Method and apparatus for programming and operating a machine tool

Method of programming an electronic processor to control an apparatus in which a tool performs a series of discrete operations on a work piece. Initially a pattern is traced manually by a tracer to reflect working of the tool on the work piece with the processor in "Record" mode and input position and location signals are simultaneously generated and recorded to reflect the relative positions of the tracer and pattern. When programmed, the processor is set in "Playback" mode and output position and location signals are fed to apparatus to position tool on work piece reflecting pattern and tracer positions. For accurate positioning of tool and work piece, pattern is a template with tooling indexes that could be made on template in "Record" mode, if desired. In the "Playback" mode, a stylus is positioned coarsely by the processor in such a manner as to engage the tooling indexes which then causes self-centering action to bring the tool and tooling indexes into alignment for accurate locations of the tool relative to the work piece. The apparatus has free moving positioning structure that permits direct manual relative movement between the pattern and tracer data to establish spatial relationships with respect to Cartesian or polar coordinates system. Position signal generator used initially in the programming mode can be used as negative feedback system in the "Playback" mode to improve performance.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to an apparatus and method for programming and 
operating a machine tool, particularly relating to, but not limited to, 
drilling printed circuit boards for electronic components. 
2. Prior Art 
Several approaches are used to drill holes in work pieces, such as printed 
circuit boards. For large quantities, fully automatic drilling equipment 
with precise mechanical components and numerical control techniques are 
used. To obtain the desired accuracy, high precision bearings, lead 
screws, etc. are used in a rigid and costly structure. This equipment uses 
a sophisticated control system and considerable time and skill are 
required to programme and maintain such devices. 
For smaller quantities a single manual drill is commonly used in which an 
operator moves the work piece by hand, visually aligns the work piece with 
respect to a drill bit, and causes the drill bit to penetrate the work 
piece. Accurate work piece/drill bit alignment is assisted by an optical 
device which magnifies the hole position pattern imprinted on the work 
piece, or by a stylus that senses a hole in a template attached to the 
work piece. For use with the stylus, normally the operator first makes a 
template of the holes to be drilled in the work piece by using an optical 
magnifier for greater accuracy. The template is attached to the work piece 
and positioned under the stylus so that the stylus rests lightly on the 
template surface. As the template is moved relative to the stylus, when 
the stylus comes sufficiently close to a hole, it drops into it and a 
solenoid, air cylinder or other means forces the stylus down into the 
hole. The downward force moves the loosely held work piece and template 
into accurate alignment with the drill bit and simultaneously clamps the 
work piece flat to the drill table so that clean, accurate holes can be 
drilled. When the stylus has accurately positioned and clamped the work 
piece, a switch is actuated to commence drilling. For somewhat higher 
production rates, a quad drill can be used in which a drilled template is 
clamped to a work table and a self-centering stylus is aligned with the 
holes. Four drill bits are mechanically linked to the stylus to follow 
movement thereof and to drill simultaneously four stacks of boards clamped 
on the table. Some problems associated with these two manual methods 
relate to relatively low production rates, operator fatigue and operator 
error. 
SUMMARY OF THE INVENTION 
The present invention reduces some of the difficulties and disadvantages of 
the prior art by providing a relatively low cost, electro-mechanical 
apparatus which can use many existing components and simple manual 
operations of the prior art manual and quad drilling machine. The 
invention is susceptible of several embodiments, one of which is an 
apparatus and method for programming the processor in which a relatively 
unskilled operator programmes the processor by performing operations that 
closely resemble common drilling of a template on a manual drill as 
described. Another apparatus and method of the invention relates to 
automatic operation of a machine from a programmed processor in which the 
machine closely resembles that used in the previously described 
programming embodiment. A further aspect of the invention relates to use 
of the same machine for both programming of the processor and for 
subsequent automatic operation of the machine. When the machine is 
operating in an automatic mode, to improve the accuracy, a coarse 
positioning means can be used initially for locating each hole to be 
drilled, after which a fine positioning, hole sensing alignment means such 
as a prior art stylus, is used to effect accurate hole location. Thus, the 
electromechanical system need not position with great accuracy which 
reduces initial cost and maintenance requirements. Furthermore, use of 
unskilled operators for programming reduces set up costs and also 
eliminates the need for dimensioning or digitizing the holes usually 
associated with numerical control (N.C.) Machines. 
A method according to the invention utilizes an apparatus to perform 
automatically a series of discreet operations utilizing a template which 
is provided with a pattern of indications of locations at which a tool is 
to work on the template or on a work piece. The method comprises the steps 
of manually recording relative movement between successive indications on 
the template and a tracer to generate positional data relating to said 
indications, and recording said positional data. The method further 
includes subsequently utilizing said recordings of positional data to 
generate relative movement between the template and an alignment means to 
attain approximate locations by coarse positioning. The method is further 
characterized by positioning the alignment means and template coarsely 
relative to each other so that the alignment means can respond to said 
indications, and utilizing directly the response of the alignment means to 
produce further relative movement by fine positioning to bring the 
alignment means axially into alignment with each of the indications in 
turn prior to operating on the work piece at the particular location. In 
one expression of the method the movement of the alignment means is 
utilized to bring successively into mutual alignment the indications on 
the template and the tool. Furthermore, after mutually aligning the 
indication on the template and the tool, the response of the alignment 
means is utilized to actuate the tool to perform successive operations on 
the work piece. Whilst manually causing relative movement between the 
indications and the tracer, an operator can visually align successively 
and accurately the tracer and pattern of indications, which indications 
are in the form of marks on the template. A working means is utilized to 
modify said indications to produce a tooling index which is in a form 
capable of being sensed by the alignment means. The method can also be 
characterized by, whilst utilizing said recordings, disabling the 
alignment means when passing between the indications to prevent 
essentially accidental engagement of the alignment means with non-target 
indications on the template. 
An apparatus according to the invention is for use with an electronic 
processor for performing automatically a series of discreet operations on 
a work piece using a template which is provided with indications at 
locations where work is to be done. The apparatus has holding means, 
positioning means, signal generating means, drive means and alignment 
means. The holding means locates accurately relatively to each other 
either a template and tracer or a template and tool means. The positioning 
means cooperates with the holding means to permit direct manual movement 
between the template and tracer or driven movement between the template 
and tool means. The signal generating means cooperates with the 
positioning means to generate a location signal to reflect accurately 
relative positions between the tracer and template for recording in the 
processor when in the recording mode. The drive means cooperate with the 
processor and positioning means so that when the processor is in the play 
back mode the work piece and tool can be located approximately relative to 
each other by coarse positioning in response to output position signal 
from the processor. The alignment means is responsive to the indications 
on the template when sufficiently close thereto as a result of coarse 
positioning to produce directly relative movement between the template and 
the alignment means to position finely the template and alignment means in 
accurate alignment prior to working on the template. The apparatus can be 
further characterized by the working means being adapted to operate on the 
template at the indications to produce tooling indexes on the template 
which are of a form capable of being sensed by the alignment means. 
Furthermore, the apparatus can have disabling means cooperating with the 
alignment means to prevent essentially the alignment means accidentally 
engaging non-target indications during traverses of the alignment means 
relative to the template. The apparatus can also include feed back 
position signals generating means responsive to relative movement between 
the tool and the work piece to reflect relative positions thereof which, 
in the programming mode, can also serve as signal generating means. 
A detailed disclosure following, related to the drawings, describes 
preferred embodiments of the invention which are capable of expression in 
method and apparatus other than those particularly described and 
illustrated.

DETAILED DSCLOSURE 
FIGS. 1 through 3 
The apparatus will be described for use in drilling printed circuit boards 
using a manual drill, although equivalent work pieces and operations using 
other tools, such as a quad drill, can be substituted, as will be 
described. An apparatus 10 according to the invention is positioned on a 
conventional manual drill table 12 and includes a positioning means 14 and 
a holding means 15. A template 18 is located in the holding means 15, the 
means 15 being a releasable member that can hold a known template by 
itself, or one or more printed circuit boards 19, or a template attached 
to one or more printed circuit boards, to form a template/work piece 
combination. For use in the template/work piece combination, the template 
has a pair of widely spaced datum holes 20 and 21 which are aligned with 
similar holes in the work piece and located with pins to hold the template 
and work piece, ie. the respective data thereof, fixed relative to each 
other as is common practice when drilling boards. 
As seen in FIG. 3, an upwardly facing drilling machine and drill control 22 
is fitted below an opening 23 in the work table. The machine has a drill 
bit 25 having a drill axis 24 and being adapted to pass through the 
opening to drill the template and work pieces as required. An optical 
magnifier, not shown, with cross wires is commonly used for accurate 
centering of the template and the drill when drilling templates. The term 
"tracer" refers to the cross wires in the optical magnifier, or a fine 
pointer or equivalent that is effectively coupled to the drill to reflect 
accurate position of the drill axis to ensure the drill drills the 
template where required. Thus the tracer has a tracer datum that is fixed 
relative to a tool datum. For drilling circuit boards using a pre-drilled 
template to improve accuracy, a conical-pointed stylus 27, mounted in a 
stylus control 28, is accurately aligned with and positioned above the 
drill bit and thus the drill axis 24 and a stylus axis 30 serve as tool 
and stylus data respectively and are fixed relative to each other, and 
also to the tracer datum. The drill and control 22, the stylus 27 and the 
control 28 are prior art devices commonly used in manual drills used for 
drilling circuit boards and thus are not described structurally in detail, 
but the operation is summarized as follows. The stylus usually rests 
lightly on the drilled template and when the conical tip thereof enters a 
hole in a template, the stylus drops a little which initiates a 
self-centering effect as follows. Downwards force on the stylus is 
increased and side walls of the conical tip engage the opening in the 
template which causes the template to be shifted slightly to align the 
hole accurately with the stylus, and thus also with the drill. The 
downwards force on the stylus also clamps the template onto the work table 
to reduce undesirable movement during drilling. When resting lightly on 
the template, the stylus status is termed "enabled", and it can be raised 
clear of the template, which status is termed "disabled". The drill can be 
actuated and raised conventionally to penetrate the template and/or work 
piece by use of a foot switch (see FIG. 4) when drilling templates, or by 
a signal from the stylus control when using a template to align the drill 
for drilling boards. Thus, when used with drilled templates, the conical 
tip of the stylus provides an automatic self-centering effect so as to 
finely position the hole in the template accurately relative to the drill 
axis and also to initiate a clamping and drilling sequence. Thus the 
drill, stylus and work table and related accessories such as the optical 
magnifier for improved accuracy for drilling the template, resemble 
closely those used in conventional machines, such as a "Uni-Drill" as 
manufactured by Excellon International of the United Kingdom. 
The invention relates to the method and means of positioning the template 
and the work pieces relative to the stylus and drill bit to enable 
programming of the processor when the processor is in a recording mode, 
and to enable automatic control of the apparatus and drill when the 
processor is in a playback mode operating under the programme. The 
positioning means 14 includes a fixed X--X ordinate arm 31 having an X--X 
axis 32 and being secured by releasable securing means 33 to the table 12 
which permits the apparatus to be removed for servicing or replacing. The 
arm 31 is a rail and carries a slider 34 thereon, which can slide along 
the arm 31. A Y--Y ordinate arm 35 having a Y--Y axis 36 extends from the 
slider 34 in a direction at right angles to the direction of the X--X 
ordinate arm. Thus the Y--Y ordinate arm 35 extends from and is movable 
laterally along the X--X ordinate arm. A support roller 37 is carried at 
an outer end of the Y--Y arm 35 and runs along the upper surface of the 
table 12 to support the arm 35 on the table to be clear of the table. Thus 
the axes 32 and 36 correspond to respective Cartesian axes of a Cartesian 
coordinate system and the arms 31 and 35 resemble to some extent common 
drafting machines used in drawing offices. A carriage means 38 is mounted 
on the Y--Y ordinate arm for movement along the axis 36 and the holding 
means 15 is connected by a double hinge means 40 to the carriage means. 
The hinge means 40 permits swinging of the holding means 15 relative to 
the carriage means 38 to maintain the template and work pieces parallel to 
the table to accommodate different thicknesses of template/work piece 
combination. Thus the holding means 15 is mounted on the carriage for 
simultaneous movement along the arm 36 and is adapted to provide accurate 
relative location between the pattern and tracer datum in the second mode, 
and between the work piece and tool datum in the playback mode so that the 
data are located accurately relative to each other as desired. 
The X--X ordinate arm has a pair of spaced apart, rotatable first loop 
rotor means 41 and 42, and a first loop of flexible tension link means 43 
passing around the loop rotor means to ensure essentially slip free 
engagement with the loop rotor means. The loop rotors and link means are 
compatible, for example, tensioned flat steel bands running on a steel or 
rubber roller having a complementary cylindrical periphery, braided steel 
cables running on grooved pulleys, or moulded, toothed plastic bands 
running on toothed wheels. Any equivalent flexible tension link capable of 
transferring power from or to the loop rotor with negligible slippage can 
be used. An inner run 44 of the loop is connected to the slider 34 and 
thus is effectively connected to the Y--Y ordinate arm 35 to move the Y--Y 
ordinate arm laterally with the loop parallel to the direction of the X--X 
axis. A stepping motor 46 is connected to the loop rotor means 41 and a 
rotary pulse generator 48 is connected to the loop rotor means 42. 
The Y--Y ordinate arm 35 has a pair of spaced apart, rotatable second loop 
rotor means 51 and 52 and a second loop of flexible tension link means 54 
passes around the second loop rotor means to ensure essentially slip free 
engagement with the second loop rotor means. An inner run 56 of the loop 
is connected to the carriage means 38 to move the carriage means with the 
loop in the direction of the Y--Y axis. Similarly, to the X--X ordinate 
arm, the Y--Y ordinate arm has a stepping motor 58 connected to the rotor 
means 51 to drive the loop 54, and a rotary pulse generator 59 connected 
to the rotor means 52. 
The stepping motors are connected to the processor and are adapted to 
rotate in accurate increments in a particular direction in response to 
electrical signals or pulses from the processor and equivalent motor means 
can be substituted. Thus, the arms 31 and 35 have first and second motor 
means connected to the processor and adapted to drive at least one loop 
rotor means of the respective arm. The pulse generators 48 and 59 are 
similarly connected to the processor and adapted to generate accurately 
signals or electrical pulses to represent rotation in a particular 
direction to indicate movement of the slider 34 or carriage 38 along the 
respective arms relative to a respective datum. Each axis has a respective 
datum and typically the intersection of the axes is chosen and programmed 
in the processor. 
The positioning means 14 is adapted for relatively low friction movement to 
permit relatively easy manual positioning of the template and work piece 
where required on the table. The roller 37 supports the arm 35 clear of 
the table to reduce drag, and the tension in the loops 43 and 54 is 
sufficient to essentially prevent slippage between the loop rotor means 
and yet permit driving of the loops and arms when the operator directly 
shifts the holding means during programming. Thus the positioning means 
cooperates with the holding means and the tracer and thus the tool to 
permit direct manual movement between the pattern and tracer data to 
establish new relative relationships therebetween. 
As will be described, in the programming mode, the pulse generators 48 and 
59 are input position signal generating means cooperating with the 
positioning means and the processor so as to generate position signals to 
reflect relative positions of the tracer and template as the positioning 
means is moved manually, i.e. is directly held by the operator. Also, in 
the programming mode, location signals reflecting relative positions of 
the tracer and template are generated by the foot switch actuating the 
drill control to initiate the drilling operation, termed a drill signal, 
which signal is combined with the corresponding position signals from the 
pulse generators as will be described. Thus the pulse generators and drill 
control are input location signal generating means cooperating with the 
positioning means and the processor to generate and record location 
signals reflecting relative positions of the template and tracer when the 
tool is to be actuated at each operation location. 
In a reverse mode, ie. in the playback mode, low friction movement is also 
desirable when the positioning means is driven by the stepping motors. As 
will be described, in the playback mode, the pulse generators may serve as 
feedback position signal generating means responsive to the movement of 
the first and second loops to reflect relative positions of the carriage 
from the respective data. Thus the pulse generators serve two different 
functions in the two different modes. It can be seen that relative motion 
and spatial relationships of the drill or stylus and template data are 
defined with respect to a Cartesian coordinate system. 
FIG. 4 
The apparatus 10 is for use with an electronic processor 64, which is shown 
schematically with some of its major components and the main 
electro-mechanical components of the apparatus 10. The processor 64 
includes interface and logic devices 66, and a central processing unit 68 
(CPU) which can be programmed as required. The CPU 68 is connected to a 
read and write memory 70 (RAM) and a read only memory 72 (ROM). A memory 
location pointer 71, maintained as part of the computer software, is used 
to address particular memory locations in the RAM 70. An operator's panel 
73 is connected to the interface 66 and has a "Waiting" mode indicator 
light 74, a "Record" switch 75, a "Drill" or "Playback" switch 76, and a 
"Completed" switch 77. The interface 66 is also connected to motor drives 
80 and 81 which are common components that process signals to the stepping 
motors 46 and 58, and to the drill and stylus controls 22 and 28 
respectively, shown integrated because they are commonly sold and operated 
as an integrated unit. The controls 22 and 28 control and also indicate to 
the processor the status of the drill, and the status of the stylus. Power 
is supplied from a power source 84 through an emergency switch 85 to the 
motor drives 80 and 81, and through an operator's foot switch 86 and the 
interface 66 to the CPU 68. 
OPERATION 
Power is supplied to the processor which is normally in the "Waiting" mode, 
as indicated by the indicator light 74. In this mode, the processor is 
waiting for a signal to either assume a "Record" mode or a "Playback" or 
"Drilling" mode. In the "Waiting" mode the computer continuously reads the 
two switches 75 and 76, and assumes the appropriate mode when the relevant 
switch is pressed. 
Initially it is assumed the operator has an undrilled template upon which a 
pattern of holes to be drilled is marked, typically by a photo-etching 
process. This is termed a blank template and this is accurately and 
securely attached to the holding means 15 so that the datum holes 20 and 
21 are located accurately relative to the holding means 15. Thus the 
template is located accurately in the apparatus so that the drill datum is 
effectively located accurately relative to the template datum. As is well 
known in the trade, to avoid hole burr problems associated with the 
stylus, a template is normally drilled in reverse to produce a hole 
pattern which is a mirror image of the desired drilled circuit board. This 
should be understood when considering the relative locations of the 
template and drill data in the following description and in the claims. 
The "Record" switch 75 on the operator's panel is pressed to set the 
computer in the recording or programming mode. For greater accuracy in 
positioning the drill relative to the template, the operator preferably 
uses the optical magnifier as commonly supplied on conventional manual 
circuit board drilling machines. The operator moves the blank template to 
an origin hole and this position is located accurately relative to the 
drill datum using the optical magnifier. A hole is then drilled in this 
position by actuating the foot switch 86 following normal manual drilling 
practice and the drill control 22 initiates a drill signal to the 
processor, thus defining a first location. This sets the memory location 
pointer 71 to indicate the first location in the RAM 70 where the position 
data is to be stored, and simultaneously clears the contents of that 
location. This establishes the first location in the template as the 
origin. 
The operator then takes hold of the work piece or holding means to manually 
move the work piece from the first location towards a different location, 
and this actuates the positioning means 14 causing it to follow the 
movements of the template. The loops 43 and 54 are shifted which in turn 
rotate the rotary pulse generators 48 and 59, assuming the template 
movement is represented as movement relative to both X--X and Y--Y axes. 
The pulse generators produce electrical pulses and direction bits 
representative of distances and direction travelled relative to the X--X 
and Y--Y axes. Thus the operator is manually and directly causing relative 
movement between the template and drill data to establish a different 
relative relationship between the template and drill data, which is 
defined as a second location. Thus, simultaneously with the template 
movement, a plurality of input position signals are generated by the pulse 
generators and recorded to reflect the relative movement between the 
template and drill data. Under the direction of its programme which is 
stored permanently in the ROM 72, the CPU 68 checks each pulse as it is 
generated and either increments or decrements contents of the pointed-at 
memory locations, the pulses being added or subtracted depending on the 
direction of travel along the respective axis. 
Again, when the template is accurately located with respect to the drill at 
the second location, the operator steps on the foot switch 86 to generate 
a a drill signal and initiate the drilling cycle. Again the CPU 68 detects 
the drilling, increments the memory location pointer 71 by as many address 
spaces as are necessary to find unused memory space and clears the 
contents of the pointed-at memory location. Thus, a second input location 
signal is generated and recorded at the second location to reflect the 
relative positions of the template and drill data at the second location. 
It can be seen that, to set the memory location pointer 71 to indicate the 
location for drilling, a portion of the location signal is generated by 
the drill operating on the template in a manner similar to the drill 
drilling the work piece in the subsequent drilling operations. The 
remaining portion of the location signal is derived from the position 
signals already entered in the CPU 68. Thus this recording of drill hole 
location does not require any special operator skill or procedure. This 
process repeats itself until the last hole has been drilled in the 
template, at which time pushing the "Complete" switch 77 transfers 
programme control back to the "Waiting" mode confirmed by the waiting 
light 74. Before the transfer, provision is made to ensure that the last 
memory location point contains all zero data, because this is needed to 
indicate the end of a drilling cycle when the work piece is being drilled 
automatically, as will be described. 
Thus all the hole position data is now stored in the RAM 70 and this can be 
used to control the apparatus 10, or similar pieces of equipment as will 
be described. When it is to be used in the apparatus 10, the drilled 
template 18 is now pinned to a blank board 19 or stack of boards using 
pins, not shown, passing through the two datum holes 20 and 21 which are 
aligned with holes in the boards to form the template/work piece 
combination. This combination is held by the holding means 15 in a manner 
similar to holding the template by itself in order that the combination is 
accurately located, with the understanding of the mirror image reversal of 
the template relative to the circuit boards. This ensures that the work 
piece combination datum is accurately positioned effectively where the 
template datum was positioned during the programming, so that the holding 
means provides accurate relative location between the work piece and tool 
datum. Clearly the work piece datum, in this arrangement, is effectively 
coincident with the pattern datum which contrasts with some other types of 
drills, eg. a quad drill, as will be described. 
When the template/work piece combination has been loaded into the holding 
means, the "Drill" or "Playback" switch 76 is actuated and the drill 
routine of the CPU 68 sets the memory location pointer 71 to indicate the 
location in the RAM 70 where the position data of the second hole is 
stored. The contents of the pointed-at memory location are loaded into two 
seperate memory locations, labelled for convenience of description, "X 
Count" and "Y Count". The CPU 68 checks to see if the "X Count" and the "Y 
Count" both equal zero and if so, the cycle is complete and the control is 
transferred back to the "Waiting" mode. The most significant bits of the X 
and Y data in two Counts are checked to establish the directions of 
rotation of the stepping motors representing movement along X--X and Y--Y 
axes. Motor direction flags within the interface and logic devices 66 are 
set to 1 or zero accordingly. 
The operator manually moves the template/work piece combination until the 
first or origin hole of the template is positioned closely to the stylus. 
Because this is the origin in the programme also, it has no location 
signals. When the stylus tip drops into the hole, the control 28 increases 
stylus force which accurately aligns the template hole with the drill and 
applies the clamping force necessary for accurate drilling. When the 
aligning and clamping are satisfactory, the drill and stylus control 22 
and 28 cause the drill to move up, drill a hole and retract, followed by 
release of the clamping force. This follows conventional stylus and drill 
control. After drilling, when the processor receives a signal from the 
drill control 22 indicating that the drill bit is clear of the work piece, 
flags are set within the interface and logic devices 66 which "disable" 
the stylus from sensing a hole. The stylus is thus lifted clear of the 
template surface which prevents the stylus from accidentally engaging or 
entering a non-target hole during a traverse of the template. A non-target 
hole is a hole drilled in the template which is not to be drilled, at that 
time, in the work piece and this might be because the non-target hole 
requires a different drill diameter, or for other reasons. 
When the stylus is disabled, signals for high speed motor actuation are 
sent to the stepping motors 46 and 58 so that the positioning means is 
actuated to shift the template/work piece combination to the second 
location. As the positioning means 14 starts to move, the pulse generators 
48 and 59 generate pulses reflecting movement relative to the X--X and 
Y--Y axes, and these pulses are detected by the CPU 68 and the X and Y 
Count memory locations are decremented once for each pulse. The value of 
the X and Y Count is checked regularly and when each of the X and Y Counts 
become less than a pre-determined number, for example 10, the 
corresponding drive is switched to a lower speed. When the Counts become 
less than the same pre-determined number, the stylus is "enabled", that is 
the stylus is dropped under light pressure to engage the surface of the 
template. Under the action of the low speed drive, the stylus approaches 
the hole and it commences to descend into the hole. At this point the 
stylus and drill controls 28 and 22 force the stylus down and executes the 
drilling cycle as previously described. A drill signal from the drill 
control 22 transfers programme control to a sub-routine which stops both 
stepping motors, clears X and Y Counts and then increments the memory 
location pointer. When the signal from the drill control 22 indicating 
that the drill is clear of the hole in the work piece is received by the 
CPU 68, programme control is transferred back to the start of the "Drill" 
or "Playback" programme. Drilling continues automatically in this manner 
until a zero block of data is encountered, at which point control is 
transferred back to the "Waiting" mode. 
It should be noted that the actual path taken by the template as it passes 
under the stylus is not of importance, but the final location of the one 
hole relative to the previous hole, or origin, is of importance. Thus the 
term "trace" or "tracing" referred to earlier does not refer to an exact 
path definition but merely a point-to-point relationship. Thus the term 
"tracer" refers to the means which permits alignment of the drill and 
template data for the original programming, and exact repeating of the 
path connecting the holes together during programming is not required 
during playback of the programme. 
From the above it can be seen that the pulse generators 48 and 59 serve two 
purposes, as follows. In the programming mode, when the operator manually 
moves the template for drilling, the stepping motors generate a plurality 
of input position signals to indicate relative movement between the drill 
datum and the template datum to result in the desired final position. In 
the playback mode, when the stepping motors move the template and work 
piece combination, the pulse generators again generate a similar plurality 
of signals which are now used as a series of feedback position signals 
which are fed into the processor. The signals are now used in a closed 
loop negative feedback system to improve performance of the device by 
reducing inaccuracies in final positioning of the work piece prior to 
drilling, by assuring that the holder does in fact attain the desired 
location. Although optional, this additional accuracy using feedback is 
easily attained with negligible increase in costs. 
The stylus and drill means have the respective axes 30 and 24 aligned with 
each other, ie. are fixed relative to each other, and function in a manner 
similar to the prior art manual machine, and thus are not described in 
detail. However, the relative high accuracy or fine positioning of the 
well known and low cost stylus and drill combination is used to advantage 
with a relatively low accuracy or coarse positioning of the relatively low 
cost positioning means 14 of the invention. The accuracy of the 
positioning means 14 is dependent on resolution of the pulse generators 
and stepping motors, and general mechanical errors in displacement of the 
holding means as it travels relative to the respective X--X and Y--Y axes. 
A good condition, high precision stylus can usually detect a hole for 
accurate alignment therewith when the stylus crosses an edge of the hole 
sufficiently to generate sideways forces, which is typically within about 
1.0 mm of the hole center, depending on hole diameter. This discussion is 
simplified but this limiting factor can be called "hole detection ability" 
of the stylus. For the initial programming, the pulse generators and 
positioning means should be able to resolve template movement to a degree 
or within a tolerance considerably less than the hole detecting ability. 
Similarly, the stepping motors should have a resolution or positioning 
ability to cause movement of the slider 34 and carriage means 38 to within 
the hole detection ability of 1.0 mm. By selecting compatible components, 
the stepping motors and simple loop and rotor system can position the work 
piece coarsely and yet sufficiently closely to a target hole in the 
template to enable the stylus to take over and to fine position the 
template to the required high degree of accuracy. Thus, for compatibility 
between the coarse and fine positioning devices, the coarse positioning 
tolerance, which includes the programming tolerance, must be less than 
hole detecting ability of the fine positioning means, otherwise the coarse 
positioning means might stop the template before it has come under the 
influence of the stylus. This would result in a malfunction of the device 
preventing further operation until corrected. 
In summary, when programming, the drilling operations produce in the 
template a plurality of holes at relatively accurate locations relative to 
the template and stylus data and simultaneously generate position data. In 
the playback mode, the template/work piece combination is positioned 
coarsely in response to the position data, but sufficiently closely to the 
desired location to be within range of the alignment means. The hole is 
then located finely with the alignment means which automatically positions 
the work piece combination and drill data accurately relative to each 
other. The template/work piece combination is automatically clamped 
accurately in the desired location prior to drilling, is then drilled and 
after drilling is repositioned by repeating the operation. Preferably the 
alignment means is disabled during traverses between locations to prevent 
essentially accidental engagement of the alignment means with non-target 
holes in the template. 
Because drilling is initiated only by the stylus locating a template hole 
accurately and not directly by a signal from the position data in the 
processor, it follows that a hole can be drilled only in the correct 
location as determined by the stylus and template. Thus, if for some 
reason, the positioning means stops the template in the wrong location 
that is outside the hole detecting ability of the stylus, the stylus will 
not be permitted to drop and thus a hole drilling sequence cannot be 
initiated. Thus the processor cannot generate spurious hole drilling 
instructions without verification by the template/stylus alignment. Thus 
the positioning means is effectively fail-safe with regards to hole 
locations and, theoretically at least, holes cannot be drilled in the work 
piece except first by verification by the template. 
Thus, the high precision attained with the conventional well proven stylus 
and drill combination can be attained with a relative low cost "add-on" 
template positioner and processor. The processor can be simply programmed 
by an unskilled operator, and the same combination machine and processor 
can be operated in a playback mode and maintain desired accuracy with a 
drilling operation initiating means that is effectively fail-safe. 
Alternative and equivalent structures can be derived from this basic 
apparatus, as will be described. 
In summary, it can be seen that the present invention has many advantages 
over the conventional automatic positioning devices. For example, the 
positioning means 14 can be of relatively low cost construction and can 
include enough free play between components so that dust contamination is 
not a problem. This contracts with the particularly strict cleanliness 
requirements of high precision N.C. Machines. Also a massive, solid 
structure is not required to maintain accuracy, instead the relatively 
light positioning means can be simply attached to an existing drill table. 
Motor means for the positioning means, that is the stepping motors or 
equivalents, can be directly connected to the main moving parts of the 
positioning means, thus eliminating any need for gear reduction devices 
and precision lead screws. The elimination of gear reduction devices 
and/or lead screws is particularly important, because not only does this 
reduce costs, but it also permits the operator to manually move the work 
piece freely during programming. This free movement is essential for fine 
movements and accurate positioning, and results from the low mechanical 
resistance to movement of the direct drive when "reversed," ie. when 
"driven" manually by the operator. 
Because the positioning means 14 can be easily attached to drilling 
equipment which is commonly available in many drilling shops used for 
printed circuit boards, a manufacturer need only purchase and fit the 
positioning means and electronic processor, thus eliminating duplication 
of table, drill, drill sequencing control, optical magnifier and stylus 
positioning heads. Whilst the device is relatively simple and easy to 
maintain, should it fail it can be quickly removed and the operator can 
revert to conventional manual methods of positioning and drilling. 
ALTERNATIVES AND EQUIVALENTS 
Endless loop and rotor means has been described for translating rotary 
motion of the stepping motors into linear motion and vice versa and 
together with the stepping motors thus function as drive means operatively 
connected to the electronic processor and cooperating with the positioning 
means, so that, in the playback mode, the work piece and tool data can be 
located relative to each other at the desired location in response to 
output position signals from the processor. This is a low friction, low 
cost drive means which is easily adaptable to different sizes, easy to 
service and is relatively tolerant to dust. Alternative drive means for 
linear motion along the Cartesian axes can be substituted, such as a rack 
and pinion arrangement, a friction roller on a straight track, or a 
direct-acting pneumatic or hydraulic cylinder. Such equivalent drive means 
would cooperate with the axes of the Cartesian coordinate system and can 
be adapted to generate electrical signals, or to accept electrical 
signals, as in the previously described embodiment. Also, electrical 
stepping motors have been shown to drive the loops, but clearly equivalent 
AC or DC servo motors, or pneumatic or hydraulic cylinders could also be 
substituted as alternative motor means. Also, other position signal 
generating means or feedback means can be substituted for the rotary pulse 
generators, for example synchros, resolvers, optical diffraction gratings, 
potentiometers and variable inductance devices. 
Furthermore, in the operation of the processor, one particular programming 
strategy has been described to show how data from the various devices is 
processed and stored, and how the various control signals are generated 
and utilized. Clearly, a variety of programming strategies and/or any 
number of digital or analogue control devices can be substituted to obtain 
the desired recording and playback operations. 
The processor has been described in a basic form which does not disclose 
other aspects which would normally be incorporated. It would be desirable 
to have provision for loading hole data out of the RAM 70 and onto other 
storage media, such as magnetic or paper tape for long term storage of 
hole position data. Similarly, hole position data could be programmed into 
a suitable memory or other data storage means from a digitizing machine or 
other programme source, which programme can then be applied to the present 
apparatus for positioning templates. Clearly, an auxiliary power supply to 
preserve contents of RAM 70 should be provided to protect the memory if 
the main power supply failed. Also, memory capacity can be expanded for 
storing and subsequently using hole position data for more than one 
template. It is helpful if there is a provision for cancelling data that 
has been entered in error and replacing it with correct data. The 
operator's panel will also likely have switches and read out devices for 
controlling and monitoring the main power supply, recording the number of 
holes and boards drilled, etc., as well as other conventional control 
source data. 
The apparatus could be used for programming drilling of work pieces other 
than templates, although it is preferable that the pattern be planar 
because the positioning means disclosed cannot accommodate wide variations 
from a plane defined by the Cartesian axes. That is the positioning means 
only permits movement of the pattern datum with respect to the tracer 
datum generally within the plane of the pattern. If the apparatus were to 
be used purely for programming a processor which was not required to 
operate with a conical pointed stylus on a drilled template, it would not 
be necessary to produce a template with accurately drilled holes. Thus the 
optical magnifier or fine pointer could be used to trace a simple flat 
hole pattern of a circuit photo reduced onto film. Thus no drilling would 
be performed during programming and the drill signals for the programme 
could be initiated by a simple switch to indicate point of working of the 
tool on the work piece. This method can be summarized as follows. The 
pattern is located accurately in the apparatus so that tool and tracer 
data are located accurately relative to a pattern datum, which relative 
position is defined as a first location. With the processor operating in a 
record mode, generating and recording at the first location a first input 
location signal to reflect the relative positions of the tracer and 
pattern data at the first location to establish an origin at the first 
location. This is followed by manually and directly causing relative 
movement between the pattern and tracer data to establish a different 
relative relationship between the pattern and tracer data defined as a 
second location. Simultaneously a plurality of input position signals are 
generated and recorded to reflect the relative movement between the 
pattern and tracer data. At the second location, a second input location 
signal is generated and recorded to reflect the relative positions of the 
pattern and tracer data at the second location. If desired, the input 
location signal can be triggered by a manually operated switch because the 
tracer need not necessarily be simulating drilling or operating on the 
template similarly to subsequent operations on the work piece. In the 
playback mode, the alignment means and template are eliminated and the 
work piece and pattern data are fixed relative to each other. The first 
location is established as the origin for the tool by visual alignment and 
the remainder of the holes are drilled relying on accuracy of the 
positioning means with or without the negative feedback system. 
In another alternative, the apparatus permits use of templates drilled 
previously on a manual machine, in which case the apparatus would not 
require use of the optical magnifier for programming. The processor could 
be programmed using the stylus to engage the holes in the template, 
because the hole location signals are generated when the stylus detects 
and enters the hole. 
In another alternative, discrete machining operations on the work piece or 
template other than drilling could be effected, for example spot welding, 
punching, or other processes. These operations do not require duplication 
on the template in the programming mode as described below. In the 
programming mode there is no requirement for actual marking of the pattern 
because the operator merely establishes the input location signals by use 
of a manual switch when the pattern is accurately located, possibly using 
an optical magnifying device as the tracer. However, for use in the 
playback mode where highly accurate location of the tool is required, it 
is preferable that the template is operated upon in some manner to produce 
tooling indexes which can be detected by a fine positioning means. The 
tooling indexes could be merely an indentation on the pattern surface, ie. 
a center punch mark, a chemical or magnetic interaction with the template, 
or some other process which results in a tooling index on the template, 
which index is detectable and registrable by a suitable alignment means 
which can be mechanical, electronic, magnetic, etc., to enable fine 
positioning of the two data within the desired tolerance. The term 
"alignment means responsive to the tooling indexes on the template" refers 
to general structure capable of detecting and registering accurately with 
each tooling index, and thus is considered equivalent to the prior art 
conical stylus engaging and aligning with a suitably sized hole in the 
template. Thus, in the playback mode, the work piece and tool data are 
positioned coarsely in an approximate location by the output position 
signals controlling the positioning means in response to programme data 
only. This to be within range of the alignment means, which when 
"enabled," can detect and cooperate with a tooling index causing the 
template and work piece to be positioned accurately, ie. located finely, 
in an accurate position. Thus the alignment means has an axis and it can 
be seen to be responsive to the tooling indexes on the template by 
detecting and cooperating with the tooling indexes on the template when 
sufficiently close thereto to position finely the work piece and tool data 
to align the tool and template as required. Similarly to the stylus, 
disabling means are provided to cooperate with the alignment means to 
prevent esentially the alignment means accidentally engaging non-target 
holes during traverses of the alignment means relative to the template. 
Yet a further alternative relates to use in existing machines where the 
template and work piece is fixed, and the stylus and the drill are shifted 
manually. This arrangement is sometimes used in multi-drill head machines, 
for example in a quad-drill manufactured by Excellon International of the 
United Kingdom. In this arrangement, a movable, self-centering stylus 
cooperates with a fixed drilled pattern or template, and movement of the 
stylus is transferred through mechanical linkages to four drill heads 
operating simultaneously and in parallel motion to drill four fixed stacks 
of templates. This machine, which is used for larger production runs than 
are normally performed on a manual drill could benefit from certain 
aspects of the present invention. In this structure, as in the previous 
embodiment, the stylus and tool have respective data fixed relative to 
each other. Clearly the mechanical linkages now serve as positioning means 
cooperating with the holding means and the tool to permit direct manual 
movement, as previously described. The holding means are clearly clamping 
devices which locate the pattern or template and work pieces to the 
machine bed. Position and location signal generators, and drive means 
would cooperate with the linkages to reflect, and produce, relative 
movement between the stylus/tool and pattern/work piece. 
FIG. 5 
The apparatus of FIGS. 1 through 3 disclosed movement of a pattern or work 
piece which is defined relative to two mutually perpendicular Cartesian 
axes. An alternative positioning means 90 uses a polar coordinate system 
which contrasts with, but is considered equivalent to, the Cartesian 
system. The relative movement between the tracer and pattern data, or the 
tool and work piece data, is defined with respect to a polar coordinate 
system having a central axis 92 generally normal to the plane of the 
pattern or work piece, and a radial axis 93 within the plane of the 
pattern or work piece and extending from the central axis. The radial axis 
93 can be swung about the central axis and its position is measured as an 
angle 94 relative to a fixed angular datum 95. The positioning means has a 
swinging arm 96 corresponding to the radial axis 93, the arm being 
journalled for rotation about the central axis 92. A carriage means 97 is 
mounted on the swinging arm for movement therealong and a similar holding 
means 98 is mounted on the carriage for movement along the swinging arm. A 
template, work piece, or combination thereof designated 99 is held in the 
holding means and radial spacing 100 of the work piece relative to the 
central axis 92 is measured on the radial axis as shown to define one 
coordinate of the work piece location. Position of the work piece is 
further defined with reference to the angle 94 of the radial axis from the 
angular datum 95. 
The swinging arm 96 has a pair of spaced apart, rotatable loop rotor means 
104 and 105, and a loop of flexible tension link means 107 passes around 
the loop rotor means to ensure essentially slip free engagement of the 
loop rotor means. One run 109 of the loop is connected to the carriage 
means 97 to move the carriage means with the loop in the direction of the 
radial axis. A first stepping motor 111 drives the loop rotor 104 to move 
the loop and thus the carriage means 97. A second stepping motor 113, if 
necessary through a reduction gear which is not shown, is connected 
directly to a bearing shaft, not shown, carrying the arm 96 so as to swing 
the arm relative to the angular datum 95. 
Thus, the first and second motor means are connected to the processor and 
adapted to drive at least one loop rotor means and to swing the swinging 
arm respectively. Similarly to the first embodiment, first and second 
rotary pulse generators 115 and 116 cooperate with the loop rotor 105 and 
the arm 96 to serve as input position and location signal generators and 
also as feedback position signal generating means responsive to movement 
of the loop to reflect relative position of the carriage means and the 
central axis, and to be responsive to rotation of the swinging arm 
relative to the angular datum thereof. It can be seen that the polar 
coordinate system of FIG. 5 provides an equivalent positioning means to 
the Cartesian system of FIG. 1. In all embodiments, the positioning means 
cooperates with the holding means to permit direct manual movement between 
the pattern and tracer data to establish new relative relationships 
between the pattern and tracer data.