Efficient way to fabricate a mold ?

Discussion in 'Fiberglass and Composite Boat Building' started by antonkov, Apr 12, 2020.

  1. antonkov
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    antonkov Junior Member

    Many thanks to KD8NPB for his post, the most informative in this thread.

    To answer the post above. Seems like too many years of experience come with a flip side. The eye gets blurred, innovation fades out, creativity gets contained by previously established routine and choice of materials. If tomorrow someone puts a new product or technique on the market, the argument that they have been doing something the old way for dozens of years and for a reason will still stand regardless of the new advantages, hence I listen to this kind of reasoning but taking it with a pinch of salt.

    Having a degree in experimental physics I understand the materials and processes on a much different level than what it takes to build a mold. I understand the desired properties of my end product and I see multiple options on how to arrive there. Reconstructing the historically authentic way of doing something is not my goal but doing what I need efficiently is. Efficiency is a very subjective term and obviously the solutions of DIY builder in a garage and of an industrial engineer at commercial plant will be very different.

    I liked the mold building method used in the original post video. Given the facility and instruments used, this couple did a great job. In his video comments Andres sais they were lucky to get a good deal on carbon fiber, hence his choice of the laminate. I am sure that having a different facility or different deal or different requirements would have made some changes in their story one way or another. Solutioning for a given result and under given conditions is what I am interested to discuss.

    regarding building on the lowdown of tooling for 46tf cat that will be used in production ... , don't even want to start, pls. read carefully
     
  2. ondarvr
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    ondarvr Senior Member

    I congratulate you on your degree in experimental physics, its no easy thing.

    My post did get you to respond.

    I teach tooling for a living, I'm on the front lines of the new and creative products. I've traveled most of the world teaching people how to build tooling.

    It's also my job to look for new innovative things to investigate.

    What I can tell you is while there are very creative people trying to come up with new methods, it comes down to what's actually available for materials in the market place.

    Over the last several decades some very promising methods and products have been introduced, few to none have actually made it into the tooling arena due to the cost and the difficulty of doing it correctly every time.

    In tooling you get one chance to make it right, anybody can make the 5th one right even if it's by luck. That's why tooling is so difficult and cost so much to have done.

    You do the experimenting on the hatch cover mold. If after a few years you can achieve the desired result consistently, and are willing to gamble on scaling up to a much larger mold, then go for it.

    Years ago it was 3D printed tooling, it was a great idea, I helped a customer build a 36' cat hull mold.

    We explained a few things he needed to take into consideration prior to it going to Oakridge for the final cutting. He didn't exactly follow the recommendations and ran into some problems that could have easily been avoided.

    The tool was completed, but after that the project kind of died.

    This type of tooling can be done, but the technology still has limitations and high costs.

    You can make epoxy tooling, but the perceived advantages don't play out in the real world unless you actually need the physical properties of the epoxy. And introducing carbon adds another level of difficulty and expense.


    I work with probably the largest and most advanced tooling builder there is (they arent located all that far from you) and even with a full staff of composite engineers and doing advanced military and aerospace tooling, they have a tough time truly improving on the methods.

    These are the reasons that when someone comes here and says they have grand ideas on new methods of building tooling, but have no practical knowledge on the subject, I tend to ask questions, listen, then present some hard learned lessons.

    Currently you aren't using the best products or methods to rapidly build tools, learn what works and why, then try to reinvent the wheel.

    You may be able to do it, somebody will eventually, but the costs are high and so is the time invested.
     
  3. ondarvr
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    ondarvr Senior Member

    And if you want the name of a local supplier I can pass it along to you.

    He can assist you in choosing the correct methods and products to help ensure you're successful.

    He's very good, one of the best there is.
     
  4. antonkov
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    antonkov Junior Member

    Those are all valid reasons and sound correct although, unidimensional. Out of strong/light/quick-to-build/economical/... axises you are fixing on the certain one, and that one isn't exactly DIY friendly.
    Advanced military and aerospace are working on totally different project resources and their solutions are obviously different. But not every project has the same initial requirements.

    There are numbers of DIY builds covered on this site, builds from different DIY-oriented architects. I believe all these people who dared to undertake these builds crave for any bits of wisdom that could make their projects cheaper, lighter or less risky. And nevertheless, their solutions are very different from the industrial (otherwise they would have gotten an industrial quality and configuration boats built in a wrong economy of scale fo far more than a dealer price)

    My moulding surface is 3-6 sq.m, by using textured urethane or urea paint on the final part I can allow for a coarse finish of the mould, which saves me quite a bit of chemicals and labour.
    Using infusion saves me on the resin and fumes. Using pressure-resistant and less absorbing core saves me on the mould weight and fabric cost. Perhaps, there is something else I didn't think of that can make a break the project.
    I welcome any experience and ideas that get the job done. Those methods that either don't provide the required result or cannot be accomplished within the given resources are not helping by the definition, even if they are well established in the industry.

    It is never a fixed solution that fits all, rather a continuum of tools and methods that need to be configured for the given result and resources.
     
  5. antonkov
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    antonkov Junior Member

    on the subject of making it (DIY) efficient... infusion or not, seems like there is not much to do with the surface layer, it is required, if not for capturing surface finish, then for providing a seal for infusion (the mould isn't expected to be airtight). the question is how much of a layer build-up is sufficient to make a strong and reliable seal. KD8NPB uses 2 layers of gelcoat and 2 layers of 90mil chop (i.e total >5mm) before the infusion, wonder if it could hold on a lighter laminate given adequate dry layup contouring and careful vacuum bag placement.
     
  6. ondarvr
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    ondarvr Senior Member

    Infusion doesn't reduce your costs, what's saved on resin is spent on consumables.

    You mentioned building these boats for a possible business venture, or at least that's how I read it. If that's the case the tooling needs to be stiff to hold its shape, you don't want flex.

    It also means they need to be built strong enough to last through many years of use, hopefully building enough parts off them to pay for themselves.

    You can spend less time on getting the surface texture perfect, but this only helps you cut the time and cost of building the mold, it adds time and cost to every part made off of the mold. This really comes into play if you plan to build many more parts in the future.

    Even when someone doesn't need a good surface for the parts being built they typically try to achieve a good surface on the mold because a poor surface leads to difficulty in demolding parts. The more parts you make the more difficult the demolding becomes. Difficult demolding then begins to destroy the mold.
     
  7. ondarvr
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    ondarvr Senior Member

    The skin needs to be substantial enough to holds its shape while loading the glass and other things.

    The mold is required to be air tight for a project like this, and due to the stresses needs to be built to hold up against the vacuum.

    You can infuse on a skin, but the skin then needs to be thicker to hold up, sort of defeating the purpose. Although cores are applied this way sometimes.
     
    Last edited: May 1, 2020
  8. ondarvr
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    ondarvr Senior Member

    What people tend to find out is the method and products used by KD8 are what will work the best in covering most of the requirements for tooling.

    For one-off tooling there are places where time and money can be saved, but that's a completely different conversation
     
  9. antonkov
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    antonkov Junior Member

    My real world experience from infusing flat panels on average 6-8sq.m, divinycell core, total of 2000g/sq.m unidirectional glass:
    1) vacuum bag - costs roughly the same as one liter of resin and is reused 2 times,
    2) spiral polyethylene tube for vacuum perimeter is reused some 5-7 times, costs cents per panel
    3) spiral polyethylene tube for resin flow is reused 2-3 times, costs cents per panel
    4) flow media is not reusable and costs a fraction of a litre of resin
    5) vinyl intake tubes are not reusable and cost 30c/ft, I use two resin ports and hence 2ft per panel
    6) peel ply, gloves, mixing stick, mixing bucket are same infusion or not
    7) no need for brushes, roller, acetone clean up, etc

    if wetlayup was even possible on my footage, my resin use would easily double, which on ~12kg of fibre would translate to nearly tenfold increase in extra cost vs. saving over consumables.

    I am sure other setups can be made more wasteful, but it's not fair to generalize based on them exclusively. If that's what you are teaching students that don't know otherwise, you might be doing more harm than good.

    I am yet to infuse my first mould and sure there will be lots to learn, but so far I don't see what makes infusing a mould fundamentally different in economy vs infusing the final parts.

    Regarding the surface finish, yes, it is understood the glossy surface will release easier. But aiming for a glossy final part calls not only for glossy mould but also for right mould laminate and layer staging to avoid print through. But what if ideal glossy isn't required on the final part, what if minor print trough is acceptable, why overengineer pretending it's an advanced aerospace project?
     
  10. ondarvr
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    ondarvr Senior Member

    Again, you are using your very limited experience on the subject to determine what your over-all cost may be in the future.

    The mistake many fabricators make is they expect infusion to lower their cost of production. In some situations this may be the case, or it could increase the cost. What most fabricators find is that overall the costs are similar.

    Every part is different, for some parts infusion is undoubtedly the best method, other times it doesn't make sense to use infusion.

    Reusing many of the materials can create issues, tiny fragments of hardened resin can puncture the bag and ruin an otherwise successful infusion. So most fabricators dispose of everything but some fittings that are designed to be reused.

    Some shapes or sizes require more expensive bagging material, or custom made bags.

    The thicker the part, the more resin you may save with infusion, but per square foot on thin parts the resin savings go down fast, so the real cost goes up.

    If you are comparing a resin rich CSM laminate to an infused biax laminate then infusion saves a great deal of resin.

    A thin hand laid Biax may not use much more resin than a thin infused biax laminate. So the total cost of infusion can be high compared to hand laid.

    As the resin content goes down, so does the cross section dimension of the part, which may result in a part that has more flex than desired. Now you may need to include other materials or designs to bring the flex into the range required.

    These additional materials or designs all come with a cost, sometimes that cost is significant.

    I haven't seen any of your designs or molds, so I have no idea if it will cost you more or less than you expect. But rarely does anything related to building molds or boats cost less than expected, it can easily go up by a factor of 3.
     
  11. ondarvr
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    ondarvr Senior Member

    IF the surface is glossy, then print or similar surface irregularities don't have as big of an impact on longevity of the mold.

    If the final parts are going to be painted, then minor irregularities in the surface will be sanded out, so it doesn't make much of a difference.

    If the parts are gel coated in the mold, then the cost is high to make them look good after assembly.

    Un-gel coated parts can take more of a toll on the mold, and the gel coat is a plus if the parts are painted, it makes for a good substrate.
     
    Last edited: Apr 25, 2020
  12. KD8NPB
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    KD8NPB Senior Member

    Tooling is not where someone should cheap out. I've spent the majority of my industrial composites career repairing the badly built tooling of my predecessors. I have a pair of molds right now that I cannot use, because they were very resin rich and parked outside, upside down on top of the plugs after completion. After postcuring in the sun and weather for years, it was decided to try to finish the mold and put it in production. The postcuring caused the yacht mold to shrink 1.79" versus mold #1 off the same plug. Because of this, we cannot share parts between the molds because they don't fit. The shrinkage was not symmetrical, and it required 5 weeks of rework by a staff of 11. It was too late to stop, because you don't know the outcome until the mold is off the plug, and you can't take the mold off until you've welded about $10,000 worth of steel on it along with a rotating cradle.

    Your product will start and end with your mold. A poor mold will cause a poor product, or in some cases, no product at all because it stuck in the mold and destroyed the part and the mold during extrication.

    The only way to guarantee success is to adhere to manufacturers TDS specifications.
     
  13. trip the light fandango
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    trip the light fandango Senior Member

    When spraying on gelcoat , try using exhaust fans that are close to the floor, Polyester fumes sink I believe .
     
  14. antonkov
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    antonkov Junior Member

    right, styrene vapor is 3.6 times heavier than air, good point! I positioned my exhaust intake up above thinking the incoming cold outside air will push the fumes and that it will help the overall circulation (apart from the fact that overhead volume is not as useful as the space down in the corners ) although, in the summer it may not work as good.

    Styrene in the process is still making a major hassle for me. Looking for a proper commercial workshop and if not the gelcoat spraying, my options would be so much better and numerous. Don't have much noise, dust is easy to manage, but styrene is a deal killer.

    The gel coat, why do we need it? what specific property of the gel coat makes it required on top of the resin? I see how it makes sense in PE system, but If tooling was all epoxy-based, would it still require a layer of fortified resin to achieve something that resin or laminate cannot?
     
    Last edited: May 1, 2020

  15. trip the light fandango
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    trip the light fandango Senior Member

    It's the wax content isn't it? it s remarkable for its longevity, and paint covering epoxy isn't nearly as hard wearing or lasting , ..well ceramic coating/baking must be.. I suppose gelcoat with polyester then using epoxy doesn't solve your problem..
     
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