Tolerances:
* In order to be able to produce round caps made of soft PVC reliably, we require minimum wall thicknesses of 1.7 to 2.0 mm, depending on the inner length.
The use of dipped round caps to protect anchor bolts, threaded rods and fastening screws during the construction, repowering and dismantling of wind turbines offers two major advantages.
The production of round protective caps using the dip moulding process is economically very interesting. In contrast to injection moulding, only simple and therefore inexpensive dipping tools are required for production. The dipping moulds are heated in an oven and dipped into a bath of liquid PVC. When the hot moulding tool comes into contact with the PVC paste, also known as plastisol, a thin skin initially forms on the outer contour of the round cores, which develops into the desired wall thickness of the round caps by the end of a defined dwell time in the dipping bath.
The wall thickness to be achieved depends on the temperature of the mould, the dwell time of the mould in the dip tank and the viscosity of the PVC material. The minimum wall thickness required depends on the internal length of the cap, which in turn is controlled by the immersion depth of the mould cores.
After removing the dipping mould from the dipping bath, the excess PVC material runs and drips off, whereby flow marks and drop formation at the closed end of the rectangular caps cannot be avoided.
The multi-cavity mould with the PVC layer is then heated again to achieve the rubber-elastic properties of the PVC material. This work step is often referred to as gelling.
After cooling, the round caps are manually removed from the cores using an auxiliary tool.
Our PVC dipped parts are manufactured with a salt-free heat transfer system - completely without lithium nitrate or potassium nitrate - for Maximum purity and safety. The result is particularly clean, dimensionally stable and durable PVC dipped parts and PVC coatings that meet the highest quality requirements - manufactured in an environmentally friendly way, with improved occupational safety and easier disposal.
The standard soft PVC used by HAMCO from the Covytec® 3841, which will be used primarily for processing, has a Shore A hardness of 85, offering a good combination of dimensional stability and damping properties, and, in black, exhibits good resistance to UV radiation and weathering.
The phthalate-free and F&DA-compliant formulations of Covytec® 9977 BIO 68 Shore A and Covytec® 1649 BIO with a Shore A hardness of 82 also permit the import and Use of round caps in the US market.
The Wall thickness is measured non-destructively at the open end of the cap. Due to the process, it increases continuously towards the closed end of the immersed caps. Drain marks and drain drops At the closed end, they cannot be completely avoided due to the nature of the process.
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| Inside Ø [mm] | Standard height H [mm] | Height H min. [mm] | Height H max. [mm] | |
|---|---|---|---|---|
| RD - Cap | 30 | 50 | 35 | 580 |
| RD - Cap | 32 | 50 | 35 | 420 |
| RD - Cap | 33 | 50 | 35 | 400 |
| RD - Cap | 35 | 50 | 35 | 500 |
| RD - Cap | 36 | 50 | 35 | 350 |
| RD - Cap | 38 | 50 | 35 | 400 |
| RD - Cap | 39 | 50 | 35 | 400 |
| RD - Cap | 40 | 50 | 35 | 350 |
| RD - Cap | 41 | 50 | 35 | 350 |
| RD - Cap | 42 | 50 | 35 | 520 |
| RD - Cap | 45 | 50 | 35 | 500 |
| RD - Cap | 48 | 50 | 35 | 310 |
| RD - Cap | 49 | 50 | 35 | 400 |
| RD - Cap | 51 | 50 | 35 | 400 |
The minimum and maximum wall thicknesses that can be achieved depend, in particular, on the thermal energy stored in the metal immersion cores heated in the furnace and the components to be coated, the dwell time of the metal cores and components as they are immersed and cool down in the immersion tank, and the geometry and viscosity of the PVC material.
Generally speaking, thicker insert cores – for example, round insert cores with larger diameters used in the manufacture of round caps – also allow for greater wall thicknesses to be achieved. To protect screw connections, Round caps for the construction of wind turbines manufactured, for example, with a length of 400 mm and a wall thickness of 4.5 mm.
When coating components with geometries that are sometimes complex, the wall thicknesses of the coating must be determined through practical trials.
To ensure that the dip-moulded parts can be easily removed from the differently shaped mould cores after the gelation process, they must have a sufficient minimum wall thickness. If the wall thickness is too small, the dip-moulded part may become deformed or turn inside out during demoulding.
The required minimum wall thickness depends on the specific geometry of the die-cast part. We therefore specify the technically necessary minimum wall thickness in our quotations.
Depending on the geometry of the part being dipped, the dipping cores are immersed in and removed from the dipping tank at different speeds and to different depths.
If the immersion core remains in the immersion tank for too short a time, the resulting PVC layer will be too thin to allow the part to be demoulded subsequently without deformation and in a process-reliable manner. In such cases, the dwell time is increased to ensure a sufficiently thick wall.
The wall thickness of our dip-moulded parts is measured non-destructively at the open end of the component. To do this, we use a calliper whose measuring jaws make only light contact with the inner and outer surfaces of the soft PVC part. This method provides reliable results and is entirely sufficient for dip-moulded parts. Compared with injection-moulded parts, the wall thicknesses are designed with a comparatively generous tolerance of ± 0.2 mm. As the requirements for dimensional accuracy are generally less stringent, this measurement method enables reliable and practical quality control.
No. Neither the PVC dip moulding process nor PVC dip coating allows for a completely uniform wall thickness to be achieved along the entire length of a product.
The wall thickness is influenced by various factors, including the dwell time of the dip-moulded part or the component to be coated in the plastisol, the thermal energy stored in the mould or component, the geometry of the dip-moulded part or component, and the viscosity of the soft PVC used.
Generally speaking, the greatest wall thickness occurs where the heated dip core or component first comes into contact with the plastisol. This area remains in the dip tank for the longest time during the dipping process, allowing the thickest layer of PVC to build up there.
In the case of a simple cylindrical cap, the wall thickness is therefore greatest at the closed end and decreases gradually towards the open end.
As the coating is built up predominantly through the thermal energy stored in the dip core or the component to be coated, and as the PVC layer that has already formed acts as a thermal insulator, there are physical limits to the wall thickness that can be achieved. Minor variations in wall thickness are therefore inherent to the process and cannot be avoided from a technical point of view.
Large and small quantity requirements Direct processing
Large and small quantity requirements
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