When you compare quotes from China injection mold manufacturers, the numbers only mean something if you know what sits behind them. Two quotes for the same part can differ by thousands of dollars because one uses hardened tool steel and the other uses a softer pre hardened steel that will not survive the production run. This guide explains the steel grades, tolerances, cavitation, and lead time factors that define a China built injection mold, so you can compare offers on an even basis.
Mold steel grades and what they mean for your program
The steel grade drives both the price of the tool and how many shots it will last. Common grades in China tooling include:
- P20 (1.2311): A pre hardened steel used for prototype and lower volume production molds. Machines easily, holds moderate tolerances, and suits programs in the low hundreds of thousands of parts.
- 718H: An upgraded pre hardened steel with better uniformity than standard P20, common for mid volume production tooling.
- H13 (1.2344): A hardened hot work steel used for high volume tools, hot runner systems, and abrasive or glass filled resins. Higher cost, far longer tool life.
- S136 (1.2083): A stainless mold steel for optical, medical, and high polish cosmetic parts, chosen for corrosion resistance and its ability to take a fine polish.
- NAK80: A pre hardened steel that polishes and textures well, used where surface finish matters but full hardening is not required.
A quote that does not name the steel grade is not a quote you can compare. Ask for it every time.
Tolerances and what drives them
Injection molded parts are held to a molding tolerance, not a machining tolerance. Most features can hold a standard commercial tolerance economically, while a few critical dimensions can be held tighter at added cost through steel safe conditions and post molding checks. The material matters here too, since an unfilled resin with high shrink cannot hold the same tolerance as a filled, dimensionally stable one. A good manufacturer will tell you which of your dimensions are realistic to hold and which need a design change.
Cavitation, cycle time, and cost per part
Cavitation is how many parts the mold makes per cycle. A single cavity tool is cheaper to build but slower per part. A multi cavity or family tool costs more up front but lowers the piece price at volume. The right cavitation is a function of your annual volume, so the tooling decision and the part price decision are linked. Share your yearly volume and a manufacturer can model the tradeoff instead of guessing.
Surface finish standards
Surface finish is specified against the SPI scale, from high gloss A grades down to textured D grades. The finish affects steel selection, draft requirements, and polishing labor, so it belongs in the quote alongside the steel grade and tolerances.
Lead time factors
Lead time on a China built mold is driven by cavitation, part complexity, the number of side actions, and the finishing the part requires. A simple single cavity tool moves faster than a multi cavity tool with lifters and a textured cosmetic surface. The honest way to handle lead time is to confirm it in writing at quote stage, tied to the specific tool, rather than quoting a generic number.
How to compare China mold quotes fairly
Put every quote on the same sheet and confirm all of these: steel grade, cavitation, tolerance callouts, surface finish, hot or cold runner, included T1 sampling, and written lead time. When those line up, price differences become meaningful. When they do not, the cheapest quote is often the most expensive tool once you account for a short lived mold or a missing side action.
TK Mold USA quotes every one of these line items in plain terms, with a US based engineer to walk you through the tradeoffs before you commit. Send your part for a transparent, comparable quote.