GB2173426A - Component placement machine - Google Patents

Abstract

A component placement machine comprises an X-Y table (12) on which substrates (58) are mounted in known positions, first and second carriers (34, 36) mounted respectively adjacent first and second of said known positions, the carriers (34, 36) respectively each carrying two placement heads (44, 46; 58, 50), the heads on each carrier being spaced apart by the same distance, and two component supply means (22, 23) at opposite sides of the table (12). The carriers (34, 36) can be moved to carry the heads (44, 46; 48, 50) between first and second placement positions in register with a substrate (58) mounted at an adjacent one of the known positions, at which the head places a component at a desired location, and the pick-up location at which the head can pick up a component from an adjacent one of the component supply means (22, 23). The heads can also deposit tools on, or mount tools 52 from, movable tool supports 28. <IMAGE>

Description

SPECIFICATION Component placement machine This invention is concerned with component placement machines for placing electrical or electronic components on substrates, for example printed circuit boards.

It is necessary to place electrical or electronic components, for example so-called 'chips', flatpacks, S.O.-style transistors, leadless chip carriers and the like, on substrates, for example printed circuit boards, in the assembly of electronic or electrical circuitry. In the handling of electronic components, especially in placing various components on printed circuit boards, it is essential that the components be positioned precisely at a desired location and in a desired orientation, and that the components be so positioned rapidly. In order to operate efficiently it is desirable that any machine for positioning such electrical or electronic components occupies a minimum of factory space while being capable of placing components as rapidly as possible on substrates mounted in the. machines.A further desirable feature of such machines is that a wide variety of components can be handled by one machine without stopping the machine to remove one supply of components and replace them by a supply of different components, or at least keeping any stoppage for this reason to a minimum.

Many machines have been proposed for accurately placing components on substrates.

Some previously known machines have included so-called pick-up or placement heads by which components are picked from a component supply and placed in a desired position and orientation on a suitable substrate. US patent specifications numbers 4135630 and 4290732 both describe machines for picking up electrical components and placing them, in desired orientations, at desired positions on a suitable substrate. The placement heads of the machines described in each of these US patent specifications have means by which the components are held on the head, for example, a vacuum or suction tool, and socalled pawls or fingers by which the components are positioned accurately in correct orientation on the pick-up head.Machines of this type are capable of accurate positioning of components of appropriate size and can be arranged to handle a variety of different components, for example so-called flatpacks, S.O.

style transistors, leadless chip carriers and the like as well as 'chips'.

These known machines are capable of handling a wide variety of components but the rate at which components may be placed by these known machines, is not as great as would be desirable. Furthermore the ease with which it is possible to adapt the machines to deal with a wide variety of different components is restricted. It has been necessary to provide different placement heads to deal with widely varying components, or to change various parts of the heads manually with consequent loss of production.

The applicants have also supplied a component placing machine, under the designation MOPS500, for placing electrical components in predetermined positions on a suitable substrate for example a printed circuit board which comprises a bridge member on which is mounted for sliding movement transversely of the machine, a head support member which carries two placement heads. Tw carriages are mounted for movement in the X direction along parallel paths beneath the bridge member, each carriage being associated with one of the pick-up heads. On each of the carriages is a tool support for supporting a plurality of tools for supply to the associated pick-up head and on which components supply magazines are mounted.Between the two carriages is mounted a substrate support, namely a socalled X-Y table, on which substrates may be located for placement of components thereon.

This machine is so constructed and arranged that the operative parts of the placement heads of the MOPS500 are able to handle a wide variety of components without stopping the machine to change any parts of the head manually. However, the MOPS500 does not handle components as rapidly as desired, despite having a high production rate.

It is one of the objects of the present invention to provide an improved component placement machine by which a wide variety of components can be placed rapidly on substrates.

According to the invention a component placement machine is envisaged which comprises an X-Y table, means for mounting one or more substrates in known positions on the X-Y table, a first carrier mounted adjacent a first of said known positions and a second carrier mounted adjacent a second of said known positions, each of said carriers carrying two placement heads spaced apart by the same distance, component supply means disposed at opposite sides of the X-Y table, and means for mounting the first and second carriers for movement to carry the placement heads between respectively first and second placement positions in register with a substrate mounted at the adjacent one of the first and second known positions at which placement positions the appropriate head places a component carried by the head at a desired location on the substrate and a pick-up location at which the head is disposed in register with an associated pick-up position of an adjacent one of the component supply means.

Preferably a machine according to the invention is so constructed and arranged that the carriers position a head on the first carrier at its pick-up location in register with the associ ated pick-up position of one of the component supply means and a head on the second carrier at its pick-up. location in register with the associated pick-up position of the other of the component supply means so that heads of the first and second carriers pick-up components simultaneously, or substantially so, from opposite ones of the components supply means.

Conveniently the component supply means of a machine according to the invention comprises two carriages- mounted at opposite sides of the X-Y table, each mounting a plurality of component magazines and each carriage being mounted for movement along a first path extending in the X direction whereby to present a component at an outlet position of a selected one of the magazines at the pick-up position associated with one of the placement heads, the carriers being mounted for movement along parallel paths extending in the Y direction at right angles to the first paths to move each head between its placement position and its pick-up location in register with the associated pick-up position.

Suitably each head comprises a tool holder having means for interchangeably mounting a tool, the machine comprising a tool support for supporting tools for mounting in the tool holder. Preferably there is a tool support associated with each placement head and each tool support is mounted on the means for mounting the first and second carriers. Each carrier is movable along its path in the Y direction to move one of the heads into alignment with a preselected position on the associated one of the tool supports whereby to deposit a tool on or mount a tool from said preselected position on the tool support.

Suitably, means is provided for connecting the tool, mounted on a head, to a source of vacuum so that components engaging the tool may be held against the tool by vacuum. Conveniently, the placement heads of a machine embodying the invention may also comprise jaws comprising orienting faces disposed to cooperate with orienting faces of the other jaws of the head to engage a component-held on the tool and orient the component in a desired position relative to the placement head, the orienting faces of the jaws engaging edge portions of the component as the jaws are moved inwardly towards one another thus to urge the component into a desired position on the pick-up tool.

machine according to the invention is preferably so constructed and arranged that a head of the first carrier at the first placement position and a head of the second carrier at the second placement position, are operated to place components on substrates mounted on the X-Y table simultaneously, or substantially so.A machine in accordance with the invention may be so constructed and arranged that the head at the second placement position places its components substantially simultaneously with the head at the first placement position, but slightly later than that head, the machine being arranged so that between placement of a component at the first placement position and placement of a component at the second placement position, the X-Y table is operated to make slight adjustments (of the order of a few millimetres, for example less than 0.1 millimetres where the substrates are identical and a fiducial correction system is in operation, or much more where substrates of different configuration, or different parts of the same substrate, are being operated on) to the position of the table relative to the placement positions. Adjustment may be made in either or both of the X-Y directions.The actual sequence of component placement is preferably optimised by a suitable computer programme, operated on a separate computer, the output from which- can be loaded into computer means (not shown) of the machine.

There- now follows a detailed description, to be read with reference to the accompanying drawings, of a component placement machine embodying the invention. It will be realised that this machine has been selected for description to illustrate the invention by way of example and that the invention may reside in any novel feature of the machine taken alone or in combination with other features. In the accompanying drawings: Figure 1 is a plan view of the component placement machine embodying the invention; Figure 2 is a view in side elevation of the illustrative component placement machine; and Figure 3 is a front view of the illustrative machine.

The illustrative machine comprises a frame 10 on which is mounted an X-Y table 12 at a central region of a bed 14 of the frame 10.

The X-Y table 12 is mounted on rails for movement in the X direction (lengthwise of the bed 14) and in the Y direction (transversely of the bed 14) and provides a support for substrates, for example, printed circuit boards, on which components are to be placed. The X-Y table may be moved in the X and Y directions by means of suitable drive means 16, for example Rohlix drives, in known manner. An optical position determination system of known construction is disposed to indicate the precise position of substrate holder 18 of the X-Y table to computer means (not shown) of the illustrative machine.

Also mounted on the bed 14 are rails 20, one set at either side of .the X-Y table 12, extending in the X direction. On each set of rails 20 is mounted a carriage 22, 23 of component supply means of the illustrative machine. Each carriage 22, 23 is arranged to mount a plurality of component magazines 24, for example tape feeders and stick feeders of known construction. Each of the component magazines is mounted on its carriage 22, 23 in a known position. The carriages 22, 23 are arranged to be moved in the X direction by suitable drive means 26, for example Rohlix drive mechanisms driven by suitable electric motors, in known manner.Means, for example rotary encoders driven by tooth belts on the carriages, are associated with each carriage 22 to indicate the precise position of the car riage 22 in the X direction of the machine to the computer -means, as is well known. Each of the carriages 22, 23 may be moved on the rails 20 to present a component at an outlet position of any selected one of the magazines 24 mounted on the carriage 22, 23 at a pick up position under the control of the computer means.

The illustrative component placement ma chine further comprises a bridge member 30 which extends across and above the bed 14, above the central portion of the bed at which the X-Y table is located. Mounted on the bridge 30 are rail systems 32 which extend transversely of the bed 14 (in the Y direction) parallel with the horizontal upper. surface of the bed 14. Mounted for sliding movement on one of the rail systems is a first carrier 34 and on the other of the rail systems 32, a second carrier 36. Wheels 38 mounted for rotation on the carriers 34, 36, run on the associated rail systems whereby to permit said sliding movement while supporting the carriers accurately.The carriers 34, 36 are moved along the rail systems 32 by Servo motors -40 which rotate shafts 42 mounted for rotation on the bridge member 30 and drive the carriers 34,36 through Rohlix drive mechanisms. The position of each of the first and second carriers 34, 36. transversely of the machine (in the Y direction) is verified by an optical encoder system (not shown) of known construction, information on the position of the carriers 34, 36 being supplied to the com puter means of the illustrative machine.

Mounted on the first carrier 34 are two place ment heads 44, 46 having their centres spaced apart by a known distance. Placement heads 48, 50 are mounted on the second car rier 36, the centres of the heads 48, 50 being spaced apart by the same distance as the centres of the heads 44, 46.

Four tool supports 28 of known construc tion (one associated with each of the place ment heads 44, 46, 48, 50) are mounted on the bridge member 30. Each of the tool sup ports 28 is mounted with its centre line in register with the centre line of its associated placement head when carrier 34, 36 carrying that head is in a central position on its rail system 32. Each tool support 28 comprises a housing 29 provided by a base having a plu reality of recesses in which tools 52 are sup ported in a plurality of positions. The housing 29 is secured to outer end portions of slide rods 31 mounted for sliding movement in bearings in a bearing block 33 secured to the bridge member 30. A cylinder 35 of a piston and cylinder assembly is secured to the bearing block and a piston rod thereof is secured to the housing 29.When the piston rod is extended from the cylinder by admission of air under pressure behind the piston the housing 29 is moved in the X direction from beneath the bridge member 30 to project beneath its associated placement head, in a tool loading position (shown in chain dot line on Figure 2) for exchanging a tool. After a tool has been exchanged the piston rod is retracted into the cylinder by admission of air pressure in front of the piston, thus retracting the housing 29 to an out-of-the-way position beneath the bridge member, where it is clear of the heads thereby permitting the carrier 34, 36 to move the heads with no fear of the heads fouling the housing 29.

The tools comprise a nose (on which a component may be mounted when the tool is in use) which projects from a collar of the tool at the opposite side of the collar to a shank.

The tools are received in the recesses of the base of the housing 29 supported by the collars with their shanks projecting upwardly. A slide member is slidable on the base having a slot therein extending in the Y direction, the slot being sufficiently wide at all parts to permit the shanks of the tools accommodated in the recesses to project upwardly through the slot. The slot has enlarged portions dimensioned so as to allow clearance for each tool to be withdrawn from its recess through one of the enlarged portions of the slot when the enlarged portion is aligned with the recess.

However when the slide member is moved so that the enlarged portions and recesses are not in register, portions of the slide member overlie the collars of the tools in the recesses thereby retaining the tools in the recesses.

The slide member is moved, at appropriate times in the machine cycle to permit tools to be changed, by a piston/cylinder arrangement (not shown) on the housing, under the control of the computer means.

Each of the heads 44, 46, 48, 50 comprises a body portion mounted for rotation in bearings carried by the carrier 34, 36, and a tool holder 54 mounted for vertical sliding movement within the body portion. The tool holder 54 comprises means for interchangeably mounting a pick-up tool 52 with a datum face thereof positioned at a predetermined position relative to the tool holder 54.

This tool holder 54 comprises a socket in a lowermost end portion thereof, in which the shank of a tool can be slidingly received. The tool holder 54 further comprises retaining means resiliently biased into a recess in the shank of a tool received in the socket to retain the tool on the mounting means. The retaining means conveniently comprises a plurality of balls held captive in the tool holder 54 but projecting into the socket, the balls being resiliently biased into the socket by a resilient rubber sle#eve surrounding the lower end pot- tion of the- tool holder 54 and operating on portions of the balls projecting from their housing in the holder to urge the balls in-.

wardly -of the socket. A tool thus mounted in the tool holder 54 is accurately located at the predetermined position relative to the holder 54 by engagement of the collar of the tool 52 with a lowermost location face of the holder 54. Means is provided for moving the tool holder 54 vertically by a known distance which is communicated to the computer means of the illustrative machine, for example by means of a rotary encoder which provides a digital indication of the position of the tool holder whereby the computer means can control the vertical position to which the tool holder is moved.Likewise means is provided for rotating- the body portion in which the tool holder 54 is mounted; for example stepping motors of known construction may be used torotate the body portion through a predetermined angle controlled by the computer means according to the orientation at which it is desired to place a component on a substrate on which the head is to operate.

Each of the placement heads 44, 46, 48, 50 also comprises a plurality of, viz two, oppositely disposed pairs of orienting jaws 56 of known construction, mounted for movement towards and away from a component carried by and abutting a datum face of a tool 52 mounted on the tool holder 54 when the holder is in an appropriate location position whereby to engage and orient the components. The tool 52 used is selected to be of the most appropriate construction for handling the particular component in question. The jaws 56 are secured in accurate location at lower end portions of arms which are pivotally mounted on the body portion of each placement head.Each pair of jaws 56 may be moved in synchronism towards one another under the control of the computer means to engage and orient a component carried by a pick-up tool 52 mounted in the holder 54 at an appropriate stage in the cycle of operation of the illustrative machine.

As herein before mentioned the X-Y table 12 comprises a substrate holder 18 which provides an upwardly facing support surface on which substrates of rectangular shape may be mounted: this support surface is conveniently provided by upwardly facing surfaces of a pair of parallel rails extending in the X direction and spaced apart a sufficient distance- that edge portions of the substrate are received thereon, the rails having upstanding outer edge portions which engage edges of the substrate so that the edges lie substantially in the X direction.Boards on which components are to be placed may be mounted directly on the support 18 or, alternatively, in accurate location in known manner on palettes (not shown) which themselves are mounted, in known manner, in accurate location on thesupport 18, the palettes with the board mounted thereon in this instance being regarded as the substrates. A substrate 58 on which components are to be placed, for example a printed circuit board, is conveniently mounted in a known, datum position adjacent either the first or second carriages 34, 36.One convenient way of locating the substrate 58 on which components are to be placed provides that each substrate 58 has two location holes therein at diagonally opposite corners, one of the two holes providing a datum position for the substrate 58 itself At each of the two known positions on the X-Y table are disposed locating means by which substrate 58 can be located at the respective one of the known positions and clamp means by which the substrate 58 may be clamped in said known position (such locating means and clamp means being- of known construction).

One convenient locating means may comprise two spaced pneumatic cylinders secured to the substrate support 18 with piston rods arranged to project upwardly therefrom, the piston rods being positioned to register with location holes of a substrate. When a substrate is to be placed in one of the known positions it is rested on support surfaces of the substrate support and moved into position with the location holes aforementioned substantially aligned with the piston rods (which at this time are retracted). When the substrate 58 has been placed in this position, the pneumatic cylinders are actuated to extend the rods so that conical, guiding, leading end portions of the rods enter the holes and thereby locate the substrate 58 accurately on the substrate support 18.A substrate 58 may be clamped to the substrate support by suitable clamp means, for example comprising pneumatic cylinders mounted on the substrate support.

Where the substrate ~58 comprises a palette carrying a printed circuit board, or the like, means (not shown) are provided for mounting the board accurately at a known position on the palette. Where greatest accuracy is desired it is desirable to have a so-called fiducial correction system. In this system, when the pattern of conductors is printed on the printed circuit board, reference marks are also printed thereon, these being accurately positioned in relation to the conductor pattern. A machine comprising a fiducial correction system has means, conveniently optical, positioned to observe the reference marks and note the X and Y errors of these marks from a datum position. The X and Y errors of two reference marks can be used to indicate, to the computer means errors in pattern orientation (which may be due to inaccurate printing of the pattern relative to the substrate mounting holes or to inaccurate drilling of the holes) and scaling errors in X-Y dimension (the optical system projecting the pattern onto the board may in some cases project a pattern which, while being the correct shape, may be slightly larger or smaller than intended). From these errors the computer means is arranged to recalculate the actual positions for placement of components using the theoretical positions programmed in the machine. This may result, where necessary, in slight movement of the X-Y table even where placing on identical boards, as mentioned herein.

The construction and arra#ngement of much of the illustrative machine described herein is generally similar to the construction and arrangement of similar parts of the machine describe by way of example in our co-pending patent application number PCT/GB 84/00015 filed 23rd January 1984. Attention is directed to this specification for further details of the carriages 22,23 the X-Y table 12 (referred to in our aforementioned co-pending patent application as a substrate support), the construction and operation of the carriers 34, 36 (corresponding to a head support member which runs on a rail system as described in the afor ementioned specification, there being only one such support member), the placement heads themselves, and the tools supports.However, the machine described in said PCT application comprises only two placement heads mounted on the single head support member of the machine. In a machine otherwise similar to the illustrative machine described herein, substrates may be arranged to be fed to the X-Y table, for example by suitable feed means as described in our co-pending UK patent application number 8331348 to which reference is directed.

The construction of the illustrative machine is such that two substrates may be mounted on the substrate support 18, one in the first of said known positions and the other in the second of said known positions, the two boards being identical so that both of the boards can be populated with components sir multaneously, one by the heads 44, 46 carried by the first carrier and the other by the heads 48, 50 carried by the second carrier 36.Alternatively the machine can be arranged to operate so that approximately half of the components on- a board are placed by the heads 44, 46 and the rest by the heads 48, 50: where this second system is being operated it may be applied to two identical boards one at each of said known positions or to a single, much larger, board which extends over both of said known positions, the heads, 44, 46 carried by the first carrier 34 populating one half of the board while the heads 48, 50 carried by the second carrier 36 populate the other half of the board.Where the heads carried by the first carrier 34 are arranged to populate only approximately half of a board (with the remainder of the board being populated by the heads carried by the second carrier 36) it is possible to handle a larger number of components in a single machine than where both sets of heads are populating identical boards completely. Where two identical substrates are mounted one at the first of said known positions and the other at the second of said known positions and the pair of heads 44, 46 are arranged to populate approximately half of the board, it is necessary to move the partly populated board from the first of said known positions to the second of said known positions adjacent the carrier 36 for completion of population by the heads 48, 50.In the illustrative machine this will be carried out manually but in a machine comprising a suitable board feed, for example as referred to in our aforementioned British patent specification, the boards will be moved from one station to the next automatically under the control of the computer means.

The illustrative machine is constructed so that both of the carriers 34, 36 can be moved independently of one another and the heads on each of the carriers are likewise independently operable. However, in the normal operation of the machine the carriers are moved in synchronism so that when a head of the carrier 34 is at the first placement position (in register with the first known position of the X-Y table 12) and the other placement head on the carrier 34 is at a pick-up location (remote from the placement position) in register with one of the pick-up positions also associated with that head, and with one of the carriages 22, 23 e.g. the carriage 22, the carrier 36 is disposed, likewise with one of its heads at the second placement position in register with the second station and the other of its heads at a pick-up location in register with an associated pick-up position, also associated with the other of the carriages 22, 23 e.g. the carriage 23. In the drawings the head 44 of the first carrier 34 and the head 50 of the second carrier 36 are arranged, respectively at the first and second placement positions, whilst the head 46 of the carrier 34 is at a pick-up location in register with a first pick-up position associated with the carriage 22 and the head 48 of the second carrier 36 is at a pick-up location in register with a second pickup position associated with the carriage 23.

The heads 44, 50 will place components carried by them at the placement positions simultaneously, or substantially so, whilst the heads 46, 48 will pick up components from the pick-up positions simultaneously, or substantially simultaneously, with operation of the heads at the placement positions. After the head on the carrier 44 has placed its component and the head 46 has picked up its component, the carrier 34 will be moved by the motor 40 to move the placement head 46 to the placement position and the head 44 to a pick-up location in register with a first pick-up position associated with that head and with the carriage 23.Likewise, after the head 50 has placed its component and the head 48 has picked up its component, the motor 40 associated with carrier 36 will move the carrier 36 to transport the placement head 48 to the second placement position and the placement head 50 to a pick-up location in register with that head and with a second pick-up position associated with the carriage 22.The carriers 34, 36 will move along the rail means 32 simultaneously, or substantially so, in opposite directions under the control of the computer means As the carriers 34, 36 are moved along the rail systems 32, the carriages 22, 23 are moved along their rails 20 by the drive means 26 to move the outlet position of a component magazine mounted on the carriage to the appropriate one of the first and second pickup positions, under the control of the computer means, so that the component to be picked up by the one of the heads approaching the respective# carriage 22, 23 is presented at the pick-up position appropriate to that head.

From time to time, in order to handle a wide variety of components, it will be necessary to change pick-up tools 52. The- computer means is arranged at such times to cause the appropriate one of the cylinders to be operated to move the housing 29 related to the appropriate head 44, 46, 48, 50 to present the housing 29 at a tool loading position while the computer means causes the appropriate one of the carriers 34, 36 to travel along the rail system 32 to move the appropriate one of the heads 44, 46, 48, 50 on that carrier 34, 36 into alignment with a position on the housing 29 at the tool loading position, preselected by the computer means, whereby to deposit a tool 52 from the tool holder 54 on the housing 29 and to then move the head further to -bring the head into alignment with a further position preselected by the computer means and to mount a tool 52 from the further preselected position of the housing 29, in the tool holder 54.The operation of the machine is optimised to change tools as infrequently as possible, whilst bearing in mind the necessity to move the X-Y table 12 as little as possible, so as to achieve maximum efficiency of operation of the machine Where two identical substrates 58 are mounted on the X-Y table 12 the carriers 34, 36 are preferably arranged to move precisely in synchronism, in opposite directions, and the heads at the placement position of each carrier are arranged by the computer means to place their components simultaneously at identical positions on the two substrates: this ensures the most rapid operation of the machine (together with optimisation of tool changes and that of travel of the X-Y table).Where a fiducial correction system is in operation to achieve greatest accuracy, however, the heads may actually place components only substantially simultaneously if different corrective X-Y movements have to be applied to each substrate, though placement will occur simultaneously if no correction has to be made, or the same correction applied for each substrate.

This method of operation achieves substantially double the output rate of known machines of generally similar construction having only one carrier carrying two placement heads (as compared with the four placement heads of the present machine) for example the machine described in our afore mentioned PCT patent application, commercially available from the applicants as the MOPS500, the illustrative machine occupying little or no additional factory floor space than the previously known machines referred to: a much more efficient use of factory space is thereby achieved.

However, where the carriers 34, 36 are used in a second mode in which they each populate approximately half of a substrate (irrespective of whether or not two substrates are mounted in the machine or one large substrate) it may not be possible to operate the heads at the placement positions simultaneously because the components to be placed on each half of the board may not be intended to be placed at precisely corresponding positions. However, the operation of the machine is optimised so that components are placed in the same cycle by the heads carried by the carriages 34, 36 at positions corresponding as closely as possible.Where the placement positions on the substrates do not correspond precisely but are only approximately the same, one of the heads will be caused by the computer means to place its component at its placement positions slightly before the component carried by the head on the other of the carriages at its placement position; between placement by the first of these heads and the second of these heads, the computer means will cause the X Y table to operate to make a slight adjustment (including, if necessary, a correction generated by the fiducial correction system) so that the substrate is moved to bring the appropriate placement position into register with the second of the placement heads to operate. The operation of the machine is optimised so that the head carried by either of the carriers 34, 36 may operate first, depending on the relationship between the previous position at which components were placed on the substrates by the preceding heads, the location of the various component magazines on the carriages 22, 23, the need to effect a tool change (if one is required) and such factors. In some cycles of operation the machine may be arranged to operate so that no component is placed by the head of one of the carriages at the placement position if this is the most efficient mode of operation.In this second mode of operating the machine components may be placed at the first and second placement posi tions simultaneously or only substantially si- multaneously depending whether or not the placement positions on the substrates correspond exactly: the delay between placement by the first and second heads where the positions do not correspond exactly being sufficient to operate the X-Y table to make adjustment to the position of the X-Y table relative to the placement positions, so that the second placement head to operate is in register with the appropriate position on the substrate.

The heads will, however, still be arranged to pick-up the next component as the other head on a carrier places its component, thereby keeping the operating cycle as short as possible. When operating in this latter mode the output rate of the machine may be somewhat less than double the output rate of a machine having only two heads but nevertheless makes significantly better use of available factory floor space than many heretofore known machines.

Claims (11)

1. A component placement machine comprising an X-Y table, means for mounting one or more substrates in known positions on the X-Y table, a first carrier mounted adjacent a first of said known positions and a second carrier mounted adjacent a second of said known positions, each of said carriers carrying two placement heads spaced apart by the same distance, component supply means disposed at opposite sides of the X-Y table, and means for mounting the first and second carriers for movement to carry the placement heads between respectively first and second placement positions in register with a substrate mounted at the adjacent one of the first and second known positions, at which placement positions the appropriate head places a component carried by the head at a desired location on the substrate and a pick-up location at which the head is disposed in register with an associated pick-up position of an adjacent one of the component supply means.

2. A machine according to claim 1 so constructed and arranged that the carriers position a head on the first carrier at its pick-up location in register with the associated pick-up position of one of the component supply means and a head on the second carrier at its pick-up location in register with the associated pick-up position of the other of the component supply means whereby heads of the first and second carriers pick-up components simultaneously, or substantially so, from opposite ones of the component supply means.

3. A machine according to either one of claims 1 and 2 in which the component supply means comprises two carriages at opposite side of the X-Y table each mounting a plurality of component magazine and each carriage being mounted for movement along a first path extending in the X direction whereby to present a component at an outlet position of a preselected one of the magazines at the pick-up position associated with one of the placement heads, the carriers being mounted for movement along parallel second paths extending in the Y direction at right angles to the first paths, to move each head between its placement position and its pick-up location in register with the associated pick-up position.

4. A machine according to claim 3 wherein each head comprises a tool holder having means for interchangeably mounting a tool, the machine comprising a tool support associated with each head mounted for movement in the X direction to present the tool support at a tool-loading position and each carrier being movable along its path in the Y direction to move one of the heads into alignment with a preselected position on the associated one of the tool supports whereby to deposit a tool on, or mount a tool from, said preselected position on the tool support.

5. A machine according to claim 4 wherein the tool supports are mounted on the means for mounting the first and second carriers for movement, in the X direction between the tool-loading position and an out-of-the-way position clear of the heads.

6. A machine according to any one of the preceding claims so constructed and arranged that a head of the first carrier at the first placement position and a head of the second carrier at the second placement position are operated to place components on substrates mounted on the table simultaneously, or substantially so.

7. A machine according to claim 6 so constructed and arranged that the head at the first placement position places its component and the head at the second placement position places its component substantially simultaneously but slightly later than the head at the first placement position, and that, between placement of a component by the head at the first placement position and placement of a component by the head at the second placement position, the X-Y table is operated to make adjustment to the position of the table relative to the placement positions.

8. A component placement machine constructed, arranged and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.

9. A method of operating a component placement machine according to claim 1 wherein a head of the first carrier at the first placement position and a head of the second carrier at the second placement position are operated to place components on substrates simultaneously, or substantially so.

10. A method according to claim 8 wherein the head at the second placement position is operated to place its component slightly later than the head at the first placement position, the X-Y table being operated between placement at the first placement position and placement at the second placement position to make slight adjustment to the position of the table relative to the placement positions.

11. A component placement machine comprising an X-Y table, means for mounting one or more substrates in known positions on the X-Y table, a carrier mounted on support means adjacent the, or one of the, known positions, at least one placement head mounted on the carrier said placement head mounting an exchangeable tool, the carrier being mounted for movement to carry the placement head between a placement position adjacent the, or one of the the, known positions and a pick-up location remote therefrom and a tool support mounted on said support means for movement between an out-of-the-way position in which the tool support is clear of the heads and a tool-loading position in which the head can be moved into alignment with a preselected position on the tool support whereby to deposit a tool on, or mount a tool from, said preselected position on the tool support.