Rapid prototyping #2

3d product design development strategy consultants Plastic Design

Rapid prototyping #2

Last month we got you up to speed with 3D printing, this month we’re introducing ‘proto-forming.’ That’s a buzz word we have created to encase everything that falls outside of 3D printing additive technologies. There are several ways to create prototypes and models without using 3D printing. These methods are as follows: thermoforming, vacuum casting and CNC machining.

Prototyping utilising the three methods above usually come with high start-up costs, so it is unusual for businesses to have these in-house. Out of the three machines CNC machines are the most attainable, however industrial sized models are very expensive. Below shows the three different machines side by side.

3d product design development strategy consultants Plastic Design

 

CNC Machining

3d product design development strategy consultants Plastic Design

How does it work?

CNC machining is a ‘reductive manufacturing’ process whereby an automated, programmable machine tools a solid block of chosen material. The materials that are available to be CNC machined are wide ranging.

What is it used for?

CNC machining is ideal for creating components that require great precision and fine detail. It is frequently used to create fixtures, tooling and other end-use parts. CNC machining is a perfect solution when multiple identical copies of the same part need to be produced. This is easily achieved by a CNC machine as the computer can run the same process for an unlimited amount of time.

The pro’s

  • Cost-effective
  • Short-lead times
  • Wide choice of materials

The con’s

  • Unit cost of parts created by CNC machining are more expensive than injection moulded parts.

 

Vacuum casting

3d product design development strategy consultants Plastic Design

How does it work?

Vacuum casting has additional steps within its process, some of these steps are manually intensive. Firstly, a single master is created by using an SLA master model. The mould is crafted out of silicone rubber and is then cast by pouring resin into the mould and placed in the vacuum chamber.

Once the silicone rubber mould is removed from the vacuum chamber it leaves behind a ‘bubble free’ casting. This creates a highly accurate, functional simulated plastic part in fine detail which can replicate patterns, dimensions, profiles and textures.

What is it used for?

Vacuum casting is a fast and cost-effective method for creating small batches of production quality end use parts and prototypes in polyurethane (PU) resins and cast nylon.

The pro’s

  • Cost effective
  • Low volume runs
  • Fine detail and accuracy
  • No requirement for expensive hard tooling

The con’s

  • Limited material choice
  • Silicone master mould can deteriorate rapidly in sun and open air
  • Only a single material can be formed at one time
  • Finishing touches be can costly and labour intensive
  • Up to 25 casts from each tool

 

Thermoforming

 

3d product design development strategy consultants Plastic Design

 

How does it work?

Thermoforming is a very simple plastic moulding process whereby a sheet of plastic is heated to an elevated temperature and formed over the top of a mould. The plastic sheet then takes the shape of the mould when it meets it. The moulding is then normally trimmed to make a usable product.

There are other variables within the thermoforming process which can affect the outcome of the process. For example, there will be differences between parts formed over a male or female mould.

What is it used for?

Thermoforming is used by a variety of different industries for applications such as packaging, automotive parts, machinery parts, building products, signs and displays.

Thermoforming has some interesting process developments that can add value to applications. These include sheets incorporated with nano-composites and also converting thick sheet applications to composite sheets which result in thinner walled parts that are ideal for weight-sensitive applications. Commonly, the plastic sheets that are used for thermoforming are made from HDPE, PP PMMA, Polycarbonate, HIPS or ABS.

The pro’s

  • The sheets used in thermoforming are usually of a much higher quality and durability than the plastic materials used in other moulding methods.
  • Low cost
  • Short lead times
  • Low tooling costs
  • Variety of self-coloured and paintable plastics
  • Multiple options for finishing, patterns and textures

The con’s

  • Can be costly if high-quality plastic sheets are used
  • Only one side of part is defined by mould
  • Parts including sharp bends and corners are hard to produce
  • Internal stresses are common



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