I've been messing around with some small DIY projects lately, and I keep seeing people talk about casting versus injection molding. From what I gather, casting seems simpler and cheaper for small runs, but injection molding looks like it gives way more precise results if you're making a bunch of identical things. I'm kinda torn here...does injection molding justify the extra cost and complexity, or is casting good enough for most hobby-level stuff? Curious what others here prefer and why.
"casting seems simpler and cheaper for small runs, but injection molding looks like it gives way more precise results if you're making a bunch of identical things."
You're on the right track here. I've done a fair bit of casting for small home projects—cabinet knobs, custom hooks, decorative accents—and honestly, casting usually hits the sweet spot. Injection molding is great if you're scaling up or selling stuff commercially, but for hobby-level work, the cost and complexity rarely pay off. Unless you're after super-tight tolerances or mass production, casting is plenty good enough and way easier to manage at home...
I've found casting pretty forgiving too, especially if you're still tweaking your design or experimenting with materials. Injection molding is definitely precise, but the upfront costs and complexity can be a real headache if you're just trying stuff out or making small batches.
"Unless you're after super-tight tolerances or mass production, casting is plenty good enough and way easier to manage at home..."
True, but I'd add that precision isn't always about mass production. Sometimes even small runs need tight tolerances—like if you're making parts that have to fit together snugly or align perfectly. In those cases, you might find yourself spending extra time sanding, filing, or adjusting cast pieces to get them just right. Not impossible, but it can get tedious fast.
If you do go the casting route and want better accuracy, consider using silicone molds instead of rigid ones. They're flexible enough to capture fine details and release easily without damaging delicate features. Also, pay attention to your mold prep—air bubbles are your enemy here... tapping or vibrating the mold gently before curing helps a lot.
Good points about silicone molds—I’ve had pretty good luck with them myself. One thing I’d add though, is that even silicone molds have their limits when it comes to precision. Sure, they capture detail beautifully, but if your mold isn’t properly supported or reinforced, it can deform slightly under the weight of the casting material. Learned that one the hard way when I was making some small interlocking parts for a prototype. Everything looked perfect until I tried fitting them together... and then spent way too long sanding and adjusting. Not fun.
Injection molding definitely has the edge if you need consistent, repeatable accuracy. But like you said, the upfront costs and complexity can be a real barrier—especially if you’re just prototyping or making limited runs. I’ve found a decent middle ground using resin casting with pressure pots. It’s a bit more setup initially, but applying pressure during curing really helps eliminate air bubbles and shrinkage issues. You can get surprisingly tight tolerances without the huge investment of injection molding equipment.
Also, if environmental impact matters to you (and it definitely should), casting can offer more flexibility in choosing eco-friendly materials. I’ve experimented with bio-based resins and recycled fillers that work well with silicone molds. Injection molding typically locks you into specific plastics, many of which aren’t exactly green-friendly.
Bottom line, it really depends on your project goals. If you’re just experimenting or doing small batches, casting is usually the way to go. But if precision and repeatability become critical, you might have to bite the bullet and invest in injection molding—or at least find a shop that can do small runs affordably.
Good points about silicone molds—I’ve had pretty good luck with them myself.
Injection Molding Worth It for Precision Parts, but Casting Usually Enough
Good points made above about silicone molds deforming under weight. I've run into similar issues myself, especially with small, detailed components that need to fit precisely. Injection molding is definitely superior if you require tight tolerances and repeatability. But for most hobby-level or limited-run projects, casting with resin and a pressure pot setup usually gets the job done without breaking the bank or complicating things unnecessarily.
