EP1472074A1

EP1472074A1 - Method for producing a plastification system that comprises wear-protecting layers varying across its axial length

Info

Publication number: EP1472074A1
Application number: EP02787941A
Authority: EP
Inventors: Paul-Eberhard Kortmann; Bernhard PÖLTL
Original assignee: Mannesmann Plastics Machinery GmbH
Current assignee: Mannesmann Plastics Machinery GmbH
Priority date: 2001-12-14
Filing date: 2002-12-12
Publication date: 2004-11-03
Also published as: WO2003051610A1; DE10161363A1

Abstract

The invention relates to a method for producing a plastification system that comprises a wear-protecting coating (6, 8) with wear-protection properties that vary across the axial length. Said wear-protecting coating is applied to the surface of plastification, mixing or conveying screws and/or to the interior surfaces of plastification cylinders (7) of plastics processing machines. According to the invention, a strip (1), containing a coating material, is applied to the surface of the plastification, mixing or conveying screws and/or to the interior surfaces of plastification cylinders (7). Said strip varies in kind or composition in different axial sections of the plastification, mixing or conveying screws and/or to the interior surfaces of plastification cylinders (7), adapted to the kind of wear prevailing in the respective axial sections. The strip (1) is then thermally treated so that a wear-protected surface is obtained.

Description

Process for the production of a plasticizing system with wear protection layers varying over its axial length

description

The invention relates to a method for producing a wear-protected plasticizing or compounding system according to the preamble of claim 1.

In a plasticizing or compounding system for plastic machines, solid plastic raw material is drawn in in a feed zone. This is conveyed and mixed by a snail. In a melting area, the dissipated energy melts the plastic material with additional temperature control. Two different types of wear occur in the feed zone and the melting area. Abrasive wear prevails in the feed zone and corrosive wear in the melting area. The plastic is still solid in the feed zone. It is therefore also called the solid zone. Here, in the screw channel and on the free inner wall of the plasticizing cylinder, predominantly grain sliding wear occurs with the characteristic abrasive wear damage. The active flank on the screw flight, ie the flank of the screw flight pointing in the direction of conveyance, is most stressed by the high pressures occurring there. The processing of plastic material with inorganic color pigment can lead to considerable signs of abrasion wear in this zone, in particular under the high pressures occurring in the feed zone, which has a positive effect on conveying. The wear and tear is decisively influenced by the pigment hardness and concentration. Serious signs of wear occur in the solid zone on injection molding machines when processing filler-containing plastic masses and, to an even greater extent, on single-screw and twin-screw extruders when compounding and extruding filled masses. With increasing ^{'Atifschmelzen} the plastic mass the natural mobility of the pigment or filler is increased, until they can move freely. The pigment or filler particles can then roll off. All wear will then decrease. In the melting area there is a transition from grain sliding wear to rinsing wear, ie grooving wear or erosion. Erosion corrosion is gaining importance in the melt area. Due to the high processing temperatures in the plastic machines, the molecular chains are partially broken. The resulting degradation products have a corrosive effect on the plastic machines. But the plastic itself can also attack the plastic machines. During the melting of the plastic emerging additives such. B. Flame retardants can also be corrosive. Are corrosive contaminants such as water, carbon dioxide, chlorine gas, hydrogen halide, acid residues and electrolyte solutions.

EP 0801 690 B1 discloses a method for producing a wear protection coating on the surface of plasticizing screws for injection molding machines, in which a metallic, hard metal or ceramic material is applied by means of a spray jet using the high-speed flame spraying method. A disadvantage of this coating of plasticizing screws for injection molding machines is that it can only be optimized for a certain type of wear. Adaptation to differently stressed areas with different spray materials is difficult. Another disadvantage of the high-speed flame spraying process is that the process is expensive and lengthy, that only a comparatively simple geometry can be coated and that the coating is sensitive to impact or shock.

From DE 3943 344 C1 it is known to provide a plasticizing screw with a wear protection layer by winding a winding tape consisting of a wear-resistant metallic material on the top of the web of the screw webs and fastening it there. In this way, a wear protection layer with uniform properties is created over the entire length of the screw flights. Optimization is only possible with regard to a certain type of wear.

From EP 1 029 629 A1 and EP 1 048 920 A1 it is known to provide the inside of tubular workpieces with a wear protection layer by applying the layer material in a band shape to the inner surface of the tubular workpiece and then treating it thermally. Here too, a uniform wear protection layer is produced, which can only be optimized with regard to a specific type of wear.

In order to be able to take into account the various types of wear described at different points on the plasticizing screw and in the plasticizing cylinder and to provide surface areas adapted to them, it is proposed in CH 445457 to provide a screw or a housing for a screw with slats or to build them up from such slats. The slats for the screw can be provided on the outside with a ring made of particularly wear-resistant material such as hard metal or the like. By using lamellas with different outer sides, these can be assembled to form a screw, which has a surface made of different materials over its axial length in different areas. In the same way, Mellen be assembled with an inner ring to a cylinder that has an inner surface with an axially varying wear protection layer. This process is complex and expensive. In addition, the worm has the additional disadvantage that the webs are not continuously continuous, but are formed by offset of the individual lamellae, so that edges are formed on which plastic melt can easily deposit and burn.

Proceeding from this, the object of the invention is to specify a method for producing a wear-protected plasticizing or compounding system for plastic machines, which offers wear protection optimized for the respective type of wear at low costs and a rapid production process, and enables the armoring of complicated structures ,

This object is achieved by a method having the features of patent claim 1. Advantageous refinements and developments can be found in the subclaims.

The wear protection coating varies on the different axial sections of the plasticizing, mixing or conveying screw and / or the plasticizing cylinder. The type or composition of the wear protection coating is adapted to the types of wear prevailing at the corresponding axial sections by applying a band containing a coating material to the surface of a plasticizing, mixing or conveying screw or to the inner surface of plasticizing cylinders. The composition of this belt varies at different axial sections of the plasticizing, mixing or conveying screw or the plasticizing cylinder. The composition of this band is adapted to the types of wear prevailing at the corresponding axial sections. The tape thus applied is then thermally treated, so that a wear-protected surface is created. Depending on the surface to be coated, the belt can be applied and thermally treated in different processing stages of the plasticizing, mixing or conveying screw, i.e. already on the blank of the screw base body in the event of a coating of the web surface of the screw or on the finished machined plasticizer -, mixing or conveyor screw in the case of a coating of the screw base. Another advantage is that the belt can also be used to repair an already worn screw.

In an advantageous embodiment of the invention, the band is inserted into a spiral groove in the screw main body and then thermally treated. In other Spanish lifting operations, the main screw body is processed in such a way that the area of the main screw body that is protected from wear remains as a web. This procedure has the advantage that the tape is well fixed in the groove and does not slip sideways.

The tape is preferably glued onto the screw base. This is the easiest and cheapest way of fastening.

In an advantageous variant of this, the band is fixed on the screw base by a ceramic support cylinder or a wire mesh. Compared to gluing the tape, the glue is not required in this variant. This does not cause problems with the adhesive's combustion residues during the heat treatment of the tape.

The thermal treatment is preferably a soldering process. The tape is firmly bonded to the screw base without being distorted by excessive thermal stress. This thermal treatment preferably takes place in a vacuum oven. This avoids oxidation processes on atmospheric oxygen.

In an alternative embodiment of the invention, the thermal treatment takes place by means of an induction coil. This is a quick and space-saving alternative to the vacuum furnace. In order to avoid oxidation processes on atmospheric oxygen, the thermal treatment by means of the induction coil is preferably carried out with a blanket of inert gas.

In a further alternative to this, the thermal treatment is carried out using a flame. This is a very inexpensive guarantee.

In an advantageous embodiment of the invention, the band is applied to at least one flank of the webs of the plasticizing, mixing or conveying screws. This also protects the flank areas of the webs from wear and prevents corrosion or erosion of the webs from the side of the flank.

In a preferred embodiment of the invention, the belt is applied to the base of the plasticizing, mixing or conveying screw. The base of the plasticizing, mixing or conveyor screw is armored and protected against wear. In a further development of the invention, a tape containing a coating material is applied to a worn area of a plasticizing, mixing or conveying screw after its mechanical pretreatment for repair purposes. The strip is then thermally treated, so that a wear-protected surface is created in said area. The surface is preferably machined. As a result, a screw that is no longer ready for use can be put back into use at low cost.

In an advantageous embodiment of the invention, the plasticizing cylinder is designed in two parts in such a way that a cylinder sleeve with a wear protection coating is inserted in an outer plasticizing cylinder. This has the advantage that only the cylinder liner is exposed to a thermal load during a heat treatment, such as the sintering on of a wear protection tape. The outer plasticizing cylinder is not thermally stressed. This avoids the risk of warping due to thermal stress. The connection between the outer plasticizing cylinder and the cylinder liner can be made by shrinking on.

The wear protection coating in different axial sections of the plasticizing, mixing or conveying screw and / or the plasticizing cylinder is preferably optimized for abrasive, corrosive or adhesive wear.

In order to effectively counter the prevailing types of wear, the wear protection coating in the feed area for plastic raw material of the plasticizing or compounding system is preferably aligned primarily against abrasive wear and in the melting area of the plasticizing or compounding system is primarily aligned against corrosive wear.

In an advantageous embodiment of the invention, the wear protection coating on the top of the web of the plasticizing, mixing or conveying screw is different from the wear protection coating on the web flanks of the plasticizing, mixing or conveying screw and the screw base. In the gap between the screw web and the inner wall of the plasticizing cylinder, the wear is determined by the gap width and the dimensions of the filler particles. When there is a large gap, wear mechanisms occur as in the screw channel, ie on the web flanks of the plasticizing, mixing or conveying screw and the screw base, and on the free part of the inner wall of the plasticizing cylinder. The combination of plastic, filler and metal is created. This results in grain sliding wear and erosion like in the worm channel. at In a small gap, however, a so-called three-body abrasion occurs with the metal-filler-metal combination, depending on the filler particle size. In this case, it turns out to be an advantage to wear the protective coating on the top of the plasticizing, mixing or conveying screw primarily against adhesive and abrasive wear, and the wear protective coating on the flank of the plasticizing, mixing or conveying screw and the screw base primarily against corrosive and abrasive Align wear.

If there is a small gap, the three - body abrasion with the metal - filler - metal combination occurs in the gap between the screw flight and the opposite inner wall of the plasticizing cylinder. Wear mechanisms such as in the screw channel occur on the free part of the inner wall of the plasticizing cylinder. The combination of plastic, filler and metal is created. This results in grain sliding wear and erosion. When the screw rotates, the inner wall of the plasticizing cylinder is temporarily covered by the surface of the screw, sometimes it is exposed and forms the boundary of the screw channel. Therefore, the two wear mechanisms abrasion occur on average over time as on the surface of the screw and grain sliding wear and erosion as in the screw channel. It has therefore proven to be advantageous to design the wear protection coating on the web top of the plasticizing, mixing or conveying screw differently from the wear protection coating on the inner surface of the plasticizing cylinder in order to take account of this different composition of the types of wear.

In a preferred embodiment of the invention, the plasticizing cylinder is modularly composed of individual axial cylinder segments. This facilitates the coating of the inner wall of the plasticizing cylinder. In particular, this facilitates the application of various wear protection coatings over the axial length of the plasticizing cylinder if the cylinder segments are matched to the various wear protection coatings.

The individual axial cylinder segments preferably correspond to different priority working areas of the plasticizing or compounding system. Different forms of wear and tear occur in these different priority work areas of the plasticizing or compounding system, so that the cylinder segments are closely approximated to the various necessary wear protection coatings.

One or more of the following materials are used as coating materials in the strips, depending on the types of wear on the screw and barrel: AI, B, Co, Cr, Mo, Nb, Ni, Si, Ti, W, AlO-ZrO, AL-TiO, Co-Cr, Co-Ni, CO-Mo-Cr, CrC- NiCr, CrC-Ni, Cr-Ni, CrO, NiCrAI, NiCrMo, TiC-CrNi, VC-CrNi, WC-CrC-Ni, WC-CrC-NiCr, WC- Co, WC-Co-Cr, WC-Co- NiCr, WC-Ni, WC-VC-Ni, ZrO-AlO, ZrO-MgO. When choosing, it is crucial that the screw segment and the corresponding barrel area do not have the same material composition, but complement each other in the minimization of the forms of wear that occur. The material to be processed on the plastics machine can also be a determining factor in the selection of the material combination.

An embodiment of the invention is shown in the drawings. Show it:

1 is a plan view of a basic screw body of a plasticizing, mixing or conveying screw, which is spirally wrapped by a band containing a coating material,

2 shows a screw body of a plasticizing, mixing or conveying screw, in which a band containing a coating material is inserted into a spiral groove and annealed in an induction coil, in a plan view,

3 shows a plasticizing, mixing or conveying screw with a wear-protected surface layer on the peripheral surface of the webs in a top view.

Fig. 4 is a half cut open along its longitudinal axis plasticizing cylinder with a wear protection coating on its inner surface

5 cross section through a screw base body with wound tape and fixation of the tape by a support stocking,

Fig. 6 cross section through a screw base with wound tape and fixing the tape by a support cylinder.

A belt 1 containing a coating material is wound spirally around an optionally previously machined screw base 2 of a plasticizing, mixing or conveying screw (FIG. 1). The tape 1 is provided on its inside with an adhesive and therefore adheres to the screw base body 2 independently. In detail A, the tape 1 resting on the screw base body 2 is shown in a section through the screw base body 2 along its longitudinal axis. Tapes 1a, 1b and 1c with different chemical compositions can be applied at any point. In this way, different coating materials can be applied to different axial regions of the screw base 2 of the plasticizing, mixing or conveying screw. The application of the different coating materials is very easy and offers maximum flexibility. You simply cut off a tape 1a and add another tape 1b to it seamlessly and repeat this step with the subsequent tapes 1c and so on, so that the joints are barely recognizable and the impression arises that tape 1 simply continues , This procedure is repeated as many times as further coating materials are desired. The length of the axial areas with a specific coating material can be freely selected with this technology. The screw base body 2 with the band 1 composed of different sections is then annealed. The tape 1 melts briefly and forms a soldered connection with the screw base body 2. With this brief melting, the joint between two strip sections, ie between 1a and 1b and between 1b and 1c and so on, also closes. Subsequently, material is removed from the areas of the screw base body 2 that are left free from the tape 1, so that the base 4 of a screw is formed and the areas left on which the tape 1 is soldered remain as webs 5 of a screw. The surface of the webs 5 are now armored by a wear protection coating 6, as can be seen from FIG. 3 and data view C.

It is also possible to apply a tape 1 with a chemical composition that varies over its length. In the case of standard screws, a tape 1 could be applied with a varying chemical composition that results in a coating that is optimally adapted to the various types of wear that occur in the plasticizing or compounding system for plastic machines.

In a further development of the invention shown in FIG. 2, the tapes 1a, 1b, 1c and so on are inserted into a spiral groove, so that the top of the assembled tape 1 as a whole is flush with the surface of the screw body 2. In detail view B, a section through the screw main body 2 along its longitudinal axis clearly shows the flush closure of the band 1 on its upper side with the surface of the screw main body 2. To solder the strip 1, the screw base 2 is pushed axially through an induction coil 3. The adhesive burns on the inside of the tape 1 and the tape 1 melts briefly and forms a connection with the screw base 2 in the form of soldering. Subsequently, in this example, too, material is removed from the locations of the screw base body 2 that are left free from the tape 1, so that the base 4 of a screw is formed and the areas left on which the tape 1 is soldered remain as webs 5 of a screw. The The surface of the webs 5 are now armored by a wear protection coating 6, as can be seen from FIG. 3 and data view C.

4 shows a plasticizing cylinder 7, which has been cut open half along its longitudinal axis, with a wear protection coating 8 on its inner surface. For its wear protection coating 8, several wide coating tapes 1a to 1e, optimized depending on the type of wear, were applied to the inner surface along the circumferential direction. Subsequent annealing briefly melts the strips 1a to 1e and forms a soldered connection with the screw base body 2. In addition, the joints between the tapes are closed. In this way, a continuous wear protection layer 8 is created with sections 8a to 8e which contain different wear-reducing substances, depending on the respective requirements.

If one wants to do without the tape 1 being glued to the screw base, the procedure according to FIG. 5 can be followed. First, the tape 1 is wound onto the main screw body 2 and then an expandable support stocking 9 is put on. In this way, the band 1 is mechanically fixed on the screw base 2. If necessary, the position of the band 1 can be readjusted through the braid of the support stocking 9. For example, a non-stick coated wire mesh can be used as a support stocking.

Instead of the support stocking 9, a support cylinder 10 can also be used, which according to FIG. 6 is formed by an upper half-shell 11 and a lower half-shell 12, which have an anti-adhesive film 13 on their inside. The half-shells can have a bed 14 in their interior to give the inside of the support cylinder a certain flexibility, which has an advantageous effect on the position fixing of the band 1.

LIST OF REFERENCE NUMBERS

Belt made of individual sections 1a to 1e of different material composition Snail base induction coil base web Wear protection coating with different properties 6a to 6c plasticizing cylinder Wear protection coating with different properties 8a to 8e

Claims

claims

1. Process for the production of a plasticizing system with a wear protection coating (6, 8) which has wear protection properties varying over the axial length, the wear protection layer on the surface of plasticizing, mixing or conveying screws and / or on the inner surface of plasticizing cylinders (7) applied by plastic machines, characterized in that on the surface of the plasticizing, mixing or conveying screws or on the surface of the base body of the plasticizing, mixing or conveying screws and / or on the inner surface of the plasticizing cylinder (7) a coating material containing band (1) is applied, the composition of which varies at different axial sections of the plasticizing, mixing or conveying screws and / or the plasticizing cylinder (7), adapted to the prevailing types of wear on the corresponding axial sections, and that connect the tape (1) undergoing thermal treatment so that a wear-protected surface is created.

2. The method according to claim 1, characterized in that the tape (1) is tapes 1a, 1b, 1c, ... of different compositions that are applied, the tapes 1a, 1 b, 1c, .. butt and that the tapes 1a, 1b, 1c ... are then thermally treated so that they form a connection with the surface to be coated and the joints between the tapes disappear.

3. The method according to claim 2, characterized in that the belts 1a, 1 b, 1c, ... one or more of the following materials AI, B, Co, Cr, Mo, Nb, Ni, Si, Ti, W, AlO -ZrO, AL-TiO, Co-Cr, Co-Ni, CO-Mo-Cr, CrC-NiCr, CrC-Ni, Cr-Ni, CrO, NiCrB, NiCrAI, NiCrMo, TiC-CrNi, VC-CrNi, WC -CrC-Ni, WC-CrC-NiCr, WC-Co, WC-Co-Cr, WC-Co-NiCr, WC-Ni, WC-VC-Ni, ZrO-AlO, ZrO-MgO contain, the bands 1a , 1 b, ^ .... contain different materials or different material combinations.

4. The method according to claim 3, characterized in that successive belts 1a, 1 b, 1c, ... each contain different materials or different material combinations.

5. The method according to claim 2, characterized in that the strips 1a, 1b, 1c, ... one or more of the following materials AI, B, Co, Cr, Mo, Nb, Ni, Si, Ti, W, AlO- ZrO, AL-TiO, Co-Cr, Co-Ni, CO-Mo-Cr, CrC-NiCr, CrC-Ni, Cr-Ni, CrO, NiCrB, NiCrAI, NiCrMo, TiC-CrNi, VC-CrNi, WC- CrC-Ni, WC-CrC-NiCr, WC-Co, WC-Co-Cr, WC-Co-NiCr, WC-Ni, WC-VC-Ni, ZrO-AlO, ZrO-MgO contain, the bands 1a, 1 b, 1c, ... each contain the same material or the same material combination in different concentrations.

6. The method according to claim 5, characterized in that successive belts 1a, 1b, 1c, ... contain the same material or the same material combination in different concentrations.

7. The method according to any one of claims 1 to 6, characterized in that a first belt 1 a and a second belt 1 b are used for the melting zone of the screw.

8. The method according to claim 1, characterized in that a continuous belt (1) is used, which has a chemical composition varying over its length.

9. The method according to claim 8, characterized in that the band one or more (combination) of the following materials AI, B, Co, Cr, Mo, Nb, Ni, Si, Ti, W, AlO-ZrO, AL-TiO, Co-Cr, Co-Ni, CO-Mo-Cr, CrC-NiCr, CrC-Ni, Cr-Ni, CrO, NiCrB, NiCrAI, NiCrMo, TiC-CrNi, VC-CrNi, WC-CrC-Ni, WC- Contains CrC-NiCr, WC-Co, WC-Co-Cr, WC-Co-NiCr, WC-Ni, WC-VC-Ni, ZrO-AlO, ZrO-MgO.

10. The method according to claim 8 or 9, characterized in that the band varies in its length profile in its material composition.

11. The method according to claim 8 or 9, characterized in that the band contains a single material or a single material combination and the length of the concentration of the material or the material combination varies.

12. The method according to any one of claims 1 to 11, characterized in that the wear protection coating (6, 8) in different axial sections of the plasticizing, mixing or conveying screw and / or the plasticizing cylinder (7) optimizes for abrasive, corrosive or adhesive wear is.

13. The method according to any one of claims 1 to 12, characterized in that the wear protection coating (6, 8) in a feed area for plastic raw material of the plasticizing or compounding system is coated primarily against abrasive wear and in a melting area of the plasticizing or compounding system primarily against corrosive Wear is coated.

14. The method according to any one of claims 1 to 13, characterized in that a different wear protection coating (6) is applied to the top of the web of the plasticizing, mixing or conveying screw than on the web flanks of the plasticizing, mixing or conveying screw and the screw base, whereby the wear protection coating (6) on the top of the web of the plasticizing, mixing or conveying screw is primarily oriented against adhesive and abrasive wear and the wear protection coating (6) on the web flanks of the plasticizing, mixing or feeding screw and the screw base is primarily aligned against corrosive and abrasive wear is.

15. The method according to any one of claims 1 to 14, characterized in that the wear protection coating (6) on the web top of the plasticizing, mixing or conveying screw is different from the wear protection coating (8) on the inner surface of the plasticizing cylinder (7).

16. The method according to any one of claims 1 to 15, characterized in that the plasticizing cylinder (7) is composed modularly from individual axial cylinder segments, which correspond to different priority work areas of the plasticizing and compounding system, and that bands 1'a to 1 'e applied with different wear properties and then thermally treated.

17. The method according to any one of claims 1 to 16, characterized in that the continuous band (1) or the bands (1a, 1b, 1c, ...) are inserted into a spiral groove of the screw base body (2), then treated thermally and that the screw base body (2) is further processed in such a way that the area of the screw base body (2) which is protected from wear by the belt (1) or the belts (1a, 1b, 1c ...) remains as a web (5) ,

18. The method according to any one of claims 1 to 17, characterized in that the band (1) or the bands (1a, 1b, 1c, ...) on the screw base body (2) by a support cylinder (10) or a support stocking ( 9), for example a wire mesh, is fixed.

19. The method according to any one of claims 1 to 18, characterized in that the thermal treatment takes place in a vacuum oven.

20. The method according to any one of claims 1 to 19, characterized in that the thermal treatment is carried out by means of an induction coil (3), preferably with a blanket of inert gas.

21. The method according to any one of claims 1 to 20, characterized in that the band (1) or the bands (1a, 1b, 1c, ...) on at least one flank of the webs (5) of the plasticizing, mixing or screw conveyors is applied.

22. The method according to any one of claims 1 to 21, characterized in that the belt (1) is applied to the bottom (4) of the plasticizing, mixing or conveying screw.

23. The method according to any one of claims 1 to 22, characterized in that for repair purposes on a worn area of a plasticizing, mixing or conveying screw or a plasticizing cylinder (7) after its mechanical pretreatment, a belt (1) or belts (1a, 1b, 1c ) are applied.

24. The method according to any one of claims 1 to 23, characterized in that a two-part plasticizing cylinder (7) is used in such a way that a cylinder sleeve with a wear protection coating is used in an outer plasticizing cylinder, which has a composition varying over the axial length.

25. The method according to any one of claims 1 to 24, characterized in that the band (1 ') or the bands (1'a - 1'e) in the plasticizing cylinder (7) contains a different material composition than the band (1) or the bands (1a, 1b, 1c, ...) of the screw in this axial area, so that the friction partners of the plasticizing cylinder on the one hand and the screw on the other differ in their material composition.

26. The method according to any one of claims 1 to 24, characterized in that the band (1 ') or the bands (1'a - 1'e) in the plasticizing cylinder (7) and the band (1) or the bands (1a , 1 b, 1c, ...) of the screw in this axial area each contain the same material composition in different material concentrations so that the friction partners of the plasticizing cylinder on the one hand and the screw on the other hand differ in their material concentration.