How to make a mold?

[Guest Anonymous]

I have the spoiler from the euro 2 kit and I want to make a mold of it.What is the best to use to accomplish this task?Thanks To all.

[Owen]

I hope you guys start a big long thread on this or write a tech article!

Owen

 

 

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http://www.homestead.com/s30z/index.html

[Jeff]

Chris,

 

Multi part molds are necessary if the part you are casting has a negative draft. In other words if it turns back on itself whatsoever then it will not release from the mold.

 

We use sheet wax to create dams that enable the mold to be cast in sections. You turn the fiberglass up on the wax to create a flange. Remove the wax and apply PVA to your newly formed flange before you lay up the next section of mold. You create a matching flange at this point.

 

Drill the flanges and bolt them together to form your full mold for casting your new part. When the part sets up just unbolt the flanges and remove your mold in sections.

 

It is a fairly easy process if you just take your time. Fiberglass is very forgiving if you make a mistake.

[Trevor]

Wax the part really well with Turtle wax. Apply PVA as a parting agent. Spray on one layer of tooling gelcoat. Lay up alternating layers of fiblerglass mat and cloth. The first layer should be 3/4 oz "angelhair" mat. Use laminating resin (the other kind has wax in it). Succeeding layers of mat should be the heavier stuff. Cross-section of a mold should be twice the thickness of the finished part.

Let the resin cure, pop the original part out.

[Guest Anonymous]

Trevor,

 

I am planning on doing some fiberglass molding as well as some carbon fiber stuff, although, that is down the road on my list.

 

You sound like you have some experience with FRP molding. I have read just about every book I could find on the topic and to be honest it almost sounds too easy. One of my Dad's neighbors molded up a carbon fiber front end for a Triumph race car. He said that he had no prior experience working with FRP molding. He told me the only drawback to the parts he did was the fact that he had to paint them to match the car, he said they turned out that good!!

 

Anyway, when I get to that stage of my project I may have to "pick your brain" some for some tips, along with Pete, Terry and anyone else who cares to chime in...The one thing I am having a difficult time with in understanding the mold building process is fabricating "multi piece molds" for the different drafts on the fenders, etc...How does one make the mold in different sections? Like I said, I have read several books on the topic but it is just not the same as being able to actually see it being done. We only live ~50 minutes apart and I am in Richmond several times a week, maybe we can get together.

 

Chris

[blueovalz]

Excellent information here. The only thing I can add, is that you don't want the mold to kick too fast (i.e get too hot) when you make the mold. The heavy mass of the mold allows more heat build-up, and a chance of the mold becoming distorted slightly. Also, very thin (thickness of the surface) original parts will be distorted by the weight of the more massive mold while the glass is still wet, so a staged mold may need to be made to keep from distorting these delicate original pieces. Lastly, if the mold is to made of a large piece, then wooden frames blended into the mold will help stablize the shape of the mold (hoods, doors, etc).

[Guest Anonymous]

Fellas,

 

Thanks for the information on the mold making process!!

 

Jeff, does the sheet wax remain in the mold or is it removed? This is one of the things I don't understand as it is difficult to picture in my mind. The books I have on FRP molding covers this process but there are no pictures. Also, were does one source sheet wax?

 

Terry, I am planning on making a one piece front end with a removable hood. I was going to bolt the fenders and air dam up on the car and take all of the measurements, ie. how far apart the fenders are from one another, etc...then build a wooden frame to mount the fenders and air dam on that would replicate them being on the car. I had planned on the wooden from for extra support due to the weight of the mold. Does this sound like a good idea?

 

Thanks again!!

 

Chris

[blueovalz]

This sounds a lot like the way Mikes one-piece was done. Double and triple check your measurements 'cause once that glass goes on, its too late to change it. Be sure to brace it up real well. Any exposed holes that were used to hold the steel panels onto the car (lips on the hood side of the fenders) should be taped over. This will prevent the resin from "riveting" itself into these holes (provided the hood is not part of all this). All this said and done, I would think, since the parts are coming off the car anyway, that you instead would do this while the parts are on the car. You can fill the seams with clay (which by the way can be used much the same way as the sheet wax is). Without looking at the front end, I would say the dam portion and fender lips are going to be a problem with a true "one piece" due to the afore mentioned "draft" that Jeff brought up (but, again, that's just a guess).

[Jeff]

Chris,

 

The wax does not stay in the mold. You lay the mold up in sections and use the wax to create your flanges. Once the flange is created you remove the wax and then use your fiberglass flange as backing when you lay up the adjoining flange and mold section.

 

You can buy high temperature sheet wax online from McMaster-Carr, www.mcmaster.com, sorry can not remember how to embed a link. Just go to their site and search on wax, if your not familiar with them you will be amazed at the diversity of products they carry.

 

I do the estimating for a specialty construction firm that does a lot of work for the entertainment industries. I could snap some digital photos of a multi-part mold and e-mail them to you. You can contact me at jmcelyea@nassal.com.

 

If you make a nice enough mold you could probably sell parts to some of the other members.

 

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1972 240Z - Major Rust Repairs Underway

[blueovalz]

Jeff

 

I've only used clay for the flange stops in the past, but if I were to start using this wax sheet you speak of, how do you attach it to the buck so that the mold material can be pushed down into the corner (point was meets buck). Thanks ahead.

[Jeff]

We use wax instead of clay to make a larger flange when we are working on a large mold, life a front end.

 

You place a bead of clay as a support to keep the base of the wax from moving while you lay up the glass. We then superglue, yes superglue, triangular shaped wax gussets to the back side of the wax flange. These keep the top of the wax from deflecting while your laying up the glass.

 

We do use clay as well, but the amount of clay required for a large flange is cost prohibitive. Hope this helps.

[Trevor]

All great points in this discussion.

 

Thanks for the tip on sheet wax (sure it would have to be high-temp since the resin produces heat as it kicks). For years I've been using masonite and clay - even for simple one-time-use flange dams.

 

Terry brought up the support bracing - very important with a long thin wobbly shape like an air dam mold.

 

Very very important on a full body panel that is expected to be dimensionally accurate enough to bolt onto a steel unibody.

[BLKMGK]

Good tips guys! Here's one I picked up for making 'glass parts that I've yet to try. Make the part out of cardboard - like say a glove compartment. Then when it's looking like what you want punch many holes in it. Place some glass matting on it (optional) and then slather resin on it. The holes will allow the goo to reach both sides for strength. When dry it should be strong enough for use Mind you I've NOT tried this but for something like a glove compartment it ought to work. This tip from a street rod magazine.

 

Hrm, now I wonder how hard a center panel would be to make in carbon fiber? I could use the stock type vent maybe but allow myself room for a custom A/C panel and a better radio mount. Maybe even gut one of the panels in the grage to make it... someone already did this didn't they? I saw a pic somewhere and it looked darned nice!

[DavyZ]

If you have not visited Bryan F's site for carbon fiber, do so! It is worth the look: http://bryanf.com/

 

Somewhere I was surfing the internet today on Z car stuff and someone had taken an old musty glove box out, spread out the pieces, traced the pattern on thin sheet steel, and bent it all in place. He also used pop rivets to hold the thing together. After shooting it with paintable undercarriage stuff(why?), it looked pretty good.

 

David

[Trevor]

Another method for making a one-off part like a glove box or heater duct is to carve it 3-D and slightly under sized from a block of polystyrene foam. It can be complex with a lot of under cut which complicates a normal female mold. Lay up the 'glass matte and resin over the outside. Then disolve the foam out with acetone. It leaves a hollow 2- 3- 4- 5- 6- ?-sided box.

Some cautions:

Polyester resin dissolves the foam too (Or use epoxy resin.), you have to make a barrier between the foam core and the fiberglass.

I've used latex paint, plastic wrap, and duct tape.

The "Goop" that comes out is nasty toxic waste.

[Drftn280zxt]

can someone post a pic of what their molds looks like? Pictures would help a lot so that I have a good idea of what it is I'd be making eventually. I figure that if I'm going to try to make a widebody kit for my 280ZX 2+2 I may as well make a mold of it incase of future damage. Thanks

[olie05]

heres some good info on fiberglass body molding:

http://www.hotrodder.com/32Blowpar/page11.html

[Drftn280zxt]

I'm still a little confused. THey made it seems like the mold is just one sided. I would've thought that you make one side of the mold lay in a bunch of glass then put the back mold of top of that. With hoods you need a way to attach to hood to the car. the easy wasy is pins but what if you want to use the original opening mechanisms? I also thought the molds themsleves were made of clay, these are fiberglass. And the whole gel thing is confusing. Thanks for posting the site but are than any other that are informative yet understandable to a novice. (hands on I've never even worked with fiber glass, just done some reading to understand how to lay up fiberglass. The waxing is also confusing. Is he talking about car wax for shinyness and protection or some other kind of wax?

 

In the case of making custom body components would taking an autobody class be an excellent idea, or is that really only good for learning how to repair stuff?

[hanomon]

When I mounted the PCM in the void where the wiper assembly was, I molded it with that expanding foam STUFF from a hardware store. The part was placed into one of those thin plastic gerocery bags which allowed the foam to conform very tightly to the part to be housed.

 

The result was great! The PCM popped right out and left a nice snug perfect fit. That STUFF has good thermal properties also. (although flamable when ignited) we torched a piece as an experiment and it burns real good!

 

Another old-school (trick) technique I'll share here from my surfboard manufacturing days. Save yourself a lot of sanding by laying a piece of waxpaper over the area (especially when using matt or hair) will leave a nice smooth texture. Any lumps/bubbles can be rolled out while it is still workable and you can see right through it. Be sure to peal it off SHORTLY after it begins to kick. Waiting too long here will melt the wax and actually bond to the paper, making the after sanding step a nightmare.

[Drftn280zxt]

Hanomon do you have any pics of this process? What does PCM stand for? The foam you are referring too, is it that insulating triple expanding foam used to fill in holes where water leaks can occur on houses? How does only the outside of the foam expand leaving the the part touching the car really smooth or does the contact portion on the car also expand and get lumpy. Where do you get clay dividers to divide up the parts when making molds, or can this be done with other materials?