool and process engineering for adjusting the process settings, a comprehensive engineering approach with plastics expert help will help save time and resources for design, tooling and processing. And avoid nightmares to management.
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With advances in globalization, many times the design teams, engineers, testing facilities, prototyping facilities and other teams are not under same roof.
One of the biggest challenges faced by engineers today, is not just to design parts made of composite material with absolute confidence, but also to optimize the entire manufacturing process to get the best performance of the material itself.
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This article discusses causes and possible solutions to some of the plastic injection molding defects that can be observed on a part.
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