Abstract

This paper deals with the design of a new weaving machine based on a new mechanical structure and a specific motions control. The controller inserted in the control system which allows the synchronization between each slave axes on the textile machine and the master axis, according to a dynamic timing angle diagram. This configuration allows the modification of each mechanism parameters independently as well as the quick and easy change of the timing angle diagram. A structural analysis of the machine is presented. The machine is designed and build with 9 frames and a rapier moving in y and z axes. The weaving diagram is important for making fabrics with this machine. The method and the principle of transfer to each axis control are precised and the parametric flexibility available with this machine is shown. Compared to the traditional loom, the control system used in this machine is the main point. This flexibility allows a very quick machine setting for manufacturing various 2D, 3D fabrics, and the possibility is given also to fill the fabric with textile and non-textile picks. One of the main interests of this kind of machine is to conceive and obtain fabrics design which are not weavable on a traditional loom. In perspective, the development of such a machine provides to carry out new weaving functions in a very next future.

Keywords: Weaving machine; 3D Weaving; Controller; Synchronization axis; Electronic cam

Introduction

The world fibrous material consumption is strongly increasing particularly for industrial applications. As far as Europe is concerned, nowadays, 27% of fibers are dedicated to housing application, 34% for garment and more than, 38% for technical applications. The annual growth of this market is around 5 to 7%. This growth is due to the very high mechanical performances of textiles fibers which are very thin and flawless and which give very high ratio mass/performances.

Based on these performances, a very large number of woven, knitted and non-woven fabrics are developed to fit with specific applications. Since few years, many technical applications were developed with more and more complex textile structures far from traditional fabrics. The industrial demand asks for specific properties based on a combination of different textile structures which implies the evolution of classical structures towards more complexity i.e. the evolution of flat weaving to 3D in shape weaving. Moreover, the introduction of the functionalization of these structures leads to develop hybrid textile structures combining textile and non-textile materials.

The weaving technology is one of the oldest technologies. This technology consists in interlacing two yarn networks, one in machine direction (x) and one in cross direction (y) and this technology is also considered one of the most versatile. In fact, the mechanical properties of fabrics can be adjusted as a function of (x) and (y) properties. So that, the main function of a weaving machine is to interlace (x) direction yarns (warp) and (y) direction yarns (weft) respecting a given weave pattern [1].

There are three basic motions used to produce a fabric by ensuring the interlacing between warp and weft yarns. These three essential motions are as illustrated in Figure 1, [2]: shedding, weft insertion and beat up.

During the weaving process, warp yarns have to be let-off and the produced fabric has to be taken-up. These necessary two motions are auxiliary movements that are warp let-off and fabric take-up [3,4]. In traditional weaving, in order to get different weave structures the movement of the warp yarns has to be controlled and changed before each weft insertion.

To perform warp yarns movement, warps that allow the same interlacing pattern have to be grouped in the same frame called harness. By lifting the harness up or down, the groups of yarns will move either upwards or downwards [5]. The shed forming mechanisms to control warp yarns [6] are classified in four groups: crank, cam, dobby and Jacquard.

Each shedding mechanism can be mounted on any weaving machine. This shedding mechanism needs to be properly timed and synchronized with the beat up mechanism. The running of the weaving machine requires a given sequence of movement to control its various weaving functions given by dedicates parts and all of these functions must be accurately timed and fixed to ensure a regular sequence [3]. Usually, these mechanisms are driven by one main motor [7] and the movement is distributed to the different functions with the help of shafts and gears [8].

So that, these functions are synchronized together, as shown on the loom timing angle diagram (Figure 2).

It should be noted that the timing angle diagram can be different for each loom and fabric design. However, the five basic motions of a loom have to be completed in one pick that is 360° [2,3]. Figure 2 shows a typical loom timing angle diagram (weaving diagram). The time required for each operation is represented by the number of degrees of rotation of the main motor shaft.

Indeed, once and while the machine is running, the order of movements is fixed and the modification of parameters is strictly impossible during the weaving operation (shed height, harness speed, reed stroke and filling). Designing new textile structures including both textile and non-textile structures requires the development of a new weaving machine based on a concept of fully independent movements unlinked to the main shaft, providing more flexibility [9-17].

Weaving Machine Structure Analysis

In order to highlight the functions of the weaving machine, the FAST (Function Analysis System Technique) approach is used [9,18,19]. The Figure 3 illustrates the functional decomposition of the weaving machine.

Interlacing warp and weft yarns is a main function (MF) of this diagram. Many basic and secondary functions are described to highlight different mechanisms of a loom. Based on the above described FAST diagram, weaving machine manufacturers developed a machine design as shown in the Figure 4.

This design allows the individual monitoring of basic weaving functions, but the synchronization is still a mechanical one and is always driven by the main shaft.

Problematic

The mechanical synchronization between the five mechanisms on the conventional weaving machine must be done once before starting the machine.

That induces strong limits for conventional looms i.e.:
• Impossibility to modify the stroke of the frame during the weaving cycle.
• Impossibility to change the crossing point between the warp and the weft ends.
• Impossibility to insert pick at different height (z axis).

The following Figures 5a and 5b show the possibilities of obtaining multi-layered fabrics filled with different picks.

This allows a wide range of fabric structures, structures that can be modified during weaving.

Shed heights can be modified during the weaving cycle, as well as the number, the position and the moment of pick insertion to strengthen the 3D structure. Occasionally non-textile (i.e. metal component) inserts (or warp yarns) are possible to improve the rigidity of the woven structure. The new machine makes it possible to obtain fabrics with specific and complex structures.

To produce new woven hybrid structures, a new weaving machine concept is requires allowing quick setting as well as weaving parameters modification while the machine running. Such a machine requires a complete redesign and redevelopment of the mechanical structure and the setting up of a specific control tool. The Figure 6 shows the control system design of the new weaving machine.

In order to develop each function on the machine, recent weaving machines are based on multi servomotors design, but the main functions of the machine are still the same as well as the movement synchronization. The following parameters (shed height, frame height, reed stroke, frame speed, insertion speed, let off motion velocity and take-up motion velocity) are fixed. The suggested new design allows controlling all these movements independently and to control and redesign the movement synchronization at each pick. These modifications allow to change various setting of the machine while it is running. The paragraph bellow describes this new concept and describes the development of this new weaving machine as well.

Weaving Machine Structure Analysis Improvement

Based on the FAST diagram shows in Figure 3 & Figure 7 gathers the main functions both for a classical weaving machine and for the new concept of weaving machine.

Added systems for new machine:

• Systems related to the function BF.2 :
The choice to motorize each frame leads to relay the movement of each frame to the rotation of its motor. To apply a vertical movement to the frame, it is necessary to use a motorized pinion-rack system.

This system is composed of a polyamide rack, a polyamide pinion, and a brushless servomotor with a gearbox that can increase the torque up to 40 times [10].

At the beginning, the machine is reset in initial position, from the detection of an index (fixed on frame), by an infra-red sensor.

• Systems related to the function BF.3 :
The choice of dedicating a specific motor for the filling system individually led to use a system consisting in of two motorize y and z linear axes supporting the rapier and clamps (1 up 8 rapiers).

The stroke of the filling system is defined and protected with the help of inductive sensors integrated by the manufacture.

Systems related to the function BF.4 :
The beat-up system consists in one motorize linear axe supporting the reed driven by a linear axis. The stroke of the filling system is defined and protected with the help of inductive sensors integrated by the manufacture.

Design of the new weaving machine

The new prototype to produce specific hybrid fabrics is presented Figures 8a and 8b.

The machine is 360 mm width, and 1 up to 8 picks can be inserted in the shed as well as different devices, equipped with 9 frames.

Figure 8a and 8b show the weaving area (only 2 frames are designed, 1 and 2). The reed and the horizontal take-up are represented.

All mechanisms are driven by independent motors. The rapier moves in two directions y and z to achieve 3D fabrics structures and hybrid structures. The Figure 9 shows the prototype of the new machine.

Safety of mechanical axis and sensors

Securing the mechanical axes of this machine is a sensitive point. Their stroke is limited and can lead to destruction if these mechanical limits are exceeded. Although software stops are put in place to ensure this security, it is necessary, according to the rules used in the use of linear axes in industry, to use sensors to fix the stroke of axes, leading to the motor stops once the limits have been reached, and to stop down the movement of the axes (Safe Torque Off - STO security function). Inductive position detectors are usually used in linear axes. Based on machine security ISO standards, [20-22], drive solutions equip their linear rails with such sensors. Machine axis systems are equipped with them to march with ISO standards.

Other sensors are located along the machine axis, such as IR sensors, to define a reference or origin position of the axes. Their use makes it possible to define the initial position of each of the axes before setting up an electronic synchronization by the machine control system. IR sensors were preferred to inductive sensors for the precision of the position to be identified. Eventually, many sensors for measuring yarn tension could be placed to control them by the machine control system. Generally, these sensors allow a better control of the weaving machine.

Control system architecture

Servomotors associated with a speed drive (Lexium 32A), has been selected to provide the various movements on the machine. These products are marketed by Schneider Electric [11]. A planetary gear was mounted on the motor’s shaft to control the speed range of frame, which allowed increasing the torque required to drive the racks and reduce the friction among various machine parts.

A controller named LMC058 has been used for keeping the synchronization of each moving axis on the machine. It is an up to date controller type with all basic logical integrated functions, i.e. communication modes via network and motion control function dedicated to multi-axes control. The controller permits to synchronize the various axes of the machine [11], with quick response times, via CANopen and CANmotion, communication modes [12].

The LMC058 controller ensures the control of the machine via a Human Machine Interface (HMI) [13], Ethernet protocol, and the synchronization of the various axes via Lexuim32 speed drive.

The whole set of functions is defined by software, so that have to manage the safety with the help of specific sensors, as given previously.

A distant PLC (OTB1E0DM9LP) has been used to manage the various safety sensors on the machine with the help of an ASI (Actuators Sensors Interface) bus.

This PLC communicates with LMC058 by an Ethernet protocol to control the limitations imposed by the hardware and by the initial origin of the various axes by using different sensors.

Figure 10 shows the design implemented in the weaving machine prototype, where each axis is synchronized to the master axis motion (the reed). The control program is associated with “SoMachine” Software.

The architecture of this software is the standard CoDeSys (Controller Development System) [14], which is widely used by automation manufacturers [15].

This standard uses programming languages according to IEC 61131-3 [16].

This program allows to develop the dialogues by HMI, regulates the speed drive parameters (acceleration, deceleration, PID corrector, …), supervision, communication by network and ensures the security of machine.

Electronic cam implementation

A program depending on a digital CAM profile has been done by using the LMC058 controller, this program is written with the help of Ladder, Grafcet (SFC) and CFC.

From this CAM profile, the “SoMachine” Software allowed us to generate the master CAM profile which corresponds to a virtual axis, which control slave axes (for example: reed axis, frame axes, and more). Based on this virtual axis, the timing angle diagram has been defined, as shown at the Figure 11.

All parameters of each moving axis can be changed very quickly at each pick during the weaving by using this type of CAM profile.

Figure 12 represents an electronic cam created for a frame. So that, programing the height of this frame is very easy by changing the electronic cam parameters.

On the right table appears the axis setting, X represents a master axis position and Y the slave axis position corresponding to. The left figure displays an evolution of slave axis according to master axis.

Figure 12-a shows the frame reaching the 60 mm level at pick (p), while reaching the level 30 mm at pick (p+1) as shown Figure 12-b.

New timing angle diagram

Generally, in the field of weaving, the timing angle diagram Figure 2 is commonly used to fix the execution times of the various tasks of the machine compared to the movement of the reed taken as reference.

The proposed innovative solution gives the possibility to choose a new axis like reference. This axis will be considered as Mast axis on which the new timing angle diagram is based [17].

For example, the Figure 13 shows a new timing angle diagram, where the reed’s axis became directly slave of the Master axis chosen, with a cycle time different from that of the Mast axis. On this figure, the time of one cycle equals twice the reed cycle.

During one timing angle diagram of 360°, one cycle of the Master axis has been done whereas two cycles of reed axis were done.

On the other hand, while the cams running, it is possible to carrying out other movement synchronized with the axes movement by using “markers”, (i.e. it’s possible to insert 2 or 3 picks without beating up or changing the number of picks/cm at any time of the timing angle diagram).

Therefore, changing the cam profile to modify the shed height, harness speed, reed stroke, and the time of weaving fabrication, is easy and quick as well.

Representation for axis position

A clock representation is used to represent the position of any axis in real time as shown in the Figure 14. This representation fits with the SoMachine environment.

The control of the new weaving machine is based on the use of the virtual Master axis where all other axes are synchronized with it.

Based on the Master axis, the machine is reset before starting and all axes are positioned in origin position 0 with the help of electronic cams.

Setting Parameter advantages

The flexibility of the new machine is considerably increased. The presence of many mechanisms (associated with independent motorized axes) multiplies the possibility to adjust many parameters (original positions, safety limit runs, lengths of the continuous movements, in two directions, accelerations, decelerations, and more).

At the level of weaving cycle, the advantage is evident compared to the conventional machine. Manufacturing times are really reduced and do not require downtime for modifying the fabric patterns during manufacture.

The possibility to define cams profiles, with adjustments of parameters (during the weaving cycle), is an undeniable gain, thus avoiding long and tedious interventions at the mechanical level (change of profile of mechanical cams) and necessitating production stops.

The number of parameters is therefore consequent. The control of the machine is then more precise and the study of the influence of certain parameters during weaving can be undertaken more easily, knowing that it can be accessed independently.

Based on the parameters just mentioned, we quickly reach a number of 7 parameters at least (which can be expanded) for each of the axes. If we consider 9 frames, the reed, the tractor and insert axes, the number of parameter reaches 91.

The use of a virtual synchronization axis based on the weaving clock cycle put in place completes this set of parameters (6 minimum parameters).

But above all, the adjustment of the parameters, depends to weaving characteristics (pattern or structure of the fabric to be made, cycle time, and more), and defining the main operating conditions of the machine, during the weaving cycle. These characteristic weaving parameters are therefore filled in by the machine user before the weaving starts.

In the end, some of its parameters are fixed by default but adjustable if needed. Others are adjustable in real time to adapt to woven fabric manufacturing.

Based on above described and demonstrated, the number of parameters of our multivariate control system can quickly exceed 100 which is more than in the case of the conventional machine, where a large part of these parameters were fixed by default before weaving and are interdependent due to a mechanical cam shaft.

In summary, most of these parameters allow to position each of the mechanisms according to the master axis, in relation to their positions in the weaving diagram.

It is difficult in this publication to list all these parameters and show their impact in weaving. The authors merely give a nonexhaustive list of modifiable parameters.

These parameters will appear on the curves illustrating the control principle of the motorized axes in the weaving cycle. Among these parameters, some are adjustable by the operator, some others by the programmer.

Setting of the weaving machine by user

At the beginning, the user fixes the principal weaving parameters, as Length of woven fabric (LT), diameter of Yarn (∅y), Period weaving (Tw) and so on. The diameter of yarn permits to fix horizontal take up feed (Tractor). Others, associated by Clock weaving, permit to set different axis as a Master, or each frame and more.

The clock weaving defined the position to start and to end the action for each mechanism. This is hereafter described in setting Period CAM profile section.

The weaving machine can make different structure of product. The type of woven fabric is also important. It is defined to programming, at the level to each axis CAM profile. The user has the possibility to set parameters by HMI and start/stop the weaving at any time, in simple and fast way.

Setting of weaving machine by programmer

As above described, the number of parameters is very high i.e. considering 7 parameters for each mechanism axis taking into account 14 indexed axes (with the master axis), the number reached at least 98.

So that to summarize and illustrate this purpose, the following Table 1 shows an example of the distribution of the minimum number of parameters per axis.

For frames and vector axis one finds same parameters, as the following Table 2 shows. The Usr unit, is a unit defined in Somachine for users, in regard to axis cinematic (presence or no presence of gear). This is a usual and common unit adapted to each axis (with cinematic different) for users. It is applicated to many variables values (or parameters) as position, speed and more for motors.For reed or tractor axis, its necessary to fix the increment (step) movement, the length advance and forward movement, as well as initial and final position during the movement of reed axis (Table 3). The left figure displays an evolution of slave axis according to master axis. For each axis one can add, the speed setting, acceleration and deceleration for each axis, as precise in setting Table 4 of Master.

As definition, weaving cycle is traduced by cycle Clock weaving. In programming, the Master axis represents the reference for this cycle Clock weaving. All axis movement are defined according to this axis (New timing angle diagram, NTAD).

Setting Period CAM profile

CAM profile is a functioning sequence, edited to program movement of each mechanism in relation to Master axis, and according to new timing angular diagram. AT_M is chosen by default. Here corresponding to time gap between one insertion and after, the follow. The Cam period APC_(Index_axis) is defined from pattern of woven fabric if it is regular the value is 360° (AT_M). And if it is defined by a multiple (Kp_M) of 360°. We show two examples below. The setting CAM requires that the positions at the beginning and end of CAM profile edition are the same.

In Figure 15, we are observing a regular pattern APC is equal to APM. In this case, a period Cam corresponds to two cycle of weaving, or two strikes of reed. The frame for warp yarn 1 is placed to high position before the starting weaving sequence.

In the second example, the specific pattern of woven fabric requires 1080° for APC_M. Here, AT_M is chosen as time gap between one insertion and the first after. More settings are possible to adapt itself to various pattern. This is yet another illustration of the flexibility we have for this machine (Figure 16).

Principle & methodology programming

The procedure for configuring and defining the weaving cycle is carried out according to following steps:
i. Weaving parameters is given by users.
ii. The clock weaving is defined on the program.
iii. The virtual Master axis is set in programming.
iv. All CAM profile for each axis set and edited in programming.
v. When the setting is complete, the machine can be used.
vi. During weaving, user can be change some parameters.

This procedure is fixed but it’s very easy to adapt settings by the user during the weaving with the control panel (HMI).

Complex fabric weaving program implementation

The following example of programming is given to illustrate the realization of a simple hybrid fabric which consists of two extern layers with more inserts (Ii) and with 2 no-textile inserts (I1, I2).

All three successive filling sections A, B, C, a non-textile insert Ii is introduced into the structure to rigidify the fabric, as shown in the Figure 17.

The cyclical sequence of this structure is a period equivalent to the distance between the A section and the E section, which corresponds to four intervals (AB, BC, CD, and DE), in that, the reed moves twice backward/forward (360° master), as shown in the Figure 18.

The Figure 17 shows the cam profile of the frame 1 (L1) programmed on 720° for one example of fabrics as Figure 19. The frame 1 moves down to -20° (- H1) and then moves up to +20° (H1).

At the beginning, each axis is initialized to a position given in degree. For frame 1, this position is 20° (H1).

H1 corresponds to the shed height of frame 1 at the weaving cycle beginning. One can observe a frame inversion and her come back to the origin position.

The frame 2 moves two times between positions 10° (H2) and 20° (H1), as shown in the Figure 20. For the frame 8, the frame moves twice between positions -10° (-B2) and -20° (-B1), as shown in the Figure 21. Period weaving (Tw) on Figure 18 is given in number of strokes by reed.

The Figure 22 shows the cam profile of the frame 9 programmed on 720°. As frame 1, frame 9 moves down to -20° and moves up to +20°.

The reed moves four times backward / forward during the 720°, as shown in the Figure 23. Figure 24 defines the cam profile for rapier. Sections AB, BC and CD consist in 2 picks and DE consists in 3 picks (2 textiles, 1 non-textile).

Conclusion

The development of the machine control program ensures the synchronization of the various axes on the machine with carrying out the safety of their axes. By using this system, a large number of parameters can be quickly modified which allow more flexibility on the weaving process.

So that, the synchronization of the machine is not mechanically based (synchronization based on the main shaft) that allows any timing angle diagram. With the implementation to the LMC controller in this machine, various settings of the machine can change independently while it is running. Such a system permits fast multi axis synchronization with precision and increased reliability.

In a next future, the flexibility of the system, LMC Controller will simplify the integration of new devices in our weaving machine. The machine is designed and built and a first set of tests has been successfully carried out.

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