In the dip-moulding process, flexible plastic parts are produced by immersing a suitably shaped and preheated dip mould into liquid PVC plastisol. Unlike in injection moulding, the component is not formed by injecting molten plastic into a closed mould. Instead, the wall of the dip-moulded part is formed as a layer of plastisol builds up on the heated surface of the dip mould.
Depending on the type of Covytec® used, a plastisol with the appropriate formulation is processed. On the Overview page for Covytec® models You can view the available material types and download the relevant material data sheet directly.
The dipping core is responsible for shaping the resulting dipped part. Its geometry corresponds to the internal contour of the finished component. Before dipping, the dipping mould – which, depending on the design, consists of several dipping cores – is heated to a specified temperature in a furnace. The dipping cores are then dipped into the liquid plastisol.
Once the dipping mandrel has been removed, a viscous layer of plastisol initially remains on the surface. Excess material runs off the dipping mandrel. The amount of material remaining on the dipping mandrel determines the subsequent wall thickness of the dipped part.
Even whilst in contact with the hot dipping core, the PVC particles contained in the plastisol absorb the liquid plasticiser. This results in the formation of a viscous mass which adheres to the mould surface and does not yet possess the final properties of the finished soft PVC.
Once it has been removed from the bath, the dipping tool is returned to the oven. Further heating at slightly lower temperatures continues the gelation process that began in the plastisol bath. During this process, the remaining liquid components evaporate from the material, and the rubber-like elastic properties typical of soft PVC develop. At the same time, the material shrinks further.
Following this final heat treatment, the finished moulded part is removed from the mould core. The mould core is then available again for the next production cycle.
In simple terms, the process can be understood as the interplay between form, heat and material:
The dip core determines the geometry and provides the heat required for the formation and initial gelation of the PVC layer. The geometry and temperature of the dip core, the properties of the plastisol and the duration of immersion all influence the wall thickness, material distribution and surface finish.
A distinctive feature of the dip-coating process is that the wall thickness is not usually completely uniform across the entire dipped component. Depending on the geometry, the material thickness may vary within the component.
In a typical dipped round cap, the wall at the closed end is thicker than at the open end. The area that first comes into contact with the plastisol during dipping has the greatest wall thickness.
The wall thickness of a dip-coated part is largely determined by the heat transfer from the dip core to the plastisol. As the thickness of the adhering material layer increases, so does its heat-insulating effect. Consequently, less heat reaches the outer areas of the plastisol and the further build-up of the layer slows down.
The temperature of the dip core also changes during the dipping process. As more heat is transferred to the plastisol, less heat is available for the subsequent build-up of material.
In addition to these thermal factors, the viscosity of the plastisol, the dwell time of the dipping core in the plastisol and the geometry of the dipping core also influence the resulting wall thickness. Furthermore, after the dipping process, material that has not yet fully gelled may drain off and thereby shift within the mould.
The actual wall thickness that results is therefore the outcome of the interplay of various factors and cannot be considered in isolation from the specific component geometry.
Find out more:
We have set out in the FAQ on wall thickness and geometry of dip-moulded parts explained in detail.
The immersion core gives the immersed part its internal geometry whilst also providing the heat required for the formation and initial gelation of the PVC layer. Its surface forms the internal contour of the finished component.
The design of the dip mould depends on the desired component geometry. This allows for the production of components with varying diameters, lengths, radii and steps. At the same time, the specific characteristics of the dip moulding process must be taken into account, in particular the distribution of material and subsequent demoulding.
The surface of the immersion core may also be transferred to the internal contour of the finished immersion part.
Like any manufacturing process, the dip-moulding process also has its technical limitations. These arise in particular from the continuous build-up of the material, the drainage of excess plastisol and the subsequent demoulding.
It is not usually possible to achieve a perfectly uniform wall thickness across the entire component geometry. The wall thickness may vary within the component, depending on its geometry. Furthermore, the material may be distributed differently at edges, tips, radii, corners or steps than on straight surfaces.
Even after the mould has been removed, the layer of material has not yet fully set. Excess plastisol may run off or shift within the mould. This can result, for example, in material build-up, drips or flow marks. Whether these phenomena are significant depends on the functional and aesthetic requirements of the component in question.
Another limitation arises from the demoulding process. The finished moulded part must be able to be separated from the mould core. Consequently, certain geometries – particularly undercuts – can complicate the manufacturing process or require additional design solutions.
These specific features form an integral part of the submersion process and must be taken into account from the outset when designing a submersible component.
Further information on wall thickness, material distribution, surface appearance and demoulding can be found in our FAQs on the dip-moulding process.
As well as enabling shaping, the dip-moulding process also offers flexibility in terms of the properties and design of the finished dip-moulded parts.
By using different soft PVC formulations, it is possible to achieve varying degrees of hardness and, consequently, different levels of flexibility and dimensional stability. Depending on the application, properties such as grip, shock absorption, abrasion resistance or electrical insulation may also be key considerations.
Dipped parts also offer a wide range of options when it comes to colour schemes. The desired colour can be freely selected from the available standard colours. Depending on the application, factors such as colour-coding or health and safety requirements can be taken into account. Special colours are also available.
Diving equipment with sufficiently large and easily accessible printing areas can also be printed on, for example with logos, markings or other information. The specific printability depends on the shape and size of the intended printing area.
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You make your enquiry and we clarify the details. If necessary, our experts will advise you or show you alternatives.
HAMCO will prepare your quotation within 24 hours of defining your requirements.
After your approval, we build the customised tool for your component
We can create a product sample for you on request
After approval of the sample, we go into series production
The goods are packed and handed over to the forwarding agent
You will receive the goods within 14 days of ordering.
Whether the dip-coating process is the right solution for a bespoke component depends on the specific application and the technical requirements. Geometry, function, material properties, stress conditions and production volume must all be considered together.
HAMCO provides support in selecting and designing the right solution – from standard immersion parts to bespoke manufacturing based on drawings, samples or technical specifications.
What is crucial here is not the process alone, but the interplay between the requirements, the component and the manufacturing process.
To find out which standard dip-moulded parts HAMCO offers and which bespoke dip-moulded parts can be manufactured to your drawings, samples or technical specifications, please visit our Product page: Diving equipment.
You now know how the PVC dip-coating process works. The key question for your component, however, is: is producing it as a dip-coated part really the right solution for your application?
You can find out which standard HAMCO models we offer and which customised immersion parts can be manufactured to your drawings, samples or technical specifications on our services page Immersion parts.
Large and small quantity requirements Direct processing
Large and small quantity requirements
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