They look great!, you've really ironed out all the bugs in the process to arrive at a consistent result
Thanks Mark, much appreciated. I've been at it for a while and like everyone else, experiment and adopt the things that seem to produce good results. The one small aspect of this part I may change on the next go is to eliminate the third gate in the center. If you look closely at the castings you can see a slight flaw in the filter gland under that central gate. It’s a combination of the local mold underhang and probably more so due to flow impingement on the mold surface. Easy enough to clean up the casting but do I mess with success on the next one?......probably. I try to top gate my lost foam castings where I can and had envisioned some undesirable things happening if I didn’t include that third leg but it may just be my imagination. The low(er) density foam gating system and coating seem to be a good combo. I’d like to develop a better understanding of why the top half of the castings have the surface residue and the bottom half is very clean. I have some theories. It is easily removed and doesn't seem to affect the castings other than initial impressions. I don’t recall having seen the blue hue in the surface residue before but I think it may be the remnants coloring/dye in the pattern coating. I’ll work on that in future iterations. Best, Kelly
Kelly, Very nice job! Thanks for leading the way, I've learned a lot from you. I have a couple more part to cast for the FIRST robotics team CNC router before I start machining the castings. I'll post some pictures when I get a little farther.
By the way I saw the same discoloration thing on my Z axis slide casting that was 12" long. Also I got the same little bit of extra metal in the overhangs at multiple different levels. I have concluded that it is either an air bubble in the slurry coating or sand simply not filling up the undercut completely. I think I didn't vibrate long enough near the end when the bucket was full.
It happens on them all. It's just a matter of degree. My drywall mud coatings turn shades of brown and black. I think the black is burnt polystyrene. This casting actually had a bluish hue.....the commercial coating is blue/grey. Overhangs are tough. It takes the right frequency, amplitude, and directional vibe excitation. Tipping the flask during vibe can help. I have some ability to control that stuff on my molding rig......but not smart enough to guess the recipe on one shot. The location on my casting circled above combines three bad conditions. There is a slight overhang. The metal flow impinges in the location of the overhang making the more loosely packed area under the overhang more like to destabilize. It's at the top of the flask which means the flask is nearly full (in my case 300lbs of sand) so it's harder to excite that much mass with small vibrators. Using some fresh sand locally in those and intricate areas helps. My sand is two years old and I've never changed it. As long as your mold media is refractory and is dry, it will work in lost foam. Shape of grain can matter too (hey we're hobbyists, we take what we get), but dry is very important because slightly moist sand is much harder to excite and pack with vibe. Best, Kelly
Gotta love the styrene smell from the sand. Back in my 20s I built 3 polystyrene polymerization plants with the guy who developed polystyrene working for DOW. My shoes picked up the smell so bad I had to leave them outside!
I media blasted the castings, drilled the mounting holes, and dressed the cosmetic surfaces on the belt sander. I also checked the fit of the filter element to insure shrink achieved the needed gland perimeter and it looked good. The machined edge on the filter gland was still fairly sharp and made it more difficult to seat the filter. If the surface finish of the filter gland could be improved, along with radiusing the corners of the gland perimeter ribbing (to make seating and sealing the filter element easier) of the foam pattern, I think this could be cast as a net shape casting that only requires the mounting holes to be drilled and some light cosmetic belt sanding of the raised lid features. That will be the goal going forward. Best, Kelly
Kelly, it looks great!! "but" you should switch to a stainless steel shot for blasting. the finer stainless has no trouble going through a sand blaster and the finish it leaves is bright and beautiful. Like it was freshly cast...
I hear ya. The blast cabinet at work is loaded with garnet........if you don't paint or otherwise seal them, because of all the surface area, media blasted castings stain terribly when they come in contact with oil......sometimes even handling them will do it But I wasn't going to change the media for one piece. I am planning to get a small cabinet for my home shop and will definitely have some shot on hand when I do. Much easier to change media in small cabinets with small hoppers. I've also been thinking about building a vibratory polisher. I really like the modeled finishes and the tumbling also de-burs and breaks the edges......just have to have the right media. Best, Kelly
The pin router patterns are fairly easy to make and once they’re done, variations on the original are even easier to make. Being a Ford guy, I decided I’d make a logo pair for myself so I just screwed a piece of mdf to the original, made an identical copy, then cut out the ribs freehand and added the oval in the center. Makes foam lid patterns like this Copies come much more easily after the templates are made and bugged out. Will sand the filter glands and attend to some other details on these copies I set up my hot wire cutter and sliced the foam blanks from 2” thick foam board stock. A couple of them weren’t very flat. There may have been some residual stress in the thicker board stock or maybe it was induced by the heat of the hot wire…..dunno. They get screwed and taped to the templates so not a problem machining them but just another reason for gluing them together in pairs to cast them. Best, Kelly
I had another go at the air filter today. Here’s the coated pattern ready to go. As mentioned earlier, I did eliminate the center gate immediately below the sprue. I did include a couple small bridging posts to help maintain flatness of the pattern while pacing the flask. Here’s an 8-minute video of the pour and demolding. The pour was 32 seconds of total duration. Wow, this was my best lost foam pour ever, especially on a part this size. The first 12 seconds or so was just filling the cup. After the typical lost foam pause, you can tell from my pouring speed the pattern started taking metal. No flame, no smoke, no burp…..nah-da. I poured a little cooler and the casting was much cleaner. Here’s the resulting raw casting A little communing with the carbide blade on my table saw to de-gate. A little wire brushing and belt sanding to clean them up Here’s a comparison of the gland finish. Better, but I think I can still improve it. Here’s the second set of castings along with the first set. Looks like I can put the rest of the patterns together and go to it. Best, Kelly
Nice parts. The Jag guys with triple su's would loves something like that. XKS unlimited could sell them easily for you. https://xks.com/ First thing we have to do is dump that ford logo.
Kelly is a good businessman. I’m pretty sure he knows where the moneys at! Reliable vehicles with reliable parts don’t break down very quickly. Aftermarket businessman make a huge living off, substandard parts which lose copy right after 10 years. If the mother company does does not own the mould or die, then it’s almost free game right from the start. But if a signature or name has been put in it, 10 years... The patent office will not allow for signature copyright for 99 years. But, Visual shape with minor changes are free game. For example, if you make a jeep aftermarket part, you can’t put any jeep logos on it/them. Jeep wrangler is one of the highest financially sought after aftermarket companies for reproduction parts. Jeep owners abuse their vehicles beyond any other vehicle on the market. The other situation is the jeep wrangler has a cult following as one of the most reliable off-road vehicle ever made that parts are easily accessible by thousands of after market vendors. Jeep wrangler drivers don’t mind experiencing the valley of death and or the wrangler trail and replacing thousands of dollars of parts to make their next to experience more enjoyable. They realize OEM are substandard. This is why die hard Jeep Wrangler Rubicon owners spend $40,000 on the vehicle and spend another $40,000 in aftermarket upgrades. There is stupid money out there. I had a neighbour that has a brand new Ford Shelby. Maybe a $70,000 car. He’s almost dropped another $50,000 into it with aftermarket parts. A trailer company made money on him because he needed to buy a trailer to pull it to the drag race track. Court system has made money on him a few times because his muffler is too loud, The court system has made a few dollars on him because he squawks his wheels well taken off from the red light, and a few more dollars for speeding. This is the rich giving back to the poor in my eyes. I’ve made a few dollars off him for custom parts ... Friday morning he passed away (46). My conscious is a little bit clear as he didn’t pass away with any of the parts I produced for him. But, he became crazy stupid with the need for speed. As I get older, I would rather reproduce wheelchair parts, then super chargers parts for stupid race cars.
Just to be clear, the logo parts are one offs just for me and my collection, not for sale. I will no doubt make a few of the non-logo filters for other enthusiasts interested in these parts and racing period but it's hobby level stuff fellas, not business. Best, Kelly
Happy Thanksgiving Everyone. I got in a morning casting session before the family festivities. I loaded the flask with two patterns and used my A20 to knock out two more castings. No pictures but here’s a video of the mold prep, pour, and result. Best, Kelly
