Not sure what that means but your coated pattern looks very good. Yes, in most cases the sand will become hot enough to melt the plastic. The same goes if you attempt spread a tarp or plastic sheet on the ground and demold on top of it......a mess results. If you walk on the hot sand, it will melt the stitching in the soles of your shoes and you will be gluing them back on so they dont flop on your feet......ask me how I know that! The cup looks good but I cry foul! you owe us a post on how you made it. Yes, pours from great heights can challenge your manhood. Standing on a platform can help but is dangerous when handling molten metal and should be avoided. I think I like what I'm seeing but that's another foul for not having made a previous post about your vibration table!! Looks like a spring table with grinder, assuming with eccentic weights on each end instead of a grinding wheels. Which is efficient. How much power is the motor? Just be careful with the eccentric weights. If they come off, they're like strong projectiles. Weights welded on a disc are good. That's a small fold flaw. Was it at the very bottom of the pattern at 6:00 O'Clock? It can be a combination of hesitation and feed system design. That is usually an artifact from the intial molten metal contact with the sprue and/or small turbulence in the cup causes some oxidation that gets trapped in the initial molten metal stream. It's birth is usually signalled by a flash of flame and puff of black smoke. It shows at the very bottom of the part because it was the first metal into the mold and correspondingly to reach the bottom. If you ran the runner across the opening in the disc and past the bottom of the pattern, and attached to the bottom half of the pattern that flaw likely would have ended up in the lower part of the feed runner instead of the pattern. Sometimes I have attached a small "Bob" (small volume of foam) to the bottom of the runner just so it attracts that initial part of the poor. Best, Kelly
In my last post I made an error. I used Jointfinisher instead of jointfiller. It's what you guys know as drywall mud. Over here we have two stages of filling a dry wall joint....first you use filler which can applied in a thick layer and drys rather quick and (as you probably can guess) you finish with a thin layer of Finisher. I used the thinned filler during my first poors but it's the finisher which gives the best result. I dipped the part two times. The Adam's shaker deck.... It's from the same familiy as my Franken cup ... as cheap and rough as it can get. I used a found base frame to start off....the upper deck is laying on that frame. Between 4 spings and bolts which aren't loaded, its just to prevent the upper deck from faling off. The vibrator is just a ( harbour freight style ) cheap old grinding wheel with (on one side only) an imballanced weight.... It will eat itself at some point !! Stuff has fallen off before and rapidly fixed .... For my big poor the imbalance wasn't big enough so i just welded on extra weight. The electrics are hanging excitingly loose I know.....in the beginning all was nice and tidy ( honestly ) but it got shaken and fell apart....the "tyerip-system" is more forgiving. 120 Watt motor keeps usage economical Regards Koen
Yes, here in the US is the similar. In fact, the first coat is usually used with a fiber/paper tape and is "setting" type compound, meaning it will harden after mixture like plater of paris. Finishing compounds ar non-setting air drying formulas. Many o fthem contain additives that make them spread and dry well and those same things make it more permeable and better lost foam coating. I like it. I almost did the exact same thing on my molding rig. My rig is spring mounted too. The idea for spring tables like this was an idea I borrowed from makers of concrete figurenes and statuary. The vibration makes for a hard life on the machine. The motor and bearings internals will eventually fail from the abuse, but since the dutration of use is low, it may serve a long time in this purpose. Commercial lost foam molding machines have variable frequency drive motors like that in multiple axis. OK, you are forgiven.... Best, Kelly
The cup, As I can't source the proper material in Belgium to make a reusable pooring cup I've decided to go on using a sand one. Drye sand and sodiumsilicate 4% and..... me I'm using ....carbonic acid ...yep the thingy we put in sodadrinks and beer... Over here if you need MIG welding gass there are two options ...hiring a bottle ( 15€ a month for the bottle itself not the gass). ..or buy a bottle ( 250€ + the cost of testing it from time to time) all pretty expensive if you ask me ....certainly because i do not weld daily, nor professionally... The option I took was going for a bottle of carbonic acid which you can get at the local beverage store....you put down a deposit (70€) when you go an get it ...no limitation on the time you keep it .....refill costs about 35€ .... people over here use it when they buy a keg of lager beer ....mostly bars, restaurants etc... And yes I also weld with it (MIG) I made the innershape in styrofoam and laid a layer of plastic tape around it to prevent stickyness. Ones the sand is in I open the mouldaa tiny bit and "poor" in some gass ( its heavier then oxygen soo) I just use my MIG, taking the pressure off its wire feed so only gass comes out... Hope you like it, Koen .
I also did two castings today, First there were two rings ....coupled them together to save time. All went pretty much as planned. As there was still some time left in the day I decided to cast the second headlight housing too. To prevent that residue I ended up when casting the first headlight housing I glued on some extra styrofoam (on the bottom). The casting sand was still pretty hot from the first poor....I did mix it with a bit of cold sand ..... All went pretty uneventful but when I demoulded I noticed there was a pretty big faul .....happened during the shaking proces..... I must have been too hasty .... or does hot sand behaves different from cold? Both poors were at 770°C Thanks for watching! Koen
That flaw is from the sand being displaced (“a leaker”). That is caused by either insufficiently packed sand, insufficient height of sand mold above the pattern, or combination of both. Sometimes if your coating is thick, you can get a chisel under the edge, pry, and the whole flaw will separate from the casting. If the pattern was positioned in the mold leaning the opposite direction with that feature exposed upward, it less likely to occur. Did you try to extract and empty the sand cup for reuse or just let it freeze in place? Best, Kelly
Hello, I thought I could easily repair the fault(s) in my last casting but I've decided it just wasn't good enough. Soooo ... I'm gonna have another go ... I've flipped the piece and tried another gating set up which hopefully will make the finishing less of a hassle.... the thing is quite "all over the place" in the lathe... There will also be a bit more sand on top of it .... Hope this will do the trick. Thanks for watching. Koen
Hi guys, I started worrying and I ended up with a horse ... I made a box to mount the fillerneck in....thought it would look cool ... The fillerneck comes in under a double angle which made it quite interesting to construct... Its walls are 6mm thick. Now I'm not sure about the gating I made... so any imput is welcome! Being aware of the risk of faillure I made two extra fronts. If casting the whole box in one go goes entirely wrong I can maybe use them two spares as a front and attach a box ( made out of 1mm alu) to it. I started gating them, started worrying (again) and realised I ended up with a horse (shape) .... Last weekend I fired up the furnice to recast the headlight holder....but the burner started acting funny and to make matters worse my pyrometer joint the misbehaviour.... I took a gamble, continued my poor.....and lost... Luckily it's just a hobby Keep you posted, Koen
Yesterday I fiddled a bit with my old oil burner....it was behaving odd. I thought I fixed it but when I started it today it got back in its old habbits. Sooooo.... decided to activate the newer (spare) German burner..... man that was something completely different....got the air flow on maximum for a good rumble.... After a couple of minutes: liquid aluminium!! Time to test the new pyrometer. I completely made a new unit so I could test both at the same time. The old one was reading 550° C with liquid aluminium....definitely off!! Time to test the new one ...CRIKEY!..already 800°C ... The poor itself went smooth but in the result there is a big fault on the front .... I really don't have a clue how this could have happened...that part was on the top of the casting ....
Koen, did you even figure this out or try it again? I wonder if the coating failed right at the end of the pour. There also seems to be quite a bit of gating at the top of the part. I am not an expert for sure. My last sand mold where the aluminum metal was too hot >800C did not look very good around the sprue and runner either.
I think I got a bit carried away when building the gating....combined with excessive heat in my aluminium ....the odds were already against me even before I started my poor.
