Rapid tooling speeds medical equipment to market

Space Puzzle Molding is a hybrid technique of joint rapid tooling and rapid prototyping technologies, and provides low-cost, simplified moulding tools made of aluminium.

The multinational Siemens group is one of the world's largest manufacturers of electrical, electronic and engineering products.

Some of Siemens' products such as car navigation aids, phones and home media items, home appliances and mobile phones are produced in quantities reaching millions for the mass markets they serve.

Others, in the high capital-cost business area such as the medical equipment application considered here, are more specialised and market volumes from a few hundred to the low thousands are typical.

One branch of medical diagnostics is angiography, the X-ray imaging of the various vascular systems in the body such as heart and lung components, kidneys, also the brain and the retinal vascular areas.

Angiography itself is a medical imaging technique using very low-dose X-rays to highlight the presence of a radio-contrast substance, catheter introduced, which travels via appropriately selected arteries direct to the affected area, giving shadow pictures of the inner openings of the openings and intricacies within the blood filled structures in the cardio-vascular system.

The relatively mild invasive procedure of catheter insertion is necessary because blood and the surrounding tissue have closely similar radio densities and as such would have no significant contrast in an X-ray image.

The term computer tomography or CT (alternatively referred to as CAT scanning, the acronym for computed axial tomography) refers to the rotating of X-ray sources, usually two or three in number around a specific target deep within a patient's body.

Each captured X-ray image is two-dimensional but modern computer software can present the combination of these images as an accurate and well defined 3D picture.

Furthermore it can be viewed live, and in near-real-time video.

The Axiom Artis dTA installation is a remarkable development in the field of tomography.

Operating at lower exposure levels than conventional CT scanners the X-ray head and receptor unit can be swung through an arc of approximately 220 degrees and the resulting series of images can be processed by a unique piece of software called syngo DynacCT to yield CT-like images previously unavailable in the basic angio-lab environment.

This technique has been termed ACT (angiographic computed tomography).

The information viewable is not exactly the same as a full CT scan but may be sufficient in some cases to render a full-power scan unnecessary.

Indeed in some reported clinical experiences the angiograph information was absolutely complementary to the CAT data, greatly assisting diagnosis and subsequent treatment.

With instruments such as the Axiom Artis dTA the quality and precision of every functional component is paramount and Siemens' design team search all available processes and avenues to ensure the economic and technical objectives are met.

This means that items such as plastic mouldings must utilise top quality tooling even though the volume of production may be in the low hundreds per year.

A set of nine parts makes up the moulded housing for the X-ray sensor comprising - a split top half, a substructure moulding front fascia, two functional strips and three composite mouldings with metal inserts for locating and clip functions.

The fascia is designed to house a plane screen insert.

The reverse half is in two matching sections fitting precisely together and with apertures for control buttons.

Overall dimensions of the complete unit are 500 x 400 x 150mm.

Materials specified for these items are: ABS for the small functional clips, glass-filled polystyrene for the four large housing parts and POM (polyacetal) for the long strips.

POM is a material known for its excellent hardness, stiffness and ductility.

It has good friction and wear resistant properties and high dimensional stability over a wide temperature range hence it is ideal for such applications as this.

Space Puzzle Molding (SPM), the patented process operated by Protoform, is recognised to provide the ideal route for complex precision plastic parts in volumes from prototype through to the low thousands.

This medium-volume production capacity encompasses such products as medical equipment, short-run custom automotive, specialised photographic applications, prototype and alpha/beta trials in the evaluation and design finalisation of consumer products using the production intent materials, marine and avionic and electronic instrument housings and controls.

New market areas are constantly emerging as the word spreads about the process capability and product quality.

Basically the process from the design stage through to the finished product follows the best practices of production injection moulding.

There are no compromises or limitations to take onboard when choosing Space Puzzle Molding.

The differences between this technique and full injection tooling for mass production are all in the method of tool construction and subsequent handling on the production lines.

All SPM tools are ultimately designed to fit into one of a range of suitably sized standard outer bolsters of unique, patented character.

The main parts of the tool that actually create the shapes and forms, the sliding cores and loose inserts are precision milled on high-speed, multi-axis, state-of-the-art machines using tooling grade aluminium or steel if the tool requires it.

They are finished on the external planes to a size around 20% only larger than the actual component itself.

This saves tremendously on material, time and hence cost but the benefits do not stop there.

In any early tooling there needs to be flexibility to allow mould flow and post-moulding effects to be evaluated and, if necessary adjusted.

SPM tooling accepts and facilitates such changes and adjustments like no other because the individual parts of the "puzzle-like" assembly are easily modified or replaced, doing so at the lowest cost and on timescales without impacting greatly on product flow.

Design iterations and niche market variants can often be accommodated by a change of inserts only and it is not unusual for a single set of tooling to have multiproduct capability.

This can be particularly useful in a spare-part situation where a few pieces of an earlier design may be required at a later date, or perhaps the parallel introduction of high/low specification models with different requirements for control apertures.

The near contact-volume envelope SPM tooling splits when removed from its supporting bolster structure.

Demoulding is a very slick, manual operation, since little automation is required to operate the core and inserts beyond a set of custom hand tools and extraction devices tailored to each component.

Couple the above advantages of Space Puzzle Molding with the fact that it is a rapid tooling technique, giving production quality items in short-series manufacture, and the synergy with companies in the low to medium volume markets such as top-end medical equipment becomes clearly apparent.

The Protoform formula, made up of tooling cost, timescale, production rate and item cost makes a perfect match for items from 2g to 2.2kg shot weight and generally within the dimensions 800 x 400 x 200mm and in quantities up to 3000 items.

In the case of the components for the Axiom Artis dTA for Siemens, the requirement was for 880 sets to be delivered in batches to a schedule matching the production rate of the instrument.

This was achieved comfortably by Protoform, which concludes every project with a customer questionnaire designed to provide feedback on performance and possible areas to improve the service.

The survey comprises 23 questions ranging from: friendliness and approachability of technical and production staff, through technical competence, process flexibility, quality, and finally price and delivery issues.

The survey is specifically designed to be super-critical and extends beyond normal expectation to an absolute maximum score of 130%.

The Siemens customer survey comprised 15 very goods and eight goods covering the 23 points with no criticisms or negative responses whatsoever, yielding a commendable score of 108%.

The project is ongoing and further quantities of components can be made available as the demand for the instrument proceeds.

In cases where the demand is initially for early-to-market quantities and the ultimate market is a mass production situation, then the CAD data and moulding information can be made available on request to the production toolmaker providing a significant aid to a smooth transfer when appropriate.

With 9000 moulding projects completed over recent years, Protoform has an invaluable bank of experience in house for any client to tap into.

On average a set of tooling is completed every working day speaking volumes for the popularity, suitability and synergy with its markets, of this unique process.

The SPM method, Space Puzzle Molding, is a hybrid technique of joint rapid tooling and rapid prototyping technologies, and provides low-cost, simplified moulding tools made of aluminium, using state-of-the-art CAD software and high speed CNC machining methods, working from client's CAD data.

With these moulds, one can call off both prototypes and batches of plastic parts in production intent materials.

mouldings so produced are Class A, quality perfect and series identical.

They are manufactured to exacting standards using semi-automated methods on standard injection moulding machines.

Space Puzzle Molds comprise individual pieces like parts of a puzzle precisely interfaced and secured to the injection machine in a unique patented device which is product-envelope categorised common to many sets of moulds.

The SPM process is Ideal for complex parts.

New iterations/design variants can be readily introduced by changing the individual inserts and elements that make up the tooling.

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