The Pros and Cons of Prototype Machining

One of the most popular manufacturing techniques is CNC machining or what is known as prototype machining in prototyping.

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This popular technology is used for creating prototypes in a subtractive process, in a way that works opposite of 3D printing. In this process, the material is gradually removed from the block to form the part.

How do you know whether prototype machining is the right technique for your design? We have the answers here.

What is Prototype Machining?

To understand what prototype machining is, we need to look into how CNC machining works. The process begins with a 3D digital design using CAD software. It is a computer program that translates a series of instructions to the cutting tool of the CNC machine. This set of instructions are called G-code.

When these G-codes are relayed to the machine, it will automatically work on the block of material and translate the design into a part. It does not need further supervision as the machine does things autonomously.

Pros of Using Prototype Machining

There are many reasons why a company should use machining to produce a prototype including speed, quality, plenty of material options, and likeness to the final part.

It is a digital process

One of the biggest advantages of using CNC machining is its digital element. The process is purely digital with the CAD software sending instructions to the cutting tools to create the prototype. After reviewing this prototype, it is the same digital design that will be used to create the final part. That means it has the same dimensions and is highly repeatable.

This digital design is also easy to alter in case there are modifications needed along the way. The engineers only need to do the modifications on the file for the next prototype.

Prototypes have consistency and quality

We are not saying that computers are perfect but prototypes made through prototype machining shows high fidelity to the design. It is also highly repeatable with the same quality. This is quite a feat, especially when developing iterations of the prototype and when you make the final product using the same machine.

You can choose from a wide range of materials

3D printing may work with parts that do not have a mechanical purpose or do not require strength. It may be less expensive but the material options are limited.

Prototype machining, on the other hand, offers a variety of material options, including those that are extremely strong and durable like metals.

Proximity to the final part

The last advantage of prototype machining is its ability to create parts that have a high resemblance to the final part. This is not possible when you use other prototyping techniques. Thanks to the materials that can be used in prototype machining, engineers can make prototypes using almost the same materials to understand the form and function of the final part.

Cons of Using Prototype Machining

Despite its benefits, prototype machining has certain limitations too. Here are some of them.

More Costly

One of the reasons why some manufacturers are looking for an alternative technique to prototype machining is its cost. Machining workshops need big pieces of machinery that require huge investment. Product developers look for a cheaper prototyping process if the business has to cut on costs during this stage.

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Few Geometrical Limitations

Another disadvantage of prototype machining is its geometrical limitations. Although the 4-axis and 5-axis offering of some CNC machines offers flexibility, it is not enough to accommodate elaborate structures.

Amount of Waste Material

Since prototype machining is a subtractive process, it uses more material than what goes into the part. This material is cut away from the block and usually ends up like chips and gone to waste. Thus, using prototype machining will incur a higher material cost.

Conclusion

We have enumerated the pros and cons of using prototype machining for product development. It is a better alternative considering its benefits but you should not disregard its drawbacks too. For more questions about the prototype machining, get in touch with a machining contractor near you.

What are the Different Types of Rapid Prototyping?

Stereolithography (SLA) or Vat Photopolymerization

This fast and affordable technique was the first successful method of commercial 3D printing. It uses a bath of photosensitive liquid which is solidified layer-by-layer using a computer-controlled ultra violet (UV) light.

Selective Laser Sintering (SLS)

Used for both metal and plastic prototyping, SLS uses a powder bed to build a prototype one layer at a time using a laser to heat and sinter the powdered material. However, the strength of the parts is not as good as with SLA, while the surface of the finished product is usually rough and may require secondary work to finish it.

Fused Deposition Modelling (FDM) or Material Jetting

This inexpensive, easy-to-use process can be found in most non-industrial desktop 3D printers. It uses a spool of thermoplastic filament which is melted inside a printing nozzle barrel before the resulting liquid plastic is laid down layer-by-layer according to a computer deposition program. While the early results generally had poor resolution and were weak, this process is improving rapidly and is fast and cheap, making it ideal for product development.

Selective Laser Melting (SLM) or Powder Bed Fusion

Often known as powder bed fusion, this process is favoured for making high-strength, complex parts. Selective Laser Melting is frequently used by the aerospace, automotive, defence and medical industries. This powder bed based fusion process uses a fine metal powder which is melted in a layer by layer manner to build either prototype or production parts using a high-powered laser or electron beam. Common SLM materials used in RP include titanium, aluminium, stainless steel and cobalt chrome alloys.

Laminated Object Manufacturing (LOM) or Sheet Lamination

This inexpensive process is less sophisticated than SLM or SLS, but it does not require specially controlled conditions. LOM builds up a series of thin laminates that have been accurately cut with laser beams or another cutting device to create the CAD pattern design. Each layer is delivered and bonded on top of the previous one until the part is complete.

Digital Light Processing (DLP)

Similar to SLA, this technique also uses the polymerisation of resins which are cured using a more conventional light source than with SLA. While faster and cheaper than SLA, DLP often requires the use of support structures and post-build curing.

An alternative version of this is Continuous Liquid Interface Production (CLIP), whereby the part is continuously pulled from a vat, without the use of layers. As the part is pulled from the vat it crosses a light barrier that alters its configuration to create the desired cross-sectional pattern on the plastic.

Binder Jetting

This technique allows for one or many parts to be printed at one time, although the parts produced are not as strong as those created using SLS. Binder Jetting uses a powder bed onto which nozzles spray micro-fine droplets of a liquid to bond the powder particles together to form a layer of the part.

Each layer may then compacted by a roller before the next layer of powder is laid down and the process begins again. When complete the part may be cured in an oven to burn off the binding agent and fuse the powder into a coherent part.

Applications

Product designers use this process for rapid manufacturing of representative prototype parts. This can aid visualisation, design and development of the manufacturing process ahead of mass production.

Originally, rapid prototyping was used to create parts and scale models for the automotive industry although it has since been taken up by a wide range of applications, across multiple industries such as medical and aerospace.

Rapid tooling is another application of RP, whereby a part, such as an injection mould plug or ultrasound sensor wedge, is made and used as a tool in another process.

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