Dear *|FNAME|*,

We've hardly got over TCT and we are on the run up to Euromold 3-6 Dec. This is the annual big fair at Frankfurt that pulls together the European RP industry.

I shall be there for at least 2 days - it's big! Last year we saw the launch of new FDM machines, updates to EOS hardware, Sintermasks new machine and others, including specialist niche processes. It's an exciting if gruelling show to do. So why go?

Well, we can't afford to sit back; we need to keep discovering new technologies, new materials and new machines. Opportunities for cost reductions, value creation, product enhancements and innovation is what it is about and Euromold is where it's at!

But don't worry if you can't make it consider me there on your behalf. In fact if you have anything you would like me to research for you whilst I'm there let me know; save yourself 2 days and talk to me!!

I remain, at your service,

tim@plunkettassociates.co.uk

Did You Know?

I'm just back from China! It's not my first time and I'm been back to continue my quest to seek out new suppliers and services that can deliver value for us. Consider me your Jean Luc Picard of the RP sector!

Whilst China may no longer be the 'final frontier' it offers opportunities for the wary and well researched. This is not the place to type your requirements into Google, make a phone call and place an order – what you see is definitely not what you get.

I make the effort to actually go to China so that all my clients can be assured of service, delivery and quality standards. I have seen the operations we use and met the people in the flesh! Developing robust relationships with quality suppliers who can reliably deliver, is absolutely critical.

It's my belief that there's much value to be derived from sourcing in China and whilst we may currently be hearing of many factories closing, for example the toy industry having an awful time, I want to be personally reassured so that you can have confidence, that for our sector we can get what we need, when we need it, to a cost and quality we expect – every time.

More on the trip next month…

What Does Henry Ford know about RP?

In last month's Outside the Box, I suggested you might consider CNC for larger parts, rather than RP. In this issue I look at some of the drivers and what we should be considering and expecting from CNC.

Henry Ford said "Any customer can have a car painted any colour that he wants so long as it is black". Choice was not an option. When Stereolithography arrived in the UK, its capability was awesome and choice extremely limited. Since then other processes have come to market and most importantly CNC has been fighting back.

Why Chipping Away Builds Value!

CNC has two major advantages over RP techniques:

1. You can use a wider range of materials giving greater opportunity to optimise material properties (ABS/PA/POM(acetal)/PC/PP/PMMA/PTFE/PBT for example)
2. There is minimal, practical constraint on size and volume of the part due to it being subtractive and not an additive process.

Most RP processes run with specific materials that have been formulated and optimised for a particular machine. Unless you're in a Rapid Manufacturing (RM) scenario, none of these materials will be those utilised when in full production. The two issues are the material properties themselves and the anisotropic properties that result from the build layering – meaning that even the FDM process which uses ABS and PC will not give "production properties".

When using CNC the materials are typically extruded in slab form and then machined, getting us significantly closer but still not matching grade or moulded grain flow of the production part. For materials such as PP, PTFE and Acetal this is a considerable advantage over anything that RP can offer and for clear parts CNC in PMMA or PC offers a very high level of clarity that again RP cannot match.

To go better requires a prototype mould tool and to actually inject the required grade in a limited run, pre final tooling release. This way the material characteristics are fully validated pre production, however the downside remains cost and lead time.

It is important to differentiate between achieving a functional prototype and qualifying the production material through the prototype. The potential to misinterpret RP material properties was evident in a recent project where the SLS part functioned beautifully but when the part was moulded in ABS, the clip features did not offer the required degree of rigidity. This was resolved by a simple tool modification to increase the clip section and hence the strength. Machining the part in ABS at the outset could well have resulted in the prototype breaking, the question is, would this have been deemed as a failure or an indication of the real problem?

The lesson to take from this is that RP will give form, fit and a growing level of function, but in achieving function, the material may be over specified relative to production material because of the limited options available. CNC gives you the opportunity to use the correct material, albeit without moulding, and as such must be a worthy consideration.

It's True – Size Matters

RP prices are driven by overall component envelope and usually material volume. The latter applies as the process is additive and thus the greater the volume the more process time there is in 'drawing' the part.

CNC is clearly subtractive and hence the opposite is true. Machining time is affected by the volume of material that needs to be removed to give the desired geometry. That said, significantly more material can be machined away in a single pass than can be sintered by a laser in say SLS.

Whilst RP bed sizes have grown over the years, CNC easily outstrips what is available today. However that is not the key issue, the decider is frequently economics. Looking at a typical Western CNC operation, CNC may struggle against RP, even for quite large parts. However, we are now in a global economy and when we look at the resources, machines etc that are available through the Far East, CNC can offer significant cost advantages over RP, especially as the part size/volume rises. Handling complexity will always be a strength of RP, but CNC is steadily eroding this advantage and offering an ever increasing challenge.

You may be thinking so what are the downsides of CNC? Well, complexity can necessitate fabrication of the part, for example deep thin slots being impossible to machine. However the benefits of better accuracy, no layering and crispness of detail make CNC a very serious contender for your next project.

Tips on Utilisation and Actions to take:

• Make internal radii as large as possible - also good from a stress or moulding perspective
• Think tooling – e.g. can you avoid a side action by coring out from the rear? This will facilitate machining as well and avoid the undercut
• Money can be saved by for example; not coring out non functional areas because unlike RP and moulding wall sections are not an issue
• Wall sections down to 0.5 mm are feasible, below this they need to be reviewed
• Think three axes; the more that can be done like this the lower the cost. Resorting to four or five axes is feasible but will cost more!
• Certainly consider parts at 300mm plus and smaller if volume is high

And one final tip – you can always call me to see how CNC can be of commercial benefit to your business – we are not like Henry Ford!