Re: vacuum and molding?

Check your local library for all this info. Making RV molds and resin casting should be covered in the model railroading and jewelry sections. As for vacuum forming, I made one from plans I found in a (very) old Mechanics Illustrated, 20 years ago.

Don't ask, I've looked and looked for that book in the last 10-15 years and still haven't found it :-(

-- Chuck Ryan snipped-for-privacy@REMOVEearthlink.net Springfield OH

Lots of tips in the RMS FAQ

RMS FAQ:

Specific vacform info:

As to vacuum forming. I bought Walsh's early edition and it was a book on how to build your own machine. I did so, but was not that impressed with results. It did allow forming much larger sheets than my Mattel machine, but the depth of the draw was still VERY limited.

As to res>

i'd cheerfully pay for a repro. have you written the publisher?

That issue was in a box of books my grandmother left me upon her death. It was from the mid 60's IIRC

-- Chuck Ryan snipped-for-privacy@REMOVEearthlink.net Springfield OH

For casting, the namesake group on groups.yahoo.com is highly recommended. Plus, for a tutorial, visit

all the basic fundamentals for serious homemade casting are explained. Those shown are 1/72 vehicles. With bigger parts you need no vacuum chamber, just get dusty the mold cavity with some talcum powder before pouring the resin, in order to reduce air bubbles.

About vacuum forming, here is the theory:

depending on your needs, your tooling could span from the rough smash molding with a candle and a sheet of clear plastic to replace an old canopy, up to solutions like this: often, a box with a grilled or finely drilled side, a vacuum cleaner, an oven and a frame to hold the plastic sheet all together are the solution for most homemade vacuum forming needs. HTH

-- Luca Beato -

del plastimodellismo su

Depth of draw is limited by several factors:

1) How hot is the plastic sheet? The hotter the plastic, the easier it forms, and the deeper it can draw. Of course, there is a fine line between not enough, and too much heat. If the plastic is too hot, it will likely wrinkle in the nastiest places!

2) Power of the vacuum unit. Most home vacuum cleaners really don't have that much suction, so a shop vac, or something like a Kirby high-dollar sweeper works better.

3) Material thickness: Obviously, the thinner the material, the deeper it will draw. Also, some materials vac-form easier than others, particularly with clear plastic. I've found the best clear plastic to be PET-G, which is the stuff plastic soda bottles are made from, as it vacforms with minimal distortion (on the other end of the spectrum, clear PVC often stretches in a very clumpy fashion, not good at all for clear parts). The best thickness I found for model car windshields was .020", but for smaller parts, like aircraft canopies, I'd go with either .015" or even .010". Just keep in mind that vac-formed plastic is stretched down the sides of a mold, and when you stretch plastic, it gets thinner, often markedly so.

As for vac-form machines geared toward the hobby, I heartily recommend that anyone wanting to vac-form model parts keep an eye out for a used Ron Charles Vac-former. I believe that RC & Associates is out of this biz now, but their machines were highly advertized in FSM 10-15 years ago. While quite expensive new, they are extremely well-built, virtually industrial grade machines, with incredibly powerful suction units (actually, they were buying their suction units from Kirby, the vacuum-cleaner people, a centrifugal unit). $800-$1000 new, I've seen Ron Charles units go for not much more than $100 on eBay over the last couple of years. The only caveat with an RC machine is the heating elements, as they are the old-fashioned ceramic cone-shaped part, wrapped with nichrome wire coils, and if the machine has had any heavy use, the coils do burn out. They can be a bit hard to find, as most local electrical supply houses don't carry them, and often, my experience was that the counter-personnel had never even seen one! But, with some digging, these heating elements can be found, they are still made for certain applications. This makes the RC machine well worth searching for, it's a tremendous unit.

Art Anderson

where all the basic fundamentals for serious homemade casting are explained.

chamber, just get dusty the mold cavity with some talcum powder before pouring the resin, in order to reduce air bubbles.

and depending on your needs, your tooling could span from the rough smash molding with a candle and a sheet of clear plastic to replace an old canopy, up to solutions like this: Most often, a box with a grilled or finely drilled side, a vacuum cleaner, an oven and a frame to hold the plastic sheet all together are the solution for most homemade vacuum forming needs.

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How To Go Plastic Modelling by Chris Ellis has a couple of pages on it and could scan those in.

I've also remembered a vacuum forming machine that some guy made using modellers brass tubing connected to a spare plastic vacuum cleaner fitting with the other ends fed through a bench table with a sheet of ply perforated with holes.

I could knock up a diagram and post them to a bianry group if you like ?

Richard.

Thanks Jack. At present I use a Mattel 1965-dated machine for canopies and such small parts, while for bigger parts I made a plywood box too. The grate was cut from an aluminium made roof-soundprofing tile, whose holes are

1 mm wide and spaced 3 mm. I sealed it around with silicone caulk. The frame to hold the plastic sheets was cut from aluminium L-shaped bars. The complex is powered with a hot air gun, or an electric ring, and a 1500W vacuum cleaner. Do you have experience with female mold vacuforming and, in particular, on how to obtain crisp engraved panel lines on the finished parts?

-- Luca Beato -

del plastimodellismo su

parts, while for bigger parts I made a plywood box too.

holes are 1 mm wide and spaced 3 mm. I sealed it around with silicone caulk.

1500W vacuum cleaner.

how to obtain crisp engraved panel lines on the finished parts?

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My vacc machine is dirt simple, a section of plywood with hole in it, with a vacuum motor/fan unit attached. I use deep metal picture frames for the plenum with heavy gauge metal screen over them, and similar size picture frames to hold the plastic sheet. Turn on the vacuum, heat gun the plastic, then slap it over the form and presto! Swapping out the plenum boxes and frames are instant, and if I need to do a smaller, say half size item, I simply mask off the plenum and heat only half of the sheet, or mask the frame too and heat only half-size pieces.