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Product category: Rapid Prototyping
News Release from: Leonardo Computer Systems | Subject: JP5 process
Edited by the Engineeringtalk Editorial Team on 24 August 2000

Affordable Laminated Object Modelling -
by hand!

In the JP5 process you simply import an STL file into the JP5 software, which slices up your model. You then cut the slices from standard label paper using a standard vinyl sign cutter. It works!

Rapid Prototyping Systems have been the technology evangelists' darling of the 1990s Academia, and the Government alike have been promoting this relatively new technology as the means to shorten design times and improve the quality and effectiveness of new designs

But up until now there has been a major stumbling block for the majority of potential users - high cost! This has been partially solved because large organisations, unable to justify £500,000 for a big machine for their own work, have promoted themselves as Rapid Prototyping Bureaux.

In turn, separate specialist Rapid Prototyping bureaux have evolved.

More recently, smaller, less expensive machines have become available, but these still cost £50,000 or more for something that can build reasonable sized models.

This is still out of the reach of many small companies, or those who have relatively infrequent needs for physical prototypes.

However, there is an old adage the goes "an engineer is a person who can do for a penny what any fool can do for a pound".

The JP5 Rapid Prototyping process is a lesson in simplicity conceived by such a person.

In the JP5 process you simply import an STL file into the JP5 software, which slices up your model.

You then cut the slices from standard label paper using a standard vinyl sign cutter (rather like an old pen plotter).

After that, the slices are assembled into the prototype on a simple registration jig made from a slab of wood with two metal pins in it.

The finished prototype is then coated with glue to make it strong and resist moisture.

JP5 is therefore essentially LOM (laminated Object Modelling) by hand.

At this stage, you will almost certainly be thinking "what!", "Mickey Mouse", "Heath Robinson" and other such negative thoughts, having been conditioned to think of Rapid Prototyping as an expensive, mysterious, high-tech machine based process.

Well, that is just what I thought, that is what many journalists thought, and what many current JP5 users thought, so you are not alone! Fortunately although many of us find it hard to overcome our prejudice, the world is populated by many open minded souls who tried it and love it.

JP5 really does work, and makes excellent prototypes, sometimes faster, sometimes better and always cheaper than expensive machines.

So read on and be prepared to be amazed.

JP5 is written with the Silver Modelling Engine, a solid modelling kernel along the lines of Acis or Parasolid.

Silver also appears as SilverScreen which is a BRep facetted Solid Modeller, a copy of which is provided free of charge with JP5.

So, even if you haven't got a 3d CAD Solid Modeller, you can design your prototype using JP5's SilverScreen.

On the file menu you can open an STL file produced by your in-house 3D modeller, or a SilverScreen Model file.

STL files can be in binary or ASCII format.

STL files are notorious for having defects, and often being difficult to import, however 3 years experience has been built into the JP5 import routines, so it is unlikely that import will fail.

If it does for any reason, the file can be sent in for a fix, this fix is then incorporated in future software updates.

Some JP5 software settings must be made: Set up the software driver for the vinyl cutter - a normal Windows printer driver; Input the chosen slice label material sheet size and thickness; Set up the sizes and pin spacings of the registration board.

A board (18mm faced chipboard with accurately positioned 5mm holes for the registration pins), is supplied with the JP5 system.

This is normally a board capable of taking a full sheet of label material (0.2mm thick coated adhesive label paper mounted on a silicon release substrate).

A full sheet is 500mmx700mm, but the system can also use half sheets (500mmx350mm), or quarter sheets (350mmx250mm).

A full sheet costs approximately £1.

If you wish you can make your own boards, and input the vital dimensions to JP5 which will then utilise them.

Once all the settings are made, you can start work.

Simply orientate the model sensibly for slicing (JP5 contains rotate commands), and hit SLICE.

The system will immediately tell you how many slices there will be, on how many sheets, and how many rows and columns of slices it can fit on.

Unlike conventional LOM, where only one slice is possible per sheet, JP5 minimises the usage of paper (and work!) by placing as many slices on the sheet as possible.

If all is well, hit continue and in a few minutes the sheets containing the slices can be viewed on the screen.

There are several software controls that can be used.

To invert sections to make them easier to build, to prevent the wrong parts sticking to the backing sheets.

Controls to rearrange slices in their stacks, and to build a big model in separate sections.

It isn't easy to describe all these controls here, but suffice it to say that the JP5 software contains comprehensive controls that have been developed to ensure a trouble free build Cutting the Slices On a standard system, JP5 utilises a standard vinyl sign cutter.

This machine has a rotating carbide drag knife instead of a pen, and can exert a finely controlled cutting force on the knife.

Speed is also carefully controlled together with cutter offset.

The slices are made by cutting though the top layer of label paper, but not through the backing paper, thus preserving perfect alignment of the slices.

Holes and slots for the registration pins are cut right through the material, so that each sheet, and its slices can be accurately located by the registration pins.

Now certain sheets must be weeded.

This means removing any areas of material that represent voids within the model using a craft knife.

This is a easy process at which one quickly gains the necessary skill.

Unlike the LOM machine where the end result is a solid block of paper containing the model, and where outer sections must be broken away, and the model cleaved up to remove internal empty sections.

A JP5 model is produced 'clean' with the internal surfaces ready created and the outer surfaces exposed.

As well as saving time, this gives you a model that requires very little finishing.

The first sheet of slices is attached to the registration board with tape, precisely aligned using the pins.

An adhesive is sprayed onto the slices.

The next sheet of slices is placed on the pins face down, and light pressure is applied.

The backing is peeled off leaving the second sheets slices, stuck to the slices on the first sheet.

The exposed surface of the second layer of slices is sticky.

The process is repeated until all the sheets of slices have been placed, each stuck firmly in place with the preceding slices' adhesive.

The end result is a series of sub-sections of the model accurately positioned on the first sheet.

These sub-sections each have their own adjacent sub-registration holes.

The sub-sections are then assembled together, using the sub-registration holes for alignment (they are sticky both above and below).

PVA adhesive, Shellac, or any sort of glue will seal the surface of the prototype, but Superglue is the favoured coating, this can be applied with a brush.

Models coated with this material (which penetrates into the outer surface), become hard and rigid.

They can then be readily filled, sanded and polished to achieve a finer finish if desired.

Pristine models have a very good natural surface finish.

JP5 models are surprisingly accurate.

The signcutter cuts to within 0.025mm and thus inaccuracies across the model only stem from misalignment of slices.

Models therefore tend to be accurate to within 0.1mm.

They are often better than this.

Through the model, accuracy within 1% of thickness is regularly achievable.

It is possible to regulate accuracy by taking into account total thickness, and making ajustments to paper thickness within the software.

Without a glue coating, JP5 models are pliable.

If the model is secured to a rigid mating surface when the glue is applied, accurate, strong and distortion free models are possible.

Very thin sections are not easily handled if they are deep.

Whilst sections 1mm thick are possible, a minimum section of 2mm guarantees a good realistic model.

Small bosses and similar features are not easy to do, but can often be represented by a turned pin etc embedded in the model.

It is possible to leave voids in the JP5 model and insert pins or sheet metal pieces to improve rigidity, something you cannot do with any other Rapid Prototyping process! It is reckoned by pundits that some 70% of Rapid Prototypes are built purely to test aesthetics, appearance and 'touchability'.

JP5 models readily meet most of these demands very economically.

JP5 makes paper moulds directly, simply hit "Convert to Mould" and the system places a void representing your model, within a block of slices, ready for immediate use as a mould The initial outlay on software and cutter is £5,000, which gives a capability of building models up to 500mm square.

A typical 1.5 cubic inch model would cost just £3.00 for materials and take an hour to slice and build, an 8 cubic inch model would cost £40.00, and take 4-5 hours to slice and build.

So, basic material costs are almost negligible.

Who uses JP5? Some example applications are: Industrial and Product Design , Medical implants, Medical instruments, Pharmaceutical, Machine components, Small Castings, Car Trim Mouldings, Flameproof equipment, Military clothing accessories, and many others 10 British Universities have installed JP5, where it is used for teaching and research.

Approximately 1 in 10 of the UK's Rapid Prototyping facilities is a JP5, and this is now growing fast.

With the least expensive decent sized Rapid Prototyping machine costing at least £50,000, it's hard to believe that such a simple system as JP5, based on standard materials and equipment can build satisfactory prototypes, but it does! With 3 years of intense development, JP5 is capable of building excellent prototypes quickly and economically.

Most people are obliged by the high costs of ownership to use a bureau based Rapid Prototyping service.

Whilst bureaux do a great job, they take away the immediacy of having your own prototyping facility, and can become very expensive if you need to make several models to refine a design concept to the ultimate.

Ownership of a JP5 system that costs about the same as a decent 3D CAD package offers you speed, release from the high costs associated with bureaux, and the opportunity to refine your design to be significantly better than your competitors.

Doubters are invited to attend a JP5 demonstration.

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