I probably should have asked specifically for 'how' instead of 'what'. Do I set the mold face down (same direction as in the photo) and tap on the back? I tried that but it didn't seem to do anything.
However, it will be hard for this board to verbally and/or visually explain each and every step of foundry practice. So, I strongly suggest you spend some quality time reading and looking at YouTube to get a sense of the process. Don't just rummage randomly through YouTube though as there is a preponderance of just plain BS there. Choose one or two "real" folks and watch a whole series of their videos. A few folks that come to mind are "OldFoundryMan, " "Ironsides," and, "Luckygen." I know there are many more and hopefully folks here will make more suggestions. But, ignore people melting down aluminum cans and making ingots by the railcar load. There are countless bozo's doing really stupid things and trying to look cool to their "steampunk" friends. Also looking at Third World casters can be quite enlightening. Their livelihood depends on making parts with rudimentary equipment. So, they often necessarily boil the process down to its essentials. And consult the US Navy Foundry Manual available online for free as a huge source of fundamental information. And use the American Foundry Society glossary of terms to look up words (oddly "rap" is not there) as well as various large foundries websites that also publish word definitions to help would-be customers understand the lingo. It is obviously important to understand the language and to use standard definitions so we can all communicate clearly. Denis
Nice drawing. You should add one more rapping direction---an important one---UP as an assist to extraction. The way I do that in most cases is to put a light pull on the spike while very lightly rapping uoward on the drawspike. That is aided by using some sort of drawspike with a flat washer-like head rather than a trumpet head. The spikes I use most of the time were made from GRK R4 general purpose screws to the heads of which I welded short cross bars, to tap on, and above that a washer oriented vertically, to grasp. Pics added. Denis
I'm wondering if some sort of, ahem, light weight vibrator might work for rapping with very small pieces like jewelry to keep the pattern displacement as small as possible.
Looks like I'll be spending a lot more time on Youtube... Andrew Berry has a great channel for making jewelry, but not much about casting specifically. @Shoe/Skelter: That list of 'real folks' will help a lot. It's hard to know good info from BS when you're just getting started. @SRHack: The 'lightweight vibrator' didn't work well for me, but I might have just been too careful with it. I saw a guy use his scroll saw as a vibration table thought. That's on the list of things to try.
Raven, my guess is using a table and vibrating the flask might be counter productive and settle the sand more firmly into the pattern recesses.But you never know for sure unless you try something. All else is theory. Personally I was thinking of vibrating the pattern, and for that, imagined fairly high frequency buzz, but little displacement and against a spike.
My unasked for comment. In general: Let’s see. People have been doing foundry work for about 2000 years that we know do and probably a lot longer. While it is often tempting when you are starting out to imagine innovations in the process, I would recommend first spending time learning tried and proven methods. Then, if those methods are somehow deficient, based on experience, make improvements. While it is true, a person new to the craft could look with fresh eyes and make wonderful discoveries, that has not been what happens most of the time. The reality is that much time and effort is usually spent before discovering a well-established solution. Now for the specifics: Rapping with sharp taps whether of very small magnitude in the case of delicate parts or using a heavy rapping fork for larger pieces has a very particular benefit. The sudden sharp impact moves the pattern a small distance but the sand itself tends, because of inertia, tends to stay put. So, especially with drawing a pattern, the sand which tends to stick to everything, the pattern included, shears off the slick talked or graphite surface of the pattern. It is analogous to some random piece of wood accidentally glued to my table saw table. Vibration, even strong vibration is unlikely to dislodge it. But, if I place a screwdriver against the piece and use a small hammer to give it a sharp smack, it will shear of and come clean. Quick movement and sand inertia is also why side-to-side rapping compresses sand right at the boundary of the sand and pattern and creates a tiny space to allow the pattern to come free. So, my suggestion, if getting to successful casting practices as soon as possible is the goal, is to avoid rabbit holes, use what is known to work. Innovate if needed, but only when proven methods fail. And have fun. Denis
Vibration is hardly an innovation, while I don't think 3D printing, or Petrobond have been around for 2000 years either, so apparently new methods (like say in the last hundred) are okay here. Shearing a glued block off of a tablesaw with a sharp blow would be roughly equivalent to shearing off a greensand core with the same. I'm not sure how that logic applies. But as I said all is theory without actual experiences of the specific and suggestions are merely such, not truths.
The youtuber in question was using his scroll saw to vibrate bubbles out of a liquid or something, not trying to release a pattern from sand, so I'm not saying it would work. Your comment was certainly asked for; sorting out fact from fiction and learning what works is why I'm here. Please feel free to offer any advice you may have. Innovation is all well and good, and bouncing ideas around can lead to surprising places, but there's a reason the fundamentals stick around. It's much the same in the tattoo world. Seems like every new generation thinks they can break all the rules and somehow make bad practices work, then they're surprised when their super-detailed outline piece turns into a solid blob within a year.
Thanks for the video Denis. Sometime all a person needs is a little visual/video. It made me want to go make some draw spikes... @Raven_Ta2 , looking forward to see how it goes for you. Thanks for letting us run around a bit in your thread.
It looks like a 14g body jewelry bar will work as a makeshift drawspike. Might have to add matching threads to future patterns if my printer will handle that kind of resolution.
if you got your heart set on vibration here is the proper tools https://www.freemansupply.com/products/foundry-tools-supplies/other-foundry-supplies/vibrators I have found them to be more trouble then valuable in petrobond V/r HT1
