Molds and production plastic parts, with the right process for each application.
We design and build molds for injection molding, blow molding, rotational molding, thermoforming, thermopressing, EPS and polyurethane. The mold defines part quality, cycle time and unit cost: that’s why we start by choosing the right process.
A plastic part is designed once; the mold repeats it hundreds of thousands of times.
Almost every plastics process has one thing in common: the polymer takes its shape inside a metal mold that controls geometry, finish, cooling and ejection. A well-designed mold produces consistent parts cycle after cycle; a poorly engineered one causes sink marks, warpage, flash and production stoppages that no machine adjustment fully corrects.
The first decision is the process. A solid, precise part calls for injection molding; a hollow container, blow molding; a large seamless tank, rotational molding; an open thin-walled tray, thermoforming. Choosing by habit rather than by geometry and volume is the fastest way to make a project more expensive.
Fundimoldes integrates mold design, component casting, machining, EDM, polishing and maintenance, so we can deliver everything from prototype molds to high-production tooling and support it throughout its service life.
Typical industry values; they vary with polymer, geometry and your equipment.
A process for every plastic part.
Plastic injection molds
Cavity, core, feed, cooling and ejection systems.
02 / 06Rotational molding molds
Hollow parts, tanks and containers in metal molds.
03 / 06Thermoforming molds
Vacuum-formed plastic sheet for trays, packaging and housings.
04 / 06Blow molding and extrusion blow molding
Bottles, containers, and hollow parts.
05 / 06Thermopressing molds
Controlled pressure and temperature for fibers and composites.
06 / 06EPS injection molds
Expanded polystyrene for technical packaging and lightweight components.
How the process is chosen: geometry, volume and investment.
Geometry rules processes out; volume and tooling budget decide among those that remain.
| Process | Part type | Pressure | Typical mold | Ideal volume | Mold investment |
|---|---|---|---|---|---|
| Injection molding | Solid, complex, high dimensional accuracy | Very high | P20, H13 or stainless steel | High | High |
| Blow molding and extrusion blow molding | Hollow, thin-walled: bottles and containers | Low (air) | Aluminum, with steel neck inserts | High | Medium |
| Rotational molding | Large, hollow, seamless: tanks and containers | None | Cast aluminum or sheet steel | Low to medium | Low to medium |
| Thermoforming | Open, from sheet: trays and packaging | Vacuum or low pressure | Aluminum; resin or wood for prototypes | Medium to high | Low to medium |
| Thermopressing | Fibers, composites and thermosets | High, with heat | Steel with integrated heating | Medium | Medium to high |
| EPS injection | Lightweight foam: technical packaging and insulation | Low (steam) | Vented aluminum | High | Medium |
| Polyurethane | Rigid or flexible foams, integral-skin parts | Low | Aluminum or steel, depending on run size | Low to medium | Low to medium |
| Vulcanizing | Rubbers and technical elastomers | High, with heat | Steel | Medium | Medium |
Six systems at work in every cycle.
An injection mold is a machine in its own right. Each system handles one stage of the cycle, and all of them must be balanced with one another.
Cavity and core
They form the part. Their finish transfers directly to the plastic and their size includes the polymer’s shrinkage.
Feed system
The sprue, runners and gates carry material to each cavity. A hot runner eliminates runner scrap and shortens the cycle.
Cooling
Channels or coils that remove heat. Because cooling dominates the cycle, its design defines productivity and warpage.
Ejection
Ejector pins, plates and sleeves that release the part without marking or deforming it.
Actions
Slides, lifters and side cores for undercuts, threads and holes that aren’t in the direction of mold opening.
Venting and guiding
Air vents of hundredths of a millimeter prevent burn marks; leader pins and interlocks ensure precise closing.
Not every mold needs to last the same.
The SPI classification, an industry reference, relates expected service life to mold construction. Specifying the right class keeps you from paying for a high-production mold for a short launch, or falling short on one for mass-market products.
| SPI class | Expected service life | Typical construction | Use |
|---|---|---|---|
| 101 | More than 1,000,000 cycles | Hardened steels in cavities and wear components | Mass-market products, continuous production |
| 102 | Up to 1,000,000 cycles | High-quality hardened or prehardened steels | Medium to high production, abrasive materials |
| 103 | Up to 500,000 cycles | P20-type prehardened steels | Medium production, the most common class |
| 104 | Up to 100,000 cycles | Mild steel or aluminum | Low production, limited runs |
| 105 | Fewer than 500 cycles | Aluminum, resins or low-cost materials | Prototypes and validation |
Every polymer demands a different mold.
The plastic’s shrinkage, abrasiveness, corrosiveness and processing temperature translate into decisions on the mold’s steel, dimensions and cooling.
| Polymer | Typical shrinkage | Traits | Implication for the mold |
|---|---|---|---|
| PP · polypropylene | 1,0–2,5 % | Lightweight, chemically resistant, allows living hinges | High shrinkage and tendency to warp: uniform cooling |
| HDPE · high-density polyethylene | 1,5–3,0 % | Tough, impact resistant; a staple of blow molding and rotational molding | Generous dimensional compensation and cooling control |
| ABS | 0,4–0,7 % | Rigid, good surface finish | Good dimensional stability; polished or textured per design |
| PC · polycarbonate | 0,5–0,7 % | Transparent, high impact resistance | Hot mold, high-gloss polish, robust gates |
| PA · fiber-filled polyamide | 0,3–2,0 % | Mechanical and thermal resistance | Fiber is abrasive: hardened steels; shrinkage varies with direction |
| POM · acetal | 1,8–2,2 % | Low friction, precision for gears | Careful venting and shrinkage control |
| Rigid PVC | 0,2–0,5 % | Rigid, economical, self-extinguishing | Releases corrosive compounds when it degrades: stainless steel |
Reference ranges; final shrinkage depends on material grade, wall thickness and processing conditions.
From part design to first sample.
A plastic mold is validated at the first shot, but it’s won or lost in the first weeks of engineering.
Part analysis
Wall thicknesses, draft angles, undercuts, material and annual volume.
Mold concept
Number of cavities, parting line, runner type and mold class.
Thermal design
Cooling or heating circuits, including embedded coils.
Ejection and actions
Ejector pins, slides and lifters defined on the final geometry.
Manufacturing
Casting, CNC machining and EDM of plates, cavities and inserts.
Fitting and finishing
Polishing or texturing, shut-off fitting and full assembly.
Trial and correction
First samples, part measurement and fine-tuning of the mold.
Lifetime support
Preventive maintenance, repair and engineering changes.
Six rules for stable, economical plastic parts.
Applying these rules before the mold is built avoids costly corrections in steel.
Uniform wall
Differences in thickness cool at different rates and cause sink marks and warpage. In injection molding, most parts work well between 1 and 4 mm.
Ribs instead of mass
To add stiffness, use ribs 50–60 % of the wall thickness instead of thickening the part.
Draft angles
0.5° to 2° on vertical walls; more on textured surfaces, which grip the mold.
Corner radii
They improve material flow and reduce stresses. An internal radius of at least half the wall thickness is a good starting point.
Undercuts with judgment
Every undercut requires a slide or lifter that makes the mold more expensive and complex. Redesigning to avoid them usually pays for the review on its own.
Gate location
It defines where weld lines appear, how fibers orient and which zones get packed. It’s decided together with the part’s function.
Common defects and where they’re solved.
Many defects are blamed on the process when their origin is in the mold. Telling them apart saves weeks of trials.
| Defect | What causes it | Mold-side solution |
|---|---|---|
| Shrinkage cavities | Thick sections that keep shrinking after the surface solidifies | Uniform walls, local cooling and gates that allow packing |
| Warpage | Uneven cooling or shrinkage between areas of the part | Balanced cooling circuits and control of fiber orientation |
| Flash | Material escaping through the parting line or clearances | Tight shut-offs, rigid plates and parting-line maintenance |
| Short shot | The material solidifies before the cavity is full | Properly sized runners and gates, sufficient venting |
| Weld lines | Two flow fronts meeting at a lower temperature | Relocate gates and vent the meeting zone |
| Burn marks | Trapped air that compresses and heats up at the end of filling | Correctly located and sized vents |
Industries we serve with plastic molds.
What we’re asked most about plastic molds.
Which process is right for my part?
It depends on the geometry (solid, hollow or open), size, material and annual volume. In the technical review we compare the viable alternatives and their impact on mold cost and cost per part.
How many cavities should my mold have?
It is calculated from the annual volume, the expected cycle time and the capacity of the machine it will run on. More cavities lower the cost per part but raise the investment and the balancing requirements.
Steel or aluminum mold?
Aluminum is faster to machine and cools better, ideal for prototypes, short runs and low-pressure processes. Steel is the choice for high-volume injection and abrasive materials.
Is a hot runner worth it?
At high volumes, yes: it eliminates runner waste and shortens the cycle. For short runs or heat-sensitive materials, a cold runner is usually more convenient.
Can you repair or modify a mold you didn’t build?
Yes. We assess its condition, capture the geometry by 3D scanning if there are no drawings, and carry out the required repair, engineering change or maintenance.
What do I need to get a mold quoted?
A 3D model of the part or a sample, material, annual volume, the machine it will be used on and finish requirements. With that information we define the process, mold class and scope.