As this is getting quickly off topic. In order to save myself a kicking. I have taken the liberty of moving the thread to a topic called meetings but still in the UK reprap area. Please post furthers to this discusion there. Cheers aka47by aka47 - United Kingdom RepRap User Group
Current proposal Somewhere in Sheffield, Pref Monday of Friday Evening, Date TBA. aka47by aka47 - United Kingdom RepRap User Group
Sheffield looks to be a current hot favorite. Current suggestions for days (not actual dates) is either a Friday or a Monday evening. I guess this makes it easier for folks who are coming from farther a field to juggle work commitments. If we have enough folk ( 6 - 8 ) I will approach Sheffield Uni (not sure who or how yet) and see if we can loan a meeting room or some such. Initial suggestionby aka47 - United Kingdom RepRap User Group
Ok Thats two of us, anymore takers (In principle at least) the when and where exactly we can sort out when we know roughly how many ???? cheers aka47by aka47 - United Kingdom RepRap User Group
Nathan Thanks for making me feel good. I thought I was a freak as I was the only person I knew who had developed an allergy to Polyester, It makes finding clothes problematic. Your a star.... cheers aka47by aka47 - Plastic Extruder Working Group
How far south are you Ian ??? Sheffield is sort of south for us up north but may not be south enough ?? (Sheffield is fairly convenient for Manchester, Leeds, Doncaster and York at least good rail links and motorway wise, I am not suggesting in any way that folk should drink and drive) aka47by aka47 - United Kingdom RepRap User Group
Question Is it worth having a meet at some place centrally up north ?? Just for a chin wag and a pint if nothing else ???? I am not picky about where/when.. Just a thought. There does look to be enough common ground to make it worth while. aka47by aka47 - United Kingdom RepRap User Group
In terms of purely signaling (The physical Layer in networking terms) the currently emerging standard is LVDS (Low Voltage Differential Signaling) and is built in as common to some of the leading programmable Logic Silicon (Xilinx Spartan3e). aka47by aka47 - Controllers
On the DC Servo Driver. Admittedly progress has slowed somewhat but has definitely not stopped. aka47by aka47 - Controllers
On the topic off topic, topic of vacum vessel lift. Beg to differ, not anti gravity at all, buoyant lift. A very different concept. (Much beloved by Scuba Divers and Airship Owners) If you can pre lift orbital payloads to 100KM up before launch your fuel requirement is significantly reduced and your payload to launch vehicle weight ratio becomes much more favorable. (A Gravity, Mass and decreasby aka47 - Let's design something! (I've got an idea ...)
I have time if someone can supply materials and molds. Although I am UK Based. Cheers aka47by aka47 - General
On heating Is heating actually really really necessary ?? Ambient temperature airflow (room temp approx 19 to 21 deg C) so long as the air flow is increased should be sufficient. You are only really needing to carry a way the vapor so more can evaporate and ensure that the paste doesn't get too cold (evaporative cooling). If heating the air flow 35 deg C should be more than enough, with as youby aka47 - Polymer Working Group
Acetone I know it is a lot of trouble and possibly not possible or expensive but acetone recovery as well as heating the air would be better than dumping it out to the environment. Possibly using a peltier module to cool outgoing air from a fume proof enclosure and dumping the heat into warming the incoming air to the enclosure. This should also accelerate solvent evaporation. Filling the poby aka47 - Polymer Working Group
Steve Viktor and I had a discussion re some of this a while back. Viktor suggested using deposition syringes, nozzles and needles (the ends are blunt rather than pointed for insertion through something) They are available in a huge range of sizes and bores very cheaply (ie per item cost as they usually supply in packs of 100 or so) from folk who supply mainly to the surface mount electronic indby aka47 - Plastic Extruder Working Group
I seem to recall reading somewhere on the internet that a way to make improvised napalm is to dissolve polystyrene foam into petroleum until you get a suitably sticky flammable gel/slop. So I guess for folk who have difficulty getting hold of acetone, petrol may do instead. I can't say I have ever really ever tried though, legitimate uses for napalm in Suburban UK are severely limited Let usby aka47 - Polymer Working Group
Probably if you convinced them you were going to upgrade and calibrate it for them for free.... Have you made burst firing controllers before ?? (They are dead easy when you know how) aka47by aka47 - Paste Extrusion Working Group
On kilns you might want to have a google for Top Hat Kiln and also kilns generally. They are not hard to temporarily stack together out of fire brick and swaddle in glass blanket. Heating is also easier than you think, considering the temperatures that Nichrome will work up to. Heater control is very easily achieved using an arduino board and some trivial circuitry particularly if you use burby aka47 - Paste Extrusion Working Group
Demented sir In a nutshell, messing with ideas for support pastes. Currently Magnesium Sulphate (Epsom Salts). The Ball mill is to ensure the paste constituents are fine enough to go through the relevant size of dispensing nozzle/needle. To Ball mill these ingredients though you have to make a ball mill (I don't have one already), ergo some of the posts here and the details of the making on theby aka47 - Polymer Working Group
I think the one that jumps out for me from Sebastiens links is:- Fabrication of Piezo Electric Actuators using Contour Crafting Given that we have been discussing ultrasonic welding as a possibly (possibly not) useful technique. aka47by aka47 - Paste Extrusion Working Group
The Robobuilder machine looks very much like some stuff I think Adrian mentioned. The guy that was working on them was wanting to be able to print buildings. Essentially using a v Large Moving Gantry Cartesian at each site and a concrete/slurry mix. You will notice that the extruder is extruding what looks like standard clay but has a troweling attachment on the side of the nozzle. This is whatby aka47 - Paste Extrusion Working Group
There's also the option of impregnating a porous ceramic object with uncured resin. then curing it. So a two step process fab a ceramic object (porous is good) fill it with resin, not as hard as it seems if you get pore size and viscosity suitably matched it should wick the resin up. Then cure (thermoset resin perhaps). The final result will be as good as a filled plastic. (Usually very desiraby aka47 - Paste Extrusion Working Group
OK Ball Mill complete and ready for some action. The construction details is anyone is interested can be found on my blog Complete with step by step pictures, good for a chortle if nothing else. I will do the actual milling for real (rather than testing it out) during the week when there are less people around to be disturbed by the noise. Hopefully we should have some fine ground Anhydroby aka47 - Polymer Working Group
Yup I agree Turning down heat quickly after fusing is good, thats why I was thinking along the ultrasonic welding lines. (Fraction of a second cycle times according to Wikipedia) Transducer + Anvil + Pressure. Hmmmm as the filament being fused onto the existing mass is v thin (0.1 mm + or should that be ++) then I was rather hoping that the existing mass )That which has already been depositedby aka47 - Mechanics
I was just wondering if there was any mileage in using Ultrasonic Welding for higher temperature plastics. Along the lines of reducing the filament diameter to the point where heating and extruding were no longer necessary, Basically dispensing filament and welding it in place ultrasonically. The whole feed mech could be a touch lighter. actual layer thickness could be governed more by the disby aka47 - Mechanics
I found some stuff on t'internet that sugests using pasta dough. They tried a range of food stuffs and pasta dough turned out the best. Cheap too. I think you will find the stuff (MIT did it) if you google Faberoni cheers aka47by aka47 - Paste Extrusion Working Group
Thanks for the tip I will bear that in mind. Anyone know much about ultrasonic welding of plastics ?? aka47by aka47 - Mechanics
Interesting. The wax mixes are as you suggest aimed at being tougher and or more flexible (Polyethylene) and particularly minimizing shrinkage during phase change. On burning the wax out, this is a bit like breaking eggs with a sledge hammer and is likely to leave residues (carbon) caked up in places you don't want it. Sure it is probably the only way with Polystyrene (including the black noxioby aka47 - General
OK Something i stumbled upon whilst rummaging around on t'internet. Fabaroni An RP machine that a group of folk at MIT have had a session trying to extrude things with that are essentialy foodbased. There best extrudable from all that they experimented with (and some must have been just for fun) tuned out to be Pasta Dough. The crazy thing is that now it has been mentioned you get one of tby aka47 - Polymer Working Group
What size are you thinking of casting ???? I have a good book or two on casting Pelton Runners for Micro Hydro Work and they are using Investment casting. The wax components are cast then joined with a soldering iron and rods of wax are joined on the same way to form the network of runners, gates and sprue's etc. All Very Clever. OK Some inexpensive wax mixes. Roman Wax 2 parts paraffin waxby aka47 - General
Ni chrome is indeed very readily and reasonably inexpensively available even with out cannibalizing toasters (although that is for free if the toaster is goosed). I don't think the issue is really the heating element/method. More how do we adapt a very successful design to be able to handle thermoplastics that have a higher melting point. For the purposes of discussion we can consider the plastby aka47 - Mechanics