5 minute read
A FLY IN THE OINTMENT
from TCT EU 28.1
by TCT Magazine
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WORDS: GRAHAM TROMANS A FLY IN THE OINTMENT GRAHAM TROMANS IS ONE OF THE FOREMOST INDUSTRY CONSULTANTS, HIS HISTORY AND EXPERTISE HAVING INSTALLED ONE OF THE FIRST SLA MACHINES IN THE UK IS SECOND TO NONE. AS A MEMBER OF THE TCT EXPERT ADVISORY BOARD WE’VE ASKED GRAHAM TO TELL US A CAUTIONARY TALE FROM 3D PRINTING’S DAYS GONE BY.
The year is 1990, I - a Principal Engineer at Rover - am installing one of the UK’s first 3D Systems SLA-500 machines in the Canley site, Coventry. I’m in the process of calibrating the machine having just returned from training in Valencia, U.S.A. when there’s a knock on the door.
It’s a director come to take a look at the rapid prototyping machine. “Can you build this?” He shows me a picture of an intake manifold, which I had no idea if we were capable of. Naturally I said, ‘yes.’
He wanted the print for a missionary meeting to convince the board of the benefits of solid CAD packages. Rover was using wireframe and advanced surface finish CAD packages, which were tricky to learn and bulky, and he was to prove how a switch to solids, despite being hugely expensive, would be worth it in the long run. The print was a key point in the argument. No pressure then.
I’d had the machine barely a couple of days when the CAD file landed on my desk. The first snag was supports; in 1990 3D Systems required you to have third-party software to generate supports, which was another £10,000. My boss said, 'absolutely no chance.'
I sat for hours on end making these generic shapes like cubes, cones and spheres; then I had to position the model on top of these shapes, I’d then open up the scan-spacing to about five millimetres to create almost an egg box underneath the parts. Each one of those was an STL file, so imagine how many shapes you need to create on an intake manifold; you have to look for all the downfacing surfaces, you have to look for anywhere you thought the part might collapse.
I put it in to build on the Tuesday morning, the SLA-500 informed me that the part would be finished in the early hours of Friday morning. The meeting to decide the CAD fate of Rover was 10.30am on Friday, not only that but the venue was 30 miles away in Longbridge. No margin for error.
An anxious 60-hour build saw me get into the office at four o’clock in the morning, watching this part rise from the vat. By hook or by crook, the part was complete. I washed it, broke all the supports off, flashed it in the PCA oven and hoped for the best. With the clock ticking and the traffic between the two sites notoriously heavy, I got it out of the oven, shoved it into a box and raced to the meeting.
I plonked this part on the desk, and said, “you’ll need these,” handing over a box of rubber gloves. The intake manifold had not cured and was still wholly tacky, touching it probably wasn’t wise.
With this being the biggest and most successful build in the SLA-500’s short lifespan, I knew I’d need it again and had to cure the thing. Looking out the window, with the sun shining, I was taken back to my time in Valencia, CA, where during our training we’d regularly cure parts in the sunlight. I took it home, put it on my patio table and went out with the wife.
Upon returning to my crown and glory, on the approach I could tell that the part was cured, but that it was also covered in little black specks. Closer inspection revealed those specks to be flies; like a roll of sticky fly tape, the engine manifold had attracted and killed thousands of the pests.
With a scalpel and some tweezers, I removed as many as I could but those that made it into the internal channels remained as a warning to always cure your parts correctly.
Nevertheless, the Rover directors agreed, thanks to this part, that solid CAD packages were the way forward.
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