There’s a great quote by Thomas Edison when asked if he felt like a failure because of all his failed attempts to invent the electric light bulb. “Young man, why would I feel like a failure? And why would I ever give up? I now know definitively over 9,000 ways that an electric light bulb will not work. Success is almost in my grasp.”

And not one of those 9,000 prototypes was made on a production line.

A situation that our clients commonly find themselves in goes a bit like this. “Yes, I know it’s not quite working yet but time is running out before the product launch next April and so we have to commission the tooling now. Management aren’t willing to let the launch date slip.”

It brings to mind a medical project in which the disposable part had been pushed through to injection moulding. The trouble was that revisions to the design were still being made. It was possible to modify the tool, but each time that happened, it took six weeks to get the next parts released before they could be tested.

Earlier in the same project, we had been prototyping the disposable component on our CNC mill. You could do a test, modify the CAD, set the mill running overnight and test the next iteration the next day.

Short development cycles demand flexibility, and for this it helps to delay tooling until you know the design works in all respects except for those specifically dependent on tooled properties. Even if you need 100 parts for a clinical evaluation, perhaps they can be machined? It might cost $10,000 and some planning ahead in validation, but that’s child’s play compared with a 12 month delay to a multi-million dollar programme.

There’s a whole suite of prototyping methods available today, such as additive methods (SLA, 3D printing, SLS, vacuum casting…) and subtractive methods (machining, laser cutting, EDM…), not to mention various ways of sealing, bending and so on.

In the next article we look at how to break down a daunting, complex problem into a series of manageable steps.

Please contact Keith Turner if you think we could help you or if you would like to be alerted to the next strategy.

When the Wright brothers were trying to make their great aeronautical leap forward, they didn’t just throw feathers and motors at the problem to see what happened. Rather they tried to determine which of the three key challenges to mastering flight was most critical: wings, engines or control? Looking at the effect of changing one variable at a time helped them to determine that the critical weakness was in control, meaning that they could innovate in this aspect and set the way to their landmark achievement.

It brings to mind a project where we were developing a cryosurgery probe to kill breast tumours by freezing. We had a functioning system that worked off a heavy gas cylinder but had recently made the exciting discovery that a simple 1 litre flask could be used to drive the probe directly from liquid nitrogen. This was easier to use, smaller, and cheaper, and so a sure-fire commercial advantage for our client. However, when we scaled our new technology up to full size it didn’t work. It wasn’t just slow, it was completely hopeless, and failed to get even remotely cool to the touch. Yet the only difference was the size.

But was it? The new flask was bigger, that’s true. But actually, the bung that sealed it was also a larger diameter. It was also deeper. And it was a different material. And the dip tube was longer to reach to the bottom of the larger flask.

On reflection, there was quite a lot different about the new system, and we had changed it all at once. This meant we didn’t know which thing we had to change to resolve the problem. There was a deadline approaching, and it was tempting to just jump to the end and try stuff in the hope it would work, but with planning we figured that we had a chance to solve the problem in two weeks by starting with the working miniature system and changing one feature per day until we had created the large system. 10 days, 10 features- surely one of those would be the key?

On day 1, we machined a new bung for the small flask out of the same material as we were using for the scaled-up system. It worked perfectly. On day 2 we scaled it up to the larger diameter- still great. On day 3 we extended the dip tube- still chugging along nicely. On day 4 we machined a deeper bung… nothing. A complete failure to freeze. It was now a simple deduction that the deep mass of rubber was sinking heat into our cryoprobe and preventing it from freezing. We added insulation around the tube as it passed through the bung and made ourselves a perfectly working full-size system. All in less than a week, which means we still had time to write the final report for our client who was visiting the next week.

This technique is widely used in science, and is particularly powerful when you have one prototype that you know works, but can’t figure out why another comes up short. If changing one variable at a time does not reveal the problem, there is probably one or more interactions between the variables. We can use techniques in a field of engineering called Design of Experiments to reveal them, but that is a subject for another day.

In the next article we look at how to speed up the development cycle by saving tooling until later.

Please contact Keith Turner if you think we could help you or if you would like to be alerted to the next strategy.

When the world’s fastest men competed for the 100m Olympic gold medal in Athens, 2004, four athletes crossed the line in a blur. But the event organisers didn’t just squint and pick a winner. Rather, they used high speed video to slow down the motion and changed the method of observation so that it became clear that the new champion was Justin Gatlin.

It brings to mind a project I once worked on where we were trying to control air flows inside a dry powder inhaler. The powder kept ending up in the wrong place, and nobody knew why. We had tried different geometries, but to no avail. Finite element modelling hadn’t helped either.

“You can’t see what’s going on because it’s opaque”, people said. Well, true to a point, but with only a little effort it was easy to prototype transparent parts and set up a video camera at 2000 frames per second to visualise the particles. It was beautiful, and you could see each particle whirling about on its journey from the hopper to its final resting place stuck on the side wall. It soon became apparent that the problem started as the particles crossed a particular join in the moulding. This enabled us to focus our attention on that particular problem spot, and we soon found a leak. It was then a simple engineering job to seal the leak and recover the performance that was expected.

We have used high speed video on numerous projects at frame rates over 100,000 per second. Sophisticated techniques can be used to quantify stresses in moving parts and relate their behaviour to material properties. There are also more sophisticated variations, such as stroboscopes and particle image velocimetry, which uses pulsed lasers to visualise the movement of particles over tens of microseconds.

Have you ever had your prototype working, only to see it do something unexpected in its next iteration? In the next article, we look at a technique for staying at the best performance.

Please contact Keith Turner if you think we could help you or if you would like to be alerted to the next strategy.