Mould Making for Injection Moulds
Your part needs a mould that holds up: we design, build and maintain injection moulds in house – since 1991 in the Saxon Erzgebirge.
Mould making at Schröder + Heidler explained
We design and build injection moulds for series production – from assessing the feasibility of your drawing through design and manufacture to sampling on our own machines. Because mould making and injection moulding are located in the same building, corrections after the first shots are implemented directly instead of being coordinated across company boundaries. Existing moulds are repaired, optimised or taken over together with series production.
Mould making in house
At Schröder + Heidler your injection mould is created where it will later be produced: in our own building. Design, manufacture, sampling and production start-up are in one pair of hands – and under one roof.
That sounds like a detail but is the decisive difference in mould making. During the first shots almost every mould reveals a need for correction: a vent is missing, cooling acts unevenly, an ejector leaves marks. Where mould making and moulding are separate, this means shipping, waiting time and coordination across company boundaries. Here, the mould travels one room further.
Since 1991 we have been producing injection moulds and plastic components for customers in the automotive, electrical engineering, consumer goods and mechanical engineering sectors. Our processes are certified to ISO 9001 and IATF 16949.
Services in mould making:
- Design of new injection moulds based on your part drawing
- Manufacture of single- and multi-cavity moulds
- Two-component moulds for multi-component moulding
- Sampling and series release in our own production
- Repair, maintenance and optimisation – also for third-party moulds
Structure of an injection mould
An injection mould looks like a solid block of steel from the outside. Inside, six assemblies work together, each of which determines the result in its own right. Depending on the part, slides and core pulls for undercuts are added.
Mould plates
The load-bearing structure that absorbs the clamping force. Their rigidity determines whether the mould stays dimensionally accurate under pressure – otherwise flash appears on the part.
Cavity and core
The forming space: the cavity forms the outer contour, the core the inner one. Both carry the surface texture of the later part.
Gating system
The path of the melt into the cavity. A cold runner produces sprue waste, a hot runner avoids it – at higher mould cost and greater control effort.
Cooling system
Channels for temperature-controlled water or oil. Uneven cooling is one of the most common causes of warpage – which makes it core design work.
Ejector system
Pins, sleeves or plates that demould the solidified part – without leaving pressure marks. Demanding on thin-walled parts.
Guiding and centring
Pillars and bushes align both mould halves exactly at every closing stroke. Across hundreds of thousands of cycles, this determines dimensional accuracy.
What does an injection mould cost?
There is no serious answer without a drawing. The range extends from a simple prototype mould to a multi-cavity production mould with hot runner and slide technology – orders of magnitude lie between them. What drives the price, however, can be stated clearly. Eight factors determine it essentially.
Strong influence
- Number of cavities – strong: every additional cavity means another forming space including gate, cooling and ejectors. In return it lowers the part price in series production.
- Part size – strong: larger parts require larger moulds, more steel and machines with higher clamping force.
- Undercuts – strong: slides and core pulls are moving assemblies, complex to design and maintenance-intensive.
- Hot runner – strong: higher acquisition cost, but less material loss and shorter cycles. Pays off from medium quantities upwards.
Moderate influence
- Tolerance requirement – moderate: tight tolerances require finer machining, more measuring effort and often additional correction loops during sampling.
- Surface requirement – moderate: high gloss or defined texturing means additional polishing or etching work on the cavity.
- Part material – moderate: glass-fibre reinforced plastics are abrasive and require higher-grade, hardened tool steels.
- Planned quantity – moderate: a mould for 10,000 parts is designed differently from one for five million. Steel grade, guides and wear parts follow from this.
From drawing to production mould
Four steps lie between your enquiry and the released production mould.
Feasibility and part analysis
We review your drawing for moulding suitability: wall thickness distribution, draft angles, position of the parting line, gate point. Where sensible, we propose design adjustments – small changes to the part often save considerable tooling cost.
Mould design
Definition of cavity count, gating system, cooling concept and demoulding. You receive the mould design for release before any steel is machined.
Manufacture
Machining, EDM, hardening and assembly of the mould components. Followed by measurement and functional testing of the mould.
Sampling and series release
First shots on our own machines, measurement of the parts, process optimisation. On request with complete sampling documentation. The mould only goes into series production once all dimensions are stably met.
Moulds last longer when someone looks after them
An injection mould is an investment intended to work for years. Wear on guides, sealing faces and ejectors is normal – it only becomes critical when it goes unnoticed and shows up on the part as flash, dimensional deviation or scrap.
We also take on moulds that were not built here. If you would like to relocate an existing series to us, the procedure is described under tool transfer.
- Maintenance and cleaning at defined intervals
- Repair after wear or damage
- Design optimisation of existing moulds, for example to cooling or venting
- Modifications when parts change
- Condition assessment before taking over a third-party mould
Frequently asked questions about mould making
It depends above all on the number of cavities, part size, any slides required, the design as cold or hot runner, and on tolerance and surface requirements. A reliable statement is only possible after reviewing the drawing and knowing the planned annual quantity.
Build time depends on the complexity and size of the mould. In addition to pure manufacturing time come feasibility assessment, design release and sampling. You receive a concrete schedule with the quotation.
That depends on the design. Moulds for prototypes and small series are built differently from production moulds intended to reach several million cycles. Steel grade, hardening, guiding quality and the part material are decisive – glass-fibre reinforced plastics are considerably more abrasive than unreinforced ones.
Yes. We maintain and repair moulds that were not built here, and take over existing moulds together with series production from another manufacturer. The procedure is described under tool transfer.
Yes. Moulds for two components differ from single-component moulds through a second gating system, a transfer mechanism and separately controlled cooling circuits. More on this under two-component tooling.
Yes. In plastics processing, ‘mould’ and ‘tool’ are used interchangeably for the form in which the part is created. ‘Injection mould’ is the more precise term, ‘moulding tool’ the more common one in everyday use.
Send us your drawing
We assess your part for moulding suitability, propose a mould concept and come back with a reliable appraisal of cost and schedule. Drawings and CAD data are treated confidentially. Or give us a call: +49 37342 8760