The question is never "what is vacuum casting". It is "I need 250 of these — which route do I take?" So here are the three routes with the numbers written down.
The Three Routes Side by Side
| Vacuum casting | Aluminium bridge tool | Steel production tool | |
|---|---|---|---|
| Tooling cost | Low, but repeated | ~$1,000–$10,000 (often $2,000–$5,000 for simple parts) | ~$10,000–$100,000+ |
| Tooling lead time | ~3 days per mold | Weeks | Many weeks |
| First parts | ~5–7 days | ~3–5 weeks | ~6–12 weeks |
| Comfortable volume | ~5–500 | ~100–10,000 | Thousands per year, ongoing |
| Cost per part | Steps up every ~20–25 pieces | Falls, then flattens | Lowest — at volume |
| Material | PU resins simulating ABS/PC/PP/nylon | Real production resin | Real production resin |
| Design still changing? | Fine — new master, new mold | Painful | Very expensive |
Tooling cost ranges above are published industry figures for context, not an EKINSUN quote. Send us the part and we will price yours.
The Shape of the Decision
Strip away the detail and it comes down to one trade: vacuum casting has almost no entry cost and a per-part cost that refuses to fall. Injection molding has a brutal entry cost and a per-part cost that collapses.
So the honest rule is not about the process at all. It is about how confident you are in the design and how many you will need over the tool's life.
| Your situation | Route | Why |
|---|---|---|
| 1–5 pieces, simple shape | CNC machining | No tooling at all. Cheapest way to get very few parts. |
| 5–100 pieces, any complexity | Vacuum casting | Complex housings are as easy as simple ones. A week, not a quarter. |
| 100–500, design frozen | Either — ask for both | This is the genuine overlap. It turns on part size and how many molds yours needs. |
| Design still moving | Vacuum casting | A revision costs a new master and mold, not a tool modification. |
| Need parts now, tool being cut | Vacuum casting, then bridge | Cover the gap without disrupting the production tool schedule. |
| Hundreds to a few thousand, one-off | Aluminium bridge tool | Real molded parts in production resin without production tooling cost. |
| Thousands per year, ongoing | Steel production tool | The only route where per-part cost stays low over years. |
When We Tell You to Go Cut a Tool
If your annual requirement is in the thousands and the design is settled, casting is the wrong answer and we will say so. Twenty molds a year to avoid one tool is a bad trade, and it is not a job worth taking on those terms.
The case where casting still wins at higher volume is when the design is not settled — a tool modification can cost a meaningful fraction of the tool, while a new silicone mold costs a new silicone mold.
The Path Most Projects Actually Take
- Cast a batch — 20 to 50 pieces in a week. Real material, real assembly, real field feedback.
- Fix what the batch exposes. Almost every first batch changes something: a boss moves, a wall thickens, a snap gets a relief.
- Cast again if the changes were significant — new master, new mold, another week.
- Then cut the tool, once nothing is going to move. Design the part for the tool from the beginning: draft angles, even walls, no undercuts you cannot resolve.
Skipping straight to step 4 is what turns a $20,000 tool into a $28,000 tool.
Common Questions
There is no single number because it depends on part size and tool complexity, but the shape of the curve is consistent. Below roughly 100 pieces, silicone molds almost always win because you are not paying to cut a tool. Between about 100 and 1,000, aluminium bridge tooling starts to compete. Above a few thousand a year, a production tool wins clearly and keeps winning.
Published industry ranges put hardened steel production tooling at roughly $10,000 to $100,000 and up, depending on size, cavity count and side actions. Aluminium bridge tools are commonly quoted between about $1,000 and $10,000, with simpler parts landing around $2,000 to $5,000. Those are industry figures, not our quote — ask us and we will price your specific part.
A temporary injection mold, usually machined from aluminium, that produces real injection-molded parts in production resin while the hardened production tool is still being made. It typically covers volumes from a few hundred to several thousand parts, at a fraction of production tooling cost and lead time.
Yes, and it is a normal path. The casting run validates the design and covers early demand; the tool gets cut once the design stops changing. Design for the eventual tool from the start — draft angles, consistent wall thickness, no undercuts you cannot resolve — and the transition is much less painful.
For one to about five pieces, often yes, especially for simple, chunky geometry. It falls apart on thin-wall housings with ribs, snap features and internal bosses, which cannot be cut from a block at sensible cost regardless of quantity.
Because the mold is consumable. Every 20 to 25 pieces needs another mold, so cost steps up in blocks instead of amortising over the run. Injection molding is the opposite — huge up front, then almost flat per part. That difference is the whole decision.