Processing methods
Tribological Part Production
We provide you finished parts made of ZEDEX® polymers at cost-effective with the optimal process in any quantity. Alternatively, we also produce entirely according to customer requirements.
Machining
The following processes are available for the manufacturing of your products:
CNC Milling
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X-; Y-; Z; 4-axis
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CNC lathe
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X-; Z-; Y-;
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CNC automatic lathe
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Long / short automatic lathe with bar loader and 2-channel control
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Conventional lathe
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Grinding
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Threads
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turn or mill
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Dressing - profiling
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Sawing
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Round
Flat
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Planing with a vacuum table
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Width < 600 mm
Width < 200 mm
Width < 100 mm
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Roughening of adhesive surfaces
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3D printing
3D printing technology (additive manufacturing) has almost no limits in terms of complexity. A wide selection of materials and a wide range of post-processing options now open up new opportunities for you. Thanks to our various self-produced 3D tribofilaments, we know exactly which material is suitable for your project and we would be pleased to advise you on this.
Let us advise you – we have a solution.
Casting
- maximum outer diameter 2000mm
- maximum casting weight 80kg
Injection moulding
- 1-, 2 components
- inserts (e.g. thread inserts)
- item weight 0.5 to 1600 g
- toolmaking
- prototype tools (aluminum)
Contour milling
- maximum thickness 100 mm
- maximum width 600 mm
- tolerances ± 0.05 mm
welding
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Coating - cladding
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Labelling
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Milling grooves
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Bonding
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Post heat treatment
Introduction
The plastic is subjected to a heat treatment, and it will be quoted as annealing.
The annealing target is to reduce the tension and increase the crystallinity of the component. All the ZEDEX® high-performance polymers are anneal treated, in order to reduce the processing-related inner tension.
When the interference-fi t temperature of pressed plain bearing bushes should be increased, two annealing at the operating temperature range are advisable. However, the admissible long-term service temperature can not be exceeded.
When is an annealing process advisable?
In the following cases, we suggest an additional annealing process and / or an intermediate annealing between machining and the final machining:
- when tight tolerances are required
- when an asymmetrical material removal or a big chip removal is required
- with a big walls´ thickness variation on the end products
- when sharp corners and edges must be machined
- when the end product have got a cross-section discontinuity
Realisation of the annealing process
The annealing should take place in a circulating air drying oven. The temperature in the oven follows a ramp function (see fig. 1).
The heating rate is 20°C per hour, whereas the cooling rate 10°C per hour.
Higher heating and cooling rates should be avoided. The holding period depends on the maximum wall thickness of the workpiece and can be taken from the figure 2. The holding temperarture depends on the material and can be taken from the figure 3.
The annealing process is completed, when the final temperature is reached. From this point on, the oven can be turned off. The workpiece should be removed from the oven only when its temperature matches with the room´s one.
Hints regarding the annealing process
An adequate large allowance must be provided before annealing. The use of a support during the annealing process reduces defl ection and deformation. The annealing process could form oxide layers on the surfaces, thus their colour affect. These layers reach, in the semi-finished products, a maximum thickness of 0,2 mm, and, normally, they are removed through machining.
Figure 1
Figure 2
Figure 3
Tensions
Processing (extrusion and injection moulding) induces technologically the chains orientation, generated in the polymers structure.
The plastic structure, after the melding process, starts to solidify in a “forced position”, which causes a strong restoring force and produces an internal tension in the plastic.
Now if additional external stresses are added, e.g. through machining, the overlapping of the internal and external stresses, could overstep the material strength resistance and create tears and even the break of the semi-finished products.
Stress relaxation, warping
Semi-finished and end-products, during a long-term storage, reduce the existing tensions, thanks to the stress relaxation.
Besides, the tensions are reduced because of the warping effect. This can also arise during the use of the end-product.
Through a plastic storage, with a temperature closed to the heat distortion temperature, the chains mobility increases and the stress relaxation accelerates. In this case, the stress relaxation and the associated warping are faster and more intensive.
If the semi-finished products are subjected to a annealing process, the warping is partially anticipated.
Degree of crystallinity
Semi-crystalline polymers have the tendency to crystallize partially. At the end of the annealing process, the material cross-section crystallinity is not uniform.
In the same way, there are differences about the degree of crystallinity of thick-walled and thin-walled semi-finished products.
Through a following warm-up of the semi-fi nished products, over the cold crystallization temperature, and a slow cooling, the degree of crystallinity increases and reaches a homogeneous level.
However, this cold crystallization doesn’t reach a high degree of crystallinity as a slow cooling directly after the melting process.
The semi-finished products, through the cold and post-crystallization, are subjected to a warping and to a change of the following properties:
- lower elongation at break
- higher density
- higher stiffness
- higher strength
- higher chemical resistance
- higher permeability
- higher wear resistance due to sliding friction
- higher PV-value
- higher thermal conductivity
- higher melt temperature
- increasing of the interference fit temperature for pressed-fit plain bearing bushes (twice annealing at operating temperature range necessary).
Execution of the tempering process
Prior to delivery, ZEDEX® engineering & high-performance semi-finished products have already undergone a post-heat treatment.
Beacuse of that, with an additional annealing process, the user can only archive a small increase in the degree of crystallinity.
Please contact us if a higher degree of crystallization is required.
