Weekend Update 6/30/13

[Sokramiketes]

Oh. My.

Those turned out even cleaner than I would have imagined.  Phenomenal. 

[mcjaco]

Oh. My.

Those turned out even cleaner than I would have imagined.  Phenomenal.

+1

[jmlaboda]

Bryan... you're taking my breath away!!!  My (adult) daughter, when she saw the shots, was equally impressed!!!

[peteski]

Wow Bryan!  That's awesome. Amazing what can be done with good equipment, CAD/CAM software, and some research and design time!

[Puddington]

.....why do I see CPR HW RPO's and combines being a topic for discussion with a few of my mates after seeing those....?

Very, very cool !!!!!!!!!!!!!!!!

[bbussey]

Here are the latest renditions of the New Haven diners.  The top one is a P-S modified Plan 4004 42-seater.  The bottom is an earlier class of which I don't know the builder that seats 38.



The tail on one of the end doors is a tooling program mistake that came after 11 hours of cutting.  Since it can be snipped and filed smooth, there was no reason to start over for what would have been the sixth time.





There still are a couple of very minor mistakes, but you have to really look for them and they aren't severe enough to warrant a retool.  I did modify the program, so they will be correct should I cut another tool.

Here's what the tool looks like.



This method is good for making a couple of sets of parts ... or for making a set of resin masters, from which rubber molds are poured to make production castings.  You have to know what your final plans are before cutting, as shrinkage factors for the resin and rubber have to be considered.

This was all done on a Sherline 2000-series mill retrofitted with the CNC kit, and using Bob-Cad software to drive it on an old workstation running XP.  I generated the G-code with a VB6 program I wrote that works from data in four SQL tables.  I created the 3D models in SolidWorks and manually took the measurements to populate the SQL tables.  This all is an expansion of what Mike Skibbe did a few years back with milling the sideframes for Fox trucks in machine wax.

[peteski]

Bryan,
you already answered couple of questions I was going to ask.    How severe is the shrinkage right now?  What brand of resin is being used?  Were the molds designed oversize to account for the resin shrinkage?

[Sokramiketes]

You are really close to just cutting your own brass tooling for injection molding.   

[DKS]

How severe is the shrinkage right now?  What brand of resin is being used?  Were the molds designed oversize to account for the resin shrinkage?

Shrinkage is 0.0065 in/in for Design Cast 305 resin. Yes, the shrinkage was factored into the molds.

Demolding is the biggest problem as there is no draft angle on any of the edges. Molds yield at least 5-6 parts as they are; with a touch of draft angle, I think the yield could be much, much higher.

Amazing what can be done with good equipment, CAD/CAM software, and some research and design time!

A little casting experience doesn't hurt... 

[peteski]

A little casting experience doesn't hurt... 

I was giving attaboys to Bryan.  But you're right, your pressure castings worked really well too.  I'll say that you have a little casting experience under your belt! 

[bbussey]

You are really close to just cutting your own brass tooling for injection molding.   

True, but with the slowdown on sales of passenger car sides, it's not a good investment.  That's the reason I bought the Sherline a few years ago, on Bob Fingerle's recommendation: to cut brass tooling for passenger car sides for the American Limited core kit.  But I got dropped by my American contractor and had to go to China to get new sides decorated; Walthers then released a RTR variant of my primary car sides; and Bob passed and ALM product dried up.

If San Juan Car ever gets the core kits back on the market and readily available, then tooling more sides is a possibility.  In the meantime, I can continue to practice on the wax. 

[dougnelson]

Very nice Bryan.  Will these sides be available for sale?f

Doug Nelson

[skytop35]

If San Juan Car ever gets the core kits back on the market and readily available, then tooling more sides is a possibility.  In the meantime, I can continue to practice on the wax. 

I've been in contact with John at San Juan Car for over a year. I received an email just before the NSE convention and the core kits are really close to being rereleased. He is having a problem with the underbody details sticking in the mold in one place. As soon as that is resolved we should start seeing the kits again.

[peteski]

Very nice Bryan.  Will these sides be available for sale?f

Doug Nelson

Quoting DKS "Molds yield at least 5-6 parts as they are", I highly doubt it. Unless Bryan redesigns the molds...

[bc6]

Yesterday I built a couple of the Showcase Miniatures F type Cab Overs.