Technology

In addition to the design of the actual product, our designers are also entrusted with the development of the plastic injection mould. However, there is never just one mould; there are always at least three of them - for the case, the cap and the plug.
Some technologies that serve the production of press injection moulds.

• 5-axis CNC SPINNER 1020 machining centre
  This piece of equipment machines components along five axes. Thus, 3D components may be produced. Moreover, the equipment is used to produce the dies for more complex designs. It is also applied in precision machining of the holes for mandrels, dies, pins and other auxiliary openings. The machine operates within a CNC programme. The team creates a programme based on the supplied drawing documentation and the equipment machines the required part on its own. The machine has a supply of tools, from which it chooses those required for the programme to be completed. The completed part is produced to an accuracy of 0.05 mm.
• 3-axis CNC MIKRON UM 600 machining centre
  This piece of equipment is used for machining parts along three axes. It is used in the production of simpler parts within the CNC programme. The chief function of the machine involves precision drilling of holes for mandrels, dies, pins and other auxiliary openings. The team creates a programme based on the supplied drawing documentation and the equipment machines the required part on its own. The machine has a supply of tools, from which it chooses those required for the programme to be completed. The completed part is produced to an accuracy of 0.05 mm.
• MAKINO EDNC 43S electro-erosion machine
  The electro-erosion machine operates via an electrical discharge between an electrode, which is made of copper, and the machined material, which must be conductive (steel, brass, aluminium, etc.). Both the electrode and the machined material are submerged in a conductive bath - electrolyte. Electro-erosion machines are used in the production of more complex parts in quenched material, where the advantage lies in the fact that the final shape is machined using an electrode and subsequently replicated, through sparking, in the machined material. Sparking may be used to produce more complex shapes which cannot be produced using traditional machining. The completed part is produced to an accuracy of 0.001 mm.
• 3D MITUTOYO CRYSTA PLUS M manual coordinate measuring machine
  The 3D coordinate measuring machine checks for production deviations that may evolve as a result of tool wear, machine inaccuracy or operator fault. The purpose is to check for any faults before the machined part is subjected to any further operations or a defective part is installed in the injection mould, where the defect could only be established during production in the injection mould. It is possible to measure, using a touch probe, the 3D shapes of all complex parts or the spacing of the drilled holes for the injection mould, where the measurement accuracy is 0.001 mm.

The production process begins with the pressing of plastic parts. We use presses from two renowned manufacturers. The machines supplied by the Austrian Engel Company are used for simpler moulds which do not require bar guidance. The most complex moulds are installed on Arburg presses. As part of cost streamlining, the heating bodies of all presses have been thermally insulated in recent years with special blankets and automatic handlers have gradually been installed on all machines, capable of instantaneously cutting off the inflow once the mould is opened. A dual injection Engel press is used in the production of two-colour parts, with two inlets for the most complex moulds.
We mainly use polypropylene as the injection material. Polystyrene and polycarbonate are also used to a lesser extent. Our pressing shop can process 10 tons of granulation product a day. Material savings are boosted by a regranulation line capable of processing the waste generated by the previous production steps in order to prepare new granulation product.

Inks are prepared in an ink shop divided into two sections – water-based and spirit-based. Most inks are produced to our own recipes. We formulate them using a special technological apparatus consisting of 2 superimposed glass bowls and stirrers. The required raw materials are fed into the upper bowl and heated to a certain temperature, which depends on the type of ink concerned, while stirred continuously. Based on the sedimentation principle, the entire content gradually moves from the upper to the lower bowl. From there, the ink is already filled into transport bottles and taken away to the assembly machines.

Customers nowadays demand ever more information on products. And we can provide them with such information using printed cases.
We use two printing technologies - screen printing and transfer foils

Template (screen) manufacture
The template consists of an aluminium frame and a screen printing fabric stuck over it. The fabric is made of polyester fibres, with a density of roughly 140 to 165 fibres per cm.
Before sticking them onto the frame, the screens must be stretched on a stretching frame. It is important that the screen is adequately stretched as this may affect the resultant quality of the print.
After that, a light-sensitive emulsion is applied to the bottom part of the screen and left to dry in the dark. A film extract (a film displaying a graphic design - text, drawing, photograph) is attached to the screen in a vacuum frame, followed by light exposure at a set wavelength. The emulsion is hardened around the drawing. The emulsion is washed away from the places that remain unexposed, thus making the screen passable.


Screen printing
The screen printing principle involves pushing UV inks through the passable parts of the template with a spatula onto the object to be printed, in this case the marker case.
In order for the printing paint to adhere well, the surface of the case to be printed must first be flamed. This activates the case surface.

Along with the template, the spatula is one of the parts that affects the resultant print quality. As the spatula passes across the layered screen, the printing ink is pushed through onto the surface of the case to be printed. In order to make the transfer perfect, the straightness and sharpness of the edge of the spatula needs to be ensured. If that is not the case, the transferred print ink layer formed will not be uniform and the printing will not be of the required quality. Only after that may the selected design be printed on the case with subsequent drying of the UV ink applied. The very term implies that the inks need to be hardened in a UV tunnel as opposed to being simply left exposed to ambient air. In the tunnel, a lamp is used to generate light of the required UV spectrum type. In addition to the wavelength, the other parameter factoring in the adequate hardening of the ink is the quality of the energy with which the hardening takes place.

Transfer foil
Heat transfer printing technology is based on transferring a graphic design from a carrier foil to the surface of the case using a silicone punch heated to a high temperature.
The required graphic design is imprinted on a special polyethylene carrier foil.
The cases to be printed are moved under the silicone roller station using mandrels. The roller is heated to approx. 240°C and revolves around its own axis. In this graphic design transfer, the entire surface must be subjected to the same pressure and temperature so that quality adhesion is ensured across the entire case surface.
In the actual application, the layer with the printed design dissolves due to the effects of the heat and pressure and the graphic design "bonds" with the substrate material to be printed.
The advantage of the transfer foil print compared to traditional screen printing is its greater attractiveness for potential customers. CMYK system-based full colour printing is possible using the transfer foil. Screen printing can only be used for monochromatic prints.

Fibre tips are manufactured in four technological steps.

• In the first step, the fibre strand is produced. Individual polyester fibres unwind from a spool precisely positioned on a reel. As they pass through a special winding machine, the fibres are clustered and tightened.
• In the next step, the strand is impregnated in a special adhesive, whose main constituent is resin dissolved in acetone, and subsequently furnace-hardened at a temperature of up to 300°C. At the same time, it is calibrated so that the required dimension and quality are achieved. During the entire operation, a great deal of emphasis is placed on the environmental aspect of the production. The releasing acetone is instantaneously combusted, a process which respects all environmental standards.
• In the third step, the strand is ground, using special mills, to the required diameter with a accuracy of 0.1 mm. Here, too, caution is exercised to make sure the dust resulting from the grinding process is disposed of in an environmental manner.
• In the last step, the strand is cut to the required length and ground to the proper shape. The grinding may be a wet (under water) or dry process. The tips produced are then deprived of any impurities and static discharges, washed, sorted and inspected.

The technology is unique. Centropen is the sole producer of fibre tips in Eastern Europe.

Tampons are produced on a special custom-built line which integrates all the technological operations into one unit.
The endless polyester strand is stretched between rolls and thus loosened. Once it contracts back, the required volume and structure form.
The already adjusted strand then enters the extruder nozzle, where it is coated with a polypropylene film. The coated strand is instantaneously cooled down and, at the same time, pressure-calibrated under water to the specified diameter. Then the strand is cut to the tampon length.
Once checked by the machine operator, the tampons are automatically placed in plastic boxes.

The assembly process is already fully automated. The attendants place the components in dedicated boxes and then simply oversee the correct operation. The machine first picks up the case, observing its proper orientation. Then the tipper, tip, tampon filled with injected ink, stopper, welded in for safety reasons, and, lastly, the cap are added. For certain untypical shapes, customised machines must be used.

The markers produced by Centropen are packed into several types of packaging.

• The first option involves paper boxes. If that is the case, the process is automated. The machine is capable of putting the box together, inserting the products into it, closing and sealing it.
• Another option involves packing them in shaped containers. In this way, mainly colour markers for children are packed. The boxes are fully transparent , which highlights the broad colour palette of the markers.
• The third option involves blistering cards, which are nowadays required mainly by small customers. This packing method is somewhat more laborious. However, it is more convenient for customers, who can see the entire product as well as all the information about it in the shop.
• The fourth packing option is shaped etues. They are used as commercial packaging for three- and four-colour sets of mainly office products. The markers must be packed manually. The production, however, takes place in a robotised worksite.
• The last packing variant for writing utensils is placing them manually in on-counter retail racks. This method is mostly preferred for products that have their own strong image, well known by customers. The best example is the Tornado children's school roller.

Due to the marked seasonal effects of sales, having a large capacity warehouse is a must. Large pallet-spot capacity also facilitates production planning and logistics processes.