Rep Rap

Anyone see BBC One Show 27/03/13 where they demonstrated RepRap ?

My initial investigation of RepRap is that it is an open source example of hobbyist/school oriented 3D printers which are also produced in various small commercial forms. They have some craft /hobby educational uses but are not in the same league as industrial machines.

The aim of RR is to be easily made by non engineers without machining facilities or knowledge - ie it uses techniques more like model railway, model boats etc. I suggest a model engineer with CNC could well just make the printer head part to try it out on their CNC mill, then design and make a more 'engineered' printer head. If making a whole makerbot a model engineer would have the understanding to perhaps make a more substantial table in the style of a wood router rather than going the more expensive full cnc mill route.

It is interesting that Stub Mandrel has raised the possibility of using a lost foam casting process. I presume he was thinking of carving the pattern in polystyrene in some way and then using this pattern for casting.

I have recently been investigating an alternative way of making a pattern in polystyrene that could subsequently be cast. This process is only in the development stage at the moment but it works like this:

A slab of fine grained polystyrene foam (Styrofoam) is taken and the required text is stencilled onto it using a black felt tip marker. The Styrofoam is pale blue in colour and the lettering black. If the styrofoam is exposed to an infrared heat source such as a halogen lamp then the infra red radiation is absorbed strongly by the black area but not by the blue area. The heat in the black areas causes the foam under it to collapse and you end up with the text showing as grooves in the polystyrene.

In a subsequent step the polystyrene could be buried in sand and a casting made from it.

I already have tested the process with fairly large letters circa 40 mm high and it works very well and I am exploring how small I can make the letters and achieve a good result.

Of course the process is not limited to text but it could also be used for simple shapes and patterns as well.

All this is very developmental at the moment but if when I have explored it some more it looks good and I can produce a good casting then, if there is interest, I could perhaps submit an article to MEW.

Mike

Hi Mike,

An interesting idea. You remind me that as boys my brother and I use to make buildings out of polystyrene and hen inflict 'war damage' on them with Airfix glue. I'm sure that's how they did the corrosive blood effects in Alien!

Without prejudicing an article, could you post a picture? I don't have a suitable lamp so I can't try this for myself.

Neil

It has been done with LinuxCNC, anyway. Probably Mach3, but I don't know.

Plunk on a Wades Geared Extruder, rig up a temperature control for melting the plastic, and off you go.

At least in theory, anyway! Every month or two I think of going down this route, then I sit down with a cold drink and settle my thoughts down. *Why* would I want a 3D printer at home?? Got one at work which I could use on a very limited basis, or there's always Shapeways (*).

Shapeways will do metals, which work much better with model locomotives than (roughly extruded) plastic does. At least one of our club members gets bits of metal from Shapeways.

(*note - Alan Hudson, CTO Shapeways and I (And others) worked on the X3D ISO-standardized protocols, and Alan uses this protocol internally for Shapeways purposes. I have no financial commitment, but have been a colleague Alan since the original Shapeways ideas came along, and quite possibly might have some computer code running @shapeways, as we exchanged open-source code many times "in the old days" (I'm really glad to see Alan and his ideas take off and do well - he's a really nice person and deserves success)

Another JohnS

Hi Neil (AKA StubMandrel), I have down loaded some photos to an album entitled "Thermal embossing"

The first photo shows a piece of polystyrene about100 mm wide on which I have written some text. The next two photos show the same piece after shining a 50 watt halogen lamp at it for a few seconds. The polystyrene foam has collapsed under the black ink due to greated absorbsion of heat in the black ink.

I only started playing with this technique this week so at the moment it is very developmental.

I have yeat to try the technique with the lettering inverted i.e. black background with the letters unblackened.

I think the technique has potential for nameplates, plaques etc.

Mike