These are not cars but I think you can see the potential.
I just wanted to let you know what I have been up to. I introduced myself as a former jeweler. That is only partially true. I was a master mold and model maker for the jewelry industry. My specialty was sea life and tourist style stuff but I love to carve anything natural history related. The other half of my job was to create and cut production molds. I have not had much time to make any molds of car bodies but I was inspired to pour some resin into a few of the jewelry molds I had stored in my workshop. Some of the casts are dirty because since this was an experiment I did not bother to clean them out. Most of these did not come out flawless but I am confident that with some practice I could produce resin casts for trade:rolleyes: (I am not interested in selling) The flashing was suprisingly thin my six year old was pulling it off before I could take the pictures. I know I could produce molds for some others to cast bodies and parts for themselves. I used four types of rubbers in my experiment. Natural (mustard yellow) Three types of silicon rubber: Clear with this I mold the most delicate items like fragile sea shells (plastic car bodies:thumbsup:) Green which has a high tear strength and is good for under cuts. Finally the Blue which is the most stiff. Please feel free to ask as many questions about services I could preform for you. I have a very well outfitted mold making workshop that is collecting dust right now. I am open to any suggestions.

WOW A 14k 55 Chevy would be so cool.:thumbsup:

Nice job on those Mike!! I will log this info into the memory banks!! I have plans to try my hand in the resin casting dept. this year, and will always welcome someone who has experience for guidance and answers. If I run into problems, I might just let you take the mold making duties..:rolleyes:

P.S. Them frogs and them goofy lizards gave me the creeps when I lived down there... I'd suffer 15-20 mini heart attacks from them critters just walking the 4 blocks to Albertsons!! :lol:

UtherJoe

I was curious, the detail is fantastic and I could not find any air bubbles. What's your technique for keeping them out of the product part of the cast.
Does the sprue tree absorb most of the air or do you use some type of pressure or injection process?

Thanks,
Paul

Paul,
Thanks for the nice detail comment. Are you asking about bubbles in the casts? It is funny you ask about the sprue I did notice it had more bubbles. It was hit or miss on the bubbles in the product. this was my first attempt. I think if I de-aired the material before pouring I could the better results. The clear molds I could see the bubbles
so before it set up i could manipulate the mold. You have to understand these molds were cut and developed to have hot wax injected into them under pressure. I am used to that process. I will need a little bit of a learning curve for these gravity feed types. The one thing I can tell already is I need a little more working time before set up I poured all these molds in about five minutes. I would like a product with an hour working time. So I could stick them into my vacuum chamber. If any one knows of a source of inject able plastic Please tell me I also have a injection pot. It is made for wax but I have been running plastisized wax for years. It just is not considered a permanent product. It is made to be burned out in a lost wax process.

UtherJoe,

Keep me in mind I love to make molds. And I love a challenge.

I was curious, the detail is fantastic and I could not find any air bubbles. What's your technique for keeping them out of the product part of the cast.
Does the sprue tree absorb most of the air or do you use some type of pressure or injection process?

Thanks,
Paul

Look at the group shot the top left lions paw shell is riddled with bubbles and the frog has one in the middle of it's back. If this were a peice wax and I was going to make jewelry out of it I would scrap it and shoot another. But I have seen guys repair much worse holes in resin cars. I just don't know what is the acceptable norm.

Paul,
Thanks for the nice detail comment. Are you asking about bubbles in the casts? It is funny you ask about the sprue I did notice it had more bubbles. It was hit or miss on the bubbles in the product. this was my first attempt. I think if I de-aired the material before pouring I could the better results. The clear molds I could see the bubbles
so before it set up i could manipulate the mold. You have to understand these molds were cut and developed to have hot wax injected into them under pressure. I am used to that process. I will need a little bit of a learning curve for these gravity feed types. The one thing I can tell already is I need a little more working time before set up I poured all these molds in about five minutes. I would like a product with an hour working time. So I could stick them into my vacuum chamber. If any one knows of a source of inject able plastic Please tell me I also have a injection pot. It is made for wax but I have been running plastisized wax for years. It just is not considered a permanent product. It is made to be burned out in a lost wax process.

You might want to consider a pressure pot if the molds silicone were degased before pouring. You can remove the bubbles this way quite quickly. All the air bubbles are compressed to were the are so small you can not see them

Roger Corrie

try this resin. I use it an by far is the best ive used. Tryed the alumilite its ok, the micromark is a better resin. 20 min pot life 16 hour demold time

http://www.micromark.com/CR-900-HIGH-STRENGTH-CASTING-RESIN-26-FL-OZ,8154.html

Problem with material is that everybody seems to have their favorite material that works for them. Another problem is that it is expensive and little car bodies don't use that much resin. I have tried a couple of resin types from Smooth on, short pot life, short demold and a longer pot, longer demold product. I myself couldn't see much difference in the finished product. I was mixing enamel paint into the resin for a colored casting and that might have something to do with not being able to tell the difference in resins. What Roger said about using a pressure pot to help with the bubble problem I know does work. But again, it is expensive to buy the pot and if you don't already have an air compressor...more money. With your experience, if you don't have all that equipment, low bubble silicone molds can be accomplished by pouring a very thin stream in a corner of the mold box while holding the material a couple of feet above the box. Good use of sprues on the master, and painting the resin on the mold sides before pouring the resin in will help the bubble resin problem. Your stuff is top drawer, look forward to seeing some more. hope this helps

You might want to consider a pressure pot if the molds silicone were degased before pouring. You can remove the bubbles this way quite quickly. All the air bubbles are compressed to were the are so small you can not see them

Roger Corrie

Roger,

The molds have absolutely no bubbles in them. I did notice bubbles in the resin. I did not degas the resin material. I think I could get a good pour if I place the
sprue material in the correct fashion. these molds were set up for jewelry injection wax. You can cheat a little on the sprueing. I was shocked that I got this good of a fill with these. If i stuck to the rule of thick to thin and maybe experimented with a exit sprue (or gate) I might be able to get good results.
Mike Manfredi

Problem with material is that everybody seems to have their favorite material that works for them. Another problem is that it is expensive and little car bodies don't use that much resin. I have tried a couple of resin types from Smooth on, short pot life, short demold and a longer pot, longer demold product. I myself couldn't see much difference in the finished product. I was mixing enamel paint into the resin for a colored casting and that might have something to do with not being able to tell the difference in resins. What Roger said about using a pressure pot to help with the bubble problem I know does work. But again, it is expensive to buy the pot and if you don't already have an air compressor...more money. With your experience, if you don't have all that equipment, low bubble silicone molds can be accomplished by pouring a very thin stream in a corner of the mold box while holding the material a couple of feet above the box. Good use of sprues on the master, and painting the resin on the mold sides before pouring the resin in will help the bubble resin problem. Your stuff is top drawer, look forward to seeing some more. hope this helps

Tom,
Thanks and I hope to produce some slot stuff in the near future.

I am not a big fan of painting the resin on the molds. The molds I produce are two or more pieces. I never even heard of the slosh mold concept till I started to research modeler web sites. (I even made a very complex 7 piece mold once.) I want to be able to cast a near finished product with easy clean up out of the mold. I hand cut all the molds no powder separation molds here. I do this so I can place the mold line in a good spot. I want to have screw posts with holes ready to tap right out of the mold. I have done component parts for jewelry why not this. The specs. are larger. I have a pressure pot for injection molds it works with heat and pressure. I also have a vacuum chamber I am wanting to try.

Mike M

Most cars can be done with a two piece mold unless there is a wing. I would pour the resin, squish in the bottom part of the two piece mold and put it in the pressure pot. Some swear by heating the mold in a microwave, and or dusting the mold with baby powder to reduce bubbles. I haven't found any advantage to doing so. I found that a heated mold causes the resin to dry faster which most of the time isn't that good of a thing, and baby powder produces a matte finish on the finished product. But Baby oil works well as a release agent, and for keeping silicone from sticking to itself when pouring a two part mold.

Tom,
when you say squish the bottom part of the mold do you mean the bottom half or the lower portion of the two mold parts?

Baby power is used with a lot of frequency in the jewelry industry but never in the pattern it is used in things we call air vents these are only useful in molds shot under pressure. The spray silicone was the best thing I used for natural rubber I have never had a problem with silicone sticking to itself it seems to be self lubricating. Wait I just read your post again Are you referring to pouring the mold half at a time?

I'll jump in with the answers since I'm here.. The baby oil/mold release for keeping the silicone from sticking is when you are making the second half of the two part mold, and to prolong the life of the mold by making the parts release better. Silicone will stick to silicone when pouring it, so the lubricant is to keep part one from being fused to part two. Yes, making a car body mold you make the first half of the mold with the inside cavity of the car filled with clay. Then you remove the clay, lube the silicone so the new pour doesn't become one with the first half, and pour the inside half of the mold. Squishing the mold means you put in the required portion of resin into the first half, move the mold around to make sure there is resin on the entire surface of the mold, and then place the second half in and squish it down. The excess resin will squish out of the top vent holes..

Utherjoe,

I just pour the silicon all over the item in the mold frame. then cut it in two parts. this is a more exacting method This way you can place mold separation lines any where you want and it locks together.
Mike

Mike, don't take anything I say about casting as anything but a slightly educated guess. I have yet to get my fingers dirty with the stuff, but I've been doing my home work. I'm assuming the mold would have to be done in two stages if the windows are open. If you're molding the part with the "glass" in you could probably do a one piece and split it. You would most likely have a difficult time getting inside the mold to seperate it at each window opening unless you were to block the windows with something (tape maybe???) I don't know.. I've yet to experiment with the stuff.. I agree though that a clean flash free body is the ultimate I would be shooting for. Precast holes for the chassis screws may be feasible, but as it only takes a couple minutes to drill them out, it may not be worth the extra work, since it could lead to rejects if they don't get filled correctly.

Utherjoe,

I have been cutting molds for almost 20 years I started in high school. Cutting windows is super easy for me. Think about it, I am used to cutting out settings for gem stones to fit into.when I get more rubber in I will take you through a pictorial. Hell you if you send me a plastic body I will send you back a mold for nothing so I can get some feed back on how you think it will work. I like the idea that you have never done it so I feel more comfortable because you wont bring and preconceived notions about how it is supposed to be done.
Mike

Mike,

Read these

http://www.vabeachho.com/Modeling/CastingClinic/Casting_Clinc_Part_1.pdf
http://www.vabeachho.com/Modeling/CastingClinic/Casting_Clinc_Part_2.pdf
http://www.vabeachho.com/Modeling/CastingClinic/Casting_Clinc_Part_3.pdf
http://www.vabeachho.com/Modeling/CastingClinic/Casting_Clinc_Part_4.pdf

This will give you a basic idea on how a two piece mold is made. Two things I do different now is I don't put all the vents. I have a pour spout to the lowest part ov the body normaly the roof. I also trim away the sides of the inside mold only leaving 4 small supports. I then use a plastic funnel and pour the resin. Most bodies this works very well sometimes I will have a stunbborn part of the body then I pur it into the outside mold and us a rounded tooth pick to forse the air out of the problem areas the insert the inside mold. If I continue to have aproblem I will then pressure cast the mold

Roger Corrie

Here is a tutorial I threw up a year or two ago. There are many ways to skin the same cat. I put a mini narrative at each photo. Here is mine. NOTE: you need to be a member for the Yahoo groups, or it is easy to register.

Link to tutorial;
http://groups.yahoo.com/group/hoslotcarcasting/photos/album/1246734464/pic/list?mode=tn&order=ordinal&start=1&&dir=asc

mmheyho, I have completed registration. I have enabled options as we discussed. I'm going to look around. puddles1976

Tom,
when you say squish the bottom part of the mold do you mean the bottom half or the lower portion of the two mold parts?

Baby power is used with a lot of frequency in the jewelry industry but never in the pattern it is used in things we call air vents these are only useful in molds shot under pressure. The spray silicone was the best thing I used for natural rubber I have never had a problem with silicone sticking to itself it seems to be self lubricating. Wait I just read your post again Are you referring to pouring the mold half at a time?


I use baby powder in my molds but only for long term storage. I lightly dust each surface(main & plug) so they do not cling together & tear.


Neal :dude:

I use baby powder on every body I cast. I breaks the surface tension and keeps bubbles from sticking so they just rise up an out. It will not prevent an air cavity die to a deep undercut those you must vent. Sometimes the way the body sets in the mold can prevent this ie sometimes it is better for the body to be on an angle to facilitate the flow of resin

Roger Corrie

Thanks guys for all the input. I am enjoying hearing about your experiences. I plan on pouring with the bumper side up. I really feel that most of my bubbles came from inside the actual material itself and not from the pour. Since most of my molds are clear I could see the fill. The two materials said shake well before
mixing together so I did. The next time I do this I will place them in a vacuum chamber before adding them together. I will also take care to sprue to the heavier sections of the model I may thicken up the thin spots before molding to improve flow rates. has anyone thickened up bodies from the inside prior to molding?
Mike

Here is a tutorial I threw up a year or two ago. There are many ways to skin the same cat. I put a mini narrative at each photo. Here is mine. NOTE: you need to be a member for the Yahoo groups, or it is easy to register.

Link to tutorial;
http://groups.yahoo.com/group/hoslotcarcasting/photos/album/1246734464/pic/list?mode=tn&order=ordinal&start=1&&dir=asc

Thanks I will check it out tonight.

There’s some great information in this thread!

If it works out for you to do, that’s a great offer to make molds for people. There are numerous Cobras that I want to do, so I would end up needing to make some in resin. This might be a good deal since it would save having to buy a bunch of rubber since there’s only one or two slot cars I would probably cast.

Not holding you to anything, but do you have a very general estimate on what the cost would be for a mold? The posts can be solid if that’s easier, I assume it would be. If you don’t want to list the price year (or if that’s against the rules), could you please send me a PM.

Pm sent

Here is a tutorial I threw up a year or two ago. There are many ways to skin the same cat. I put a mini narrative at each photo. Here is mine. NOTE: you need to be a member for the Yahoo groups, or it is easy to register.

Link to tutorial;
http://groups.yahoo.com/group/hoslotcarcasting/photos/album/1246734464/pic/list?mode=tn&order=ordinal&start=1&&dir=asc

If you look at Fastlap's excellent tutorial, subject 15, 16 pic where he is pouring what he calls the male part of the mold, here is where you need either the baby oil, or vasoline to coat the existing silicone so the two pieces male and female wont stick to each other. I bring out the clay on the wheel arches instead of flush like he does to give the male something to index on, and I pour my silicone from about 18" to 24" inches above the mold if I am not using my pressure pot, but otherwise very much the same. I skin my cat much like Fastlap does and I have been happy with the results. Screw posts are a real pain in my world. Only part I really don't like doing.

Brilliant thread.

Bit of a tangent, but somebody mentioned favoured materials. Did anybody discover what Helen Jarrells used, that had amazing flex for a resin. Now that she seems to have stopped this questions is more relevant than ever.

Brilliant thread.

Bit of a tangent, but somebody mentioned favoured materials. Did anybody discover what Helen Jarrells used, that had amazing flex for a resin. Now that she seems to have stopped this questions is more relevant than ever.

the micromark resin I posted a link for has some flex, Its not as brittle as the alumilite

See below sorry messed up edit

If you look at Fastlap's excellent tutorial, subject 15, 16 pic where he is pouring what he calls the male part of the mold, here is where you need either the baby oil, or vasoline to coat the existing silicone so the two pieces male and female wont stick to each other. I bring out the clay on the wheel arches instead of flush like he does to give the male something to index on, and I pour my silicone from about 18" to 24" inches above the mold if I am not using my pressure pot, but otherwise very much the same. I skin my cat much like Fastlap does and I have been happy with the results. Screw posts are a real pain in my world. Only part I really don't like doing.

Thanks Tom. Actually, I do build out a diamond shape of clay from the wheelwells also. When I was taking photos for this tutorial I didn't realize I had forgot to do it, until it was too late. That why it shows me "cutting in" the inside mold stops to rest on. oops! As shown in the pics, I use Vasoline to coat the inside of the mold before pouring the male plug.

For all you T-Jetter's, as far as the posts go, I saw someone who was resin casting make his mold so the posts were more of a wall or blob that came off the front or rear of the body. This way when pouring, he wasn't trying to make stand alone posts, but a continuation of the inner body so it wouldn't catch air-pockets. I know I am not being clear, because it is hard to describe. I will see if I can do a "mock up" of what I am describing "in clay" and post a picture tonight.

Tom,

Screw posts are a real pain in my world. Only part I really don't like doing.[/QUOTE]

Is the problem getting them to fill or drilling them afterward?

For all you T-Jetter's, as far as the posts go, I saw someone who was resin casting make his mold so the posts were more of a wall or blob that came off the front or rear of the body. This way when pouring, he wasn't trying to make stand alone posts, but a continuation of the inner body so it wouldn't catch air-pockets. I know I am not being clear, because it is hard to describe. I will see if I can do a "mock up" of what I am describing "in clay" and post a picture tonight.[/QUOTE]

I get what you are saying it is almost like you install a bridge. I addition to that you could increase the thickness of the walls of the post.

I used to mold component parts for a bracelet. This design needed to be tapped out the screws were maybe 1mm thick. I placed steel plugs in the mold and pulled them after hardening but before de-molding so the piece had the support of the mold as I cranked these things out. I just ordered some more molding material. I plan on making some molds next week.

Thanks guys for all the input. has anyone thickened up bodies from the inside prior to molding?
Mike
Hi Mike ,
as your used to dealing with wax ... try using freemans sheet wax to thicken the inside of bodies in areas you think could use a tad more. Place , press and Trim . Allows for a more uniform thickness in those areas that require a better flow. BTW sheet wax can be a good way to make windows as you press into the cars openings then trim for a fit . Let dry some in place then carefully remove. Pour silicone mold as normal and let set . Remove wax and voila mold is done. Clean up residue and use clear resin to make hard glass windows. that's the short version but you get the idea. BTW loving the thread !

Dennis :wave:

Brilliant thread.

Bit of a tangent, but somebody mentioned favoured materials. Did anybody discover what Helen Jarrells used, that had amazing flex for a resin. Now that she seems to have stopped this questions is more relevant than ever.
Montoya ,
i thought i heard she used some vagabond products ? I haven't talked to Helen in a long time so not sure how she is doing but hope all is well.

Dennis

Hi Mike ,
as your used to dealing with wax ... try using freemans sheet wax to thicken the inside of bodies in areas you think could use a tad more. Place , press and Trim . Allows for a more uniform thickness in those areas that require a better flow. BTW sheet wax can be a good way to make windows as you press into the cars openings then trim for a fit . Let dry some in place then carefully remove. Pour silicone mold as normal and let set . Remove wax and voila mold is done. Clean up residue and use clear resin to make hard glass windows. that's the short version but you get the idea. BTW loving the thread !

Dennis :wave:

Dennis,

Brilliant idea to use the wax to make windows.
I was wondering as a general rule of acceptance does anyone care what the
underside of the body looks like ei: if it has feeder sprues running on the underside? or if it is thicker than original. Or is the general idea that if the top looks good and it fits the chassis, let it ride.

Mike

A little excess in the more "frail" areas is ok, but top heavy is a no no.. especially with the higher profile vehicles I'm planning.. I also need to consider other things like lighting placement... too thick makes for extra trim work to fit the LEDs.

A little excess in the more "frail" areas is ok, but top heavy is a no no.. especially with the higher profile vehicles I'm planning.. I also need to consider other things like lighting placement... too thick makes for extra trim work to fit the LEDs.

Why don't you pre drill for the LEDs in the model?

That thought has crossed my mind.. I was pondering the concept of two molds..one predrilled for the lights and one not. It would make life easier if it was just a matter of spraying and lighting..

I use a strip of balsa wood for the master post. It is very easy to trim and drill. I drill the hole and mount the chassis then lay it next to the body and cut it to length. I then set it up on the chassis and trim the top to get the proper ride hight. The front posts are very easy this way. The rear you will have to sand them at an angle on most bodies.The thickness of the balsa stips I use are the with ast the indentation on the bottom of the TJET chassis where the guide pin goes. After I have both posts screwed to the chassis and it setting the way I want it with the body setting on top I mix up some 5 min epoxy set the chassi in the body wait a min or two for the epoxy to thicken the set the chassis with the body on top on a piece of track then do a final ajustment to how the body is setting and wait for it to set up

Roger Corrie

[QUOTE=mmheyho;2679933]For all you T-Jetter's, as far as the posts go, I saw someone who was resin casting make his mold so the posts were more of a wall or blob that came off the front or rear of the body. This way when pouring, he wasn't trying to make stand alone posts, but a continuation of the inner body so it wouldn't catch air-pockets.

Hey mike ,
that's plenty clear enough and you are correct on many castings this is atleast part of the reasoning. The other reasons would be post strength and or position for racing purposes. Attachment to a wall allows bad racers like me to crash more and harder without fear of breakage . By position you can place the weight were it's better served for racers I.E. the lower the better . Larger post in front or rear will allow tjets to handle quite differently etc. Hope this helps !

Dennis :wave:

s.

Hey mike ,
that's plenty clear enough and you are correct on many castings this is atleast part of the reasoning. The other reasons would be post strength and or position for racing purposes. Attachment to a wall allows bad racers like me to crash more and harder without fear of breakage . By position you can place the weight were it's better served for racers I.E. the lower the better . Larger post in front or rear will allow tjets to handle quite differently etc. Hope this helps !

Dennis :wave: [/QUOTE]

Dennis,
Your input is very valuable my focus instinctively was for solid flawless casts
I will have to keep the racers needs in mind. Keeping the weight low is a good tip.
Mike

Tom,

Screw posts are a real pain in my world. Only part I really don't like doing.

Is the problem getting them to fill or drilling them afterward?[/QUOTE]

As you can see many ways can be utilized to make posts. But bottom line they have to be strong and light. Best way I have found is I bought some styrene tubing at the hobby shop that was the same diameter as the T-Jet post and rough cut to length and screwed the tubing to the chassis. Then I began the painstaking process of sanding the top of the posts to fit the body. Getting the post length right, while making sure the body is setting centered and level on the chassis isn't easy. I used Epoxy to glue the posts. Also, after glueing the posts to the body, I would stick a toothpick into the open hole of the post for a sprue. I STILL would have to sand the posts after the cast was done most of the time to get the body plumb and level on the chassis. The posts are not easy to fool with because they are lower then the body. You don't have much room to sand them.

Hey Mike,
Any pics? Progress?
Really enjoy this thread.

Rich

bump bump

I am in the ice cream business and the season started way early for me down here. I have had little time to do any molding. Or checking in on the boards. I hope to do some after mother's day. The only thing I have had time to do is strip some die cast cars for mega G chassis. I need to buy some more resin with a longer pot life. I will post as soon as I get new results. For those of you that wanted to send me stuff for molding I would start on that stuff as soon as I received it. I would mold it in the middle of the night if I had to. I just don't place that kind of a priority on my own stuff. I am still looking for my Fire engine if you still want that tow truck done? (you know who you are Mr. Coyote :tongue:)

Mike

I did get a fire engine for you Mike, but the top of the roof is white. The all red ones were discontinued so they are very hard to find at an affordable price. I just haven't gotten around to lighting it. As far as the tow truck, I am having second thoughts of molding it with the lights and will probably need to fill them before I send it off. I also have a lighted LED sled for ya too. Hang in there..