3D printing (Was: New early P&R steel.....)

Tom Madden

On Thu, Dec 19, 2019 at 01:50 PM, Dennis Storzek wrote:
Thanks Tom, very informative. This proves to me that Shapeways is just maxed out and still found wanting. It's no longer an issue of resolution, but designing around the "wax tracks". It seems the SLA process is better suited to our parts. Compare these pix to the pix of the D&RGW coal hopper Eric presented a week or so ago.
I believe Corey Bonsall, who does the D&RGW and Utah Coal Route gons, uses a Form 2 "upside down" SLA printer where the part is built from the bottom up as it's lifted, layer by layer, out of the resin. For best results parts need to be oriented at an angle and parts of any complexity require a literal forest of supports. Shapeways had a similar process, Hi Definition Acrylate,  but they dropped it because  their trimmers lacked the skill to trim such parts quickly and without damage. In this field you can't have low prices, low wages and high skill levels across the board. For a while they offered HDA parts untrimmed but they've dropped that as well.

If you _can_ design around the wax track problem the 3D Systems' multi-jet modeling process (which Shapeways calls Fine Detail Plastic) is faster and much less expensive than any SLA. For large parts, like passenger car sides, the Form 2 and other small SLA printers won't work at all. Here are three images (front, back and detail) of a pair of car sides I got from Shapeways on Monday. These are images of passenger car parts, but they're shown for the technique and not the product. On the PCL and some other forums any discussion would involve the parts and not how they were made. I'm not ready for that discussion yet!

Those are flat with no sidewall detail. Shapeways Smoothest Fine Detail Plastic process (16 micron layers) shows minimal stairstepping on sloped surfaces. That encouraged me to design some Pullman blind and solarium ends with full rivet detail on the end sill and in the upper ends. Both regions are sloped. I also included the handrail mounting flanges and bolts on the door frame, a vertical surface on the print. 
Here's a photo showing four different ends They're castings, but the masters were printed:

Here's what the sidewall detail is supposed to look like:

And what it does look like: (Best I could do without a macro lens.)

There is a wax track below the detail, but in this case it's not objectionable. Since it's the only such detail in the area, and the wax track is short and hidden under the handrail, it's not at all noticeable. You need to pick your battles.

Tom Madden

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