CA1191952A

CA1191952A - Bandsaw performance monitor

Info

Publication number: CA1191952A
Application number: CA000436314A
Authority: CA
Inventors: Hermann Ruhl
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-09-08
Filing date: 1983-09-08
Publication date: 1985-08-13

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention relates to a monitor for indicating ongoing performance of a bandsaw while cutting into a work piece. The monitor includes both a measuring system for measuring the rate at which the bandsaw blade cuts into the work piece and a selector for selecting the profile of the cut for determining cutting rate or the area of the cut for unit of time. The monitor further includes a display for displaying the cutting rate which is used for determining performance of the bandsaw.

Description

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1 FIELD OF rHE INVENTION
The presen-t invention relates to a monitor for determining and indicating performance of a bandsaw while in operation.
BACKGROUND OF TH~ INVENTION
__ According to conventional construction, bandsaws include a cutting band or blade which is tensioned around a pair of takeup rolls with an idler tension wheel and a drive wheel for operation of the saw blade~ The drive wheel which operates at variable selectable speeds determines the blade speed which is one of the important operating parameters of the cutting action of the bandsaw. Two other operating parameters which are of importance include feed rate of the blade or the speed at which the blade is moved into the material to be cut în a direction perpendicular to the teeth of the blade and the cutting rate or the area of the cut per unit of time.
For example if it takes five minutes to cut through a ten inch square block the feed rate is two inches per minute and the cutting rate is twenty square inches per minute as de-termined by multiplying the feed rate times the width of the cut.
The cutting rate is extremely imPortant as it determines the time it takes to cut through cross-sections of various shapes and sizes. It is therefore generally used in the saw machine and blade using and manufacturing industries as the denominator -for sawing performance under different conditions.

~0 1 The actual cutting rate achieved is lnfuenced for example by the following factors: 1) the blade life which can be expressed as -the total area (in sq.in.) which can be cut with a blade while it gives a satisfactory cutting performance or which may be expressed as the total cutting time of a blade during which it gives a satisfactory cutting performance;

2) the material of the blade teeth; 3) the shapes, angles, distance between and number of blade teeth; 4) the material to be cut; 5) the shapes and dimensions of the material to be cut and 6) the design and rigidity of the sawing machine and the blade guidance system on the sawing machine.
As will be appreciated from the blade life factors listed above it is not simple to arrive at cutting rate figures which are correct for a wide range of conditions. Accordingly the saw blade manufacturers facilitate the proper setting of sawing machines for the uses of their blades by recommending cutting rates for certain conditions. Therefore the problem for the users of the sawing machines which to date have no monitors for determining cutting rates is how to set the machine to a desired cutting rate or how to determine at what cutting rate the machine is actually cutting. Conventionally the cutting rate is determined by calculating the cross-sectional area of the material and then using a stop watch or timer to determine how long the actual cut takes. The cutting rate is then calculated by dividing the area of the cut by the time for the cut. This procedure is obviously very cumbersome and for larger material dimensions is extremely time consuming.

ri ~ ' 1 Nearly all semi or Fully automatic saws are equipped with a hydraulic saw feed system and the feed rate is set by hydraulic valves with a graduated scale. The graduation is however not expressed or graduated in inches per minute feed rate since the actual feed rate is not constant at one dial setting but rather varies according to the viscosity of the hydraulic flu.id, the pump, the filter conditions and gradual changes of the control valve characteristics caused by deposits, etc.
Furthermore these feed rate indicators still require the operater to divide the length of the cut by the feedrate to calculate the time for the cut and to then calcuate cutting rate as indicated above or to multiply the feed rate by the width of the work piece being cut.
The foregoing problems have therefore lead to a standard practice in the sawing industry where the setting of the machines or saws is done according to the individual judgement of the operators and where supervisors and management do not control whether or to what extent recommended and efficient cutting rates are used.
SUMMARY OF_THE PRESENT INVENTION
The present invention relates to a bandsaw performance monitor specifically adapted to mitigate the control problems as found in the prior art by providing simple and effective means for setting and controlling bandsaw operations. The bandsaw per-formance monitor of the present invention enables the setting of bandsaws quickly and easily to maximize cutting performance and to immediately monitor the actual useage and performance of the saw and saw blade at all times.

1 More particularly the monitor of the present invention which indicates and/or controls bandsaw cutting parameters is characterized by an electronic feed rate measuring system for measuring displacement of the bandsaw blade in the feed direction, a selector system settable to different shapes and sizes of cutting profiles and a cutting rate measuring system including display means for receiving information from both the feed rate measuring and the selector system to measure lû and indicate cutting rate as the area cut per unit of time.
With this arrangement the operator of the machine is at all times aware of the cutting rate of the machine.
BRIEF DISCUSSION OF THE DRAWINGS
The above as well as other advantages and features of the present invention will be described in greater detail according to the preferred embodiments of the present invention in which:
Figure 1 is a plan view of a bandsaw incorporating a cutting rate measuring system according to a preferred embodiment of the present invention;
Figure 2 is a block diagram of the components within the cutting rate measuring system.
DETAILED DE-SCRIP-rION ACCORDING TO THE PREFERRED EMBODIMENTS
Figure 1 shows a bandsaw comprising a stationary frame F with a moveable carriage C carrying a bandsaw blade B to cut into a work piece WP. The blade is tensioned between a pair of rollers within the carriage as shown in Figure 1 and driven by a drive system (not 3û shown) such that the blade rotates in a continuous 9~ l 1 fashion about -the rollers to perform a sawing action.
The carriage moves down relative to the ~Frame with the blade in motion to cut downwardly into the work piece.
Two critical operating parameters of a bandsaw are the feed rate or displacement of the bandsaw blade which is the rate at which the band saw blade penetrates downwardly into the work piece and the cutting rate which is the area of the cut or the feed rate times the length of the contact region between the bandsaw blade and the work piece. In Figure 1 the workpiece has a rectangular configuration but could however have other shapes such as rounded configurations where the extent of the contact between the bandsaw and the work piece increases with depth of the cut. Therefore there are different cutting profiles which are used in association with the depth of the cut in determining the cutting rate.
Referring now to Figure 2, an electronic distance measuring scale 1 is provided on the frame of the saw. A
scale sensor 2 is attached to and moves with the carriage over the scale to sense degree of carriage and blade downward movement.. The movement between the carriage and the frame of the saw machine on which the electronic scale 1 is provided is measured by distance pulses which are transrnitted to two different measuring devices including a feed rate counter 3 and a cutting rate system 4. The feed rate counter 3 consists of a conventional frequency counter calibrated to show the speed of movement between the carriage and the rnachine frame in terms of inches per minute.

5~ 1 1 Although the drawings show a linear scale it is also possible to use a rotary pulse sender having For instance a gear on its shaft which engages in a racl< to obtain the required pulses for measuring downward movernent of the carriage and the saw blade.
The cutting rate system is connected to a selector system 5. This selector 5 changes the measuring or calculating of the cutting rate system 4 in such a way that the read out of the cutting rate systern reflects the product of the feed rate and the contact region between the saw blade and the work piece according to the profile of the work piece to be cut. This selector system changes correspondingly therefore the indicated values in the cutting rate system 4 to reflect the product of the feed rate and the contact region.
The rate meters may operate in a number of different manners. According to one example the rate meters consistent with fret~uency meters operate in a manner such that the incoming pulses from the value to be measured are counted for a certain time period. This time period is selected such that the pulse count accumulated during the time period corresponds directly to the value to be indicated which is the rate per unit of time in seconds, minutes, hours, etc. depending upon the particular type unit to be expressed. However the number o r pulses per unit of time has no direct relationship to the unit in which the rate is commonly expressed. For example in the arrangement shown a pulse sending system may for example be used which furnishes 100 pulses per milimeter of travel of the saw blade into the material. According to 1 this system a total of 2540 pulses enter the system for every one inch of travel at the feed rate of one inch per minute or in other words at the feed rate of one inch per minute the system receives 2540 pulses every minute. If a read out accuracy for every one hundreth of an inch is desired and if the read out indicates 1.00 at the travel speed of one inch per minute then the time base must be selected such that during the period of the time base 100 pulses enter the measuring system. According to the formula below, the time base to indicate a feed rate of l.Oû per minute must be calculated as follows.
Therefore in order to set a read out accuracy of l/lOOth of an inch the feed rate counter would be set correspondingly at a time base of 2.36 seconds which means that the counter would count lOû pulses every 2.36 seconds at the feed rate of one inch per minute.
For purposes of determining cutting rates the time base may be varied according to the contact length between the saw blade and the work piece. For instance in the example above if the feed rate is one inch per minute and the width of the cut is one inch then the cutting rate is one square inch. ~lowever, if the width of the cut is two inches and the time base is doubled then the cutting rate indicated will show double the number of pulses and this read out would then correspond to a cutting rate of two square inches per minute at a feed rate of one inch per minute. Correspondingly if the w~dth of the cut is half an inch and the time base is cut in half then the cutting rate would be .5 square inches per minute. In this fashion the cutting rate can be varied by changing the t:ime base to correspond to the cutting width or contact length between the saw blade and the material being cut.
This variability of the tirne base is achieved through the selector system 5 shown in the drawings whereby the cutting rate indicator rather than indicating a feed rate shows a cutting rate and this example is in terms of square inches per minute.
~ As will be seen, selector 5 is adapted to select materials to be cut according to not only width which would be used in a generally rectangular work piece but also to select different diameters for rounded work pieces where the multiplicatlon factor is determined according to the diamete~ or circumference of the work piece. For purposes of this description the width or diameter is referred to as the profile of the cut.
The example described above is only one method of determining cutting rates. According to a further example it is possible to use a cutting rate indicator consisting of a pulse frequency converter with selectable frequency converting ratios. The converted frequencies are then fed into a frequency counter which operates as follows.
The frequency or rate counter would be set to a standard time base of for example 1/100 of a minute or .6 seconds. It would therefore display the nurnber of pulses entering the counter within this time period. The electronic scale or scale sensor system which would operate in the same manner as described above would therefore furnish 2540 pulses at the speed of one inch 1 per minute. By selecting a cutting width of one inch the cutting rate would then be one square inch per minute.
The feed rate counter would allow pulses to enter every 1/100 of a minute during which time 25.4 pulses would be counted. The pulses however do not enter directly to the feed rate counter but rather enter the pulse frequency converter. This pulse frequency converter would be set to the ratio of 2.54 to 1 whereby the 25.4 pulses entering the converter would be displayed at the output of the conver-ter to the reduced figure of 10 pulses through the conversion factor. Therefore according to this example the pulse frequency converter would as mentioned above be set at a 2.54 to 1 ratio to make the rate counter display the numeral 10 for a cutting rate of one square inch per minute with the standard time base of 1/100 of a minute. The resolution of such an execution is in l/lOths and the decimal point must be moved by one point to the left -to provide the cutting rate correctly resulting in the display of the numeral one rather than the numeral ten.
If the width of the cut is increased to two inches rather than one inch the read out value is doubled which is achieved by changing the frequency conversion ratio through selector 5 to 1.27 to 1 rather than 2.54 to 1.
This means that with the same feed rate of one inch per minute but with double the cuttirlg width the pulse frequency converter when set at the 1.27 to 1 ratio will show 20 pulses entering the rate counter in 1/100 oF a minute which is read out again with a resolution of 1/10 at 2.0 square inches per minute. The purpose for this resolution is to keep the read out of the cutting rate as simple as possible for operator examination purposes.

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1 In still another solution to the cutting rate system design a digital programmable processiny unit is used to operate as -Follows.
The feed rate is measured in a first operation of the digital processor during a fixed time basis~ The feed rate so obtained does not have to be directly expressed in any meaningful ratio such as for example inches per minute or millimeters per minute. It does however have to be directly proportionate to the feed rate of the saw blade regardless of the manner in which it is expressed.
The feed rate value so obtained is processed in the digital processing unit by multiplying the value with a factor corresponding and directly proportionate to the profile to be cut. The product of this multiplication is then displayed at the rate indicator. In accordance with the selection of different cutting profiles the digital processor is controlled and set to the required multiplication through the selector system 5 used by the operator to input the width of the profile to be made.
In all the examples given above the time base setting which in turn results in the setting of the multiplication is done through settable binary digital switches. For purposes of assisting in the setting of the switches, setting tables may be provided which show how the binary digital switches should be set for a given width of rectangular cutting area or for diameters of round bars as described above. Additional tables can also be provided to show the code setting for tubes and other special profiles.

1 In more sophisticated versions interfaces may be provided between the binary digital switches and the selector system allowing the selection of dimensions directly in conventional units for widths and diameters as they are used in the English and metric systems.
With the system described thus far, the sawing machine operator pre selects the diameter or width of cut on selector 5 and then adjusts the feed rate of the bandsaw in such a way that the cutting rate read out shows the recommended cutting rate for the material concerned and the particular saw blade used. The operator is therefore able to directly set the machine to the data provided to him for his job or recommended by the manufacturer of the saw blades usedO Supervisory personnel can also constantly directly check whether the process is carried out according to recommended cutting rates.
The saw monitoring system can be further expanded to furnish important information on how long the saw blade being used ~ill remain in good operating condition to furnish accurate cuts and to complete the cuts in acceptable cutting time. According to this invention the blade life may be controlled by the saw monitoring system in three different ways. If for instance the cutting rate measuring system uses a pulse frequency converter to obtain a pulse output which is proportionate to the cutting rate then this frequency converted pulse rate can be fed into a blade li~e interface 6 and from there the blade life counter 7. In the blade life interface the pulses are converted into units which reflect directly 1 square inches with further control inputs from the interface 6 to a saw feed circuit ~ and a saw motor control circuit 9~ A logic control within the blade life interface 6 allows the pulses from the cutting rate system 4 which are proportionate to the cutting rate to enter the blade li-fe counter 7 only if the saw motor is operating and if the -forward saw feed is activated. The blade life counter 7 is therefore operational only when the saw is actually cutting but not when the saw frame is moving forward during other manipulations of the machine.
The blade life counting system as described and showing blade life in square inches in the counter 7 may suffer however from the problem that the square inches accumulated are incorrect if the selector 5 is wilfully or accidentally set for a different profile other than the one which is actually being cut. A practically more reliable and simpler system is therefore one in which an hour meter 10 is connected to the saw monitor circuit 9 in the saw feed circuit 8 in such a way that the hour meter totals hours only when the saw motor is operating with the saw feed forward engaged. Accordingly the hour meter becomes a blade life counter showing blade life in terms of hours.
In automatic machines it is also desirable to count the number of cuts. This is achieved by using a counter 11 and connecting it in turn to the saw feed circuit in such a way that it will be activated each time a repetitive electrically controlled motion such as clamping or engaging the saw feed forward is carried ~0 out. Again such a counting of pulses is achieved by ~ r-~ I
a.~
1 connecting counter 11 with the saw motor circuit 9 so that a count takes place only when the saw motor is engaged.
In order to correctly reflect the total blade life and the number of cuts made with the saw blade the two different blade life counters 7 and 10 and the cut counter 11 can only be reset by a key lock reset 12.
This reset will only be actuated by a key whenever the blade is changed and a correct count for the saw blade life cycle is obtained.
Other data important for control of the sawing machine are the cutting time and the cycle time in automatic machines. For this purpose two dif-ferent counters including a cutting time counter 13 and a cycle time counter 14 are connected with the electrical control system of the sawing machine. The cutting time counter 13 will again only measure when the saw motor is engaged and is connected to the saw feed control circuit in such a way that it will only count time during the engaging of the saw feed forward.
The cycle timer 14 will also only count when the saw motor circuit 9 provides its signal showing the saw motor is operating and the cycle timer will then measure the time between repetitive sawing machine operations such as engaging saw feed forward or engaging material clamping.
~ oth the cutting time counter 13 and the cycle time counter 14 are preferraby of a type to measure each cycle and to then display the measured value during a measuring period of the next cycle so that the last measured time cycle is displayed while the new cycle time is measured.

1 As a separate important operating pararneter a complete execution of the saw monitor contains al~o a blade speecl measuring device 15 which is connected to a blade speed sensor 16 which senses the speed of the idle wheel of the saw blade to obtain saw blade speed proportionate pulses from the drive system for the saw blade drive wheel.
In order to simplify the display system and to lower the cost for the whole monitoring system it is possible to feed the output of the measuring system for the blade speed, for the feed rate 9 for the cutting rate, for the c~tting time and for the cycle time into a selector device 17 which is provided with five separate push buttons for the five values and which depending upon its selected position will feed only one of these five para~eters into the read out. It is however also pûssible to have individual read outs for the different measuring systems although the one read out may be advantageous from a cost standpoint.
It is also possible to connect the two different blade read outs 7 and 10 and the number of cut read outs 11 to a single read out system with an expansion of the read out selector switch 17. However from a control standpoint it maybe more practical to display these particular values constantly in separate counters which are of a simple and space saving design.
The effectiveness and simplicity of application of the monitor can be further improved by adjusting the selector system of the cutting rate measuring system automatically to the size oF the profile to be cut. This

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1 can be done by providing a size measuring system at the saw which for instance measures automatically the diameter of a round bar or the width of a rectangular cross-section to be cut~ The measured value of the workpiece is transferred into the selector system -for the profile. This selector system requires then only a setting to either round bar stock or retangular bar stock. Only in cases of irregular profiles or tubes would it be necessary to set the selector manually For profile and dimensions of the workpiece. A typical size measuring system 2 as shown, measures distance between the clamping jaws J and Jl for the workpiece and consists of an electronic measuring scale attached to one jaw and the displacement sensor on the other jaw~ The size measuring system is connected in turn to the selector system as shown in Figure 2.
It will now be seen from the above that the operating parameters of the bandsaw may be quickly and easily discerned at any and all times of operation through the monitoring system of the present invention.
Furthermore although various preferred embodiments of the present invention have been described herein in detail it will be appreciated by those skilled in the art that variations may be made thereto without departing From the spirit of the invention or the scope of the appended claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Bandsaw monitoring means for monitoring bandsaw cutting parameters characterized by an electronic measuring system for measuring the displacement of a bandsaw blade into a work piece, a selector system settable according to shape and size of the work piece and a cutting rate measuring system including display means for receiving information from both said displacement measuring system and said selector system to measure and indicate cutting rate of the bandsaw in terms of area cut per unit of time.

2. Monitoring means as claimed in Claim 1 wherein said cutting rate measuring system consists of an electronic pulse counting system with a variable time base for calibration of said cutting rate system and wherein said selector system varies said time base according to profile of the cut.

3. Monitoring means as claimed in Claim 1 wherein said cutting rate measuring system consists of a pulse frequency converter with selectable frequency converting ratios and receiving pulses from the measuring system for measuring displacement of the bandsaw blade and providing output pulse rates proportionate to the cutting rate, the frequency measuring system connected to the output of the pulse frequency converter and selector means for selecting the frequency converting ratios of the frequency converter according to the profile to be cut.

4. Monitoring means as claimed in Claim 1 wherein said cutting rate measuring system consists of a digital processing unit programmed to measure feed rate of the saw blade and to multiply the measured feed rate by a factor relating to profile of the cut selected at said selector system.

5. Monitoring means as claimed in Claims 1, 2 or 4 characterized by a cutting time indicator consisting of a timer controlled by a saw blade feed control circuit for actuating the timer with feed of the saw blade and for deactuating the timer upon termination of the feed of the saw blade.

6. A Monitoring means as claimed in Claims 1, 2 or 4 characterized by a cycle time indicator consisting of a timer actuated by a pulse indicative of initiation of a clamping action for a sawing cycle.

7. Monitoring means as claimed in Claims 1 2 or 3 characterized by a cycle time indicator consisting of a timer actuated by a pulse indicating initiation of a cutting action for a sawing cycle.

8. Monitoring means as claimed in Claim 3 characterized by a blade life counter system for counting blade life in square inches and consisting of an output connection from the cutting rate measuring system supplying pulses proportionate to the cutting rate, a saw blade drive, and a saw feed forward icator and a counter connected to the output connection of the cutting rate measuring system, said counter having an internal on/off control activated by a drive control circuit for the saw blade such that said counter is operational only when the saw blade drive and the saw feed forward indicator are simultaneously operating.

9. Monitoring means as claimed in Claim 1, 2 or 4 characterized by a selector device connected to at least two measuring sub-systems for measuring feed rate, cutting rate, blade speed, cutting time and cycle time and allowing selection of any of such sub-systems to be connected to a common read out.

10. Monitoring means as claimed in Claim 1, 2 or 4 wherein said selector system is connected to size measuring apparatus for the work piece at the saw which supplies the selector system with size measurements of the work piece, thereby automatically assuring correct cutting rate readouts when the profile is manually selected.

11. Monitoring means as claimed in Claim 1, including clamping jaws for the workpiece and wherein said size selector system is connected to size measuring apparatus which measures distance between said clamping jaws and which supplies the selector system with size measurements for automatically assuring correct cutting rate readouts when the profile is manually selected.