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Burton
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Joined: 20 May 2012
Posts: 7
Location: VA

PostPosted: Tue May 22, 2012 8:27 pm    Post subject: *motorcycle wave* Reply with quote

Found this site via researching into vacuum forming as a way to make a new lens cover for my motorcycle as I am retrofitting an hid projector kit into it.

I wasn't content with simply reading information as it left me with more questions I couldn't source answers for.

There are two techniques I am considering.

The first would be to make a female mold using something like SmoothCast 385 (idk if it would work as I never used it) out of the existing headlight lens cover which has been modified to be slightly bulgier toward the center to give the projector enough room. Current it is a perfect fit with the existing fluted lens.

I saw this technique used here:
http://www.youtube.com/watch?v=06ZQNQ-2zUs

And here:
http://www.youtube.com/watch?v=Cox8fR1rUBI
Side note, no clue how he fracture id like that ... it doesn't look like a traditional seam used to make a multipart mold ... could just be a sloppy one. What is interesting is I can't see any holes whereas the above has holes drilled into the medium.

The reason I am attracted to this method is because of the fit required from the finished part (it must fit the existing housing near the seals perfectly if it is to be remounted), and because it doesn't look like it would take long to do. I already have plaster of paris for the vacuum box in this case and would only need to acquire the resin and a pipe + tube to plum into vacuum pump.



The second, more obvious approach, would be to build a vacuum table and take my 'test' lens cover, modify it with bondo to have a new bulge, then do a traditional pull over it. It is only about 3/4" tall, if that, and the mod would only raise it at most 1/2" near the center.

The only problem I see with this is me wanting to use lexan (for its strength and yeah I know I have to de-gas it first ^_^) and at least 1/8" thick. Since it is going on the front of my bike it needs to be able to withstand a rock hitting it, as it often happens.

This would mean I would need to invest a lot right off the bat. Luck would have it however that I have an old gast doa-p104-aa pump ... the problem however is the gasket has a hole so it can only pull 5 ... with a near gasket it could theoretically pull 29 ... if the corrosion inside the pump near the seal ring doesn't prevent this ... 35$ for a new gasket if I recall but haven't decided to test the waters on that yet.

I also have a 2.5hp shop vac sitting around, I know 5 is optimal however. And I have a 5gal carry tank I am using with my 6gal compressor (use to airbrush and hated it coming on a lot)



The good news is the community surrounding this bike is huge and there might be a demand for this shell if available so the project could pay for itself and I get an awesome cosplay/prop vacuum table out of it ^_^ But most likely only a couple will end up with this as it is the previous generation bike and the newer one looks prettier.

Anyway I am ranting ... any help is more than welcome. Thoughts on what material I should use for a female mold would be nice too. I can't mold the inside as the glass is fluted and thick requiring bondo + sanding to fix ... and then the finished lens most likely will not fit the original casing well since it would be smaller.
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Fredo
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Joined: 21 Mar 2007
Posts: 251
Location: Kingdom of Nye Area 51

PostPosted: Wed May 23, 2012 1:56 pm    Post subject: Reply with quote

Youtube makes vacuum forming into a monkey see, monkey do process, and it can be for the most part.. Most of the plastic being formed on Youtube is the easy shit.. It's diy for the most part, the hard stuff is posted by the pros. Venturing into vacuum forming 1/8 lexan is going to cost you a fair amount of money. You'll need to heat it from both sides or use a temp. controlled convection oven.

The plastic you picked is the hardest to form. The forming window is only a few seconds, then it locks up and is wasted. The heat requirements leave little room for error.

Besides that you have no idea what the light spread would be. Getting it to fit will be another can of worms.. Seems like an awful lot of bother and wasted time for just a lens cover.... Don't let this discourage you, Just wanted to let you know you're jumping into the deep end of the pool,...the end with the rocks.......Fredo
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Burton
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Joined: 20 May 2012
Posts: 7
Location: VA

PostPosted: Wed May 23, 2012 3:57 pm    Post subject: Doesn't discourage me Reply with quote

I have done many things people said they would never do because of the trouble it would take to learn the process and the time required to do it. It is kind of a bad habit of mine.

As for the lexan, yes it is probably the hardest to form but steps can be taken to make it more likely a success ... a simple search on the book of knowledge shows this. Like using 400 grit sand paper on the mold, covering the mold with felt, preheating mold, etc etc


The problem I am running into in my mind right now is do I want to use an epoxy clay to create the female mold or some other product ... And if I use it what would be the release agent?

I know J-B WELD, an epoxy putty not really a clay, doesn't like to adhere to oily surfaces, or waxed ones for example. Getting it to stay in one place while it cures would be a test of patience however. And it could be pricey to cover a small headlight with 3/8" of material (might need less idk).

Also do I go with the conventional two part mold or simply drill holes in the female form or both ^_^

Either way this is going to be fun ... as most mods to my bike have been. The clear cover is a must as the stock cover would touch the lens of the projector I already purchased. So it will be made ... eventually, out of lexan (i hope) or some other strong material.

I have worked with acrylic a lot in the past, even going so far as to make leg guards for my bike to ride in winter. When I use to do sculpture I would drive nails through the sides of 1/4" acrylic without fracturing it or bubbling it ... all with a paint stripper too hehehe ...
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jdougn
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Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area

PostPosted: Wed May 30, 2012 7:10 am    Post subject: Reply with quote

Hey Burton, welcome to the forum. Looks like you're jumping right in on an advanced project. I'll throw a couple thoughts out.

First thing, how bout some pictures to help us see what you're working on? Makes it a lot more fun for us!

You'll need a regular vacuum pump to pull 1/8" plastic. A shop vac will probably not provide enough vacuum, especially if there's much detail or depth.

You can do a lot of mold making with Bondo and fiberglass resin. In my personal experience, fiberglass resin will get soft when it gets hot enough and can deform. Bondo seems to hold up just fine.

Both Smooth-on and BCC Products are good sources for mold making materials. Smooth-on has a lot of mold making DIY videos and tutorials. They both have epoxies and urethanes designed to work with the high temps and pressures associated with vac forming.

I use BC8009 High Temp Urethane for molds. I sculpt the original shape from MDF (sort of like plywood but with no grain), make one good pull, then use the good pull as a mold to cast the BC8009. I like the BC8009 because it can be worked with woodworking tools and sanders for fine tuning mold details. BCC makes a bondo just for the BC8009 but regular Bondo also works with BC8009 and does well for alterations or changes to the shape. I've got molds that have been through over a hundred cycles with no signs of breakdown in the mold.

One of the moderators, Spektr, has a lot of experience with vac forming polycarbonite transparencies. He is also willing to offer a lot of advice if you're willing to listen.

Well, this is just a start. You've got a long ways to go yet but are headed in the right direction.
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Burton
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Joined: 20 May 2012
Posts: 7
Location: VA

PostPosted: Sat Jun 09, 2012 3:28 pm    Post subject: Reply with quote

I will hit some pictures up shortly. I took them but I have to run out to the store to get brake cleaner for my bike so I can finish rebuilding the front brakes. (been waiting for the plaster to dry out and it took two weeks >_<)

I just tried a test pull on one of the plaster casts. Didn't go well. I think my vacuum source isn't pulling fast enough and the temperature of the acrylic wasn't high enough (test was with acrylic not lexan)

I had the oven set to 300 for a while ... it barely sagged. Pulled it out and it didn't seem plastic at all just stiff but tried a pull anyway with no results.

Put it back in at 350 till it sagged some more and tried again, no results.

When I get back from shopping I will try at 350 for a longer period of of time to ensure it heats equally then do another pull to rule out the vacuum source.
(which is a 10 gal carry tank with 25in pull stored in it) I used a air venturi to create the vacuum in the tank, it can get up to 30in by itself but can't sustain too long.
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Burton
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Joined: 20 May 2012
Posts: 7
Location: VA

PostPosted: Sat Jun 09, 2012 4:31 pm    Post subject: Project pictures Reply with quote

I dont have images of my failed attempt or my vacuum rig but if there is interest I can take some.

http://www.flickr.com/photos/71805301@N05/sets/72157630090212786/
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Burton
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Joined: 20 May 2012
Posts: 7
Location: VA

PostPosted: Sun Jun 10, 2012 4:28 am    Post subject: Second pull (more pictures) Reply with quote

http://www.flickr.com/photos/71805301@N05/sets/72157630090212786/ three new photos added to photo stream. If you dont like the quality speak up I have a professional camera but have been using cellphone.

My second pull wasn't as bad as the first but still nothing I can use. The vacuum didn't seem to ... well... get a proper vacuum.

It kept trying to suck air in despite having a seal. However it did form better, and I imagine spending an hour in the oven at 350 helped to some extent.

I pulled from oven, placed on female mold, turned on tank source (at 25in) and it kept sucking till it was at 0in >_<
Since then I have sealed the plaster on all sides except the female mold to ensure the vacuum isn't sucking air through the side wall. (I remember when I made the molds I blasted pressurized air through the tube and it ejected water from the sides of the mold nearest the end of the tube)

So today I will again attempt to get a proper pull, and if the vacuum action is better then I know it was the plaster interfering. If all remains the same then I will try to use the air ventri inline with the mold and rely on the compressor to continuously pull around 25in Hg ... might drop to 20in Hg over time but it will be better than the 11gal carry tank I think.
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jdougn
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Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area

PostPosted: Mon Jun 11, 2012 6:03 am    Post subject: Re: Second pull (more pictures) Reply with quote

Burton wrote:
...Since then I have sealed the plaster on all sides except the female mold to ensure the vacuum isn't sucking air through the side wall. (I remember when I made the molds I blasted pressurized air through the tube and it ejected water from the sides of the mold nearest the end of the tube)...

Not bad for the first attempt and you're figuring out what you need to do to get the set up to work. Sealing the plaster and running the vacuum at the same time is the next step for sure. Looking forward to seeing how this works out for you!
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Burton
Newbie


Joined: 20 May 2012
Posts: 7
Location: VA

PostPosted: Tue Jun 12, 2012 7:52 pm    Post subject: Reply with quote

what is a good heat resistant sealant for the plaster?

The sealant I used dripped a little into the mold and when the acrylic made contact with it it helped transfer some of the filler bondo + sealant to the acrylic >_<

The 'alpha' lens was from the bad pull attempt I had but it is currently on the bike and functioning. Can't really tell if the sealant helped or not though and I still think the acrylic simply isn't getting fluid enough.

The last pull was done with just the air ventri as the vacuum source, plus using my hand in a glove to push the acrylic down into the mold. It seemed to be pretty stiff when doing so as well ...

I guess I should have mentioned I am using a gas oven as I am sure it will be different than an electric one. Was thinking of putting some type of fan in there to mix the air better but can't think of one that would work.

Ok enough ranting. Probably wont attempt another pull till this weekend anyway. And that assumes my new brakes dont come in for the bike as it will take priority.
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jdougn
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Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area

PostPosted: Mon Jun 18, 2012 6:29 am    Post subject: Reply with quote

There are other guys on here that have way more experience with acrylics and clear plastics than I do, which is essentially zero. But I seem to remember that it cools really quickly and only allows a few seconds of work time.

For sealing around the edge of the platen you might try the D-shaped weather striping. Some foam weather striping allows air to move through it. The adhesive on the D-Shaped weather striping will probably only be good for a couple pulls at most but I've found it works really well.

A few coats of lacquer will work to seal the plaster but lacquer will also transfer to the plastic when hot. I've also heard that felt can be applied to the mold to keep the face of the plastic smoother but this is not something I've tried.
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