Re: 3D printing

Robert kirkham

Yes - that's true. As Tom indicates, Shapeways rendered the first draft of those ladders without a problem, so my guess is that the change in spec was a business decision, not technological.

Not sure whether I reported on my progress after that. I was able to send an order for my CPR 1937 ARA ladders to ADC and received them back with .2mm rungs (~.008" or scale ~11/16" in real life) - three or four out of an order of 120 didn't survive. Am now working on a drilling jig to make installation easy. First try had too much wiggling to be precise.

Meanwhile, I've also designed a few other models including a CPR single sheathed automobile boxcar model with inverted 5/5/5 Murphy ends. The siding didn't print very well - I used very close to scale board shape and no real grooves - and that didn't work. Too subtle to be rendered as drawn because of the slight grain of the printing process and (in my opinion) poor quality control at Shapeways. I'm re-drawing the car sides again to improve the rendering of the wood sheathing. Since that version I've learned to insert scale rivets and nut heads, so the new version will be better detailed.

I find the models are usually a learning experience & sometimes a step forward to better models. But I keep at it and am very happy with the progress, slow as it is. The ability to create unavailable parts is real now. I find the drawing is more of a challenge than anything else. One starts to understand the manifold challenges a manufacturer has when designing a product for market. Proto-dimensions do not cut it for some things- the technology can't render the smallest shapes. So as one draws, one learns cheats that may help capture the essence of proto shape at a level that works for the process. Or they may just look coarse and you have to try again. That means $$ go to development, rather than to finished models. A real cost of learning. Fortunately I have at least one friend who has been willing to share the cost of some of the more costly experiments.

To me, moving along the drawing learning curve is the big challenge; learning what the technology is presently able to do and designing to those constraints is easier but another learning curve; finding suppliers willing to do our small lots another; having the perseverance to continue after the first few disasters - well, good thing it's a hobby.


From: "pullmanboss" <pullmanboss@...>
Sent: Tuesday, August 28, 2012 8:55 PM
To: <STMFC@...>
Subject: [STMFC] Re: 3D printing

We seem to have this conversation every couple of months. The last time it came up we heard about a step backwards in the available technology. See Rob Kirkham's post #108304 from this past March 29. Rob reported that Shapeways was no longer able to deliver parts (ladders) with 0.3mm (0.012") features (rungs), and now required 0.6mm (0.024") minimum thickness on such features. Looking at the Shapeways web site, I see that's still the case.

That's not a limit of the technology. I suspect, from Shapeway's standpoint, very fine freestanding features like ladder rungs fall in the "more trouble than it's worth" category.

Tom Madden


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