WO2014079601A1

WO2014079601A1 - Optimization of setup families

Info

Publication number: WO2014079601A1
Application number: PCT/EP2013/069087
Authority: WO
Inventors: Alexander Pfaffinger; Christian Royer
Original assignee: Siemens Aktiengesellschaft
Priority date: 2012-11-21
Filing date: 2013-09-16
Publication date: 2014-05-30
Also published as: DE102012221259A1

Abstract

A method for associating printed circuit board types with setup families comprises steps of detecting setup families, of detecting printed circuit board types, of detecting an association between the printed circuit board types and the setup families, the association being optimized in respect of a first quality criterion, of determining a second quality criterion for the association, the second quality criterion being different from the first quality criterion, and of changing the association between the printed circuit board types and the setup families in order to optimize the association in respect of a second quality criterion, with the first quality criterion being observed.

Description

description

Optimization of setup families The present invention relates to an automatic assembly line for the assembly of printed circuit boards with components. In particular, the invention relates to the determination of an assignment of PCB types to Rüstfamilien. An assembly line is set up to assemble a printed circuit board with a number of components. It is possible to differentiate between a variant production and a Festrüstungsfertigung. In the variant production, the PCBs to be produced are divided into setup families ("clusters") for a short planning horizon (about 1-5 days) .A setup family is a quantity of printed circuit boards that can be produced with a predetermined number of components on the assembly line The amount of component types needed for this will be

Armor called and is usually included in a set of shuttle tables. A changing table is usually upgraded in the pre-equipment for the assembly of printed circuit boards with components matching types of components and subsequently disarmed. The removal and subsequent upgrading of all changeover tables of a production line in the pre-assembly area requires processing times in the range of about 6-10 hours. Variant production is used in particular for so-called "high mix low volume" assembly, ie when frequently changing printed circuit boards are to be populated in short runs.

In order to organize the loading operation, a subset that is assigned to a set-up family is selected from a number of jobs each relating to the loading of a predetermined number of boards of a board type. The corresponding armor is upgraded and the circuit boards are populated while already the Setup family is determined, which is then to be populated. It happens that the placement line is finished with the placement of the current setup family before the armor upgrade for the following setup family has been completed. In this case, the placement line must be stopped, which can be associated with additional costs.

The object of the invention is to perform an assignment of PCB types to Rüstfamilien such that production stoppages of the assembly line are minimized. The invention solves this problem by means of a method, a computer program product and a control device having the features of the independent claims. Subclaims give preferred embodiments again.

A method according to the invention for assigning circuit board types to setup families comprises steps of detecting setup families, detecting circuit board types, detecting an assignment of the circuit board types to the setup families, the assignment being optimized with respect to a first quality criterion, determining a second quality criterion of the assignment wherein the second quality criterion is different from the first quality criterion, and changing the assignment of the board types to the setup families to optimize the association with respect to a second quality criterion.

In this way, an assignment of PCB types to Rüstfamilien that has already been created by conventional means with respect to a first quality criterion can be optimized in a separate step. Processing problems that can arise while optimizing both quality criteria, in particular excessive complexity of the problem or processing, can be avoided in this way. In addition, the separate optimization with respect to the second quality criterion can be based on an already proven optimization method with respect to the first quality criterion can be built so that proven processing means or sub-methods can be used. In a preferred embodiment, the modification is performed such that the first quality criterion is at least met. This can ensure that a real improvement of the assignment can be achieved by the described change. Changing the assignment with regard to the second quality criterion is thus possible without risk.

The first quality criterion may involve a minimization of the number of setup families. A minimized set-up family is a common optimization criterion.

It is also preferred to record quantities of printed circuit boards of the circuit board types of the set-up families, and a production time is determined for each family which specifies how long the component line requires for equipping all the circuit boards of the set-up family to be populated, the second quality criterion being based on a distribution from production times to the setup families. As a result, the setup families can be re-optimized with regard to their production times.

In a first variant, the second quality criterion relates to a maximization of the production times for a subset of the set-up families. In other words, the production times of selected setup families can be maximized. Since the sum of production times remains unchanged across all set-up families, production times of other set-up families must be reduced. A set-up family with a long production time can advantageously be realized as a fixed-arm set-up family for which armor remains firmly equipped on a number of changeover tables. Expenses and costs when changing the set-up can be reduced. In a second variant, which can be combined with the last-mentioned variant, the second quality criterion relates to an exceeding of a predetermined threshold value by the production times of each set-up family. The production times of the set-up families can thus be better balanced. In particular, it can be ensured that the production time of each set-up family is longer than it usually takes to upgrade the armament of a time-dependent set-up family. A standstill of the assembly line to wait for the completion of the set-up work can be avoided.

In a further embodiment, the second quality criterion relates to maximizing the number of jobs in a subset of setup families. This can improve the formation of festivals.

In another embodiment, quantities for mounting the printed circuit boards of the printed circuit board types of the setup families are again recorded and the second quality criterion relates to maximizing the number of printed circuit boards to be loaded in a subset of the setup families. As a result, the circuit boards of the thus maximized setup families can be equipped more efficiently.

In yet a further embodiment, quantities of printed circuit boards of the printed circuit board types of the setup families and, in addition, placement positions of all printed circuit boards to be assembled are also detected. In this case, the second quality criterion relates to a maximization of the placement positions in a subset of the set-up families.

It has been found that the printed circuit boards of such an optimized set-up family can also be equipped very efficiently.

In a preferred embodiment, the changing comprises a pairwise exchange of board types between setup families. lien. Properties of the original set-up families can remain unchanged. In particular, the number of setup families can remain the same. In a further embodiment, the changing comprises remapping a board type to another setup family.

Preferably, changing the assignment comprises optimizing with respect to the second quality criterion by means of a mixed integer optimization model. Such a model is also called an IP model. Among other things, it is characterized by the fact that not only a local, but a global optimization can be carried out with it, so that a found assignment can not be surpassed by another, not found assignment.

In one embodiment, the assignment of at least one circuit board type to a set-up family is fixed for optimizing with regard to the second quality criterion. The complexity of the optimization with regard to the second quality criterion can thereby be reduced. In addition, a deemed beneficial assignment can be made immutable in this way.

A computer program product according to the invention comprises program code means for carrying out the method described, when it runs on an execution device or is stored on a computer-readable medium.

A control device according to the invention for the assignment of printed circuit board types to a set-up family is set up to carry out the method described above. The above-described characteristics, features and advantages of this invention as well as the manner in which they are achieved will become clearer and more clearly understood in connection with the following description of the embodiments. games, which are explained in more detail in connection with the drawings, wherein:

Fig. 1 an assembly system;

Fig. 2 is an illustration of the formation of setup families for the placement line of Fig. 1;

3 is a flowchart of a method for allocating

PCB types to Rüstfamilien represents.

FIG. 1 shows an equipping system 100. The equipping system 100 comprises one or more equipping lines 110 and a control device 115. The control device 115 allocates circuit board types 122, whose associated circuit boards 120 are to be loaded on the equipping line 110, to a setup family 124. A set-up family 124 is a set of circuit board types 122 whose printed circuit boards 120 can be populated on a placement line 110 without requiring a change in the configuration of the assembly line 110, particularly with respect to blanked components.

Each placement line 110 includes an optional transport system 125 and one or more placement machines 130. Each placement machine 130 includes one or more placement heads 135. Each placement machine 130 has a number of change tables 140, each of which includes a predetermined number of feeders 150. Instead of a shuttle table 140, another swap body can be used, such as a change car.

The changing tables 140 each include a plurality of feeders 150, of which only one is shown by way of example in FIG. Each feeder 150 maintains a supply of devices 155 of a predetermined type of device 160. For the feeders 150 has the shuttle table 140 has a capacity that is usually expressed in tracks. A track is usually 8 mm wide and the number of tracks of each shuttle table 140 is limited, for example to 40. Components 155 of the same type of component 160 are usually provided in a belt, on a tray or in a tube. Each component type 160 comprises a plurality of components 155 which are interchangeable with respect to the printed circuit board 120, for example resistors having the same resistance value, the same load carrying capacity and the same design.

The components 155 are arranged in their respective packaging in a suitable feeder 150. Each type of device 160 requires a mating feed device 150 that requires a predetermined number of tracks on the change table 140, which tracks are usually required to be adjacent to each other. Each feeder 150 may be configured to maintain different components 155 and, typically, different feeders 150 may be attached to a shuttle table 140.

Each placement head 130 is configured to receive a component 155 from a shuttle table 140 and deposit it at a predetermined position on the circuit board 120. In this case, the printed circuit board 120 is usually stationary on the transport system 125 with respect to the automatic placement machine 130. If a printed circuit board 120 is required which requires a component 155 of a type of component 160 which is not present on one of the shuttle tables 140, it is customary not to provide a feed device 150 on one of the mounted shuttle tables 140 with the required components 155, but rather the shuttle table 140 is completely replaced by another, already equipped with the appropriate components 155 shuttle table 140. For this purpose, the changeover table 140 to be loaded must have been previously upgraded accordingly with components 155. This process is called pre-installation and may require an hourly processing time. Since a change of change tables 140 on the placement line 110 is usually associated with a production stoppage, the aim is to carry out the changeover tables 140 that is as rare as possible. For equipping a predetermined amount of printed circuit boards

120, armor 165, 170 may be formed, each containing inventories of devices 155 of predetermined device types 160, such that each circuit board 120 of the set may be fully populated with components 155 of the armor 165, 170. An armor 165, 170 may be realized by a number of shuttle tables 140 having predetermined supplies of components 155. In the illustration of FIG. 1, a hardshell 165, whose shuttle tables 140 are mounted on the line of delivery 110, and a variant arm 170, whose shuttle tables 140 are arranged separately in a Vorrüstbereich of the production line 110 provided. The armor 165, 170 are wholly or partially interchangeable on the placement line 110. There may also be other armor 165, 170 may be provided.

The decision as to whether an armor 165, 170 will remain armed on a number of shuttle tables 140 when the shuttle tables 140 are removed from the line 110 or disassembled as a variant line 170 when not in use by the shuttle tables 140 is usually dependent on such many change tables 140 are available and how long a change of armor 165, 170 may take a maximum. Figure 2 shows an illustration 200 of the formation of

Rüstfamilien 124 for the placement line 110 of Figure 1. In the upper part of a number of orders 205 is shown, the placement of printed circuit boards 120 predetermined Leiter- plate types 122. The orders 205 relate to a predetermined period and usually only relate to a part of the actual orders 205 to be processed during this period. Additional orders 205 for the same period can be added at short notice.

Each job 205 is associated with a board type 122. Furthermore, further indications may optionally be provided, in particular a quantity 210 of printed circuit boards 120 of the printed circuit board type 122, a production time 215 of a printed circuit board 120 on the assembly line 110 of FIG. 1 or a number of placement positions 220 indicating how many components 155 are represented by the placement line 110 are to be loaded on each circuit board 120.

In a first step, based on the information of the existing orders 205, a number of set-up families 124 are formed, in the representation of FIG. 2, by way of example, three set-up families 124. The assignment of printed-circuit board types 122 to set-up families 124 takes place with respect to a first quality criterion. In a preferred embodiment, the first quality criterion relates to the number of setup families 124. The fewer set-up families 124 are formed, the better the assignment with respect to the first quality criterion is optimized.

It is proposed to subsequently change the assignment so that a second quality criterion is improved. Preferably, the assignment with respect to the first quality criterion is at least not worsened. In the given example, therefore, after the change in the assignment, no more than three setup families should be indicated, to which the printed circuit board types 122 of all jobs 205 are assigned.

In a preferred embodiment, the second quality criterion is determined on the basis of production times. In this case, the second quality criterion can be found in a first may be formed to represent maximizing the production times of a subset of setup families 124. In a second variant, the second quality criterion can reflect whether the production times of all setup families 124 exceed a predetermined threshold; these two variants can also be combined, so that the production times of a subset of setup families 124 are maximized as long as the production times of all Set-up families 124 are at least as large as the predetermined threshold.

FIG. 3 shows a flow diagram of a method 300 for assigning circuit board types 122 to setup families 124. The method 300 is set up in particular for running on the processing device 115 in FIG.

In a first step 305, jobs 205 corresponding to the representation of FIG. 2 are detected. In a subsequent step 310, an assignment of printed circuit board types 122 to setup families 124 is determined according to a first quality criterion. In a subsequent step 315, the particular allocation and optionally further information is provided. The steps 305 to 315 may be performed, for example, by means of an allocation device provided for this purpose. Alternatively, the steps may be performed integrated with the subsequent steps, in particular on the same allocation device 115.

In step 320, the information provided in step 315 is captured. Optionally, further information can be acquired in a subsequent step 325, in particular those that are included in the orders 205. Then, in a step 330, a second quality criterion is determined for each of the setup families acquired in step 320. Thereafter, in a step 335, the assignment of board types 122 to setup families 124 is optimized with respect to a second quality criterion. The second quality criterion differs from the first quality criterion and can be formed in several different ways. In one embodiment, the second quality criterion may be formed based on production times 215 of setup families 124. For example, in other embodiments, the second quality criterion may also include maximizing the sum of the numbers 210 of populating boards 120 or the placement positions 220 for a subset of the setup families 124. Preferably, the modification in step 335 is performed such that the first quality criterion is at least no worse than the allocation after step 310.

When changing the assignment in step 335, one or more constraints may be considered. For example, properties of the shuttle tables 140 that are to carry an armor 165, 170 of the setup families 124 may be taken into account. In a step 340, for example, a fixed assignment of a predetermined component type 160 to a predetermined changeover table 140 can be taken into account. In a step 345, a maximum filling level of a shuttle table can be taken into account.

In a step 350, it may further be considered that a subset of board types 122 should be assigned to the same setup family 124. Conversely, it may also be considered in a step 355 that a subset of circuit boards 122 should be assigned to different setup families 124.

Changing the assignment in step 335 is preferably done by means of a mixed integer program (integer program). In a preferred embodiment, individual board types 122 are selectively swapped between the existing setup families 124 to change the association, or from a make family 124 reassigned to another. If the second quality criterion improves as a result, it is possible to further optimize on the basis of the changed assignment, otherwise it can be discarded in order to carry out a different confidence.

In an optional step 360, it is checked whether the second quality criterion with respect to the assignment changed in step 335 exceeds a threshold value. As long as this is not the case, step 335 can be iterated again until a sufficiently good association has been found. Changing the assignment can also be scheduled in order to prevent overoptimization, which may not be solved.

Optionally, in a subsequent step 365, an assignment of component types 160 to changeover tables 140 can be determined. This association can also be performed implicitly in step 335. In a final step 370, the changed assignment of board types 122 to setup families 124 is output.

Mathematical background

By using mathematical methods, much better solutions can be achieved for the assignment of PCB types 122 to setup families than with methods previously used in practice.

To determine an optimized allocation of PCB types 122 to the setup family 124, an automatic optimization can be used, for example on the basis of a local search method or a metaheuristic algorithm. Preferably, however, an IP model (Integer Program or Mixed Integer Optimization Model) is used for the change in step 335. One of the main methods in the field of mathematical op- Optimization is linear optimization, which deals with the optimization of linear objective functions over a set that is constrained by linear equations and inequalities. The linear optimization is the basis of the solution methods of the (mixed) integer linear optimization.

Advantages of Linear Optimization:

global optimization approach,

easily expandable.

very good standard commercial solver (SCIP, CPLEX,

Ilog, Xpress), which are widely used and proven in practice.

for a determined solution it is known how far away it is from the optimal solution (Gap).

In the following, an example of an IP formulation for optimizing the described assignment of printed circuit board types 122 to a setup family 124 is given. indices

C Quantity of device types 155

R amount of printed circuit boards 120

R _c Quantity of printed circuit boards with component type c

Cl amount of after optimization with respect to the first

Quality criteria specific set-up families (starting solution)

Cl_fix Amount of Garaging Equipment families (subset of

CD

Z selected subset of pairs, each consisting of a module type r and a set-up family cl assigned in the starting solution

parameter

Width ^c Space consumption of a type of building element c in tracks Cap _d Number of traces of device types used in the

Armor of the armor family cl have space

VxodTime _r Production time of the module type in the planning time

Binary variable

Assign _rcl has the value 1 if a board type r is the

Setup family cl is assigned, otherwise the value

0

Setup _c cl has the value 1, if the component type c in the

Armor of the setup family cl must be equipped, otherwise the value 0

IP formulation

Optimizing the assignment of PCB types

Setup families 124 can be performed as follows maximize Z - Σ ProdTime _r Assign _{r cl}

reR cleCl fix '

S. t

Σ Assign _rfil <1

cleCl ce C; cl Cl

re "Width _c Setup _ccl <Cap _{cl cle F}

CEC

^ÄSSi S ⁿ r, cl = ¹ (r, c /) e Z Setup _CICI G { ₉ \} ce C, cl Cl

Assign _rcl £ {0,1} r R, cl Cl

To further improve the assignment, further constraints may be given to the solver performing the ΜΙΡ optimization, some of which are exemplified above with reference to steps 340 through 355, respectively. The optimization with respect to the second quality criterion is then carried out so that the specified boundary conditions are met.

Although the invention has been further illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims

Claims 1. A method (300) for mapping circuit board types (122) to setup families (124), comprising the steps of:

- detecting (320) printed circuit board types (122);

- detecting (320) setup families (124);

- detecting (320) an assignment of the printed circuit board types (122) to the set-up families (124), the allocation being optimized with respect to a first quality criterion;

Determining (330) a second quality criterion of the mapping, wherein the second quality criterion is different from the first quality criterion;

- changing (335) the assignment of the board types (122) to the setup families (124) to optimize the association with respect to a second quality criterion.

The method (300) of claim 1, wherein the changing (335) is performed such that the first quality criterion is at least met.

3. The method of claim 1, wherein the first quality criterion relates to a minimization of the number of setup families.

4. The method (300) according to any one of claims 1 to 3, wherein

- Numbers (210) to be populated boards of printed circuit board types (122) of the setup families detected (325), - for each set family (124) a production time (215) is determined, indicating how long the assembly line (110) for equipping all Printed circuit boards (120) of the set-up family (124),

- and the second quality criterion on the basis of a distribution of production times (215) to the setup families

(124) is determined.

The method (300) of claim 4, wherein the second quality criterion relates to maximizing the production times (215) for a subset of the setup families (124).

The method (300) of claim 4 or 5, wherein the second quality criterion relates to exceeding a predetermined threshold by the production times (215) of each setup family (124).

7. The method (300) of any one of claims 1 to 3, wherein the second quality criterion relates to maximizing the number of jobs (205) for a subset of the setup families (124).

8. The method (300) according to any one of claims 1 to 3, wherein

- Numbers (210) to be populated boards (120) of the board types (122) of the setup families (124) are detected, and

the second quality criterion relates to a maximization of the printed circuit boards (120) to be assembled in the case of a subset of the set-up families (124).

9. The method (300) according to any one of claims 1 to 3, wherein

Number of pieces (210) of printed circuit boards (120) of the printed circuit board types (122) of the set-up families (124) are detected,

- Placement positions (220) of all boards to be loaded are recorded (325) and

the second quality criterion relates to a maximization of the placement positions (220) for a subset of the set-up families (124).

10. The method (300) of claim 1, wherein the changing (335) comprises a pair-wise exchange of circuit board types (122) between setup families (124).

A method (300) according to any one of the preceding claims, wherein said changing (335) comprises remapping a printed circuit board type (122) to another set-up family (124).

The method (300) of any one of the preceding claims, wherein changing (335) the association comprises optimizing for the second quality criterion using a mixed integer optimization model.

13. The method of claim 12, wherein for optimizing with respect to the second quality criterion, at least one of the assignments of circuit board types to setup families is fixed.

14. A computer program product with program code means for carrying out the method (300) according to one of the preceding claims when it runs on an executing device (115) or is stored on a computer-readable medium.

15. Control device (115) for assigning printed circuit board types (122) to a setup family (124), wherein the control device is configured to execute a method (300) according to one of claims 1 to 13.