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"To validate or not to validate, that is the question"

Jul 9, 2020

We received the following question :

"You keep using this phrase 'validation' or 'validated'. What exactly does this mean, and should I do it?"

Validating a design simply means testing a design repeatedly until you are certain that it prints correctly with a slight tolerance for minor changes in temperature, etc.

If a design isn't valdated, it should never be used for any projects or production runs, as it may have printed successfully and in adequate quality once or twice, but if (for example) a design is hastily tested and then used for a run of 50 prints, how many of these prints will fail? What happens mid-print if the room temperature rises by a degree or two - Will the design still print correctly? Finding your design isn't printing as it should during a production run creates what could be described as 'a bit of a panic', and you have get back to the drawing board with an extra pressure on your shoulders to resolve the issue as quickly as possible.

Validating isn't a term you hear a great deal in the hobbyist world of 3D plastic printing, as practically anything you design in a CAD program will print in plastic as a 1:1 replica. For 3D plastic printing, users may find that they need to tweak their model slightly in their CAD program after a few test prints, just to perfect the outcome, but they very rarely need to experiment with the parameters to get their models to print. In fact, on this note, we have a 3D plastic printer in the Choc Edge studio and we've just realised that we've never actually had to touch the settings (which are the factory defaults) as it prints everything flawlessly as is.

3D printing in chocolate is, however, a slightly different process. When designing 3D models with the intention of printing them in chocolate, it's vital to remember that whatever you design will not only be printed in liquid chocolate, but also without any kind of external support / raft / scaffolding, and in a resolution suitable for chocolate that is lower than the latest micro-fine plastic printers.

This design process involves far more consideration than that required for plastic printing, as you need to be creative but at the same time not let your imagination run wild. While designing your model, keeping an image in your head as to what the design will look like building up layer-by-layer in liquid chocolate will help to keep you grounded - If you don't think the tiny details you've have added to your model will print in 0.8mm liquid chocolate, remove them and keep everything simple, compromising however you can.

Once a suitable design has been created, the next step is to test it by generating a G-code using the default parameters and seeing what the outcome is. If the print is a success, it should be printed again immediately with the same batch of tempered chocolate. If the print fails the second time, the first print may have only been successful by chance or serendipity, as we've witnessed moments (often during days of unusual weather) when temperature / humidity suddenly changes and a design that should be impossible to print has actually printed, albeit not perfectly, but it does prove that designs need to be properly validated by having their success rate tested and documented.

If the design appears to have printed twice without any flaws, such as missed layers or areas of collapse, it's a good sign that the default parameters used to generate the G-code are suitable for the design, and no further tweaking of these parameters in required. In this case, the design should now go through a validation process. To validate a design, it should be printed multiple times, with slight changes to the external factors that affect the success of a print. A validation example could be as follows; The print should be repeated 20 times under recommended conditions, followed by 20 prints with a slight increase in ambient temperature, followed by 20 prints with a slight increase in room humidity, followed by 20 prints using chocolate that has been tempered but kept heated (and without re-seeding) for more than 30 minutes, etc. This careful validation process may involve printing the same design up to 100 times, and from that quantity, the aim is to have a success rate that is as close to 90% as possible (understanding that there must be a tolerance for 3D printing models in liquid chocolate).

If a design simply will not print after testing it with a variety of parameters, the design is likely to be unsuitable for printing in chocolate, in which case it should be reworked with a little more consideration for the restrictions highlighted in our literature.

So what if your design appears to print without issues having tested it once or twice? This all depends on the purpose of the design. If you simply want to print a piece of 3D cchocolate for display in a cabinet in your chocolate store, then as long as you have a perfect print, there really is no need to validate the design. Likewise, if you want to create a photoshoot of a collection of 3D printed chocolates for a store website, there is no need to validate your designs if they have printed accurately. It is only when you plan to print the design in large quantities that the repeatability factor and success rate becomes important. We ourselves have a number of designs on file that are never given to clients simply because they were created as one-off items for an event, magazine article or TV appearance and we had no need to validate them.

If you are undertaking a production run, the design needs to be valiated so there are no suprises when it comes to the success rate calculated at the end of the run.

For a dozen prints of the same design, we would again suggest seeing how many perfect prints you can make without fully validing the design, but for full scale production, especially under strict time constraints, you really need to have that confidence that your design has been validated, and that leaves only the chocolate preparation and temperature control to manage.

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