Here’s my entry fellas. Yup, lost foam…what else would you expect it be? LoL. I cruised through Michael’s and Hobby Lobby back when David announced the contest and found nothing interesting and frankly hardly anything in Styrofoam at all…just a couple big tombstones. So the heck with that, I decided to make my own. Conscripted into service were my newly made hot wire cutter, a razor knife, some abrasive paper, and a little hot melt glue. To make the web, I cut a sheet of foam to 3/16” thickness that would fit into my sand rig, tapped the limits of my artistic ability, and used a Sharpie (felt tipped marker) to sketch my best rendition of a cobweb ….that at least stood a chance of being successfully cast. After 15 minutes of razor knife work I had two webs. Why two? ……Because it’s foam fellas. For the spider bodies, Sharpie and hotwire the profile, a little rough carving with the razor and then some shaping with abrasive cloth, coarse then fine. I used a fine tip Sharpie to draw the markings on the backs of the spider bodies. The solvent in a Sharpie mildly attacks the foam so a couple re-tracings is sufficient to penetrate the foam pattern enough for the symbol to cast through. This came off about as quickly as making the webs. Before I moved on to attaching the legs, I decided it would be helpful to sprue and mount the spider body. The web itself is going to be like a metal fluidity test in progress. The spindly spider legs will also be at risk of pouring short. So I decided to gate at some of the more central web nodes and one straight up the center to the spider’s body in an attempt to minimize the run lengths of molten metal. For the runner feeding these gates, I just laid the web on top the foam plank left-over from cutting the web sheets, marked the node locations around the perimeter, and hotwired the gate profile that lined up with the target nodes. Then it was just a matter of sticking the small vertical gates to the nodes on the web with hotmelt and attaching the runner to the other end of the gates. I then shaped a pedestal gate/mini sprue and mounted the spider body on it. With the spider body mounted, I started on the legs. The legs took a little more time because there were 16 of them in all for the two patterns and because I was cutting fitting and gluing. I alternated between the hotwire and razor knife…..I couldn’t decide which method I liked best. A few dots of hot melt and the legs and mandibles were in place. Now for some detailing. I already mentioned the felt tip impression on the back of the spider bodies. For the eye’s I sure could have used some small foam beads….where’s an old bean bag when you need one? I had to settle for a few small pieces I gouged out with some small hole punches. The second pattern was made the same way except I added a little snack. At this point the patterns were really starting to take shape. Here they are mudded up. I was going to try a dip but was running out of time and by the time I doinked around with that they’d be done so I brushed the mud. All I need to do now is add a foil sprue and they’ll be ready to go. Don’t think I’ll have time to cast until late this weekend. Like Mark says…..I think they’re going to be a three candle pour. Best, Kelly
It's casting day and the results are in. Here is the first one sprued up and going into the bucket. I just sprinkled sand from a quart cup until it covered, vibed for a short while, added sand and then vibed for a few more minutes.……the moment of truth…gravity fed pour at 1750F ……..Should have lit three candles – poured short, even with the good omen of the spectator. Well….let’s try it again…..this time invoking Plan B with a vacuum assisted pour as pictured below and further discussed here in my sand rig post: http://forums.thehomefoundry.org/index.php?threads/lost-foam-process-and-my-rig.145/ -And again at 1750F. …..time to blow out the candles….that pretty much did it. Other than removing the main sprue, I debated whether to de-gate them because they sit nicely on the runner. I thought they’d present better if I removed the runner and left some of the gates to serve as legs so they sit like a trivet but removed the small sprue to the spider body so it was only perched on the web by its legs. Here’s both pour de-gated. My intent for the entry was to fuse the physical insect features with some of the more unique lost foam process capabilities, compromising for castability where necessary. The result, is more of a caricature than attempt at realism, yet yielding a casting that would be difficult to produce without expandable pattern approaches, especially for the total invested time. I think I have between 5-6 total hours invested into both of them. They do have sort of a droid look to them but that’s what happens when a machine designer attempts artwork. I didn’t quite get the entire snack bug to cast through. Looks like he already chewed off the wings and secreted a little digestive juice on the bug…..but I’m declaring casting success! If I ever made them again, I’d be tempted to try to make a version with the spider mounted off to the side so they could be used as a seasonal cooking trivet…..these are more likely lawn and garden ornaments. Here it is after media blast and tumble. Grayer and less metallic but uniform color. B’Dee-B’Dee-B’DeeBa…..Duh-Dhat’s all folks....... Best, Kelly
Things are bad enough here without making castings of them!, found this fella in a backyard on Thursday when I picked up some branches, the body is about two inches long and the outstretched legs on the vine it's hanging off are six inches tip to tip. I have been stuck on a large bridge on the highway with one running around my neck and nowhere to pull over to get rid of it. Other times I'm frantically winding up the windows as they run over the outside of the windscreen before diving into the air vents at the base of the windscreen as you try to shut the vents. I know exactly how Ellen Ripley in "Aliens" felt
Mark, I would have driven off that bridge. Kelly... Oh crap, if those legs and skinny strands of silk actually fill, I might be in trouble here. I still hope they do though, just to see it done successfully. Good luck! Jeff
Thanks Jeff. Risk of a failed pour is definitely present.......that's part of what makes it fun. I'll have two cracks at it. In the land where everything can kill ya, I shouldn't have to ask but......venomous? Seems like most of the larger spiders are not but can deliver a good bite. Best, Kelly
Kelly, the Huntsman/Giant Crab Spider are technically harmless....unless you have a heart condition, or you're driving with one in the car with you. Can you have a decent sized pouring cup with enough extra height to have some hydraulic pressure to the aluminum?. I'd be getting the metal to glow a dull red or hotter for that pour. Tobho, that particular spider runs really fast, your primitive brain kicks in, I tried flicking that spider away when it grabbed the vine midair like a ninja and froze there. I was looking at some more pics of my encounters with them, it's always in October.
Yes I can and plan to do so. That is plan A. Combined with a very hot pour. I poured my vacuum impregnation insert (lost foam AL and own thread in this section) at 1800F and that's what I plan for first go. I would never have dreamed of pouring that hot but in LF, I really don't see any ill effects from it nor do I see shrink defects even where the are significant differences in casting cross section. If plan A fails, Plan B is to use vacuum assist. My sand rig can pull ~8"Hg and even with that low level of pressure differential across the molten metal in the cup, it dramatically increases the metal propagation speed. Have you seen my sand rig? It's simple; pretty much a metal 5-gal bucket with a vibrator, vacuum plenum, and vacuum motor. I can start another post if you are interested. In fact, I use a household 3-stage central vacuum motor which is powered by a universal brush motor and if I do need to invoke Plan B, I may even dial the speed/pressure back a bit because the most significant issue I've had thus far with vacuum assisted LF is the differential pressure destabilizing and partially ingesting sand in the sprue and gating system. With low velocity metal speeds, the runner and gate design is pretty much a non issue and I can just haphazard cut and stick blocks together. With vacuum assist, I need to make the gate and runner sections filleted and more streamlined and it also helps to coat them with mud or foil tape for a little additional support. I did not pay particularly close attention to this on the gating system for the pieces in this thread. They are just chunks of foam stuck together. Best, Kelly
You've given a fair bit of thought about how to make it work and yet it's pushing the method to the limit, I look forward to the results!. One method I'd like to eventually try is the vacuum sand casting method where the flask is under a vacuum and a thin plastic membrane like sandwich wrap was placed between the pattern and the sand. The sand has no binder yet the vacuum on the membrane keeps the sand packed.
Have a look here Mark: http://forums.thehomefoundry.org/index.php?threads/lost-foam-process-and-my-rig.145/ Best, Kelly
The difference a vacuum makes could not be more pronounced, although the non vacuum casting came close. There's a fair distance to travel to fill the fly, I'd love to see computer flow simulation of that casting that metal flow software can do .
Added one last photo to post #2....that's a wrap. Good luck Jeff and thanks for your entry and great post. Hopefully we'll have a few last minute entries. Best, Kelly
