Wie entwirft man eine Spritzgussform?

Designing an Spritzgussform involves several key steps like material selection, cavity layout, and part geometry considerations for optimal results and high production efficiency.

Understanding mold design principles is essential for efficient production and high-quality output. Whether you are designing a new mold or optimizing an existing tool, these factors directly influence mold performance, cycle time, and overall cost savings for manufacturers.

Was sind die Grundprinzipien von Spritzgießwerkzeugen?

Spritzgießformen sind für die Herstellung von Hochpräzisionsteilen unerlässlich. Dabei wird geschmolzenes Material in einen Formhohlraum gespritzt. Diese Technologie kommt in vielen Branchen zum Einsatz und gewährleistet eine schnelle und gleichmäßige Produktion.

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Verfahren zum Spritzgießen injects molten material into a mold cavity under high pressure, where it solidifies to form the desired product. Mold design ensures the product can be easily removed and closely matches the expected dimensions.

The materials, structure, and layout of injection molds directly relate to the quality, efficiency, and cost of the final product.

Die Grundprinzipien der Konstruktion von Spritzgießwerkzeugen umfassen mehrere wichtige Schritte

Preparation of molten plastic is the first stage. The plastic raw material is melted by the shearing action of the screw and the heater.

Injection: The molten plastic is forced into the mold cavity through the nozzle with help of pressure exerted by the screw.

Holding Pressure and Cooling: The injection molding machine keeps this pressure for some time to ensure that the cavity is filled and then starts cooling process as the plastic starts to set.

After the plastic solidifies, the mold opens and the ejection system — typically pins, plates, or sleeves — pushes the finished part out of the cavity. Proper ejection design ensures the part releases cleanly without deformation or damage to critical surfaces.

Was sind die Materialien für die Form?

Mold materials are essential in manufacturing processes like injection molding, ensuring durability, precision, and quality. The choice of material affects production efficiency and the final product’s characteristics.

Die Wahl des Formenmaterials hat einen großen Einfluss auf die Lebensdauer der Form und die Qualität des Endprodukts. Gängige Formenwerkstoffe sind Stahl und Aluminium.

Stahl

Steel molds offer superior hardness, wear resistance, and heat treatment properties with significantly longer working life than aluminum — ideal for high-volume production where dimensional consistency is critical.

The main drawbacks of steel molds are longer machining times and higher material costs compared to aluminum. Steel is also significantly heavier, which increases handling difficulty and wear on mold-change equipment. However, the longer tool life usually offsets these disadvantages in high-volume applications.

Gängige Stähle:

P20-Stahl¹ is a versatile pre-hardened mold steel (28–36 HRC) widely used for mold bases and large cavities. It offers excellent machinability and polishability at a cost-effective price point for medium-volume production molds.

H13 is a hot-work tool steel for molds operating at elevated temperatures. It maintains hardness and thermal stability after prolonged heat exposure, with typical hardness of 44–52 HRC after treatment.

S136 is a stainless tool steel with excellent corrosion resistance and polishability. It is the preferred choice for optical lenses, transparent parts, and medical molds where surface finish quality is paramount.

Aluminium

Aluminum molds offer significant weight savings and roughly 4–5x better thermal conductivity than steel, enabling faster cooling and shorter cycle times. Easy machinability reduces tooling lead time and cost, making aluminum ideal for prototyping and low-volume production.

The main drawback is lower hardness and wear resistance, making aluminum molds susceptible to surface damage with abrasive resins. Best suited for production runs under 10,000–50,000 parts where tooling speed matters more than longevity.

Gemeinsames Aluminium:

7075 is one of the strongest aluminum grades (tensile strength ~570 MPa). Despite this, its hardness remains far below tool steel, making it best suited for prototype molds and short production runs.

Was umfasst die Gestaltung von Schimmelpilzstrukturen im Wesentlichen?

Die Gestaltung der Formstruktur ist der Schlüssel zur Herstellung hochwertiger Spritzgießformen, die Effizienz und Konsistenz während des Gießprozesses gewährleisten. Sie umfasst kritische Aspekte wie den Formfluss, die Kühlung und die Materialkompatibilität.

Mold structure design refers to the cavity, core, frame, gate, guide, and withdrawal system. All must be carefully engineered for proper efficiency, sturdiness, and easy maintenance.

Hohlraum und Kern

Der Hohlraum bildet die Außenabmessungen des Produkts, während der Kern die Innenabmessungen liefert, die miteinander verbunden sind, um die endgültige und gewünschte Produktform und -größe zu erhalten.

Material Selection: Often employ high-hardness, wear-resistant steel, such as P20 or H13 steel.

Design Points: The finished surfaces of cavity & core should be smooth so that high dimensional accuracy should be maintained for the surface finish of the product.

Form Basis

Der Formsockel ist auch das Grundgerüst des Werkzeugs und hat die Aufgabe, alle Komponenten zu befestigen und miteinander zu verbinden. Er hat in der Regel eine Standardform, um den Zusammenbau von Formen und deren Austausch bei Bedarf zu ermöglichen.

Material Selection: Usually, 45 steel or Q235 steel is adopted for the mold base to guarantee the stability of the mold base.

Design Points: The mold base should possess enough robustness and sturdiness to be able to cope with injection pressure, injection temperature and the general to and fro pressure during injection.

Gating-System

Das Anschnittsystem besteht aus dem Hauptkanal, den Unterkanälen und den Anschnitten, durch die der geschmolzene Kunststoff in die Kavität geleitet wird. Ein effektives Anschnittsystem ist hilfreich, um die Qualität des Formteils zu erhöhen und die Menge des verwendeten Materials zu verringern.

Design Points: The main runner should be as short and as straight as can be in order to minimize the pressure loss as well as cuts as much as is possible.

Design Points: Sub-runners should be properly arranged so that it would apply equal mass to the cavity.

Design Points: The nature of the gate should not in any way influence the look of the product or compromise on its strength The size of the gate used should be good.

Lenkungsmechanismus

Der Führungsmechanismus umfasst Führungsstifte und -buchsen, die bei der Ausrichtung zwischen den beweglichen und den festen Formen helfen.

Material Selection: Typically uses high-hardness steel, such as GCr15.

Design Points: The guiding mechanism should be very accurate in term of the alignment to prevent misalignment over a long period of time besides being very resistant to wear.

Auswurfmechanik

Der Auswerfer wird eingesetzt, um das geformte Produkt aus der Form zu nehmen, und normalerweise werden Auswerferstifte, Platten und Hülsen verwendet.

Design Points: Another requirement of this force is that it should be constant or smooth since a sudden force may affect the product in a negative way. The movement of the ejection mechanism should also be smooth to avoid sticking.

Was ist Flow Channel Design?

Flow channel design is the engineering of the sprue, runners, and gates that guide molten plastic from the machine nozzle into the mold cavity.

Runner design significantly influences product quality and production efficiency. The size and shape of the runner must match the material and part geometry.

Hauptlaufbahn

Der Hauptkanal verbindet die Düse der Spritzgießmaschine mit den Unterkanälen und sollte so kurz und gerade wie möglich sein, um Druckverluste und Materialverluste zu reduzieren.

Design Points: The main runner diameter should be right to promote adequate flow all the same reduce wasteful use of the materials.

Sub-Runners

Die Unterkanäle verteilen die Kunststoffschmelze auf die einzelnen Kavitäten des Werkzeugs, wobei das Gleichgewicht eine wichtige Rolle spielt.

Design Points: Sub-runner cross-sectional shapes should be best circular or semicircular to lower the resistance offered by flows. The length should ideally be as equal as possible, so that the cavity filling time is almost equal for all the lengths.

Pforten

Anschnitte sind das Mittel, mit dem die in die Kavität eingebrachte Kunststoffschmelze die Produktqualität beeinflusst.

Design Points: The gates should be placed in areas that do not affect appearance or strength. Their sizes must provide adequate fill rates while being easy to remove. Different gate types serve different product requirements.

Darüber hinaus sollte das Design der Läufer berücksichtigt werden:

Runner Balance: For multiple cavities make sure that the runners lengths and their cross sectional area as they are the primary determinet of the time taken to fill the molds.

Runner Cooling: Sufficient provision for Kühlkanäle² for the runner section so that high temperature does not influence the melt flow.

Runner Precision: Machining precision is high and the surface smooth to lower the restriction to melt flow and pressure drop.

Was ist ein Kühlsystemdesign?

Die Auslegung von Kühlsystemen ist entscheidend für die Optimierung von Fertigungsprozessen, die Gewährleistung einer gleichbleibenden Produktqualität und die Effizienz von Produktionszyklen.

Das Kühlsystem spielt bei der Konstruktion von Spritzgießwerkzeugen eine sehr wichtige Rolle, da es die Zykluszeit des Spritzgießens und die Werkzeugqualität reduziert. Zum Kühlsystem gehören vor allem die Kühlkanäle und die Kühlzeitstufen.

Kühlungskanäle

Kühlkanäle leiten Kühlwasser durch verschiedene Formteile, um überschüssige Wärme abzuführen.

Cooling channels should be positioned as close to the cavity surface as possible to maximize heat dissipation. A channel-to-cavity distance of 1.5–2.5 times the channel diameter balances cooling performance with structural integrity of the mold steel.

Coolant flow should be distributed evenly across all channels to prevent localized hot spots. Uneven cooling leads to differential shrinkage, internal stresses, and warpage in the finished part. Baffles or spiral inserts can help redirect flow to underserved areas of the mold.

Channel diameter must be large enough to maintain adequate coolant flow velocity — typically 1.5–3 m/s — without creating excessive pressure drop. Too-small diameters risk blockages from scale or debris, while overly large channels reduce flow turbulence and heat transfer efficiency.

Abkühlungszeit

Cooling time also depends with the wall thicknesses of the product, the type of material used, and the temperatures of the mold.

Sufficient cooling time prevents warpage and shrinkage while ensuring dimensional stability. The optimal duration balances part integrity against throughput — typically 60–80% of total cycle time in most injection molding operations.

Weitere Überlegungen zu Kühlsystemen sind:

Coolant flow speed requires careful control. Low speed can reduce cooling efficiency, while high speed might lead to blockage and wearing of the mold.

Coolant Temperature: Optimal temperature, as high temperature decrease the cooling rate while low temperature will cause condensation on the mould surface and may affect the quality of the product.

Coolant Quality: Keep coolant clean to avoid blockages and mold damage.

Was ist ein Abgassystemdesign?

Exhaust system design is the engineering of vent grooves and holes that allow trapped air and gases to escape the mold cavity during injection.

Das Entlüftungssystem leitet Gas aus dem Formhohlraum ab, um Defekte wie Blasen und Verbrennungen zu vermeiden, die sich direkt auf die Produktqualität und die Langlebigkeit der Form auswirken.

Entlüftungsrillen

Relief groove³ is a channel for the escape of gas and it is mostly in the parting line.

Design Points: Put location grooves where/when gas can freely build up.

Design Points: Width and depth should optimise cross-sectional area for the required venting so that there will not be any issues on the side of plastic ejection.

Design Points: Even distribution to prevent localized venting issues.

Entlüftungslöcher

Die Entlüftungsöffnungen gehören zu den Komponenten des Entlüftungssystems, die sich normalerweise in dünnen Bereichen eines Produkts befinden.

Design Points: Appropriate diameter in order not to hinder the release of gas build up while at the same time guaranteeing proper exhaust.

Design Points: Positioning should not in any way influence the look of the product and neither its strength.

Design Points: Quantity and location should be reasonable with the structure of mould and the shape of product.

Bei der Planung des Entlüftungssystems sollte auch berücksichtigt werden:

System Maintenance: They should be cleaned now and then to ensure unrestricted and unhindered flow but be checked at times to avoid tools to avoid blockages that may cause quality issues.

System Cooling: In the case of using high-temperature molds, make use of cooling means to avoid condensation of the gases during the time of venting.

Processing Precision: High precision with smooth surfaces to reduce gas flow resistance and pressure loss.

Was sind die Mold Processing?

Mold processing is the series of CNC machining, EDM, grinding, and surface treatment steps that transform raw steel into a precision injection mold.

Die Formverarbeitung ist der Prozess der Umwandlung der Konstruktionszeichnung in die tatsächliche Form durch Grob- und Feinbearbeitung, Oberflächenbehandlung usw. Aus der Analyse geht hervor, dass die Genauigkeit und Qualität der Verarbeitung sich direkt auf die Funktion und Haltbarkeit der Form auswirken.

Grobzerspanung

Die Form wird aus dem Rohmaterial heraus grob bearbeitet, wobei üblicherweise CNC-Fräsen und Drehbänke verwendet werden.

Key Points: Leave sufficient allowance for finishing.

Key Points: The optimum speed and feed rates that help in avoiding deformation of the material and gradual wearing of the tools and machinery.

Key Points: Rough machining to decrease the burr and bringing the smoother surface.

Fertigstellung

Die Endbearbeitung erreicht die Form, um die Größe und die Spezifikationen der Form zu erreichen, und verwendet das Schleifverfahren, EDM und Polieren.

Key Points: Accuracy ensure that the shape and size is correct for the mold.

Key Points: Avoid over-polishing to prevent dimensional deviations.

Key Points: Finishing the surface with the best and most appropriate equipment in order to obtain a smooth and proper finish.

Oberflächenbehandlung

Die Oberflächenbehandlung von Gussformen erhöht die Härte und die Verschleißfestigkeit der Gussformen, wobei die Verfahren Abschrecken, Nitrieren und die Verwendung einer Oberflächenbeschichtung zum Einsatz kommen.

Key Points: Select appropriate treatment methods based on mold material and application.

Key Points: To reduce mold deformation and cracks the amount of time for treatment and temperature should be controlled.

Key Points: Clean thoroughly before treatment for better adhesion and performance.

Wie pflegt man den Schimmel?

Eine ordnungsgemäße Werkzeugwartung ist entscheidend für eine gleichbleibende Qualität und Langlebigkeit beim Spritzgießen. Regelmäßige Pflege kann Ausfallzeiten und kostspielige Reparaturen verhindern.

Mold maintenance, both daily and periodic, extends service life and reduces production costs through consistent upkeep.

Routinemäßige Wartung

Key Points: Ensure the mold surface is as clean to avert temperatures and dust from penetrating the mold.

Key Points: Lubricate the guide pillar and guide bushing regularly to ensure the flexibility of the guide mechanism.

Key Points: It may be necessary to often inspect the other components of the mold, and repair or replace them in time.

Key Points: It is necessary to confirm whether the cooling channel and exhaust system are normally opened and whether they are blocked, if they are blocked, they should be cleared up in time.

Regelmäßige Wartung

Unter Wartung versteht man die allgemeine Überprüfung und Reparatur der Form, nachdem sie einige Zeit benutzt wurde.

Key Points: Inspect the mold cavity and core and look for the part of the cavity which has severely worn and repair or replace them.

Key Points: Check whether the guiding mechanism, demoulding mechanism and other parts of the mold are normal, and make necessary adjustments or replacements.

Key Points: Check whether the cooling system of the mold and the exhaust system of the mold are normal and perform the need for cleaning and clearing.

Key Points: Thoroughly clean and lubricate the mold to ensure that the mold is in good working condition.

Was sind die häufigsten Probleme bei der Formgestaltung und ihre Lösungen?

Common mold design problems include poor cooling, uneven material flow, and improper gate placement that affect part quality.

Several common issues can affect part quality and production rate if not properly addressed during mold design.

Sinkende Markierungen

Problem Description: The surface of the product is dented, which affects the appearance.

Solution: It is advised to the position as well as the size of the gate to be such that it can accommodate melt and fill up the cavity uniformly.

Solution: Maximize the cooling circuit design and layout in order to allow equal distribution of the cooling to the products.

Solution: Adjust the holding time and pressure to reduce melt shrinkage.

Blitzlicht

Problem Description: Scrap forms on the peripheral region of the product giving it a poor appearance and may not be of accurate dimension.

Solution: About the parting surface design of the mold, try to make the mold closed to the minimum.

Solution: Enhance the clamping force of the mold to prevent the mold from separating during the injection molding manufacturing process.

Solution: To check the mold, first it is required to check the guiding mechanism of the mold and the clamping mechanism of the mold.

Blase

Problem Description: There are visible pores on the body of the product or in the product itself in the form of bubbles which influences the looks and the durability.

Solution: Minimize the design of the exhaust system so as to allow the gas in the mold cavity to be released effectively.

Solution: Adjust the parameters used in injection like the speed of injection, injection force and temperature of injection molding materials in a bid to minimize generation of gases.

Solution: Check the drying of raw materials to ensure that the moisture content of raw materials is at an appropriate level.

Verformung und Verwerfung

Problem Description: The injection molded part becomes partly shrunken or distorted after cooling and the dimensional stability and surface finish of the product are compromised.

Solution: Improve on the cooling system so as to give as equal temperatures to all the injection molded parts.

Solution: Adjust the holding time and holding pressureset in the injection parameters to reduce internal stress.

Solution: Strengthen the changes in mold structure design, such as adding reinforcing ribs to make the product have uniform wall thickness and consistent wall thickness.

Instabilität der Dimensionen

Problem Description: The geometry is out of the required sizes and standards to affect the assembly and usage of the product.

Solution: Examine the correctness of machining on the mold and assembly realization of products to verify whether or not the sizes of the mold conform with the injection molding design specifications.

Solution: Control the process parameters as injection pressure, holding pressure time and cooling time should be controlled in order to have stable size of the product.

Solution: Confirm the manufacture stability of the injection molding machines in order to have ability to determine the variation of the injection molding.

Häufig gestellte Fragen

What is the most important factor in injection mold design?

The most critical factor in injection mold design is achieving uniform wall thickness throughout the part. Uneven walls cause differential cooling, which directly leads to sink marks, warpage, and dimensional inconsistency in the finished product. In our experience at ZetarMold working with over 400 materials, parts with wall thickness variations exceeding 15 percent almost always require costly mold rework to achieve acceptable quality. Beyond wall thickness, proper gate placement and an efficient cooling system layout are equally important for determining cycle time and long-term mold durability.

How long does it take to design an injection mold?

A typical injection mold design takes 2 to 4 weeks depending on part complexity. Simple single-cavity molds for straightforward geometries may take as little as 5 to 7 days from concept to completed drawings. Complex multi-cavity molds with side actions, lifters, or unscrewing mechanisms can require 4 to 6 weeks of engineering time. The design phase includes 3D CAD modeling, mold flow simulation to validate fill patterns, and multiple design review iterations. At ZetarMold, our 8 senior engineers follow a structured review process that catches issues early.

What software is used for injection mold design?

The industry standard software for injection mold design includes SOLIDWORKS and UG also known as NX for 3D CAD modeling, and Autodesk Moldflow for flow simulation and thermal analysis. These tools allow engineers to visualize cavity layout, simulate plastic fill patterns, and optimize cooling channel placement before any steel is cut. At ZetarMold, our design team uses SOLIDWORKS, MOLDFLOW, and CAD in combination to validate gate placement, predict weld line positions, and analyze cooling efficiency, reducing first-article defects by up to 60 percent compared to traditional trial-and-error methods.

Was sind die typischen Kosten für ein Spritzgusswerkzeug?

Injection mold costs range widely depending on complexity and production requirements. Simple single-cavity aluminum prototype molds start around 1,000 to 3,000 dollars, while production-grade steel molds with multiple cavities and hot runner systems typically cost between 10,000 and 50,000 dollars. Highly complex molds with side actions, unscrewing cores, or specialized surface finishes can exceed 100,000 dollars. Key cost drivers include the number of cavities, mold material choice, expected production volume, required surface finish quality, and tolerance specifications for the application.

How do you prevent flash in injection mold design?

Flash prevention starts with precision parting surface design and proper clamping force calculation. The mold parting line must be machined to flatness tolerances within 0.01 millimeters to ensure complete closure under injection pressure. Vent grooves should be sized correctly at 0.01 to 0.03 millimeters depth to allow trapped gas to escape without permitting molten material to seep through. The injection molding machine must have sufficient tonnage. At ZetarMold, our 47 presses range from 90T to 1850T, allowing precise matching of machine capacity to each mold.

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

A cold runner mold channels molten plastic through unheated passages, resulting in solidified runner waste that must be separated, reground, and recycled or discarded. A hot runner mold uses electrically heated manifold systems to keep plastic in a molten state within the distribution channels, eliminating runner waste entirely and reducing cycle time. Hot runner molds cost 20 to 40 percent more upfront due to the heated manifold and temperature controllers, but they save 15 to 30 percent on material costs for high-volume production runs and improve consistency.

What tolerance can injection molding achieve?

Standard injection molding achieves tolerances of plus or minus 0.1 millimeters for dimensions under 25 millimeters. Precision molding with optimized process control, tight temperature regulation, and high-quality tooling can achieve plus or minus 0.05 millimeters or tighter for critical features. Tolerance capability depends heavily on material shrinkage characteristics, with semi-crystalline materials exhibiting higher variability than amorphous ones. For tight-tolerance applications, ZetarMold engineers use Moldflow simulation during the design phase to predict and compensate for shrinkage before the mold is built.

Why Does Injection Mold Design Matter for Manufacturing Success?

Injection mold design is the most important factor for part quality, production efficiency, and cost control in plastic manufacturing.

This article provides practical references for injection mold designers. For custom mold design support, contact ZetarMold for expert assistance.

Learn about Injection Molding: A Comprehensive Guide: Injection molding is a manufacturing process where molten plastic is injected into a mold to create parts with high accuracy and repeatability. ↩

Learn about What is core and cavity in injection molding? The cavity and core in a typical plastic injection molding machine of an injection mold are the molding parts of the mold . ↩

Learn about Types Of Gates for Injection Molding: A Complete Design Guide : An injection molding gate is a designed opening, usually small, that controls molten plastics flow into the mold cavity. ↩

Learn about H13 Tool Steel : H13 is a hot work tool steel that has good resistance to thermal fatigue, erosion and wear, and is widely used for making molds and dies. ↩

Learn about Four Important Principles Should Be Considered In The Design Of Wall Thickness : Plastic Product wall thickness is a critical structural feature frequently discussed and considered in the design of plastic product structures. ↩

Learn about How to Determine Holding Pressure and Holding Time In Injection Molding? injection pressure includes both pressure and speed . ↩

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1. P20-Stahl: P20 Steel refers to aSTM A681 specifies alloy tool steels including P20 with typical hardness of 28-36 HRC for mold base applications ↩

2. Kühlkanäle: Kühlkanäle können laut Forschung im Polymeringenieurwesen bis zu 70 % der gesamten Spritzgießzykluszeit ausmachen ↩

3. groove: Nut bezieht sich auf Standard-Entlüftungsnut-Tiefen von 0,01 bis 0,03 mm für die meisten Thermoplaste, um Gasentweichung ohne Gratbildung zu ermöglichen ↩