Production processes 30

In this section we discuss the production processes of the Installation department. These processes are more or less similar to the processes of other departments. Therefore, we only discuss the Installation department. The specifications of the finished product determine the route and sequence of processes. The basic route for each process is identical. The products that need to be processed are either raw material that arrives from the wire drawing department or semi-finished products that arrive from or go to other departments. Figure 3.3 shows the layout of the production department. As Figure 3.3 shows, the production department is organised in such a way that the basic products are produced in a line (the blue line in Figure 3.3). Producing in a line reduces transporting costs and makes the production department more controllable. Figure 3.3 shows the 3 most used production routes. The blue route is the most basic route; the product is isolated, stranded, and then provided with an outer sheath. The red route includes a braided protection layer and the black route includes an inner sheath and a braided layer as well, after which it is provided with an outer sheath as well. In this section we discuss each of the processing steps in order to understand the trade-offs the scheduler makes when creating a production schedule. We start with the wire department, and even though it falls outside the scope of this research, to form a complete picture of the production process it is necessary to address this part of the production process as well. Sheathing machines Braiding machines Armoring machine Stranding machines Isolation machines 4 5 3 Drumtwister 3 Samenslag 3 5 6 4 24-7 1 24-8 24-6 36-2 24-5 24-4 36-1 24-3 24-2 24-1 Inte_rme diate _sto ck p_oint

Intermediate stock point Intermediate stock point

To: Inspection From:

Wire drawing

Insulation – stranding – outer sheath

Insulation – stranding – inner sheath – braiding – outer sheath

Insulation – stranding – inner sheath – armouring – outer

sheath Inte rme diate _sto ck p oint

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The wire drawing department draws wires to reduce the diameter of the core cable. The raw material TKF receives is 8mm thick copper. An 8 mm diameter copper cable is too rigid to be processed at the Installation department. To provide a large number of possibilities regarding the diameter, the cable has to be drawn to a smaller diameter. The wire drawing department consists of three machines: groftrek, middeltrek, and fijntrek. Wire drawing is a metalworking process in which wires are pulled through a series of dies (In Dutch: Matrijzen). Each die has a higher rotation speed than its predecessor whereby the cable is pulled, resulting in a longer and therefore thinner copper cable. Figure 3.4 shows an example of a few dies where a wire is pulled through.

The first processing machine, groftrek, is capable of reducing the diameter from 8.0mm to 3.0mm and anything in between. If a smaller diameter is required, the copper cable needs to be processed at middeltrek that can reduce the diameter from 3.0mm to 1.5mm and anything between. The copper cable needs to be processed at

fijntrek in order to reduce the diameter to anything below 1.5mm. The cores used at the several departments can either be solid or stranded copper. A solid core means that it consists of one drawn cable, where a stranded core consists of several stranded thinner cores. The main differences between these two types of copper cores are that a stranded cable is much more flexible in terms of bending and when diameters larger than 8.0mm are required a massive core is not possible. Having a wire drawing department is unique in the cable industry, providing TKF a competitive advantage. TKF produces a low volume & high variety product mix, resulting in a demand for a wide range of product diameters and making forecasting really difficult. Having a wire drawing department results in lower inventory of copper,

easier to provide unique diameters to the customer, and reduces the lead times because there is no vendor involved.

The insulationmachines apply a plastic insulation layer around the core wire. This insulation layer usually consists of polyethylene (PE) or XLPE because these materials are flexible, tough, and recyclable. Solid PE/XLPE in an extruder is heated to make it liquid. The core wire is pulled through the extruder that applies the PE, after which the cable is cooled down to solidify the PE before it is wound on a reel (Figure 3.5). For the end-user it is important to know which core to connect to for example an outlet or machine. To make each individual core identifiable, the colours of the plastic layer differ as Figure 3.4 shows. Only one colour of core cable can be processed simultaneously due

Figure 3.4: The wire drawing process

Figure 3.5: Various insulation cables

- 32 - to the fact that the extruder can apply only one colour at a time. To change the colour of the PE, the extruder needs to be cleaned.

Currently, TKF owns 3 insulation machines. Each machine has different characteristics, making them suitable for different products. Insulation machine 3 can only process 1,5mm² and 2,5mm² stranded cores and 1,5mm², 2,5mm², 4mm², and 6mm² massive cores. Insulation machine 4 can process stranded, as well as massive cores, with a diameter larger than 10mm². The last machine, insulation machine 5, can process stranded, as well as massive cores, with a diameter smaller than 10mm². These machine characteristics increase the difficulty of planning. For each of the insulation machines, preference is given to produce products in a sequence where the intensity of colours is either decreasing or increasing. For example, when an order consists out of a grey, black, red, and brown core, the preferred preference is black, grey, brown, and finally red. This particular production sequence leads to the shortest setup times since the time to clean the extruder increases when the intensity of colours differs too much.

The stranding machines combine several core cables by stranding (samenslaan) them around each other to make it a solid whole and appropriate for further processing. The reel with finished (processed) cables is rotating, see Figure 3.7, causing the cables to wrap around each other at the process shown in Figure 3.8. This is necessary since finished products rarely consist of a single core cable. Currently, TKF has two machines to process these cables: the drumtwister and samenslag. The drumtwister is meant for stranding cables with a diameter above 6mm, when more than 8 cores need to be combined, or when a fill cable needs to be added. The samenslag processes the remaining cables (that have: a diameter below 6mm, less than 8 cores, and no fill cable). If required, the drumtwister is capable of processing products that usually are processed at the samenslag. However, vice versa this does not hold.

Figure 3.6: The insulation process

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The braiding machines braid thin copper or thin steel wires around the cable to protect it from external forces such as a shovel or crane. It is the first of two protection possibilities for cables. A stranded cable, as well as a sheathed cable (see below) can be provided with a protection layer. Small coils, with thin copper or steel, spin around the cable in different directions providing an as high as possible coverage. Figure 3.9 shows the braiding process. The coils are on the bottom of the figure, rotating quickly while moving up and down. The unprotected cable is pulled through vertically. Due to the rotating of the coils and the vertical movement, a thin layer of copper or iron is braided around the

cable. Currently, demand in the navy and marine industry is increasing, resulting in an increasing demand in braided cables. To process this demand, TKF owns 10 braiding machines. Just as with the insulation and stranding machines, the machines differ from each other. 6 of the braiding machines are capable of braiding both a copper and iron protection layer, while 4 are capable of only braiding an iron protection layer.

Armouring is the second protection possibility is to provide the cable with a wrapped thin sheet of iron as protection layer. For armouring, TKF has two material options: a round or flat wire. A drawback of armouring is that it makes the cable less flexible compared to braiding. Figure 3.10 shows an example of an armoured cable. The protection layer is merely wound around the cable.

Sheathing is the final step of the production process. The sheathing process is comparable to the insulation process (Figure 3.11) only the options for sheathing material are PVC and XMBH. Sheaths usually are grey or black, while insulation has multiple colour options. The sheathing machines are also used to provide cables with an inner sheath. TKF owns 3 sheathing machines that have different characteristics (Sheathing machine 4, 5, and 6). Sheathing machine 4 can only apply an outer sheath of both PVC and Xmbh. Sheathing machine 5 can both apply an inner sheath as well as an outer sheath. However, this machine can only process PVC. Sheathing machine 6 can both apply an inner sheath as well as an outer sheath, but contrary to machine 5, it can only process Xmbh.

Figure 3.9: The braiding process

Figure 3.11: The sheathing process

- 34 - After each production process, cables are wound on reels to make it suitable for further processing and for transportation purposes. However, the thickness of the isolated core cables determines the number of kilometres that can be wound on a reel. Obviously, the thicker a cable is the less capacity the reel has. At other production processes, factors as whether the core cable is hammered or massive, the number of cores stranded together, and the thickness of the armour and sheath influence the reel capacity. Table 3.2 provides the

capacity for the most common product types after the insulation process. At the insulation production department, each reel can only hold cables of the same colour and diameter due to the fact that at the subsequent station each individual colour is stranded around each other. Especially at the insulation process it is important to produce full reels because the time to replace a full reel with an empty one takes, compared to the production time, relatively long.