Driver Casting Repro

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jlakes85
Posts: 209
Joined: Thu Feb 23, 2012 6:07 am

Re: Driver Casting Repro

Post by jlakes85 » Mon May 20, 2019 6:01 am

I'm in the midst of the final once over on the repro pattern and there's a few areas I want to address before painting/mounting on the match plate. What's the best filler material to use on the repro plastic?

-jlakes85

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Trainman4602
Posts: 3432
Joined: Sat Oct 16, 2004 9:26 pm
Location: New Jersey

Re: Driver Casting Repro

Post by Trainman4602 » Mon May 20, 2019 3:00 pm

Bondo Most common but Freeman makes a product called Tuf Carv it is similar to Bondo but not as hard to work with .
ALLWAYS OPERATING MY TRAIN IN A SAFE MANNER USING AUTOMATIC AIR BRAKES

Mike Walsh
Posts: 636
Joined: Sun May 06, 2007 10:14 pm
Location: St. Louis, MO

Re: Driver Casting Repro

Post by Mike Walsh » Mon May 20, 2019 4:12 pm

John Hasler wrote:
Sat May 18, 2019 7:26 pm
This is interesting:

http://www.ijirse.com/wp-content/upload ... /1160B.pdf

They are 3D printing the moulds directly with sodium silicate/sand using a process similar to the laser sintering process but with a CO2 jet instead of a laser. No pattern at all.
Yes... 3D printing of MOLDS is becoming an attractive option, especially when core assemblies become very complicated. 3D printing of cores are also becoming more commonplace as well. I was involved in a project in our foundry where we tested the viability of 3D printed cores for a fuel nozzle/handle assembly (for gas station nozzles). Worked OK... If the cores arrived in one piece. That is one drawback, they can be weaker than a glued up core assembly made of shell sand. Also, for high volume production, it's not as viable.

Now that being said, if you understand shrinkage, gating and risering, you could very well design a 3d printed mold that would only require you to 3D print the mold/core and ship it to a foundry, and they would set it up and pour it right there. When you consider how complicated porting, passages, etc., can get, you can save a LOT of time by not having to make core boxes, make sure they fit properly (remember, most folks in the hobby will be making patterns for the first time ever... not everyone has job experience like Dave, myself, and others). But it requires that you truly understand the process of casting and how the design plays into it.

Last I checked, one of the 3d printing companies is charging about 35 c per cubic inch, regardless of if the media is actually printed, or if it is "empty space" (read: port passages vs casting). They are charging for the overall volume of the part. If your driver is 6" diameter, 2" tall, you are looking at $17 per part... Not including ANY gating and/or risering. When you factor in gating and risering, you are looking at probably 12" x 12" x 6" of overall volume for the part including gating. Suddenly your price jumps up to $260.

That being said, if you know how overall molding/casting process works, then you will realize that there are ways you can reduce the overall volume of your 3D printed mold/core, while using a standard matchplate to work with the foundry's molding system.... I will leave it at that since I cannot reveal all my knowledge at once :-)

I have learned a few tips and tricks having spent the last five years in foundries -- featuring low pressure die casting, tilt pour casting, and traditional green sand mold casting, and I have barely begun to scratch the surface with a feather.

-Mike

Tharper
Posts: 34
Joined: Mon Jan 23, 2012 8:51 pm

Re: Driver Casting Repro

Post by Tharper » Mon May 20, 2019 5:00 pm

Nice job!
Over the past few years I have spent quite a bit of time working with 3D printed patterns
and core boxes. Yes, for smoothing and filling bondo works great! I usually smear it on as thin as possible
and sand. For a top coat I use automotive rattle can paint.

Here is a set of patterns and core boxes that I 3D printed. These are for the bronze fittings
for the lower water manifold on a big Wisconsin T-head motor. These were printed on a Creality CR10
which is priced less than $1000.00
IMG_1662.JPG
Here is what the complete assembly will look like:
Lower Water Manifold 1.jpg
Just as a comparison here are the patterns, core boxes and male core box masters for
the intake manifold castings. These are all traditional wood patterns - in fact that were the very first
set of patterns I ever made! The core boxes are plaster-of-paris sealed with shellac which were cheap
and worked very well. For filler on the wood patterns and the plaster core boxes I used Durham's water putty.
100_3697.JPG
IMG_4064.JPG
Again, keep up the good work!

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