By the time you read this, the first PCB drilling machines have already been delivered — and perhaps also asmbled. It is therefore high time that our description of the machine be completed. All that remains is the calibration of the machine. The machine must be calibrated before the driver software is able to deter-mine the reference point, calculate drilling coordinates correctly, posi-tion the arm(s) and turntable and rai and lower the drilling head. A number of position nsing switches play a key role in initialising the machine. In this final part we describe a complete calibration pro-cedure for the arms and turntable with the aid of the TanBoTest soft-ware, and the u of the TanBoDrive driver software for drilling PCBs.Plea note that the German wor-king title of the project, 'Tanbo' (for Tangential Bohrer) is retained in the names of the files and programs developed for the project.
Position nsing swiches
In the machine enclosure there is an optical switch situated just bet-ween the two drive shafts for the tool arms, which operates on the reflective principle. The position of the turntable
and of tool arms 1
PCB
Drilling Machine (5)
part 5 (final): ready to go!
In this final part on the construction of the PCB drilling machine, all its
functions are tested and the machine is calibrated. The machine is then ready for its first job.
mally-clod contact). If the arm is not fitted,there is no BO switch, and the corresponding switch inputs (BO1-BO4) on the circuit board are open. The software can check each arm individually to determine whether the corre-sponding drill lift mechanism is in the up position.
State 2: Drill head lift mechanism is lower position, determined via BU. All BU contacts of all arms are normally open and are connec-ted in parallel. This can work becau only one head is allowed to be in the down posi-tion at a time. Safety logic in the GAL pre-vents multiple drill head lift mechanisms from being actuated at once. And if (becau of a mechanical failure) more than one drill head should be down at the same time, this can be detected via the BO contacts.
State 3:This state is between the other two:neither up nor down. Assuming nothing has gone wrong, this can only happen during motion of the drill head. If this state occurs while the head is not in motion, the drill lift guide is probably jammed.
During drilling the Windows software can measure the time between the closing of the upper switch and the closing of the lower switch, which gives the time taken to drill the hole. A broken drill can be detected by this
and 2 can be determined using this switch. The nsor consists of a light-emitting diode (LED) which emits infrared light vertically upwards, and a phototransistor,also pointing upwards, which detects when a reflective object pass in front of the LED. For this reason there is a reflector made of metallid foil on the pointer atta-ched to the tool arm drive shaft, as well as on the underside of the turn-table.
This reflective light switch opera-tes using unmodulated infrared light and is therefore highly prone to inter-ference from other IR sources such as daylight, artificial light, and even the light from cigarette lighters!While under the circular part of the turntable the switch is completely covered, but the turntable’s two flat-tened sides, which are opposite one another, can let stray light in. And why is the turntable not a perfect circle? It saves a little material, but more importantly this is the only way that access can be provided to the nsor to allow for inspection and cleaning.
If stray light should interfere with the nsor, the turntable need only turn until the nsor is again in the dark, and then continue to turn until the nsor es light again but only over a narrow angle . In this way,the position of the reflective foil can be found. Upon subquent rotation in the opposite direction the transi-tion from light to dark must be found at the same point. Once the system has determined the position of the turntable, it then immediately knows where the flattened sides are that give ri to the risk of light interfe-rence: the software takes the into account.
The process for initialis ing the tool arms is simpler, since in each ca the nsor is covered by the turntable and is therefore protected from stray light. The system looks for (and finds!) the reflecting position of the arm.
If two arms are in u simulta-neously, there is a problem that must not be overlooked. If both arms attempt to travel to their end positi-ons at the same time, there is a risk of collision. This difficulty is over-come elegantly as follows: the Win-dows software notes the position of
the two arms at the end of a run and stores the relevant information in a temporary file. When the program is next run, the file is loaded, and so a collision can be avoided. If the pro-gram terminates abnormally (which can be the rule rather than the exception under Windows!), this file will be found to be missing the next time the program is run. In this ca the program enters manual control mode. A graphical reprentation of the drilling machine appears on the monitor: the tool arms can be drag-ged into position on the screen using the mou so as to reprent the actual state of the machine. This need not be absolutely accurate, alt-hough the machine will rely on your input.
Two microswitches are provided in the tool arms to determine which of three possible states the drill head lift mechanism is in.
爱爱小短文
State 1:Drill head lift mechanism at the top of its travel, in rest position.If no current flows in the solenoid,the force of the spring built into the lower part of the arm must push the drill head to the top of its travel and thus open switch BO (BO is a nor-
Figure 1. The T anBoT est utility tests the various microswitches and determines the operating parameters to be stored in the configuration file.
ger side and above, the left-hand arm is tool arm 1 and the right-hand arm is tool arm 2.
The switches are so vital to the operation of the machine that the switch inputs to the controller board are not fitted with a socket, but rat-her soldered directly. Although a little more tedious to asmble, the connection is more cure. A length of black PVC insulating tape should be ud as a strain relief on the cable which comes from the drive shafts,so that the connecting pins are not under mechanical stress. Ensure also that the cable is free to move.
Here is a summary of all the func-tions of the test software:
The Target box lects between out-put drive stages 0-3 for drill and coil.The Coil box can be t fro
m 0-65 to control the solenoid current from 0(off) to 65 (100 %) for the output stage lected under Target . Beware that the original solenoids are over-loaded at the 100 % tting and can-not run continuously at this current.A duty cycle of about 30 % is possi-ble. Continuous operation is possible at a tting of 26. The software swit-ches the coil off if the tting is left unchanged for 5 s.
The Drill On button switches the out-put drive for the drill motor of the l-ected target on and off.
The next four boxes are to do with the drill cycle. Each target has its own press and brake values, while the shake and hold values apply to all four targets. Each click on the
Cycle button initiates a drill cycle with the lected parameters.The Press box ts the force with which the drill is pushed down on the circuit board. This value — to a certain extent — affects the speed of drilling. If the value is too small, the solenoid will not exert enough force to drive the drill down. If it is too big,the drill can in extreme circum-stances be damaged when it hits the circuit board. The value should be t to suit the drill: a value between 24 and 40 is normal. If satisfactory operation can be obtained with a value below 25, it is a credit to the conscientiousness and care with which the asmbly has been built:congratulations!
挞皮The Brake box ts the braking value needed to cau the drilling head to come to a gentle stop at t
安宫牛黄丸pophe end of its upwards travel. If the value is too high, the head guide will rebound down before finally coming to a halt;if on the other hand the value is too low, the upper switch will be (ab)ud as a mechanical endstop,which is definitely something to be avoided. Find the tting where the head does not rebound and then add one or two to the value.
The Hold box ts the time (in units of 52 ms) for which the drill remains down after the circuit board is dril-led through. Too short a time leads to swarf not being fully cleared from around the hole on the underside of the board, while if the time is t too long, it is simply time wasted. The default value of 10 (i.e. 0.52 s) is a
Figure 2. Initialisation program for calibrating the arms and turntable.
article in this ries, without precision mea-suring instruments of any kind.
All that is required for exact adjustment is the TanBoInit software (Figure 2), which also us file. Note: if at any time during the adjustment procedure anything untoward should happen, or if you think from the way the arms are moving that a collision is imminent, click on the ‘emergency brake’ALL MOVING STOP: the machine will come to an immediate halt.
First we calibrate the arms, and then the turntable. The other way round is not possi-ble, becau the turntable can only be t up
good typical value for clean holes of all sizes.
The Shake box is aimed at the auto-matic clearing of faults. If for exam-ple the guides are very dirty and not running smoothly, the force of the spring may not be enough to lift the head fully up and operate the upper switch. This fault can be simulated by pushing the guide down a couple of millimetres so that the switch BO indicates ‘Head not up’. If the head stays in this position when it is carefully relead, then the fault con-dition has been replicated. The shake value controls how the head is driven down a small amount and then relead, without braking, so that it springs back. The force with which this is done must of cour not be so great that the drill hits the circuit board when it is not running.The Cycle button initiates a com-plete drilling cycle on the lected target. The feed time is measured and displayed (minus the Hold value). If the cycle completes with-out error, OK is displayed; other-wi, Error is displayed. If there is an error with a feed time of around 4.5 to 5 s, this indicates that the head never reached the lower posi-tion: this condition can be simulated by tting Press=0. With a feed time of around 0.5 to 1 s, the fault is that the upper end position was not rea-ched: this condition can be simula-ted as described above with Shake=0.
The values established for the drill cycle using the TanBoTest program are recorded in the configuration file.The Speed button nds data at a steadily increasing rate to the con-troller until the PC’s processor can no longer keep up with the data stream and the controller’s F IF O empties.
The Speed indication in mm/s refers to the speed of interpolation on two axes, for example to simultaneous motion of the turntable and the tool arm at the given speed. The mecha-nical maximum speed limit is around 80 mm/s. If the speed test gives bet-ter results then there is a surplus of processing power, and further axes
can be made to move simulta-neously. When trying the speed test,the stepper motors should not be connected!
The EventsOn check box, when checked, gives up some processor time during the speed test to the operating system, and hence to other process. This is done to allow other tasks to make progress.The TanBoDrive control program us a dynamic algorithm to deter-mine how much processor time to allow the operating system, ensu-ring as necessary that the system does not come to a complete halt.At start-up, the software must be informed of the address of the LPT port to which the controller is atta-ched. This tting can be obtained from the Windows system informa-tion,
and is generally 0378-037F HEX .Open an ASCII text editor with an empty file and enter on the first line the first of the numbers (here 0378). Now press Return twice and save the file in the same directory as TanBoTest . This file is procesd by all the drilling machine programs and must be pla-ced in the same directory as all tho programs.
An important part of the test pro-gram is the measurement of the transfer rate for data streams over the Centronics interface. See the text box for further details.徽菜
Adjusting the arms
After you have checked the opera-tion of the hardware — and, if neces-sary, corrected it — using the Tan-BoTest program, the machine must be adjusted and calibrated. Calibra-tion — also known as tting the zero point — prents no difficulty with a linear machine, but how can we adjust something that is circular and does not have a start or an end?Further, veral of the components of the drilling machine can be asmb-led in different ways: for example,the drilling axis can be moved to and fro by veral millimetres before being firmly screwed down. In order to calculate the X/Y coordinates exactly, the length of the arm must be known absolutely precily. It is
all done, as we said in the first
Figure 3. The arm positions for calibrating the turntable: home/wait (a), wait/home(b) and wait/wait (c).
a
b
c
with properly calibrated arms. Each arm can be moved at will using the buttons CW (clockwi) and CCW (counterclockwi). In TanBoInit, as before, which of the arms 1-4 is moved can be t via the Target box.
F irst check that all the tool arms turn appropriately in respon to the CW and CCW buttons. Select also the targets for which an arm is not fitted, and press CW and CCW. In the cas nothing should move.
The ordering of the target numbers has already been checked in the test program. The four BO switches are shown in a column above one another. If you push down
the head on arm 1, you should e
activity on BO1 and not on BO2.
Check this very carefully, since
otherwi the collision detection will
not work. The drives are extremely
powerful and are easily capable of
destroying one another!
The turntable has its own CW
and CCW buttons, while the Target
box remains always assigned to a
铜
胡辣汤怎么做好吃tool arm. Before an arm can be cali-
共青团员有什么用
brated, the turntable must be rota-
ted so that the reflective light switch
is off.
Begin with the calibration of arm 1
(target 1). Move arm 2 (if fitted) to
干冰遇水the WAIT position, as shown in
Figure 3a. In the kit of parts which
contained the brass chuck, you will
find a short polished metal pin, 20
mm long, left over. This is the only
calibration tool required. Push this
pin as far as possible, without using
excessive force, into the hole in the
aluminium shaft at the centre of the
