Re: (topic was Frank) New topic - progress is being made

Frank Sergent

Hi Tim and all,
I’m very happy to see everything going on here.
I’m not surprised the prints for the Sharon coupler did not come out well. Those files are what was used for the die cast tooling and I never tried to 3D print them. (You can still buy die cast RN87 couplers from me.) The Sharon couplers have very thin walls and are just plain tiny. Even die castings is challenge for those couplers.
I’m a little surprised your prints for the ERFTop_DLP_40X30 didn’t come out better. This file is for a mostly standard type E top with a shank that worked with the RailFlyer locos. I successfully printed lots of these on my EnvisionTec Perfactory Micro before it died. The Perfactory printer is based on a modified 1024X768 DLP projector focused to a 40X30mm build area. That gives it an XY resolution of 39 microns which is not too far off from your Photon printer. If you increased exposure time, you might do better. Using a high resolution resin would probably help too (can’t remember if Photon works with 3rd party resins or not). The only resin I ever used for investment cast items was PIC100 from EnvisionTec. PIC100 makes parts that are slightly flexible – not brittle at all, but not strong enough to be useful for a coupler. It’s burns out clean for investment casting and that’s what it’s intended for and that’s what I used it for. It’s crazy expensive and theoretically only available to people that have purchased EnvisionTec printers. I suspect you could order a bottle off the Geisswein website and no questions would be asked, but be prepared to pay $429 for that little experiment and you would still have to investment cast to get a usable coupler. There are lots of 3rd party resin suppliers and you could probably get something strong enough and not brittle from one of those guys that you could use without going to the trouble of investment casting. Just google 3d printer resin. I have to believe there is no reason an LCD based printer like the Photon couldn’t do this job, but I have never seen success there. I did not have success with my Duplicator 7 printer, but I never got prints anywhere near as good as you did from your Photon printer. I did see much success with my Perfactory Micro and prior to purchasing the Perfactory Micro, I proved I could do it with DLP projector based homebuilt printer that I put together (sadly, I scrapped that printer after I purchased Perfactory).
The Form II printer that Tom used for the S scale parts seems to have done very well with the larger S scale couplers. In my experience the Form II printer always does better than its specifications say it should. It uses a gyro positioned laser which gives it near zero XY resolution. Its a little slow, but the detail is very crisp despite the laser dot size that seems big compared to XY resolution quoted for other printers. Investment castable resin is available for the Form II and it can handle 3rd party resins if you want to experiment.
I posted some pictures in the iogroups photos section that show part of what is involved in the investment casting process. No one wants to go there unless you just have to.

Sent: Wednesday, May 01, 2019 10:11 PM
Subject: Re: [Sergent Engineering] (topic was Frank) New topic - progress is being made
The parts in my photo (above) are;
Assembled the next three parts, plus a ball, make up an RN87 (HO Scale)
The printed parts are basically useless: they do not even begin to fit together, and as such cannot be used to assemble into a working coupler.

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