Need help planning this mold

General Composites Discussions Composites Talk
#1

Following on from my previous thread in “Pattern and plugmaking” <A href=“http://www.talkcomposites.com/623/Pattern-Making-and-CAD,-need-advice”>http://www.talkcomposites.com/623/Pattern-Making-and-CAD,-need-advice

in which you can see the design and pattern making of this spoiler

My plug is now nearly ready

I’m now thinking about how to make the mould, i’m considering making a 2 part split mould as illustrated cross section below, i haven’t done this before so please add your comments on how you think it would work out or how i can do it better.

what would be the best material to use for the barriers?

#2

Why do you need the barriers so bented inward?
If you make them bented outward, you can make the mould in one piece.
What will be the technic of costruction?

#3

Ok, my reason for a two part mold is the undercut, i put an undercut where the spoiler meets the body of the car because i need this area to be a really good fit and didn’t want this to be where i trim the final part, the undercut means i can trim at the hidden part.

hope this makes sense???

i’m totally open to suggestions as to how to make this work and would really appreciate the advice.

#4

Is the Part to be painted or clearcoated to show the weave of the reinforcing? You are going to have to sand and finish the trim line anyway, so if painted use a one part mold. Otherwise make your barriers (flanges) more horizontal (concave part edge). How are you going to affix this part to car?

#5

I’d like to be able to clearcoat it and show the reinforcement, (concave part edge?)do you mean turn the barriers inward? As for fixing, I’m still not sure? Bonded or build hardware into the finished part so it can be bolted on?

#6


you mean more like this??

#7

Bonobo,

It apears the above picture you’ve provided would still lock the part in the mold and require a 2 piece mold. From what I see, the part that “touches” the vehicle (your cut line) doesn’t provide the correct draft angle for a clean part removal from a one piece mold.

-C

#8

So a two part mold is the only option if I don’t want to change my design, and only careful trimming will ensure a good fit to the body. What are my options for affixing the spoiler?

#9

basicly either hardware (pop rivets, bolts, bighead fasteners) or any type of glue (MS polymer, methacrylate).

In case of bolting, you need to drill holes in the car, which can corrode if not treated. Installers can **** up the drilling, damaging the car or drilling in the wrong place.

In case of gluing, people can make a mess of it. I think if I would need to glue it, I would use double sided tape to hold the spoiler in place, then tape everything up, (spoiler and car) then apply glue and reapply the spoiler.

#10

I’d prefer the glueing option I think.
once the part is made and trimmed there is of course a large void and only a thin edge where the spoiler meets the car, what if the spoiler was taped in place then filled with expanding foam? once it’s cured I’ll have a large surface to bond to? Could this work??

#11

Bonobo,

I would differ back to your original post as to how you were planning the mold, there are a lot of good “key” features to the original style you were thinking about.

If I were building it (which I’m not, so its just my opinion which you aren’t obligated to agree with), I would change two things…

  1. Flanging: I’m not sure how “to scale” that original design was and it may have been for “reference only” but if you make a larger flange will allot you more working area for mold alignment hardware.

  2. Under Cut: Increase your “under cut” size (depending upon how accurate your plug is and how well it fits on the vehicle). You are on the right track with that under cut and making it a bit larger will increase your bonding surface and not have such a critical trim line, so its a win win. The downside to increasing that undercut in your mold is going to be during the actual layup fabrication…

  • the larger you make the undercut the more surface area you’ll have to bond to.
    BUT
  • the larger you make the undercut the harder it is going to be to layup into that tight corner.

It is going to be a very fine line you’ll be walking when it comes to the undercut size. Those corners are going to be really tight and will have a good chance of bridging the material or be a resin pool (which isn’t aesthetically pleasing).

I can elaborate if you’d like/need, no worries. It seems like you have the correct understanding of what you’re getting into, I can’t wait to see your final product!

PS. is this going to be production or just one for yourself?

-C

#12

Thanks for taking the time to look at my plans, until now i haven’t had any feedback on the undercut idea, it’s good to know someone at least gets where i’m coming from.

the more i think about it the more i worry about laying up into those areas, i just thought i’d put the idea out there to see if anyone has done something similar or could advise a better way to achieve the results.

The flanges will have to be bigger on the real mold, probably 4 inches or so?

The idea was that if this part comes out well i would showcase it on my own car, then if there was enough interest from others in the owners community i could consider a production run.

#13

Bonobo,

You’re welcome… I completely understand what it is you’re trying to achieve and really hope this project works out for you and that all of the “business” variables align to become a profitable venture for you.

I own a business in the automotive composite industry and what you’re doing is right up my ally, I’m here to help in anyway that I can and am always learning… daily.

Questions:
What is the goal of your spoiler lip? Is this just an aesthetic carbon fiber accessory? Does weight matter?

I personally think that your mounting solution will determine the size of the undercut section of your piece (if you move forward with your first thought of the mold). Also, have you considered making this a three piece mold? Or maybe making this part in two pieces and then secondarily bonding the upper and lower pieces together.

I hope I’m not adding confusion to your project… there are many ways to get from point “A” to point “B”, some will be easy and fun, others are going to be overkill. Let me know if you want me to expand on different ways of making this piece, or if you’d rather me stop adding commentary, no worries.

-C

#14

Corban,

Firstly, here’s a very inspirational video i found:

http://vimeo.com/52611461

I’d be interested to see what kind of work you do?

Do you use CAD software? i would like to start learning some CAD but not sure which package would be most suited to the type of work i want to do?

The spoiler is mainly aesthetic, i don’t race so it’s more of a style thing.
saying that, mazda took a lot of effort making this car light so it’s only right that my part is light too, when i took the bootlid off to start making my plug i was shocked at just how featherlight it was (all aluminum).

I started this thread while still working on the plug so that there was plenty of time to explore all options of mold design, could you explian how a three part mold would work?

making the part in two pieces is also an option, i guess the second piece is just a base molded from the bootlid and bonded to the bottom of the main part using some sort of built in flanging.
again, please elaborate if you can.

You’re not adding confusion, only giving me a better understanding of my options, for which i’m grateful.

Bonobo

#15

Bonobo,

Nice video, good find.

My work primarily revolves around Lamborghini’s, Porsche’s, and Audi’s… with the occasional Ferrari, but I don’t enjoy working with Ferrari’s, Lamborghini and Porsche are my personal cars of choice. Recently there have been some Subaru tuners that have taken a liking to my work, but they want to use Polyesters rather than Epoxies, so I am going through a bit of learning with this other resin base.

Below are some options that I see… not every option, just a couple though:

Opt.1:
Go with your original design and keep the undercut small so that you don’t have a critical trim line. Vehicle attachment will be an issue unless you make a secondary mounting solution that is bonded onto the inside of the spoiler that will mate with the trunk/boot.

Opt.2:
Make the top “aesthetic portion” of the piece and the mounting base (that mirrors your lid) separately and bond them together giving you a large clean surface for vehicle attachment.

Opt.3:
Make the mold as originally planned (with a small undercut) but also have a third bottom portion of the mold that mounts to the initial two upper halves. Layup the part with the undercut, trim with the piece whilst still in the mold, put on the bottom mold portion with a fill hole and a relief hole on opposite ends (or multiple areas) and fill the cavity with a dense (non shrinking) pour foam. Note this will turn your mold into a pressure cavity and the relief holes have to be very strategic as to not warp or distort the molds in any way to insure a proper fitment onto the vehicle. The molds will need to be very sturdy for this option… but it is probably the easiest option of the three as you can keep the undercut small and there isn’t any secondary bonding. This essentially gives you a product like Opt.2, with the exception that you won’t have to secondarily bond a separate mounting panel.

Those are just a couple of options. There are MANY more, and I may be overlooking something, but given your project, those three are what I would consider going into it.

I hope that helps… I can keep expanding on how to do each if you need. No worries, let me know how I can be of assistance.

-C

#16


Corban,

Here’s a diagram of the 2 piece mold type with a small undercut and more to scale flanges, it’s hard to tell if the part would get “locked in”? do you think this configuration would work or how i could improve it?

Also, what is the best material to use for the barriers?

I’m leaning towards the idea of making a separate base part and bonding it to the main spoiler.

#17

Did you catch that TRA video on speedhunters yesterday? that’s a good clip

I think your best bet is to pull a mold of the trunkline and make that separate piece to bond to the underside of the spoiler. Also, I believe you could lengthen your undercuts if you pay attention to the radius of the tip of the spoiler, and you could even make a recessed flange for the bonding piece. I added some lines to your drawing in this very sophisticated software provided by my factory install of microsoft XP :slight_smile: enjoy

#18

Yep! I check out speedhunters every day!
TRA are an inspiration.

Are those extra lines in the first pic split lines in the mold?

#19

Btw my spoiler is loosely based on the rocket bunny s13 ducktail http://farm3.static.flickr.com/2560/3681722001_b4fc11ca5e_o.jpg

Corban,

There’s a good chance I’ll be in socal in march if you want to show me how the pros do it?

#20

I was just trying to draw parallel lines that would show how the part would separate from the mold after cure. The lines at the top to represent possible interference with the direction of the pull. I really think you’re ok without locking the part in, you just need to decide how you want to mount/bond it to the vehicle

…and I have my morning coffee reading SH, also japanese nostalgic car.