Objet Connex500

Written by Al Dean

Published Wed 5 Nov 2008

Object Geometries’ range of rapid prototyping machines has built up a following across the globe because of three key factors. Firstly, the systems are pretty office friendly in the truest sense – you can leave them in the corner of the office and they work away – the only real mess involved is the use of water to remove the support material from your model. Secondly, their speed: they can build around 30mm per hour on the fastest settings, but more on that later. Thirdly, the quality of detail that can be reproduced is excellent.

The PolyJet technology that Objet’s machines centre on uses a series of print heads which allow them to jet both build material and support material at the same time. Materials are loaded into the system using closed canisters, so there’s very little in terms of raw material handling. The cartridges slide in and it’s ready to go. What the print heads bring is the ability to create very fine layers (down to 16 microns) at very high resolutions – its finest detail capability matches that of a 600dpi printer (this magazine is printed at 300dpi). The print heads allow both build material (a range of photo curable polymers) to be deposited at the same time as support structures (which are water soluble). The end result is a very clean system, that builds layer upon layer, curing each (with UV light) as they go, to result in models that are very stable straight off the machine and just require running under a tap or water jet to clean away the supports. The last few releases of machines from Objet have seen this process refined and repackaged into a variety of sizes of machine to suit different budgets. Alongside the machine development, Objet has also been developing a range of materials that move from the standard FullCure acrylic material, through to the Vero and tango Materials. These use the same build process to create parts which are task- or application-specific. The Vero materials are intended to provide a replicate of production-intent materials using a variety of colours and currently include white, blue and black. Meanwhile, the Tango materials allow you to build flexible materials with different shore hardness values. TangoBlack and TangoGray enable a realistic rubber/silicon feel with different Shore A hardnesses. TangoBlack provides high elasticity with hardness of 61 Shore A value, while TangoGray is a slightly harder, but still flexible, material with hardness of 75 Shore A. There’s also a new TangoPlus which provides massive elongation at break (over 200%). Within the standard Objet Eden machines, these materials can be swapped out (because of the standardised material cartridges), but you can only build with one at a time.

We had a part of the suspension model from Inventor built up. The harder structural components are built, different components differentiated by colour, but what’s really fascinating is how the system can build the rubber tire in a much softer material, making it possible to really feel how it would be production.

For the brand new Connex500 machine, this changes dramatically. By reinventing the Polyjet process, Objet has developed a machine that allows you to print with two materials (and a support) at the same time. By controlling how and where materials are printed to a very fine degree (there are eight print heads, with 96 jets on each), the Connex500 allows the simultaneous use of two different rigid materials, two flexible materials, one of each type, any combination with transparent material, or two jets of the same material. What’s most interesting is the degree of control you have over the process.

Part preparation & build set-up

The process to set up a part which features different materials in a single build is obviously going to differ from the usual RP machine set-up process – the good news is that it’s in no way as difficult as you might expect. We had a test model built based on the standard Inventor suspension dataset. It features several different materials and I really wanted to see how the machine handles replication of over-moulded or dual shot parts – for which the Connex500 is ideal. Multiple bodies were exported as STL files. These were then loaded into the set-up software and you begin to assign the material values for each ‘body’.

Then select the materials you are using which can be any of the materials currently available. But the really clever bit is two materials combine to create different variants to achieve the example look and feel for your production intent. To explain further, because of the level of control (to per nozzle level), you can create much more than just two materials, as the system can create a wide range of variants by controlling how much of the structure contains one material or the other – these are referred to as Digital Materials. You select the materials you are using, then select each body from the 3d view window and assign the material you want it built in. If you want the basic material (such as VeroWhite) you simply select that and assign it to that part or body. If you want a specific Shore hardness, you can then go further and choose one of the range of digital materials available. These are selected from a drop down list and are referenced with a Shore A hardness value. The system then knows how much to combine each material into the build to achieve that mechanical behaviour. It really is that simple. Then work through each part or body in the model and assign the material values needed. The system sets it up and it’s ready to print.

There are a couple of other tricks or options available. For example, you may want a rigid part (so VeroWhite is a good choice), but you may want a slightly rubberised feel. The set-up studio has the ‘coating’ option that allows definition of a layer thickness which offsets from the surface of the part and adds a different material as a layer (of your choosing), with a lower Shore hardness, to achieve that effect.

Again a standard dataset from Inventor, built in a single piece. One thing that’s worth noting is that the casing is split into different materials, again offering you the chance to evaluate how it would feel with overmoulded or two shot injection mould processes, while others are much more rigid.

It might sound a little complex, but the process is really point and click. The only thing that needs to be decided on really, is what material characteristics you want and where on your model. Perhaps the biggest challenge for using a system like this is actually modelling the part. The good news is that Objet provide you with a wealth of information about what different materials can achieve, and a very handy booklet on how to model your components for the purpose. There aren’t specific updates for Inventor, but this will come I’m sure.

In conclusion

The Objet Connex500 is a fantastic advance in state of the art rapid prototyping. While many RP vendors are now going after the world of direct or rapid manufacturing, work similar to what Objet has done on this machine, showing that the design world can still benefit from advancements in pure prototype production. The process of prototyping dual shot or over-moulded components is a lengthy and drawn out process if you use multi-stage silicon moulding to achieve the same effect, and is typically reserved for when the design process is near completion and you need production intent samples for focus groups, presentation etc. Until now, there’s been no cost effective solution for replicating these types of manufacturing processes at the very early stages of design – when the tactile input and aesthetic qualities really need to be examined most closely. This, for me, is what the Connex500 offers and is the key to its benefits. Many are using different combinations of materials to provide products, which are engaging to the consumer, whatever industry or field those products lie within. By using different materials, you can elevate a products’ form beyond pure aesthetics and get a different tactile response that make people engage with a product.

What the Connex500 offers is a way of simulating design concepts in a cost effective and timely manner which material usage choices can be evaluated as part of the design process. This lets you out different material combinations and different form factors in a truly physical sense. That of course, will drive design change because adapting a design further based on all the digital design tools available, backed up with physical prototypes which accurately simulate the products in a real world, true feedback response-based manner. And on that basis alone, if you’re looking to bring rapid prototyping in house then it’s definitely worth further investigation because the benefits to design, of having this machine in-house and ready whenever you need it, can not be understated.

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