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Guest uncy_chris

Blue Foam Models

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Guest uncy_chris

Any suggestions on how to avoid jagged edges on cuts? I was thinking using a hot knife, but might it be a bit crude.

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Guest tom

Hi - In my experience I have used the following:

 

- hotwire - "like a scroll saw"

- extreamly sharp knife - (I wouldn't suggest a hot knife as it will not give a consistant cut and will stick as the knife cools)

- fine tooth saw and then sand with finer grades of sand paper as you go down

 

For shaping you cant beat a rasp for moving large amounts and finish with sand paper - dont apply to much pressure as then you will take out 'chunks' of the foam

 

Wear a mask!!

 

If you have access to a router bed 2D or 3D you cant beat it !!

 

cheers -

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Guest ditman

bread knife and sand paper works for me :D

 

if you use a sawing motion you get a clean cut.

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Guest newkillerstar

be careful on a band saw as the molten chunks will cool and sieze up the machine.

 

I always rough cut my shapes with a key-hole saw, or normal handsaw, form with a rasp or shure-form tool, finish with medium grade sand paper. Hot wire is great if you have access to one, but we were too po'.

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Guest kaiza

i find that our hotwire cutter is a little too hot and has a tendency to melt too much, and cause excess to burn - which then gets stuck on the wire and causes uneven cutting

 

because it also slightly melts the cut surface it sands differently to raw foam which can cause problems transitioning faces.

 

my process is bandsaw, rasp and then lots of sanding. a nice sharp (thick) snap-off blade knife with the blade all the way out gives a nice cut if you can cut all in one movement (down and sideways at the same time)

 

oh and araldite (epoxy) is the @#$@#$ for gluing this stuff, assuming you dont need to sand it afterwards.

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Guest Dan Argyle

Make a simple hot-wire cutter by wrapping a piece of wire around the end of a soldering iron. This allows you to bend the wire into any shape you like. Make sure the wire is looped. A sharp Stanley knife will allow you to cut off some of the smaller bits. Don't try to cut in one stroke, use a sawing motion, very slowly.

 

When using sand paper, make sure you only sand in one direction, preferably towards your body. If not, you're likely to scuff the foam. Car body filler does a very good job of filling in any holes, and giving a smooth surface (test the filler on a piece of foam before use, as some fillers can melt blue foam. This is of course assuming that you want to give the foam a finish. Polyfiller is an alternative, although it can become crumbly if not mixed correctly.

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Guest John Fitzsimmons

I use a hand coping saw with the set ground off the blade, or my bosch jig saw with set ground off blade

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Guest DevrajJoshi

Hot wire cutters can be a little hot but it is possible to make your own... i did for cause we had an entire module based on blue foam models. Get a piece of pipe and shape it like a question mark "?". Use duct tape or whatever to attach two D size battery cells to the bottom bit. Drill a hole in the curved upper section of the ? shape and tie through some thin wire attaching the other end of the top of the two batteries. I then used a paper clip to short the bottom of the batteries to the base of the metal fram - closing the circuit and heating the wire. Gets hot enough to deal with foam but not hot enough to burn anything.

 

Even after that though... sanding is the key to a perfect finish - work it through the various grades of abrasive paper. Time consuming but worth it.

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Guest Foamcutter

It maybe possible to access a company with a CNC hot wire machine, they should cut blue foam with a smooth finish. If the project is fairly large it could be the way to go to save a lot of dust and aching arms. Using a handheld hot wire cutter can leave ripples or drag lines that would need to be sanded out.........as l said earlier it depends on the size of the project to work out the level of hand finishing that would be required.

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Guest aedesign

:D I found a hand held hot wire cutter that ran of two D cells and was the size of a coping saw at Michael's . Basically it was a cardboard tube ( handle / Battery storage) with a simple metal cap completing the circuit, a spring inside. a real basic switch and a bent metal armature like a coping saw, and of course a wire.

 

THat said, It ate through batteries, gave wobbly cuts ( more control I think if you have a fixed blade and move the part in this case) and the foam would gum up on the wire if you moved to fast and the surface as mentioned earlier is harder than the rest because of the heat.

 

I stick to knives rasps and sand paper now. :)

 

 

AEDESIGN

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Guest Gappie
Even after that though... sanding is the key to a perfect finish - work it through the various grades of abrasive paper. Time consuming but worth it.

 

Have to agree on that one. You can use al kinds of rough methods to shape a piece of foam but in the end I always use sanding paper for the best finish. I use around 3 to 4 different types of sanding paper starting with a very course piece of paper ending up with a very fine type of sanding paper.

 

One piece of advice, be patient on this. Seen many people who take to large steps, jumping from rough methods to really fine sanding paper resulting in a lot of jagged edges and eventually ugly models because other than some people think, even the smallest dents in the foam can be seen in the final painted and/or varnished models

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Guest Foamcutter
even the smallest dents in the foam can be seen in the final painted and/or varnished models

 

You could create the rough shape in foam and coat with Foamcoat this give the foam some protection from dents and a surface that you can sand.

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Guest dave gibson

This may come across as sounding critical but I am just curious what the benifits of blue foam are. I have made numerous models of different types and avoided blue foam because it is hard if not impossible to paint, the rough cutting as mentioned in the initial question. Because I am still a young designer I am asking because if there are benefits that blue foam has over other materials, (polyurathane, etc.) I am curious to find out. Again this may sound antagonistic but it is not. Thanks :D

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Guest Gappie

In my opnion, foam is ideal for making very fast models to test a certain shape or form in a physical 3D model. A roguh model out of foam can be done in about an hour or so, and for me, is the fastest way of producing simple models which I can test. Ofcourse the finishing takes a lot more time and if you want to make a sweet looking model you can, ofcourse, use other techniques to reach the same result. Depends on what you have available in your workshop.

Regarding the painting of these models it depends on the paint your using, I always use a latex based paint which never gave me any problems with foam, while other types, like spray paint, can "melt" away the foam. It depends on the substance of the paint.

Hope this answers your question a little bit.

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