Lower Cost Self-Colouring of Engineering Thermoplastics

Colour has always been important.  Articles offered in bland coloured materials do not appeal to anyone and do not sell well.  Colours distinguish one brand from another and for the designer represent one of the most versatile tools to introduce differentiation in competitive markets.

The value of colour is not lost on manufacturers.  But, much of its value is lost during manufacturing.  In the plastics industry, OEMs and moulders are utilising new resins and processing technologies to achieve thinner walls, better quality products, shorter manufacturing cycles etc.  And yet, the standard technique for adding colour to engineering resins such as ABS, PC and PC/ABS blends is, in many cases, outmoded.  The purchase of factory coloured resins no longer fits the realities of today’s markets - lower cost solutions are available.

There is an alternative approach to producing moulded parts from pre-coloured plastics that is less costly, more productive and more creative.

Market Driven Trends - Faster Response and Lower Cost

Well established markets for coloured engineering plastics include domestic appliances, automotive and business equipment.  In all of these markets increased attention is being placed on the aesthetics of the finished part.  ‘Look’, ‘feel’ and co-ordination with the surrounding parts are all being enhanced to promote sales and gain new business in these competitive markets.  Multiple textures and materials are being assembled together and a more critical view applied to their final appearance: especially in car interiors.  Colour, gloss and mattness are integral contributors to achieving the desired aesthetic.  As such, these properties are becoming basic requirements to participate in most markets.

Globally, sales of portable entertainment gadgets such as MP3 players, mobile phones and the latest digital cameras is moving towards a more customised offering that reflects the individual personality of the customer.  In practice, this means that the number of colours and textures offered is increasing rapidly.  Examples of this trend are found in the major stores retailing portable entertainment equipment – even Marks & Spencer stores now feature a technology section.

Only a few years ago these items were mainly sold to business people in dark and sober colours. Today the designers are responding to the growth opportunities created by a technology savy public with an eye for style and something that ‘stands out’ when seen in trendy settings. The truth is that people now want more choice and satisfy their desire through selecting products in more “fashionable” colours and textures. But, the life cycle of a typical colour is short: maybe one year or so and, in the case of campaign colours they may only last a few weeks.

How do companies make coloured parts?  Normally they purchase factory pre-coloured resins from their suppliers and mould them. End of story.  Except, that’s no longer the end of the story.  There is a better and cheaper way of producing the same coloured part, a way that increases the profitability and market competitiveness of companies and which also enables them to deliver products faster, more productively and more creatively.  The technology is called self-colouring.

Self-colouring Technology is Simple and Effective

Self-colouring technology involves mixing, in the injection moulding machine a natural un-pigmented grade of resin with a pigment concentrate to produce the desired colour in the moulded part at the time of manufacture.  This is not new, unproven technology, quite the reverse, it is well known and widely practiced by moulders of polystyrene and polyolefin resins.

Increased Market Competitiveness through Cost Savings

Although it is well-established technology, many OEMs and moulders are unaware of the magnitude of the cost reduction, increased profitability and enhanced market competitiveness self-colouring of engineering plastics such as ABS and PC/ABS can deliver.

Across many industries experience has confirmed self-colouring of plastics is capable of reducing most companies’ operational costs by:

• reducing stock inventories and working capital
• reducing obsolete stock write-offs
• eliminating costly premiums for small-lot deliveries of pre-coloured polymer
• simplifying warehouse logistics
• freeing-up existing warehouse space for more productive use
• reducing energy costs associated with in-plant polymer drying
• enabling higher utilisation of moulding equipment
• reducing labour costs related to warehousing and administration
• ensuring flexibility to meet sudden market demands

 The value of these savings varies from company to company but most of the case studies indicate saving of 1% per colour moulded can be eliminated from the total operational cost of their business.

Quantifying the Economics of Self-colouring

The first stage in quantifying the economic benefits of self-colouring natural grade resins versus the costs of moulding pre-coloured plastic is to audit the existing operation. Only when an accurate picture of the existing operational costs has been completed can a grounded investment / reward decision be taken by the management.

Typically the project would develop:

• Comparisons of the resin-spend for factory pre-coloured resin with natural grade resin and colour concentrates.
• An analysis of the savings resulting from increased operational efficiency created by switching to natural grade resin.
• An analysis of the cost saving created by more efficient supply logistics.
• An analysis of the necessary investment, the repayment period and return on investment.

Many companies are initially surprised and then concerned at the hidden costs of producing parts with factory pre-coloured resins.  For these same companies, the question then changes from “What does it mean for us?” to one of “How long will it take us to get started?”

Implementation in an Injection Moulding Workshop

Normally an investment is necessary to enjoy the benefits of self-colouring.  Virtually all of the cost is in new equipment needed to store, dry, transport and dose natural un-pigmented resin grades with the colour concentrate.

Many companies adopt a phased approach to their investment decisions.  For example, the minimum requirement to implement self-colouring is a dosing unit which mixes the correct proportion of colour concentrate with the natural resin. Dosing units can be mounted directly on the moulding machine for continuous use or can be portable and moved from one machine to the next. Alternatively, larger dosing units can be located centrally to blend the components for a group of machines. A central unit is especially useful if several machines are producing parts in the same colour.

A phased approach enables immediate savings to be made, with the added benefit of limiting the initial investment. Later, the company may consider further investment for , for example, bulk resin storage in silos combined with central transportation of the polymer to the moulding machine. Alternatively, replacement of individual dryers with a central system may be more beneficial.

The financial impact of self-colouring is a step reduction in the company’s operational costs of producing coloured parts.  Typically, the savings released from the operation can be expected to repay the total investment within one year.

Increased Use of Colour Demands a Different Approach

Traditional methods of colouring plastics are now too expensive and too slow to take advantage of short life cycle markets.

Markets such as domestic appliance and consumer electronics will always have a need for short development and commercialisation cycles.  Otherwise, the opportunity will most likely be lost to the business.  Automotive applications are trending this way as well.  Products conventionally produced in neutral colours, such as computers, faxes, printers, and phones have become more colourful to enhance their broader appeal to the home user.

A final question: how would you respond, as the marketing or production director, if you received an urgent order for your best selling product, in a non-standard colour, for delivery next week?

If you are self-colouring your plastics today you could turn this opportunity into a profitable reality and steel the business from the competition?