Note: Descriptions are shown in the official language in which they were submitted.
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Processing machine and manufacturing method thereof
Technical field
The invention concerns a processing machine for the
processing of workpieces being preferably made at least
partly of wood, wooden materials, plastics, metal or the like
and having at least one supporting machine part and at least
one processing unit connected with the supporting machine
part, wherein the supporting machine part is made at least in
sections from concrete. Herein, within the framework of the
present invention, concrete is to be understood as a
minerally bonded, in particular also cementitious concrete.
Prior art
Processing machines of the above-mentioned type are widely
used in the processing and manufacture of workpieces in the
furniture and building components industries and a wide
variety of other branches of industry. The processing units
of these machines are usually built on supporting machine
parts traditionally made from steel or steel plates. The
increasing processing speeds and the dynamic forces of the
processing machines associated therewith lead to a continuous
increase in the importance of the oscillation behavior of the
supporting machine parts.
Against this background it has been proposed to produce a
machine bed, which is an essential load-bearing (supporting)
machine part, of mineral casting, that is a mixture of a
synthetic binder and additives (see for example
DE 20 2006 019 323 U1). The synthetic binders necessary for
it are, however, laborious to process and associated with
high costs.
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As alternative thereto machine beds consisting entirely or
partially of concrete have recently been used, too. For
instance, DE 37 34 895 Al discloses a concrete frame for
internal cylindrical grinding machines having a concrete bed
configured as a dual double-T-beam in cross-section. It
turned out, however, that the known concrete frame warps due
to time dependent shrinkage deformations so that dimensional
inaccuracies develop which are undesirable in the precise
(surface grinding) processing of workpieces. Even the
concrete-cast steel frames mentioned in DE 37 34 895 Al will
not change anything about this disadvantage, the more so as
these steel frames result in a complicated structure of the
concrete frame.
Summary of the invention
Therefore, it is desirable to provide a processing machine of
the generic type, which has a simple structure with low
dimensional deviations and is cheap to produce.
In one aspect, the present invention provides a method for
producing a processing machine, the processing machine
comprising: at least one load-bearing machine part and at
least one processing unit connected with the load-bearing
machine part, wherein the load-bearing machine part is made
at least in sections from concrete, the method comprising the
following steps: producing a load-bearing machine part from
concrete having a water-binder ratio of at most 0.30, heat
treating the concrete, and joining the load-bearing machine
part with the processing unit. The invention is based upon
the notion to configure the load-bearing (supporting) machine
parts, which are made at least in sections from concrete, so
as to largely eliminate shrinkage deformations without
thereby developing reactive forces which have to be
compensated for by means of laborious structures. Against
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this background the invention envisions that, in a processing
machine of the generic type, the concrete of the load-bearing
machine parts is formed by a concrete having a water-binder
ratio of at most 0.30.
In this way it is ensured that upon setting and hardening of
the concrete almost the entire amount of water of the
concrete is set (bound) within a relatively short time
already so that the water contained in the concrete is
largely removed as the main cause of the shrinkage. This
results in the base body of the surface grinding device of
the invention having only very low shrinkage deformations at
an early stage after the production of the base body so that
no distortion phenomena or other dimensional deviations
result at all. It is to be observed that this result in
order to achieve, no additional mounting or urging devices
such as steel frames or the like are necessary.
It turned out in the process that the tendency of shrinkage
of the concrete could again be disproportionately reduced if,
according to a further embodiment of the invention, the
concrete of the supporting machine part has a water-binder
ratio of at most 0.25, preferably at most 0.20.
To achieve the above-mentioned advantages, it is envisioned
alternatively or in addition to the water-binder ratio of the
invention that the concrete of the load-bearing machine part
has a bending tensile strength of at least 15 MPa. Thereby,
completely new design possibilities for load-bearing machine
parts result. For example, thanks to the concrete
composition of a further embodiment of the invention, also
the utilization of rod-shaped reinforcement inserts such as
reinforcing steel bars or the like can be renounced. Herein,
"bar-shaped reinforcement inserts" are to be understood as
such reinforcements that give a countable contribution to the
static and/or dynamic load capacity of the machine part. A
so called "constructive reinforcement" or auxiliary
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reinforcement for transport purposes, localized load
application etc. does not fall thereunder. By renouncing
reinforcement inserts, the structure of the base body is
further simplified and an extremely high design freedom in
results for the base body.
This is particularly true if, according to a further
embodiment of the invention, the concrete has a bending
tensile strength of at least 20 MPa, preferably at least
25 MPa. To ensure a high strength and durability of the
load-bearing component at the same time, it is envisioned
according to a further embodiment of the invention that the
concrete of the load-bearing components comprises fibers, in
particular metal fibers and/or synthetic fibers. It is to be
observed that, within the framework of the present invention,
fibers from a wide variety of materials may be utilized.
It is particularly preferred that the concrete of the load-
bearing component has a compressive strength of at least
90 MPa, preferably at least 120 MPa, more preferably at least
150 MPa. Thus, the load-bearing machine part is suitable
also for heavy-duty processing operations.
The load-bearing machine part may, within the framework of
the present invention, concern a wide variety of machine
parts of a processing machine of the generic type, wherein in
many cases it may also be a dynamically loaded machine part.
In some applications, the machine part's inventive
configuration in concrete may be suitable also for casing
parts or the like. According to a further embodiment of the
invention, it is envisioned, however, that the load-bearing
machine part forms a machine part chosen from the group
consisting of machine bed, support (mount), cantilever arm,
gentry beam, console, base support and housing. The
inventors have realized that the inventive configuration of
these machine parts from a special concrete allows for the
above-mentioned advantages to be particularly pronounced,
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that is to say to provide machine parts having a simple
structure, low dimensional deviations and high durability at
low prices.
A particularly advantageous method of production of a
processing machine according to the invention is defined in
claim 8. It is characterized in that the load-bearing
(supporting) machine part is heat treated after casting the
concrete and is joined with a processing unit only
subsequently. Firstly, the heat treatment of the concrete
makes it possible that the shrinkage behavior of the hardened
concrete is further improved so that the dimensional accuracy
and durability of the machine part is optimized accordingly.
Moreover, also the strength of the concrete can be increased.
Last but not least, due to the heat treatment the time
necessary for the production of the machine part can be
shortened, bringing about not only advantages in terms of
time but also reducing the number of necessary formwork
moulds and other auxiliary means.
According to a further embodiment of the inventive method it
is envisioned that the heat treatment is preformed such that
the degree of shrinkage (shrinkage value) of the concrete
after the heat treatment is at least 90%, preferably at least
95% of the final degree of shrinkage (final shrinkage value)
according to DIN 1045-1. Thereby, it becomes possible for
the shrinkage of the concrete to be largely concluded after
the heat treatment so that only negligible shrinkage
deformations occur after joining the load-bearing machine
part to a processing unit. Hereby, concrete as a material
advances into regions of dimensional accuracy hitherto
reserved only to metal supports.
In order to achieve a particularly effective and, at the same
time, gentle heat treatment of the concrete, a further
embodiment of the invention envisions that the heat treatment
is preformed at a temperature in the range of 70 C to 120 C,
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preferably in region of 80 C to 100 C. Thereby, a
particularly effective improvement of the shrinkage behavior
ensues without inducing undesirable crack formation or defect
formation in the concrete.
Moreover, according to a further embodiment of the invention,
it turned out to be advantageous to perform the heat
treatment for a duration of at least 24 hours and preferably
of at least 36 hours. Thereby, not only a rapid production
process ensues, but also a gentle and effective improvement
of the shrinkage behavior as well as an increase in load
capacity.
Short description of drawings
Figure 1 schematically shows a perspective view of a
processing machine as a first preferred embodiment of the
present invention;
Figure 2 schematically shows a perspective view of a
processing machine as a second preferred embodiment of the
present invention.
Detailed description of preferred embodiments
In the following, preferred embodiments of the invention will
be described in detail by reference to the accompanying
drawings.
A processing machine 1 as first preferred embodiment is
schematically shown in Figure 1 in a perspective view. In
the present embodiment, the processing machine 1 is a surface
grinding machine for the processing of workpieces made from a
wide variety of materials such as wood, wooden materials,
plastics, metal or the like. To that end, the processing
machine 1 comprises a processing unit 14 which in Figure 1 is
shown purely schematically. The processing unit 14 may, for
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example, be a circumferential endless grinding means or other
suitable grinding devices.
Moreover, it is to be observed that within the framework of
the present invention neither the type of processing nor the
type of the workpiece to be processed is limited. The
processing machine may, for example, be also a drilling or
milling machine, an edge banding (gluing) machine, a laser
processing machine or a processing center combining these and
other processing operations. Moreover, it may be a
stationary machine as shown in Figure 1, for instance, but
may also be a throughfeed machine in which the workpieces are
conveyed on a suitable conveyer means in a conveying
direction and are processed in the course of the conveying
operation.
In the present embodiment, a workpiece holder 16, which is
configured to hold or convey the workpieces to be processed
(not shown) during processing, is arranged below the
processing unit 14. In the present embodiment, the workpiece
holder 16 may also be a conveyer belt that conveys a
workpiece beneath the processing unit 14.
In the present embodiment, the processing unit 14 is mounted
to a support 12 which thus serves as load-bearing
(supporting) machine part for the processing unit 14. The
support 12 is made of concrete, the properties of which will
be described in more detail in the following.
The support 12 is connected through a housing 4, shown in
broken lines, to a machine bed 2 which is, in the present
embodiment, also made of concrete. Even though the concrete
of the machine bed 2 and of the support 12 may have different
properties, in the present embodiment they are designed, in
principle, with the same properties, as described in the
following.
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The concrete is a minerally bonded, in particular also a
cementitious concrete, that is not, for example, a so called
"polymeric concrete". The concrete is, thus, substantially
free of polymeric binders, although the concrete may also
comprise various synthetic additives, for example to improve
its flow characteristics upon casting.
The inventive peculiarity of the concrete is that it has a
low water-binder ratio of at most 0.30 and a high bending
tensile strength of at least 15 MPa. The water-binder ratio
is defined as the ratio between the mass of the effective
water content (kg) and the mass of the associated binder
content (kg). The bending tensile strength may be determined
within the framework of a four-point bending experiment on
prismatic test bodies, for example by means of the four-point
bending test defined in the guidelines of the German Concrete
Association (Deutscher Betonverein).
In the present embodiment, the concrete may concretely have a
water-binder ratio of about 0.18 and a bending tensile
strength of about 30 MPa. A further essential material
parameter of the concrete is its compressive (burst) strength
which, in the present embodiment, is at lest 150 MPa, wherein
the compressive strength of the concrete is defined as the
measurement value of the compressive strength according to
DIN 1045-1.
A contribution for achieving these values of strength is that
the concrete comprises, in the present embodiment, fibers
such as metal fibers, synthetic fibers or other suitable
fibers. Thereby, not only the strength values of the
concrete are increased, but the concrete is also less
susceptible to cracks, has an improved shrinkage behavior and
an increased durability. Moreover, providing fibers in the
concrete contributes to reduce the necessity of bar-shaped
reinforcement inserts such as ribbed reinforcing steel bars
in the load-bearing machine parts so that, according to the
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application and the characteristics of the concrete, it is in
many cases possible to renounce such reinforcement inserts
completely. In these cases, however, constructive
reinforcements may be present, for example to protect the
load-bearing machine parts during transport or to provide
local load application points.
By way of the exceptional properties of the concrete utilized
it becomes possible in the invention to produce a wide
variety of load-bearing (and possibly non-load-bearing)
machine parts from concrete, such as for example the machine
bed shown in Figure 1 or the support shown in Figure 1, but
also other components such as gantry beams, consoles, base
supports, casing parts or the like, even though these are not
shown in the figures.
The production and processing of the concrete discussed here,
in particular of the fiber concrete, is in principle known in
the art and thus to the skilled person, and in principle
corresponds to the approach used in the field of construction
(structural engineering). Thus, the production of the fiber
concrete may, for example, be performed according to the
guidelines of the Deutscher Ausschug fur Stahlbeton (German
Commission for Reinforced Concretes) bearing the title
"Stahlfaserbeton", (Fiber-reinforced Concrete) (21st draft of
April 2005). With respect to the production and processing
of concrete one may equally resort to the publication of the
Association Francais de Genie Civile bearing the title
"Interim Recommendations on Ultra-High Performance Fiber-
Reinforced Concrete" (2002).
Considering these known basics, the production of the
processing machine shown in Figure 1 may take place as
follows. First, fresh concrete is produced, which has the
above-described water binder ratio and is configured in its
composition to have a bending tensile strength of 25 MPa when
hardened. Then, the concrete is cast into a suitable
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formwork for the machine bed 2 or the support 12 and possibly
densified.
Thereafter, the concrete is subjected to a heat treatment in
a device not shown by storing it at a temperature in a range
of 80 C to 100 C for 24 to 36 hours. In the course of this
heat treatment, the concrete rapidly hardens, with the water
contained in the fresh concrete setting almost completely
with the binders or even evaporating to some extent. In this
way, the shrinkage of the concrete after the heat treatment
is already largely terminated.
Thereupon, the load-bearing machine part may be taken out of
the formwork already and be joined directly or indirectly
with the machine parts as well as with at least one
processing unit 14 at a desired point in time in order to
form a processing machine 1.
A further processing machine 1 according to a second
preferred embodiment of the invention is schematically shown
in Figure 2 in a perspective view. The embodiment shown in
Figure 2 differs from the first embodiment in that, firstly,
it is not a grinding machine but a processing center. Thus,
the processing machine shown in Figure 2 comprises a
processing table 26 arranged upon the base body 2, for
example in form of a known console table which may also be
made of or with concrete parts.
Further, a guide 28 is arranged on the base body 2, upon
which a cantilever arm 22 is arranged in way so that the
cantilever arm 22 is translatable along the guide 28. On the
cantilever arm 22 a processing unit 24 is arranged in such a
way that the processing unit 24 is translatable along the
cantilever arm 22. The processing unit may, for example, be
a processing mandrel in which various processing tools or
processing aggregates may be substituted according to need.
In this way, workpieces arranged on the processing table 26
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may be processed by means of the processing unit 24 in a wide
variety of manners.
Apart from the machine bed 2 also the cantilever arm 22 is,
in the present embodiment, made of concrete, wherein the
concrete has the same properties as in the above-mentioned
first embodiment. In this way, in both embodiments a novel
processing machine can be obtained which has low dimensional
deviations with a simple and cheap production and which
allows processing operations of very high dynamics.
Regarding the load-bearing machine parts 2, 12 and 22 made of
concrete according to the above embodiments, it is to be
observed that these are shown as concrete parts made in one
piece. It is to be observed, however, that the load-bearing
machine parts made of concrete may also be configured in
several parts and that they may be hybrid components, that is
components in which the concrete body is joined with other
components such as steel girders or the like. Hereby,
several concrete components and/or other parts may be glued
together. Equally, the load-bearing machine parts made of
concrete may have various mounting and anchoring points which
are made of steel, for example, and are set into the
concrete. Examples thereof are the anchoring points 6 shown
in Figures 1 and 2, to which the casing 4, the machine table
26 or other components may be attached.
