Dealing with vaccu-formed kits

[Digger1]

Howdy.

I am seriously considering getting a couple vaccu-form kits. I've never, ever done these kits so I'm really afraid to tackle one. I've been told that one false step and you're done.

I'd like hints/tips on the following:

Cutting/freeing the pieces from the sheet

reinforcing the pieces

joining the parts together

eliminating seams

special instructions for painting/detailing

[Shinnentai]

I've only built two vac kits, IIRC, but I'll give it a shot...

Cutting/freeing the pieces from the sheet

First give it a quick shot of primer (more on that in a moment). Trim around the parts with shears, leaving about a 1-1/2cm margin. Using a scriber or the back of an exacto blade, carefully "trace" the edge where the parts meet the sheet repeatedly untill you've cut through. Hold the tool at about a 45. angle to the edge of the part so that you don't end up scraping off the primer on the part's leading edge (don't worry about the beveled cut this produces). Now go around the edge with sanding sticks or a flexi-file, and sand the little bit of plastic (the thickness of the sheet left after the scribing/cutting) down 'till it's flush with the primed edge.

reinforcing the pieces

Several methods are available. You can laminate strips or ribs of styrene stock to the inside surface, or fill the interior cavity with expanding foam in the subassembly stage. I found both is nice: foam is a better support once it's all together, but laminated styrene bands/ribs help support things & keep things from flexing during basic construction. If you do lamination, use CA rather than solvent-based glue, as the plastic can get fairly thin in some areas, and will be easaly prone to melting or distorting if exposed to solvents. You can also make support ribs by pressing snakes or sheets of epoxy putty onto the inside surfaces. Yet another option is to mix up a quantity of five-minute epoxy, and slosh it around the inside surface of the part to form a hard second layer.

The two-part liquid based foams sold in RC and railroad hobby places are much much better than the spay can foam from Home Depot because they're easier to control (the spray can stuff is much harder to dose evenly within the cavity, and can easaly overexpand on you and inflate/burst the parts).

joining the parts together

Glue tabs of styrene onto the inside edges of the seam, positioning them to overlap the seam line on the inside so that they act as locators (think like the "teeth" on the big Echo Base doors in ESB, or on the door to Jabba's palace), retaining the parts in position, and reinforcing the bond mechanically. Use Ca for this too. Once that's done and checked, dry assemble the parts using bits of masking tape to hold the edges together at key intervals, and wet the seam with liquid CA or Testors/MEK (solvent is usually fine here, just don't use Tenax or Plastruct or any of the other "hot" kinds).

If it's a kit that can be built in subasseblies, build the subasseblies as stated above. Fill the subassemblies with foam, and putty/fill the seams before proceeding to combine the subassemblies. Combining the subassemblies is easy- much akin to gluing a resin kit because the sections are now solid. Be carefull with the solvents though still.

eliminating seams

Putty and sand, just like with an injection kit. Only big caveats are (1) handle with extra care: until you fill it with foam, it's still fragile compared to regular styrene kits, and (2) use a light touch if using solvent based putties like squadron or bondo, for the same reasons as with glues.

special instructions for painting/detailing

Once the subassemblies (or kit in total) are finished, you can paint/detail/decal just like a normal injection molded model. Just stay away from Laquer primer or basecoats (solvent thing again).

Hope that helps. Like I said, I've only done maybe two vac kits, so there may easaly be stuff I don't know about m'self yet.

[TER-OR]

http://www.modelingmadness.com/reviews/ ... slepv1.htm

That's my first attempt at vacuformed kits. I think I did a decent job describing my trials, I hope you'll glean decent information.

Remember, epoxy putty is your friend.

[Bar]

I've been working on a vacu-formed version of the mark1 jedi starfighter(just for me, before darth lucas sics his lawyers on my ass ).
It's based on the hasbro toy, but will have a smaller gap between the halves representing a (slightly) more accurate version than the toy itself.
The good thing will be that i can do very accurate landing gear as the whole ship will be hollow(for the most part).
I deal with a local vac-forming company who do great(and cheap) work for me as long as i do all the preparation(mounting the pieces and sealing the edges).
It really is unbelievable the detail that can be put in a vac-form model.
When i made the proto-type mounting to check for problems, the words: "copyright hasbro, made in china" were visible on the lower hull!
I use this local company to make pieces for my models all the time(i think they feel sorry for me: "poor guy. He's still making models. At his age ").
In my view, there is nothing difficult about tackling this medium(although i always get the company to run off at least ten copies of stuff i give them just so i have room for error).
It's like building an injection kit with thinner plastic, and no locating pegs.
No real challenge to the experienced modeller. And i'm sure anyone here will have no problems that someone here can't answer for them.

Bar.

[ralphee]

i too have been a lil nervous bout the vacform idea, but i just got the top hull form for my med frigate hull back and now i cant wait to get the lower hull plug complete and sent off as im dying to get my hands on, its only the basic form all detailing will be done with kit bashing and styrene to get the guts on the outside effect right but im happy with the shape ive made seeing as theres such little ref on this model, will post up some pics in the coming weeks as i should have a fairly complete hull assembled, im gonna go for vacforming on the down section too seeing as i want it hollow to illuminate it

[Shinnentai]

w33bar: An odd question perhapse, but considering the cheap one-time expense of making your own machine, why outsource the making of vaccuform parts for your builds?

[Bar]

w33bar: An odd question perhapse, but considering the cheap one-time expense of making your own machine, why outsource the making of vaccuform parts for your builds?

I always thought it would be easier to simply get people with large/expensive professional machines to do a great job first time around.

I wanted to make my own one at first, and i went to the company i now deal with to get a few pointers on making my own one, but the technician i spoke to told me what it would cost for them to do it, and it seemed a lot less hassle.

I don't know about the cost of styrene where you are, but where i get it, it's about £3/$6 for a 24inchx12inch sheet with the price rising depending on thickness. I'd be worried about not getting it right and ruining the styrene.

But if you have knowledge of how to build one of these babies, i'd be interested to hear about it as that was my idea in the first place.

Bar.