Model Engine Maker
Supporting => Casting => Topic started by: stevehuckss396 on November 24, 2013, 12:23:03 AM
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What kind of finish is best on patterns for casting. I have tried to do a very smooth clear coat but the sand seems to want to stick to it. I try to dust the pattern but the powder won't stick to the pattern either. Would a gray primer work better with a little bit of a rough finish so the parting dust will stick to it.
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Steve, I just finished my second pattern because my first pattern had the same sand sticking problem. I used enamel, nice smooth and hard. the sand stuck to it like glue! I thought it was the release I used or poor draft angles. I found some old patterns at an antique shop, the pattern finish looked like some type of none glossy dark varnish however I do not know if it was the original finish. I need to do more research. Dale
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I sanded mine, polyureathaned them, and then painted them.
I would check your parting powder.
Dave
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I would check your parting powder.
Heres what I used.
Description:
BCS parting dust (formerly PD-1) is a professional grade parting dust for use with both naturally bonded (clay) and oil bonded (Petro-Bond™) sands. It is manufactured by Asbury Graphite, Inc., and sold to foundries under the trade name "Diamond Parting #4106™". This parting is (almost) silica free. It is a mixture of porous minerals which have been finely ground. It has been formulated to be highly lubricious (marketing talk... means slick) which aids separation of cope / drag halves and pattern removal . This parting will not water proof the sand surface, so steam and gas can escape from the melted metal. This helps reduce surface porosity.
What It Does:
Parting dust coats the surface of a pattern so that the molding sand will not stick to it. This allows the pattern to be drawn from the sand and leave a clean, sharp impression behind.
Parting dust also coats the sand mating surfaces of the flask so the top half (the "cope") and the bottom half (the "drag") don't stick together. This allows the halves to be separated and the pattern removed. This separation line is called the "parting line" thus comes the name of this material: "parting dust".
How To Use It:
Simply load half a cup into an old white sock and you have a handy duster. Apply a fine dusting to parting surfaces of sand mold and patterns. New patterns will benefit from thoroughly applying a coating of parting dust prior to first time use.
Keep the sock and unused parting dust in a tightly sealed can to avoid moisture absorption. (I use an old coffee can!). I figure I use about a tablespoon per mold. At that rate 5 pounds will last a long time!
MSDS & Health Info:
Read and understand the Manufacturers Material Safety Data Sheet , MSDS, for full information about dangers.
The MSDS is available on this site and is shipped with each order.
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Steve, I just finished my second pattern because my first pattern had the same sand sticking problem. I used enamel, nice smooth and hard. the sand stuck to it like glue! I thought it was the release I used or poor draft angles. I found some old patterns at an antique shop, the pattern finish looked like some type of none glossy dark varnish however I do not know if it was the original finish. I need to do more research. Dale
Hello Dale!
What release do you use? For the record dont use pam nonstick spray. That experiment did not go good at all.
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I use talcum powder, the real talc stuff. Works for me. I also coat my patterns with polyurethane to seal them, and then cheap spray paint, what ever is on sale at WalMart.
Chuck
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I assume you have proper draft on the pattern. I find 1.5 deg is ok for petrobond, my foundry wants 2 deg.
I sand the surfaces down to 400 grit, making sure they all feel smothe. THe finish I use is just lacquer. With wood patterns it
takes 2 coats and 3 for the end grain. Sanding with 220 after letting it dry well, then go to 400 on the last sanding.
I use parting compound from BCS, don't know what's in it. Apply using an old sock. Rub in all over the pattern on a new pattern the first time, then just dust a bit on after that.
Hope this helps,
maury
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I assume you have proper draft on the pattern. I find 1.5 deg is ok for petrobond, my foundry wants 2 deg.
I sand the surfaces down to 400 grit, making sure they all feel smothe. THe finish I use is just lacquer. With wood patterns it
takes 2 coats and 3 for the end grain. Sanding with 220 after letting it dry well, then go to 400 on the last sanding.
I use parting compound from BCS, don't know what's in it. Apply using an old sock. Rub in all over the pattern on a new pattern the first time, then just dust a bit on after that.
Hope this helps,
maury
I put 2 degrees on everything that isnt round.
So is the final finish a gloss finish or the 400 grit sanded finish
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I assume you have proper draft on the pattern. I find 1.5 deg is ok for petrobond, my foundry wants 2 deg.
I sand the surfaces down to 400 grit, making sure they all feel smothe. THe finish I use is just lacquer. With wood patterns it
takes 2 coats and 3 for the end grain. Sanding with 220 after letting it dry well, then go to 400 on the last sanding.
I use parting compound from BCS, don't know what's in it. Apply using an old sock. Rub in all over the pattern on a new pattern the first time, then just dust a bit on after that.
Hope this helps,
maury
Dave
I put 2 degrees on everything that isnt round.
So is the final finish a gloss finish or the 400 grit sanded finish
That's about the finish I have on my patterns....
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That's about the finish I have on my patterns....
The varnish finish or the 400 grit finish?
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The 400 grit finish.
I sanded to 400, then poly'd it, then painted it
(http://i164.photobucket.com/albums/u27/mcandrew1894/Steam%20Launch%20Rushforth/P8200136.jpg)[/URL]
Once I got the pattern there, the foundry guys painted it again the silver color ( a fact I only just remembered) I seem to remember that this was a special paint...but this was a while ago. I would try contacting them. Nashua Foundry, Nashua NH. Ask for Pete Lyons.
Dave
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Once I got the pattern there, the foundry guys painted it again the silver color ( a fact I only just remembered) I seem to remember that this was a special paint...but this was a while ago. I would try contacting them. Nashua Foundry, Nashua NH. Ask for Pete Lyons.
Thanks Dave!
I emailed and have already gotten a responce. He wanted some specific info about what I was talking about. I wrote back with your name and a photo of the pattern hoping that will jog his memory.
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Cool!
Pete treated me really well and was a great help as I was developing those patterns. Hope he treats you the same.
Dave
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Use this photo Steve....if he needs his memory jogged.....
(http://i164.photobucket.com/albums/u27/mcandrew1894/Steam%20Launch%20Rushforth/P9010017.jpg) (http://s164.photobucket.com/user/mcandrew1894/media/Steam%20Launch%20Rushforth/P9010017.jpg.html)
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Steve, sorry it took so long to reply. I tried common talcum with petrobond. I tried the simple route. still think its my finish on the pattern. Its just an aluminum plaque but AND my first pour but its leaving me thinking there is more to this foundry stuff. However I will figure it out! With help of course! Dale
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They make special releasing agent, which is just paste wax.
Johnson floor wax works just as well.
I wipe the pattern down with a light coat of it each time before I use it, and wipe off any excess.
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After some searching on the web and asking some more advanced founders the problem might lie in the enamel coating. I am not the only one having the sticking problem believed to be from enamel coating. There are some special coatings that can be used. Others have had good luck with varnish and some lacquer coats. I guess they dry to a real hard shell finish.
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Steve, There might be some solvent reaction between the petrobond ( alchol) and the enamel on your patterns which cause the sticking. I, also, use petrobond, and all of my patterns are coated with clear shelac then rubbed with 000 steel wool, then re-coated with krylon red primer. The patterns are re-rubbed with 000 steel wool again then used for casting. The "NEW" Krylon paint in the cans with a tapered cap are enamel. The "OLD' paint with the straight caps were laquer which worked very well, but not now. ART
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:headscratch: If it is a solvent reaction would the use of acrylic car paint not be better?
Jo
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Best talk to the foundry Jo to see what they prefer depending on their sand and moulding methods. John Winters sell the traditional red pattern paint.
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I have only done a few patterns and they were all painted with two part polyurethane automotive paint. I didn't have any complaints from the foundry and the castings came out great; so I guess it was ok.
Dave