Mold & Trim Presses

Introduction

Mold and trim presses are used widely in the automotive industry to produce a variety of interior components such as; instrument panels, door panels, interior trim, insulation, and head, trunk, hood, and rear deck liners. The presses can also be used to create firewalls, foam insulators, and to trim metal parts. These automotive mold and trim presses are extremely versatile and can be custom designed to meet a manufacturer’s specific applications. Choosing a mold and trim press for automotive needs requires analysis into process cost, efficiency, and other operational requirements. The creativity and complexity of the parts that can be produced with a mold and trim press are endless, and limited to the individual tool sets used in forming.
Fig. 1: Many car interior parts are widely manufactured with mold and trim presses

Materials & Applications

There are many challenges that automobile manufacturer’s face being in such a competitive industry. In addition to producing cars that meet demands of consumers, cost and volume targets, and continuously evolving safety regulations, there are mounting pressures in creating lighter and stronger parts for improved fuel efficiency and abilities to withstand impact.

Material selection for mold and trim press processes are paramount to the success of car manufacturers. Aesthetics, formability, finish, weight, colour, touch and feel are all important. Mold and trim produced parts are often required to house and hide wires and electronics, making it easy for assembly, maintenance, and possible replacement.

Engineered plastics, with low material density, durability, and dimensional stability, have proven to be a superior choice for automotive mold and trim parts. Acrylonitrile-butadiene-styrene (ABS), polycarbonates (PC), ABS/PC alloys, polypropylene (PP), modified polyphenylene ether (PPE), and styrene-maleic anhydride (SMA), are just some of the examples of modern plastic polymers that are regularly used.

These types of plastics allow for complicated designs and complex shapes to be formed. A single piece that integrates many features can be manufactured resulting in seamless and aesthetically pleasing designs and finishes. There can be significant cost savings for manufacturers as colour can be added directly to resins, finishing techniques can give the plastics the look and feel of complementary fabrics, graining, and high/low gloss paint.

Plastic polymer materials are well suited for flexible and versatile designs that result in stylish aesthetically pleasing, scratch resistant, durable interior automobile components. Considerations for vibration, noise, UV resistance, climate, off gassing, post life recycling of material are additional challenges car manufacturers face when designing and choosing materials for their products.

Forming Processes

There are a number of automotive manufacturing processes where mold and trim presses can be utilized.  Some of these specific processes include;

Twin sheet molding:  This process involves both methods of vacuum forming and pressure forming of two sheets simultaneously within a temperature-controlled platen press.  Each sheet is first heated and vacuum formed to an individual mold, that are mounted to the top and bottom platens of the press.  The platens are brought together quickly to maintain the temperatures and the two formed sheets are bonded together under high pressure.  The resulting piece is a single hollow product that requires no additional bonding.
Fig. 2: Twin Sheet Molding Process
Twin sheet molding is a process that can accommodate many materials and sheet thicknesses and is commonly used in the automotive industry because of the lightweight and strength of parts produced as cars makers continuously strive for more fuel efficiency.  Additionally, the process allows for different materials to be used, such as metals and foam, to fill the gaps inside a twin sheet molded part for even more versatile and advantageous properties of the finished part.  Common automotive parts that can be produced with this process include fuel tanks, body panels, and any parts that may require separate interior components or interior access.

Compression molding:  A common manufacturing process that uses thermosets, thermoplastics, elastomers, and rubber materials to produce parts varying in size, thickness and complexity.  The materials used are generally pre heated and formed by pressing into a mold cavity and applying a controlled pressure.  Common automotive parts produced with compression molding include; hoods, fenders, spoilers, and smaller more intricate parts.
Fig. 3: A 3500 Ton Compression Molding Press
For more information on the compression molding process, please refer to the white paper Compression Molding 101.

Plastic thermoforming and vacuum:  Materials such as vinyl and soft touch plastics that are widely used in finished car interiors can be produced via vacuum and plastic thermoforming.  A plastic sheet is placed above a mold and heated, and a press will force a mold towards the sheet as it forms and creates a seal.  Vacuum is then applied to ensure the material takes proper shape of the mold.  The press is configured such that curing takes place under a temperature-controlled environment, and the plastic part is then separated from the mold resulting in a high-quality finished piece.  Because of factors such as material and heat application, much lower forming pressures are required with this process.  Both tooling costs and requirements for high tonnage presses are reduced, making it a viable process for parts for the automotive industry as it can be used of varying sizes and production quantities.

A number of pieces and parts for automobiles can be produced with vacuum and plastic thermoforming including bumpers, truck beds, and floor mats.  Various colours, finishes, and even environmental considerations for the materials and final parts are possible making it an important process for car manufacturers as they strive to appeal to consumers and varying individual tastes.

Establishing Process Parameters

The process for mold and trim is always specific to the individual parts being created and material being used.  Factors such as heat distribution, temperature control, and ejection methods, are just some of the variables in addition to the typical press process parameters.

Bed Size

The bed of a mold and trim press must be able to accommodate the footprint of the largest expected toolset. The orientation of the part is important for overall forming, but will also determine the overall requirements for bed dimensions. Wide access to the bed from all four sides of the press is advantageous for both automated and manual handling of materials and parts.

Tonnages and Speeds

With automotive mold and trim parts, requirements typically do not exceed 300 tons. A press with tonnage that is applied beyond what is required may cause excess energy consumption and tooling wear.

Trimming of parts requires appropriate tonnages for how the finished part will be cut based on the specific geometry, material, and tooling.

A hydraulic mold and trim press can be controlled to open and close as quickly as needed. But with mold and trim parts, the speed and cycle times for production are often driven by the necessary pressure, and heating and cooling requirements to form the individual parts and material.  The complexity of the part, surface finish, and handling are often limiting factors on how fast the parts can be produced rather than the press speed itself.

Stroke and Daylight

Enough daylight must be available between the fully retracted tool faces to allow removal of the finished part from the press. In practice, this translates to daylight that is approximately triple the press stroke. If a press will be used to produce more than one part, stroke and daylight should accommodate the largest expected tooling. Additional clearances may be required to accommodate in die cooling, in die heating, robot or feeder access, and quick-change tooling.

Fig. 4: A 250 Ton Mold and Trim Press

Hydraulic Mold & Trim Presses

Hydraulic mold and trim presses can be custom designed, and fitted with electric control systems to ensure an optimal solution for automotive manufacturing applications. Considerations for repeatability and accuracy, as well as the ability to control tonnages and forming pressure are essential for efficient and successful production. Hydraulic presses offer versatility and can be used to produce a variety of parts by interchanging tools.

Some of the options that a hydraulic mold and trim press can be fitted with include:
  • Heated platens
  • Tilting tables
  • 180-degree rotating platens
  • Rack & pinion leveling systems
  • Rolling bolsters / shuttles
  • Vacuum systems
  • Ejectors
  • Punches
  • Auxiliary circuits for core / eject functions
  • Remote diagnostics package


With an endless number of different options and packages that can be customized, hydraulic mold and trim presses remain a flexible and long-lasting option for automotive manufacturers.  Automobile manufacturers usually offer a number of trim levels with each car, and their designs can undergo refresh programs as quickly as 1-2 years.  It is important that hydraulic mold and trim presses have the ability to keep up with this constantly changing environment.
Fig. 5: Two 150 Ton Mold and Trim Press Machines

Advantages

  • Some of the major advantages of using mold and trim hydraulic presses for automotive interior parts include:
  • Efficiency – fast and repeatable production
  • Complex part design
  • Flexibility in material, colour, and finishes of parts
  • Lightweight and strong parts
  • Reduced material waste
  • Precision and accuracy of parts

Image References

  1. Fig 1: M&T_P-F1, Silvestro, Brian, Road and Track, These Are the 20 Best New Car Interiors, October 9, 2019
  2. Fig 2: M&T_P-F2, Basics of Thermoforming (https://kydex.com/technical-resources/thermoforming-processes)
  1. Fig 3: M&T_P-F3, A 1000 Heated Platen Press, Macrodyne
  2. Fig 4: M&T_P-F4, A 250 Ton Mold and Trim Press, Macrodyne
  3. Fig 5: M&T_P-F5, Two 150 Ton Mold and Trim Press Machines, Macrodyne