Injection Mold & Tooling Procurement: Steel Grades, Cavity Count, and the Ownership Clauses That Decide Who Keeps the Mold

Q: How much does an injection mold actually cost?

It depends entirely on part size, complexity, and steel. A simple single-cavity mold for a small, low-detail part runs $2,000 to $8,000 in P20 steel. A medium multi-cavity mold for a consumer product runs $10,000 to $50,000. High-precision or high-cavitation automotive and medical molds easily cross $100,000. The quote should break down steel, machining, EDM, polishing, and trial runs separately so you can see where the money went.

Q: Which mold steel should I specify, P20 or S136 or H13?

P20 is pre-hardened general-purpose steel, the default for most parts and the cheapest per kilogram. S136 (420 stainless) resists corrosion, so it is the choice for PVC, medical, and food-contact parts that would otherwise rust the cavity. H13 is hot-work steel for high-temperature resins and high-cycle-volume production. Match steel to the material and the shot count, not to the cheapest quote.

Q: How many cavities should the mold have?

More cavities mean a lower unit price but a higher upfront mold cost and longer cycle times per shot. Start with a single or 1+1 cavity mold to validate the design and demand, then reinvest in a multi-cavity tool once volume is proven. A 4 or 8 cavity mold only pays off when you are confident in tens of thousands of units, because the extra steel, the hot runner, and the balancing all cost money up front.

Q: Who owns the mold after I pay for it?

This is the clause buyers forget until they try to move production. A mold contract should state explicitly that you own the tool and can take it back after payment is complete, and that the supplier cannot use it for other customers without your written consent. Without that clause, the factory often treats the mold as its own and may refuse to release it when you want to switch vendors.

Q: What is the difference between a cold runner and a hot runner mold?

A cold runner leaves a solidified sprue and runner attached to each shot that must be trimmed and recycled, wasting material but costing less upfront. A hot runner keeps the plastic molten in the channels so every shot goes fully into the part, which saves material and cycle time but adds 20% to 40% to the mold price. Hot runners make sense for high-volume, high-material-cost parts; cold runners are fine for prototypes and low volume.

The Buyer Who Paid for a Mold He Could Never Move

A hardware importer spent $28,000 on a four-cavity mold for a plastic enclosure, happy with the unit price. Two years later he tried to move production to a cheaper factory and learned the hard way: his contract never said who owned the tool. The original factory kept it, and he paid for a second mold.

Mold procurement is three decisions in one: what steel, how many cavities, and who keeps the tool. Most buyers nail the first one and skip the third.

Steel Grade: Pick It for the Material, Not the Price

The steel is the mold's backbone. Pick it wrong and the cavity rusts, wears early, or cannot hold tolerance on a high-volume run.

Common Mold Steels and Where They Belong

Steel	Hardness	Best For	Typical Life
P20	Pre-hardened 28–32 HRC	General-purpose, most parts	~500,000 shots
718H	Pre-hardened 33–38 HRC	Higher-wear, glossy surfaces	~1,000,000 shots
S136	Stainless 48–52 HRC	PVC, medical, food-contact	~1,000,000+ shots
H13	Hot-work 44–52 HRC	High-temp resins, long runs	~1,000,000+ shots

P20 is the default and the cheapest per kilogram. S136 is stainless, so it resists the corrosive gases PVC gives off, which is why medical and food-contact parts specify it. H13 handles the heat of engineering resins and the wear of long production runs. The supplier should list the steel grade in the quote; if it just says "quality mold steel," ask.

Cavity Count: Scale After You Prove the Volume

More cavities lower the unit cost but raise the upfront price and the risk. A one-cavity mold is cheap and fast; a sixteen-cavity mold is expensive, slow to build, and useless if the design changes.

Single or 1+1 cavity: validate the design and demand first. $2,000–$8,000 for simple parts.
4 to 8 cavity: only when you are confident in tens of thousands of units. $10,000–$50,000.
16+ cavity: automotive and high-volume consumer only, where the amortized savings justify the $100,000+ price.

The trap is paying for cavities you never use. A buyer who orders an eight-cavity mold for a product selling 3,000 units a year has spent six figures to save cents per unit he will never recover.

The Ownership Clause: Who Keeps the Tool

This is the clause that separates a mold you own from a mold you rent. Write it in before the deposit clears.

Ownership: state that you own the tool and can take it back after payment is complete.
Exclusivity: the supplier cannot run the mold for other customers without written consent.
Release: the supplier must release the mold, with all drawings and files, within a set number of days on request.
Maintenance: who pays for wear, and what the shot-life warranty covers.

Without these lines, the factory treats the mold as its own asset. That is not a paperwork detail; it is the difference between owning your production and renting it.

Trials, DFM, and the Run-Off That Catches Problems

No mold is right on the first shot. A serious supplier runs a T0 trial, sends you samples, then runs T1 after adjustments. Skip the trial and you find the defects in a full production run instead of a sample box.

DFM review: get a design-for-manufacturability report before steel is cut, so draft angles, wall thickness, and gate location get fixed in CAD, not in metal.
Run-off: a pilot production run that proves cycle time, part weight, and dimensional tolerance before you accept the tool.
Documentation: request the full set of mold drawings and the bill of materials so the tool can be serviced anywhere.

Common Questions from Buyers

How much does an injection mold actually cost?

A simple single-cavity mold runs $2,000 to $8,000 in P20. A medium multi-cavity mold runs $10,000 to $50,000. High-precision automotive or medical molds cross $100,000. The quote should itemize steel, machining, EDM, polishing, and trials.

Which mold steel should I specify, P20 or S136 or H13?

P20 is the general-purpose default. S136 stainless resists corrosion, so it is right for PVC, medical, and food-contact. H13 handles high-temperature resins and long runs. Match steel to the material and shot count.

How many cavities should the mold have?

Start single or 1+1 cavity to validate design and demand, then scale to 4 or 8 cavities once volume is proven. Multi-cavity molds only pay off with confirmed tens of thousands of units.

Who owns the mold after I pay for it?

The contract must state you own the tool, can take it back after payment, and the supplier cannot run it for others without consent. Without that clause, the factory may refuse to release the tool when you want to switch vendors.

What is the difference between a cold runner and a hot runner mold?

A cold runner leaves a sprue and runner to trim and recycle, wasting material but costing less. A hot runner keeps plastic molten so every shot fills the part, saving material but adding 20% to 40% to the mold price. Hot runners suit high-volume, high-material-cost parts.

Specify the steel, start single-cavity, and put the ownership clause in writing. Compare plastic-injection and tooling suppliers with real capability data on Compare2Best.

This article is produced by the Compare2Best knowledge team and reviewed by injection-molding and tooling professionals. Updated September 2026. Mold pricing, steel availability, and tooling contract terms vary by region and supplier; this is general guidance, not engineering or legal advice.