Molding of plastics

Injection molding (injection of thermoplastics) is an activity, when injection molds are placed in injection pressses and plastic products are made. The main advantage is possibility to produce high volume series with a high degree of accuracy (in dimensions, characteristics, colour, etc.).

machinery and equipment

Spojené kartáčovny currently operate 46 1-component injection presses with clamping force from 10 to 720 tons and 8 2-component injection presses with clamping force in the range of 180 - 720 tons. Weight of produced moldings ranges from 5 to 3,100 gr., and in case of 2-component products the second component´s weight may range from 12 to 300 gr. (2-component product may weigh between 17 and 3,400 gr. ).

Presses are used for production under our own brand SPOKAR (plastic handles for brushes, toothbrushes, buckets, etc.) and also for production under brands of our business partners.

Injection presses according to tonnage:

However, these parameters does not limit our company. If it is necessary, thanks to our stable position and financial background, we are able to ensure further production technologies, which will help us to ensure manufacturing conditions for other projects.

Brands of operated injection presses:

Engel, Negri Bossi, Battenfeld

Processed materials:

Among currently processed materials there can be found in particular PP homo and copo, PS, ABS, MABS, PES, PC, TPE (multi-component injection). These materials are prepared for further processing with the assistance of our trained workers, who, on the basis of recipes compiled in advance, ensure accurate dosage, or we also apply appropriate dosage of materials directly to injection presses while using volumetric units and mixers, or we prepare materials on the basis of gravimetric units, which ensure the most precise dosage in terms of procentual representation of particular components in the dosing material.

Annual material consumption is around 4,500 tonnes

Removing plastic parts:

Handling of plastic parts is ensured in order to achieve higher production efficiency while using robots, or fully robotized workplaces, where appropriate. In terms of resolution and extent of the number of axis, the company operates both, linear robots located directly in the area of the injection press, and 6-axis robots standing outside the area of the injection press.

Linear robots:

Engel (Austria), Sytrama (Italy),Yudo (South Korea).

Preferred brands of 6-axis robots:

Fanuc (Japan), Kuka (Germany).

Robotized workplace

Robotized workplace located in the vicinity of presses are intended to provide subsequent operations leading toward finalisation of the product. These operations include product labeling, laser marking, completion of products with other plastic parts, stacking and cardboard packaging.

description of particular steps taken during injection pressing

1. Basic material, in this case it is plastic granulate for injection pressing, is sucked from the transport packaging, or from designated containers, by so-called intake plenum, and it is extracted into the hopper located in the upper part of the injection press.

2. In case that it is necessary to enrich the raw material with a dye (or colour) for further processing (lubricant, blowing agent, etc.), it will be necessary to place so-called volumetric unit with active mixer under the orifice of the hopper. These additional units will ensure accurate dosing of additional components within the range of several percent. The mixer ensures adequate mixing, which facilitates subsequent homogenization of injected materials inside the plasticizing chamber of the press.

3. After mixing processed materials in the mixer, the material is removed through the bottom orifice of the mixer by so-called screw, which is located in plasticizing chamber of the press. In the plasticizing chamber, the material is melted heating belts, and that is proceeded at high temperatures exceeding for example 230 °C in case of homo-polypropylene.

4. When the melt is homogenized by a very slow rotation of the screw, the molten plastic is injected into the mold at high pressure.

5. After injection of plastic into the mold, it is necessary to stabilise the plastic and cool and stabilize the injected product by means of the cooling system of the mold.

6. After stabilisation of the shape, the product is removed from the open mold and whole cycle of injection repeats as soon as the mold is closed again.

molds

Our company currently operates in its mold stock almost 300 our own forms, eventually there are some forms owned by our business partners. These are forms mostly made in the workshop of Spojené kartáčovny a.s., and in terms of needs of individual projects they are fitted with hydraulic, or eventually pneumatic, core movers, lockable nozzles, ironing nozzles, heat systems, etc.