3D Basics What is rapid tooling?

From Joscha Riemann

Rapid tooling is well on its way to becoming the industry standard in many application areas. In this article we have summarised definitions, applications and much more about rapid tooling for you.

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Rapid tooling is well on its way to becoming the industry standard in many application areas.
Rapid tooling is well on its way to becoming the industry standard in many application areas.
(Source: public domain // pixabay)

There is hardly an area in production that is as sensitive as tool and mould making. Moulding tools for presses, punches, injection moulding and die casting machines have been the most expensive components in any series production up to now. Often the price of the tool even exceeds the acquisition costs of the machine on which they are used. The reason is that tools are the decisive factor in determining the quality of the products manufactured on them.

Until now, the manufacturing processes for production tools have been correspondingly costly: CNC milling machines, eroding machines, precision grinding machines are in turn expensive machines that can also only be operated and maintained by specialists. Of all things, it is in this sensitive area that 3D printing using rapid tooling, which has so far been subject to reservations, is now making inroads. Until now, 3D printing has been the domain of rapid prototyping, i.e. the rapid production of a haptic model. For series production or even as a manufacturing process for tool and mould making, rapid tooling has been in use for only a short time.

What is "rapid tooling"?

Rapid tooling can be understood as "fast tool making". The "rapid" in this context usually means "3D printing". Admittedly, modern CNC milling machines with amazing production speeds are also available. Nevertheless, rapid tooling has so far remained the domain of 3D printing.

Rapid tooling through additive manufacturing is about producing moulds or testable mould models. Applications for rapid tooling include the following:

  • Deep-drawing tools for thin-film plastic parts (vacuum forming process)
  • Injection moulding tools
  • Pressing tools for soft and hard materials (e.g. aluminium sheets)
  • If necessary, also punching tools for thin materials with low tensile strength (paper, thick film, plastic, MDF, veneer wood)

Although rapid tooling also includes the production of a 1:1 mould model in the first step, it essentially means the production of a usable production tool through additive manufacturing.

In addition to the significantly faster and cheaper manufacturing processes for the moulded parts, rapid tooling in 3D printing offers another unique advantage: The 3D printing process makes it possible to specifically incorporate cooling channels into the tool that are not feasible with traditional manufacturing processes in this form. This means: with rapid tooling, you can incorporate lines for coolant in any cross-sections, radii and positions. With the previous manufacturing processes for tools, this was only possible by setting with targeted bores. However, a hole dictates its linear orientation and cross-section over its entire length. The "printed" cooling channels in rapid tooling, however, can be precisely optimised for optimum heat dissipation. The tools thermally optimised by rapid tooling can already be used today for the production of interesting quantities. In practice, therefore, a trend is gradually gaining ground: Inexpensive and thermally optimised tools from rapid tooling are gradually replacing traditional cavities made of aluminium or steel.

Rapid tooling in practice

Rapid tooling is already a standard method used today in pressureless and technically comparatively low-load production processes. It is particularly unproblematic for the following production methods:

  • Sand casting with mould halves
  • Laminating
  • Vacuum deep drawing

Sand casting with mould halves is the pressureless filling of mould halves from pressed sand. In this process, a mould core is split in half. Both halves are placed in a box. Sand mixed with a light binder is filled into this box and compacted until it has reliably assumed the hollow shape of the casting core. The core halves are removed and the two boxes are placed on top of each other. Now there is a hollow mould inside the box, which forms a negative of the core. This mould is now filled with hot metal, for example aluminium, copper or magnesium. After the metal mould has cooled and hardened, the sand is removed. After sieving and light grinding, the sand can be reused. Likewise, the casting core can be used again and again. Rapid tooling in this process refers to the production of the mould core.

Laminating is a process in which a hollow mould is made and covered in layers with fibre mats soaked in synthetic resin. The use of GRP or CFRP mats is common here. For large-format products, the mould is printed in several parts.

In vacuum deep drawing, a heated thin plastic material is drawn over a 3D-printed mould core. The air is then sucked out from under the thin material. This causes the material to nestle precisely against the mould core from rapid tooling. This process is suitable for the production of bonnets, lids, housing parts or as a mould for plaster products.

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Rapid tooling is now well on the way to becoming the new standard for processes with a medium technical load, such as injection moulding of plastics. The advantages outweigh the disadvantages to such an extent that it would be very surprising if the old processes were still being used in ten years' time. For example, a mould made by rapid tooling costs only about 1/100 of what a traditionally manufactured injection mould made of aluminium costs. Therefore, it doesn't matter that this approach to tool and mould making allows a lower number of cycles through rapid tooling. Once the design is complete, a new tool can be produced again within a few hours using rapid tooling and costs only a few hundred euros.

Rapid tooling technologies

Rapid tooling generally describes the term "fast tool making". Rapid tooling through additive manufacturing or through 3D printing are the exact terms for this new area of industrial production.

As with all 3D printing, rapid tooling primarily requires a computer workstation and a 3D printer. The computer is not only used to develop the model for the prototype. It is also used to precisely design the tool and provide the print files (usually in STL format). In addition to the usual 3D design programs, this may require a variety of other software. Simulation programs are particularly important for injection moulding processes. Temperature distribution in the component and mould as well as stress distributions in the mould during the production process can be displayed with the help of these programs. The mould and the production parameters can thus be precisely designed for an optimal result. In plastic injection moulding, this applies to the cooling channels, among other things. With their help, the solidification of the injected plastic can be precisely controlled. For example, different surface qualities can be produced during the production process: lids of housings are often ordered with a high gloss on the visible surface, while the non-visible surface can remain rough. This can only be produced by rapid tooling.

A suitable additive process for rapid tooling is SLA printing. This process uses a synthetic resin that is bombarded with a laser. Of all the 3D printing processes, SLA printing offers the smoothest surface. Rapid tooling by filament printing usually still requires a slight touch-up to smooth the contours. As an alternative to SLA printing, laser-sinter printing with plastic powder can also be used for rapid tooling. However, the FLA printers in industrial use are compelling because of their very favourable costs for equipment and raw material. Today, they offer sufficient quality so that rapid tooling can also be implemented well with them.

What are the advantages of rapid tooling?

Rapid tooling, i.e. tool and mould construction via 3D printing, offers the following advantages over traditional manufacturing processes for mould tools:

  • Significantly lower manufacturing costs
  • Considerably shorter manufacturing time
  • Fewer processing machines required
  • Shorter development cycles
  • Tools with improved cooling capacity can be produced
  • Fewer specialists required

All that is required for the production of a mould via rapid tooling is a 3D printer and CAD software. The 3D printer manufactures additively, i.e. without the production of chips and grinding dust. This makes its material consumption very efficient. If one compares rapid tooling with the processing machines that have been required up to now for tool and mould making, the advantage becomes clear: no CNC milling machine, no eroding machine and no fine grinding machine are required for rapid tooling.

Rapid tooling and its related application methods

New terms are constantly being created around additive manufacturing. Some of these are synonymous, others have overlapping meanings, but must still be distinguished from each other.

The following terms are becoming established around additive manufacturing in industrial applications when it comes to rapid tooling:

  • Direct Tooling: The tools produced in direct tooling can be used immediately in the production process.
  • Indirect Tooling: Indirect tooling does not produce a finished tool, but a test model for a tool to be produced later. It is quite resilient and can be used for the production of some prototypes and pre-series products. However, large series cannot be produced on the production tool made in indirect tooling.
  • Prototype Tooling: Prototype tooling is closely related to indirect tooling. It describes both the production of the tool prototype and the prototypes of the end product that are produced on the tool.
  • Rapid Manufacturing/Prototyping: "Rapid" is used synonymously with 3D printing. However, it does not necessarily mean its use for manufacturing in mould and tool making. Rapid manufacturing can also refer directly to the 3D printing of the desired end product. For the production of single pieces and pre-series models, one speaks of "rapid prototyping". However, if large quantities are to be produced by 3D printing, one speaks of "rapid manufacturing".
  • Rapid Repair: Rapid 3D printing processes are particularly interesting for maintenance and repair tasks. Under the keyword " rapid repair", 3D printers are used for the production of spare parts. This is extremely advantageous especially for self-sufficient, autonomous or hard-to-reach areas of operation. Already today, submarines, oil drilling platforms or hard-to-reach expeditions are equipped with powerful 3D printers with which they can produce their own spare parts when needed.

Other aspects of rapid tooling

Rapid tooling is not exclusively limited to 3D printing with plastic filaments or resins. Additive manufacturing is now possible with virtually any material. Metal printing in particular has seen tremendous progress in recent years. Rapid tooling with metal printing produces resilient tools that can partially compensate for the disadvantage of low durability under full load. Rapid tooling with metal powder produces sintered structures. These can be equipped with any geometries - especially the practical internal cooling channels. However, rapid tooling is still a very young technology that will continue to provide innovative breakthroughs here in the future.