{"id":3576,"date":"2026-10-14T14:43:54","date_gmt":"2026-10-14T06:43:54","guid":{"rendered":"http:\/\/www.lotfitrade.com\/blog\/?p=3576"},"modified":"2026-10-14T14:43:54","modified_gmt":"2026-10-14T06:43:54","slug":"how-to-calculate-the-yield-of-sand-casting-production-4ebe-a32db5","status":"publish","type":"post","link":"http:\/\/www.lotfitrade.com\/blog\/2026\/10\/14\/how-to-calculate-the-yield-of-sand-casting-production-4ebe-a32db5\/","title":{"rendered":"How to calculate the yield of sand casting production?"},"content":{"rendered":"

Hey everyone, Sand Castings<\/a><\/p>\n

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If you\u2019ve ever ordered sand castings from a supplier, you probably know that \u201cyield\u201d is one of those terms that gets thrown around a lot\u2014like, \u201cWe hit 82% yield on that last run\u201d or \u201cThis alloy has a lower yield than expected.\u201d But when I first started in the sand casting game, I had no clue what that actually meant, let alone how to calculate it. I thought it was just some random number we make up to sound like we know what we\u2019re doing (don\u2019t judge\u2014new guy nerves are real). Now, 7 years later as a sand castings supplier, I can tell you it\u2019s way more than that. It\u2019s the backbone of our production, the thing that keeps our quotes fair, and even the reason we can pass lower costs to our clients. Today, I\u2019m breaking down exactly how we calculate sand casting yield\u2014no fancy engineering degree required, just the stuff we actually use on the shop floor.<\/p>\n

First off, let\u2019s get the basics right. What is casting yield, anyway? At its core, it\u2019s the percentage of molten metal that actually turns into a good, useable casting (you know, the ones you ship to your line, not the ones we scrap). Wait, but hold on\u2014there\u2019s two types of yield people mix up all the time: numerical yield and process yield. Let\u2019s start with the one everyone means when they talk shop floor stuff, because that\u2019s the one that affects your order.<\/p>\n

Numerical yield (sometimes just called \u201ccasting yield\u201d) is the big one. That\u2019s (weight of good, finished casting \u00f7 total weight of molten metal we pour into the mold) \u00d7 100. Sounds simple, right? But if it were that easy, we wouldn\u2019t have scrap bins full of metal that went wrong. Let\u2019s use a real example from last month to make this concrete. We had a client order 50 aluminum pump housings, each 2.3 kg. So the total needed castings weight was 50 \u00d7 2.3 = 115 kg. But when we poured the mold, we had to account for more than just the part. There\u2019s the gating system\u2014those channels we run the molten metal through to fill the mold, the risers that feed extra metal to prevent shrinkage, the sprues that connect the ladle to the mold. That extra metal doesn\u2019t become part of the part, so it\u2019s scraped off and recycled. For that pump housing run, the gating and risers alone weighed 148 kg. Wait, so total molten metal we poured was 115 + 148 = 263 kg? Then our numerical yield would be (115 \u00f7 263) \u00d7 100 = ~43.7%. That seems low, but that\u2019s normal for sand casting, especially for complex parts. I\u2019ve seen yields as low as 35% for intricate stainless steel parts and as high as 60% for super simple, blocky castings.<\/p>\n

But wait\u2014there\u2019s another layer here, process yield. That\u2019s the percentage of poured metal that actually ends up as good castings, not just the math of the gating. Because even if you pour 263 kg, 115 kg should be good, but sometimes you get defects: a cold shut where the metal didn\u2019t fuse right, a shrinkage pore in the part, a sand inclusion, something that makes it scrap. So process yield is (weight of good castings \u00f7 total poured metal) \u00d7 100. For that pump housings run, we had 5 parts that had tiny surface defects we fixed with grinding, and 2 that were scrapped because of internal porosity. So good castings were 50 – 7 = 43 parts, 43 \u00d7 2.3 = 98.9 kg. So process yield was (98.9 \u00f7 263) \u00d7 100 = ~37.6%. That\u2019s why when a client asks for a quote, we don\u2019t just price for 115 kg of metal\u2014we price for enough to cover scrap, right? Because if we quoted only the part weight, we\u2019d lose money every time we had a defect.<\/p>\n

Now, let\u2019s talk about what actually impacts this yield, because it\u2019s not just random. As a supplier, we tweak every variable here to bump yield up (or at least keep it consistent) because that\u2019s good for both of us. First, part complexity. Simple, flat plates? Easy to fill, minimal gating needed, yield around 55-60%. The pump housing? Curved walls, internal passages, that needs a lot more gating to make sure metal gets everywhere, so yield is lower. Alloy type matters too. Aluminum is way more forgiving than, say, carbon steel, which has higher shrinkage rates, so we need bigger risers for steel, dropping yield a few points. Sand type? Green sand is cheaper but can cause more sand inclusions, leading to lower process yield. We use resin sand for most custom parts because it\u2019s more consistent, which keeps defects down.<\/p>\n

Then there\u2019s the gating design, which is like 50% of the battle. Back when I first started, our lead machinist, Joe, made fun of me for drawing a gating system with too narrow a sprue for a big casting. \u201cNarrow sprue = turbulence = more defects,\u201d he said, and he was right. Turbulent flow of molten metal sucks in air, creates porosity, ruins parts. So we design gating that\u2019s tapered\u2014wider at the bottom, slower flow\u2014to keep metal smooth. That cuts down on defects, so process yield goes up. We also use \u201cbottom gating\u201d for most parts, where metal enters the mold at the bottom instead of the top, so it fills evenly, no cold shuts. For that pump housing run, switching to bottom gating bumped process yield from 34% the last time we made them to 37.6% this time\u2014saved us like 15 kg of metal per batch, which adds up over 1000 parts.<\/p>\n

Scrap rate tracking is another big part of this. We log every single part that gets scrapped, and why: is it sand inclusions? Shrinkage? Wrong alloy? Last quarter, we noticed 12% of our stainless steel valve castings were scrapped for shrinkage, so we tweaked the riser size, and that dropped shrinkage scrap to 4%\u2014yield went up 5 points overnight. That\u2019s why we keep a running spreadsheet (not some fancy ERP that I still half don\u2019t get, just a Google Sheet we update every shift) of every run: part name, alloy, total poured weight, good parts weight, scrap reasons. If a new guy makes a gating mistake, we fix it, log it, so no one repeats it. That consistency is why our clients come back\u2014they know we\u2019re not guessing, we\u2019re optimizing.<\/p>\n

Wait, but a common question: do you recycle that gating and riser metal? Hell yeah, that\u2019s how we stay in business. We send all the sprue, runners, risers, and even scrap castings back to the furnace. But when you recycle, metal loses a tiny bit of purity each time, so we have to add fresh metal to each pour. That affects yield too, because some of that recycled metal isn\u2019t usable for the next run\u2019s high-quality parts. So we balance recycling to cut costs without messing up part quality, which in turn keeps process yield high.<\/p>\n

Now, how does this translate to what you, the client, care about? Let\u2019s say you need 100 bronze valve bodies for your irrigation system. First, we ask for your part drawing so we can get the exact part weight, figure out the complexity, estimate yield. For bronze valve bodies, we usually hit ~40% numerical yield and ~35% process yield. So to get 100 good parts (each 0.8 kg, so 80 kg total good), we\u2019d need to pour (80 kg \u00f7 0.35) = ~228.5 kg of molten metal. We quote you for that amount of metal, plus machining, finishing, etc. If we estimated wrong, say, actual process yield is 33% instead of 35%, we\u2019d have extra metal, but we don\u2019t charge you more. If it\u2019s higher, that\u2019s our win, not yours\u2014so we\u2019ve got skin in the game to calculate that estimate as accurately as possible.<\/p>\n

I\u2019ve seen other suppliers lowball quotes by underestimating yield, then hit you with extra charges because they poured more metal than they planned. That\u2019s a garbage move. We never do that. We\u2019ve been burned before\u2014once, we took a quick quote job for a client, guessed 42% process yield, but the part had a hidden internal passage we didn\u2019t catch, so actual yield was 31%. We had to pour 280 kg instead of our estimated 190 kg, ate the extra cost, and the client still got a fair price. That taught us to never cut corners on calculating yield, because it builds trust.<\/p>\n

Another thing: don\u2019t confuse \u201cyield\u201d with \u201cscrap rate.\u201d A lot of new clients mix these up. Scrap rate is (total scrapped weight \u00f7 total poured weight) \u00d7 100. If process yield is 35%, scrap rate is 65%. That makes sense, right? Because most of the poured metal is either gating\/risers or scrapped parts. Numerical yield is (good parts \u00f7 (good parts + gating\/risers)) \u00d7 100, so that\u2019s 35% in our example, meaning 65% is gating\/risers. That\u2019s why sand casting isn\u2019t as \u201cefficient\u201d as, say, die casting\u2014but die casting has higher upfront tooling costs, so for low volumes, sand casting is still the way to go, even with lower yield.<\/p>\n

Wait, let\u2019s test this with another example to make sure I\u2019m not messing up the math. Last week, we had a run of 200 gray iron engine brackets, each 1.1 kg. Total good parts needed: 200 \u00d7 1.1 = 220 kg. Numerical yield for these simple brackets was 52%, so total poured metal: 220 \u00f7 0.52 \u2248 423 kg. Process yield was 48%, so good parts were 423 \u00d7 0.48 \u2248 203 kg, so we scrapped 7 parts (200 target, 203 good\u2014we always overproduce a little to account for scrap, so you get exactly what you ordered). That\u2019s why when you place an order, we usually send a few extra parts too\u2014just in case, no extra charge.<\/p>\n

Common myths I want to bust: first, yield is just about metal. No, it\u2019s 100% about process. We\u2019ve had the exact same part, same alloy, same metal, just different shift workers, and yield varies by 3 points. Because the night shift guys are usually more careful with furnace temperature, mold prep, pouring speed. Temperature is huge\u2014if metal is too cold, it doesn\u2019t fill the mold, causes defects; too hot, it shrinks more, needs bigger risers, lowers yield. We check metal temp with a pyrometer every pour, no exceptions.<\/p>\n

Another myth: higher yield means better casting. Not always. If we bump yield by cutting corners on risers, we get more good parts in the short term, but those parts have hidden shrinkage that fails in the client\u2019s machine. That\u2019s a way bigger problem than a 2% lower yield. We prioritize part quality over yield every single time. A casting that fails down the line costs both of us way more than a few extra kilograms of metal.<\/p>\n

So if you\u2019re a buyer looking for sand castings, what should you ask your supplier about yield? Don\u2019t be shy. Ask how they calculate it, how they track scrap, what their typical yield is for your part type. If they can\u2019t give you a straight answer, or they act like yield is some secret, run\u2014because they\u2019re either cutting corners or don\u2019t know their own shop. We always walk new clients through our process, show them our tracking sheets, so they see we\u2019re transparent.<\/p>\n

<\/p>\n

At the end of the day, yield is a numbers game, but it\u2019s also about care. We don\u2019t just punch numbers into a calculator\u2014we adjust for every part, every alloy, every shift. We\u2019ve been refining our yield calculations for years, and that\u2019s why we\u2019ve kept the same core clients for 5+ years. If you need custom sand castings, whether it\u2019s a small batch of brackets or a big order of complex components, we can give you a clear, accurate yield calculation for your order, no hidden fees, no guesswork. Hit us up to chat through your project, and we\u2019ll make sure you get castings that are on spec, on time, and priced fairly, with full transparency on how we get the numbers.<\/p>\n

Stainless Steel Closed Die Forgings<\/a> References:<\/p>\n

    \n
  1. Campbell, J. (2015). Castings Practice: The Ten Rules of Castings. Butterworth-Heinemann.<\/li>\n
  2. ASM International. (2008). Sand Casting Design and Practices. ASM Handbook, Volume 15: Casting.<\/li>\n
  3. Steel Founders\u2019 Society of America. (2020). Yield Calculation Guidelines for Steel Sand Castings.<\/li>\n
  4. American Foundry Society. (2019). Aluminum Sand Casting Process Optimization: Yield and Defect Reduction.<\/li>\n<\/ol>\n
    \n

    Hebei Shata Machinery Co., Ltd.<\/a><\/p>\n

    Address: No.11 Cangshun Rd., Shijiazhuang, Hebei, China
    E-mail: Info@shatamachinery.com
    WebSite:     https:\/\/www.shatamachinery.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

    Hey everyone, Sand Castings If you\u2019ve ever ordered sand castings from a supplier, you probably know … How to calculate the yield of sand casting production?<\/span>Read more<\/a><\/p>\n","protected":false},"author":37,"featured_media":3576,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[3539],"class_list":["post-3576","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry","tag-sand-castings-4a4c-a3892e"],"_links":{"self":[{"href":"http:\/\/www.lotfitrade.com\/blog\/wp-json\/wp\/v2\/posts\/3576","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.lotfitrade.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.lotfitrade.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.lotfitrade.com\/blog\/wp-json\/wp\/v2\/users\/37"}],"replies":[{"embeddable":true,"href":"http:\/\/www.lotfitrade.com\/blog\/wp-json\/wp\/v2\/comments?post=3576"}],"version-history":[{"count":0,"href":"http:\/\/www.lotfitrade.com\/blog\/wp-json\/wp\/v2\/posts\/3576\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.lotfitrade.com\/blog\/wp-json\/wp\/v2\/posts\/3576"}],"wp:attachment":[{"href":"http:\/\/www.lotfitrade.com\/blog\/wp-json\/wp\/v2\/media?parent=3576"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.lotfitrade.com\/blog\/wp-json\/wp\/v2\/categories?post=3576"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.lotfitrade.com\/blog\/wp-json\/wp\/v2\/tags?post=3576"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}