THE RAPID GROWTH of Rapid Prototyping

Posted on 01/05/2015 by Tony Harrison

Once the preserve of industrial big spenders, 3D printing is the rapid prototyping and manufacturing method of choice for businesses of all types and sizes today. Tony Harrison explains what it is, how it works and how to make it pay

3D Printing – additive manufacturing, or rapid prototyping – used to be a strictly industrial process. Today, it's so mainstream there are 3D printing machines designed for consumer use. Expired patents, low cost consumables and intuitive software have democratised 3D printing.

Fast prototyping and short lead times allow for rapid response to customer feedback, and enable products to be fine-tuned and brought to market quicker than ever before.

3D printing has gained a foothold in many industries. In the aerospace, defence, rail and automotive sectors, for example – where strength-to-weight ratio and heat, smoke and toxicity resistance are crucial – parts can be produced in proven high-performance thermoplastics. In the consumer goods sector, less expensive materials can be used to produce items from collectible characters: from children's films to mobile phone prototypes. In the healthcare profession, 3D printers are creating not only medical devices, but replacement body parts, too.

Another area where 3D printing is becoming increasingly commonplace is education. Having established itself as a mainstream industrial technology, it follows that students should be exposed to the potential of 3D printing. More and more schools are investing in 3D printers and introducing them across the STEM (science, technology, engineering and mathematics) and design subjects. Pupils are learning to use the technology to demonstrate proof of concept.

There are several methods of 3D printing. Each has its distinct advantages and disadvantages, depending on product specification and aesthetic priorities – see box-out.

MAKING IT PAY

When it comes to financing your 3D printing, there are two main options. The first is to acquire your own machinery and bring the process in house. This obviously requires some capital outlay, either through outright purchase or by entering into a finance arrangement. This makes sense if your need for 3D printing is frequent or calls for large quantities of raw materials.

The alternative to in-house 3D printing is to use a bureau. Many smaller businesses are unable to justify the cost of a 3D printer together with the necessary raw materials and post processing equipment. In this scenario, a bureau allows you to enjoy many of the advantages of 3D printing without having to make the big investment. You simply send or upload your 3D print file to the bureau. The bureau then prints the product to your specification. You can collect the product or have it couriered to you.
IN-HOUSE VERSUS BUREAU
With prices of 3D printers starting at around £3,000, you could finance a machine from £99 per month. To create a product requiring five cubic inches of material would cost a further £17 at current average material costs. If this were your monthly output, your costs would be £116 per month. (This would drop dramatically if you owned the machine outright.) The same five cubic inch product would cost around £107 to have made at a bureau. If you were unable to collect the item in person, you would pay a delivery charge on top.

3D PRINTING IN-HOUSE

If you decide to bring 3D printing in house, consider these four criteria:

Your products – from proof of concept to functional parts and end products, 3D printers can produce almost anything. While strength may be key for some products, colour, resolution or smoothness may be more important for others. The build bases of most 3D printers are similar in size, though wide format models are available for larger products.

Materials – materials are key to 3D printer choice. Weight, flexibility, rigidity and durability specifications, for example, are all important considerations. Factor in your temperature and vibration resistance requirements, too. You may also need a machine capable of printing in more than one material.

People – 3D printing requires post processing. This stage is necessary to clean the end product and remove temporary structures that act as scaffolding during the build. Post processing can involve resin or acid dips and processes to blast away powders or glue-like substances. If non-factory staff will be using your 3D printer, opt for a machine that needs minimal, post processing. Bear in mind that some machines will contain toxic materials and should only be used in well-ventilated areas.

Finance, service and maintenance – discuss finance options with your 3D print systems supplier. Ask them about maintenance contracts and what services you will receive. Some resellers offer guaranteed buy back prices and technology refresh options. These can allow you to replace up to one third of your fleet of machines every year without necessarily incurring extra costs. Also, find about the cost of consumables. This will help you project the running costs of your 3D printing equipment.

Ask your supplier if they can offer you a demonstration. They may also be prepared to provide you with a machine on a trial basis.

MORE THAN ONE WAY TO PRINT IN 3D
Here are the five most commonly used 3D printing methods used in engineering today:

FDM (Fused deposition modelling)
The FDM 3D print process extrudes thermoplastic. It's ideal for prototypes, end use engineering-grade parts, machine parts and presentation materials.
Advantages – a wide variety of materials including ABS plastic, range of colour options, low maintenance costs, no toxic materials, low temperature operation, no supervision required.
Disadvantages – low resolution (ie, visible seam lines), longer build times, temperature fluctuations during process can cause delamination, supports sometimes required, lower Z-axis strength.

PolyJet
Like the traditional document printer, PolyJet uses printer heads which move backwards and forwards. The printer heads lay down a photopolymer that is cured by UV light. PolyJet 3D printing is suitable for animation models, form and fit checking and exhibition models.
Advantages – multi material product realism, high resolution, fine detail, smooth finish, strong on all axes (X,Y and Z), precise, repeatable, good range of materials, including transparent.
Disadvantages – uses 'ABS like' materials so not as durable as FDM, high cost, becomes unstable if subjected to sustained heat or sunlight, hydrophilic (swells if immersed in water for prolonged periods).

SLS (Selective laser sintering)
SLS is a powder-based technology. Using lasers, it sinters powdered forms of different materials together. This binds them to create a solid object
Advantages – uses powdered forms of multiple materials including plastic, metal, glass, etc. SLS supports full CMYK colours and can produce complex parts with no support materials.
Disadvantages – messy, high purchase price and high set up / running costs.

SLA (Stereolithography)
This technology uses UV to harden photosensitive resins into solid structures one layer at a time.
Advantages – high resolution, smooth finish, can produce complex and bulky mechanical parts, can use translucent resins.
Disadvantages – machines are large and expensive compared to other 3D printing methods, specific power requirements, resin will cure if exposed to UV light (needs be positioned in a dark room) holds high quantities of toxic resin which has a finite shelf life, requires ventilation and careful user maintenance, post processing involves a UV oven.

MJM (Multi-jet modelling) This relatively new process has been developed for quick turnaround prototyping. It works by printing layers of liquid plastic onto a flat platform, then solidifying the structure with UV lamps.
Advantages – ideal for small parts and complex geometries, wax support structures are easy to remove, high resolution and super fine detail.
Disadvantages – ultra high definition and accuracy decline as part size increases, fine layers increase build time, areas affected by wax residue are resistant to paint.

IN-HOUSE BENEFITS

Cost: in the long term, acquiring your own 3D printing equipment costs less than outsourcing to a bureau. Raw materials work out cheaper and you'll save on delivery costs. As the figures in the cost comparison illustration show, printing more than one five cubic inch product per month is more cost effective than using a bureau.

Speed: nothing is faster than producing your own product, to your own specification, in your own premises. Rapid prototyping offers a direct route to market and the chance to outmanoeuvre rivals.

Fine-tuning: as with any electronic file, you may look at 3D print design and wish to change something at the very last minute. You may spot an error, have a late flash of inspiration that improves the product or get a request from a colleague to tweak the design. 3D printing in-house gives you free reign to edit, refine and adapt as much as you need before hitting the 'print' button. By contrast, once you've sent the file to a bureau, it may be too late.

Data security: 3D print design files are subject to the same risks as any document transmitted to an external organisation. Your company may have strict security policies governing the sharing of sensitive data. However, if your 3D print function is in-house, this won't be an issue.

BUREAU BENEFITS

Cost: the cost comparison illustration shows how printing more than one five cubic inch product – or equivalent – once a month on average makes printing in-house the cheaper option. Accordingly, if your 3D printing requirements are less frequent than this, you'll save money by using a bureau.

Freedom to choose 3D print type: industrial components operating in demanding environments require a different type of 3D process to day-to-day household items or fashion accessories. With a bureau, you can choose the right option for each unique job.

An expert eye: 3D print design software can be complex. Staff at a good bureau can spot and fix any errors that may prevent your design being printed properly. They may charge for this service.

Post-processing: a big problem with some types of 3D printing, especially SLS (selective laser sintering), is the post-processing involved. This can get messy, so it's not ideal if you welcome customers to your premises or wear smart clothes to work. With a bureau, you outsource this problem.

Tony Harrison is managing director of 3D Generation, an authorised supplier of 3D print systems produced by Stratasys and 3D Systems to businesses across the UK. www.3dgeneration.co.uk

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