Patent Application
20050262977
Not Applicable
Not Applicable
Not Applicable
This invention relates generally to the field of wood cutting and more specifically to a machine and process for optimizing truss cutting. In a preferred embodiment, the machine is used in the metal plate connected wood truss industry. These trusses are used to frame the roofs of houses, apartments, and other commercial buildings. They are made of relatively short pieces of lumber, as compared to the truss itself, and connected by metal plates with specially engineered teeth to grip the wood.
Due to the geometry of the truss, the ends of the pieces of lumber are usually cut at an angle. The primary sawing machine that cuts the angles on the lumber pieces is called a component saw. This particular saw has several blades, the angles and location of which are computer controlled and very accurate. They can cut a piece of lumber to a length within a sixteenth of an inch of accuracy and an angle to a tenth of a degree. The saw is also very fast. In a typical 8-hour time period it can typically produce around 400 unique parts with an average of 10 boards of each shape resulting in 4000 pieces.
However, the standard component saw process used in the truss industry has some deficiencies. It cuts the lumber to a specific length, but the lumber is typically available in two-foot increments. The waste, called drop, can be up to two feet long. One can reduce the amount of drop by cutting some of the lumber bundles from the mill into one foot stock lengths using a bundle cutting saw. If a finished part is to be 6 feet 6 inches long, one would cut a bundle of fourteen foot lumber in half and use seven foot stock instead of the closest commercially available stock, which is eight foot. This practice limits drop to one foot or less. However, the drop can be minimized further.
Prior art systems have attempted to use software for the optimization of cutting lumber but not in the particular innovative method shown in the present invention. For example, U.S. Pat. Nos. 6,068,034 and 5,934,347 to Phelps issued May 30, 2000 and Aug. 10, 1999 respectively show a cutting system for reducing waste due to knots in the wood but fail to show a truss cutting optimization system according to the present invention. Similarly, U.S. Pat. No. 6,196,283 to Hundegger issued Mar. 6, 2001 shows a guidance system for optimizing work piece manipulation but fails to show the inventive combination of the present invention. Likewise, U.S. Pat. No. 5,088,363 to Jones et al. issued Feb. 18, 1992 and U.S. Pat. No. 6,615,100 to Urmson issued Sep. 2, 2003 show automated and computer-controlled lumber cutting and saw assemblies but fail to disclose the inventive combination of the present invention. U.S. Pat. No. 4,017,976 to Barr et al. and U.S. Pat. No. 3,931,501 to Barr et al. show systems for optimization for yields of lumber having knots but fail to disclose the inventive combination of the present invention.
Other prior art systems and methods include U.S. Pat. No. 5,418,729 to Holmes et al., U.S. Pat. No. 5,262,956 to De Leeuw, U.S. Pat. No. 4,163,321 to Cunningham, U.S. Pat. No. 4,221,974 to Mueller et al., U.S. Pat. No. 4,839,816 to Cattrall et al, U.S. Pat. No. 4,805,679 to Czinner, U.S. Pat. No. 4,887,219 to Strauser, and U.S. Pat. No. 4,546,440 to Palmberg show various methods and apparatuses for optimizing the cutting of lumber but fail to show the inventive combination of the present invention.
Further, U.S. Pat. Nos. 4,551,810 and 4,554,635 to Levine show optimization techniques for cutting sheet material but also fail to show the inventive combination of the present invention.
None of the prior art alone or in combination shows the method and apparatus taught herein.
The primary advantage of the invention is to reduce the drop or waste when cutting pieces of wood for trusses.
Another advantage of the invention is to provide a computer controlled system for cutting and optimizing wood.
Another advantage of the invention is to provide an optimization method to sort wood pieces for efficient and orderly processing.
Another advantage is to provide a system for pre-cutting wood for optimal use in truss systems and for introduction of the wood to angle cutting saws.
Other objects and advantages of the present invention will become apparent from the following descriptions, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.
In accordance with a preferred embodiment of the invention, there is disclosed method for optimizing truss cutting of lumber having the steps of entering into a computer data representative of truss members including the member lengths, optimizing the combination of the lengths of a plurality of members to be cut from stock to minimize waste, identifying the order for cutting the stock into the lengths, inserting the stock for cutting by a saw; and cutting the stock into selected lengths based on the optimization.
In accordance with a preferred embodiment of the invention, there is disclosed a system for optimizing cutting of truss members having a computer for entering and storing a plurality of data representative of truss member lengths, a control sequence in the computer that selects the combination of a plurality of member lengths to be cut, the control sequence identifies the order for cutting the wood lengths by optimizing the use of stock lumber for the member lengths, a pusher controlled by the computer for engaging the stock lumber with a saw; and a saw that responds to control signals from said computer to cut said stock lumber into member lengths.
In accordance with a preferred embodiment of the invention, there is disclosed a process for optimizing truss cutting having the steps of entering into a computer data representative of at least two truss members used in trusses including their lengths, storing in the computer the data, combining the length of a first truss member with the length of a second truss member to determine a total first length, comparing the first total length to a set of pre-determined set of stock lumber lengths, increasing by one a multiple of length of the first member length and combining it with a multiple of the second member length, repeatedly increasing the multiple by one of the length of the first member length and the multiple of the second member length until an optimal combination of multiples of the first and second member lengths is obtained to minimize waste when cut from one of the pre-determined stock lumber lengths.
In accordance with a preferred embodiment of the invention, there is disclosed a method for optimizing truss cutting of lumber having the steps of entering into a computer data representative of truss members including the member lengths, optimizing the combination of the lengths of a plurality of members to be cut from stock to minimize waste, identifying the order for cutting the stock into said lengths, inserting the stock for cutting by a saw, cutting the stock into selected lengths based on the optimization, and sorting the cut stock according to pre-determined criteria for selective additional cutting.
In accordance with a preferred embodiment of the invention, there is disclosed a method for optimizing truss cutting of lumber having the steps of storing in a computer data representative of truss members including the member lengths; optimizing the combination of the lengths of a plurality of members to be cut from stock to minimize waste, identifying the order for cutting the stock into the lengths, identifying based on pre-determined criteria those lengths that fail to meet a certain pre-determined measurement, doubling the identified length, cutting the stock in said doubled amount for the identified length.
The drawings constitute a part of this specification and include exemplary embodiments to the invention, which may be embodied in various forms. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention.
Detailed descriptions of the preferred embodiment are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or manner.
Prior to introducing the lumber into the final cutting machine, there is a need to optimize and facilitate the ordered cutting of pre-cut lumber. Such optimization is achieved through the interaction of a computer or other computational device and various automated saws and mechanisms for advancement of wood into the saws. The optimization process involved analyzing various criteria relating to the desired wood lengths and comparing those lengths with standard lengths of wood know as stock. For example, if it is known that one piece or member of a truss will be 4 feet long and another member 6 feet long, then the operator could cut a ten foot piece of lumber into those two pieces and when they are run through a component saw there would be no waste or “drop.” The system of the current invention finds the length of all the pieces in a truss or set of trusses and then determines the optimum way of cutting them so that there is a minimum of drop. The current system further facilitates the handling and movement of pre-cut lumber prior to introduction to the component saw. In most sets of trusses, using the system of the present invention will reduce the waste significantly.
Before describing in detail the computer control and optimization aspects of the present invention, an overview of the truss pre-cutting and cutting process is herein provided. The characteristics of a particular truss are entered into a computer or other processing and storage device and the optimizer software analyzes the data and produces an ordered list of the pieces to cut. In a preferred embodiment system the data entry is “automatic,” i.e. the data is obtained directly from another software program that includes information about various truss designs. The information entered may include the member name, the truss or trusses a member is used within, and the length of the member. The pre-cutter computer analyzes this list of members, finds the member combinations which will produce the least drop, and orders the list of combinations to maximize subsequent operation efficiency.
In a preferred embodiment, the pre-cutter can receive from one to six pieces at a time, although this may be varied depending on the pre-cutting equipment and may be altered to fit the situation. The usefulness of processing multiple stock pieces at the same time is the increase of volume processed, avoiding any additional machine movements. Turning now to
Board 12 is placed on advancer 14 and is moved by pusher 18 the appropriate length to be cut by saw 22. Pusher 18 is mechanically driven and computer controlled and through operation of a system more fully described below, is advanced the proper length for cutting the stock lumber into calculated lengths to minimize the waste and optimize the use of the lumber needed for the trusses that will be constructed later. Once pusher 18 has advanced board 12 the proper length as previously determined by the optimization software, saw 22 fires automatically and cuts the piece to the desired length. This is repeated for each part combination in the cut list.
This pre-cutting step is important because it, in conjunction with the optimizer software, determines what stock boards to cut and what lengths result. By analyzing the different lengths needed to build various trusses, the wood can be cut in exactly the lengths needed and done in the most optimal fashion thus reducing the drop.
Advancer 14 is marked in one foot increments 16 to help the operator to verify the proper length of lumber as directed by the computer as described. By having easy to see increments, the operator readily knows the proper length of board as directed to place on the advancer and knows where the pusher is positioned relative to the length of board to be cut. As more fully shown in
Housing 28 provides for printing of the boards with specific information later used by the operator to determine proper final cutting or storing of the pre-cut boards. The printing operation occurs simultaneously as the stock is advanced. The operator removes the resulting parts and delivers them to the proper location for subsequent processing according to the marks printed on the part. Aspects of this printing step will be further described in
Turning now to
Angle saw 30 of component saw 35 is designed to rotate into different positions to apply different angle cuts on the ends of lumber. Wood that has been designated for sawing is placed on rack 37. Rack 28 is used to store pre-cut lumber for later angle cutting.
Operator 32 uses computer 34 to determine which boards to cut, the angles needed and the other setup requirements before engaging the component saw. As later described, the pre-cut boards ar marked for immediate cutting, or storing on rack 28. Obviously, numerous modifications may be made to the racks, numbers of angle saws and the like without departing from the scope and spirit of the invention.
To further understand the benefits of pre-cutting and optimization, an example of cutting a four foot and six foot piece from a ten-foot stock length is instructive. For example, for a particular truss or trusses, 18 lengths of six foot boards are needed. In one embodiment, the pre-cutter saw can only cut from six stock pieces of lumber at a time. If a ten foot stock piece is used, one can produce 6 pieces of the four foot and 6 pieces of the six foot lengths with each cycle of the saw. Since it is desirable to reduce the set up time of the component saw to avoid alternate setups between the four and six foot pieces, it is desirable to set aside or store one of these lengths while running the other through the component saw.
The pre-cutter system and software keeps up with where each piece in the process should go. If the piece has ‘Saw’ printed on it, the operator should place it directly in the queue to be cut by the component saw.
The pre-cutter also directs the operator when to place the pieces in the Storage areas into the queue for the component saw. A flashing message is displayed on the screen indicating which storage area should be emptied into the component saw queue.
It is desirable to minimize the number of times the component saw is set up for a unique piece. Optimally, the component saw should be set up once for each type of member and used to cut all of those pieces with identical specifications at the same time. This presents an issue for the pre-cutter process, because almost every cycle will be producing two different types of pieces. The solution is to store one of those types until the total number of pieces needed is produced, then put it in the queue to the component saw.
An algorithm employed by the software control to perform this task is generally described as follows:
1. Gather and store member information from a truss data file and place it in a raw member data table. Include all the member's pertinent data such as quantity, length, end angles, name, and the truss to which it belongs.
2. Sort the table according to member name, angles, lumber grade/size, and length.
3. Create a ‘unique member’ table from the raw member table containing distinct types of these members. The trusses may contain more than one member with the same length and angles. Combine these to create one row of the unique member table, containing the total quantity and keeping up with the name of each member.
4. Remove members that can be cut out of scrap
5. Add 1/4 inch to the length to allow for the lumber stop on the saw The saw has a margin of error that is accommodated by adding a 1/4 inch of length to the member.
6. Decide if there is a need to double the length of any member so that the component saw can cut it due to the small length of the member. As previously described the component saw has large circular saw blades on each side and as these are rotated further inward to cut the member at the proper angle, it increases the minimum length board that can be cut without the blades colliding. It must be checked to see if the length, because of the angles, will be too small to go through the saw. If so, the precut piece is doubled in length and halved in quantity. It is also required to change the file that controls the setup of the saw so that a minimum of cuts are required to produce the two final members.
7. Optimize the members by using a solution table. From the ‘unique member’ table containing unique members that can be cut by the saw, a ‘solution’ table is created. This solution table contains all the possible combinations which can be cut out of stock lengths. In the preferred embodiment each combination consists of two unique members. In the preferred embodiment, the stock lengths that are preferably used in the solutions are 8, 10, 12 and 14 foot lengths. However, the system may be set to calculate using any of a set of lengths appropriate to the situation. In order to reduce the amount of pieces that have to be sorted after being cut by the pre-cutter, only two different lengths are allowed in any one solution in a preferred embodiment. An example of a solution table solving for two lengths of parts that are needed is shown in Table 1 below.
To create the solution table, the first unique member is started at a quantity of one and a second unique member at a quantity of zero. The stock length that results in the least drop length from that combination is found and enter all of the data in the solution table.
One is then added to the quantity of the second unique member and the process is repeated until the combined lengths are too long to fit in any standard stock length. One is added to the quantity of the first unique piece and the process is started over. After all of the members have taken their place in the first unique member slot, a solution table with every possible combination of members is obtained.
8. The ‘solution’ table on the drop length is sorted in an ascending order.
9. A cutting list from the solution table is produced for the operator.
It must be decided in which order to cut the members on the pre-cutter. This involves balancing two factors. First, the saw should never be set up twice for any unique member, and two, the drop should always be minimized. The solution to this is to search for the best way to finish only two unique members at a time. Before advancing on to a third type of member, one must first make sure that all of one of the other type's quantity is cut first. After completing this process, a ‘cut’ table is derived that details the flow of materials through the pre-cutter.
Finally, it is determined if the member should go into the saw queue, storage area 1 or 2, or when members should come out of the storage areas and into the saw. This creates a final cut list that is converted to a database table and read by the pre-cutter.
Turning now to
If the solution for length 1 has a quantity greater than zero, then the process goes to step 84 and sets the next available active length slot to length. If not, it removes the length from the active slot at box 80 and proceeds to query box 82. In query box 82, the process determines if for solution length 2, the quantity is greater than zero. If so, it proceeds to step 84. After step 84, the process queries at box 88 whether length 2 has been tested. If not, the process goes back to step 82. If at step 82, the solution length 2 quantity is zero, then it proceeds to step 86 where the active length is removed from the active slot. The process then begins again at step 52. by proceeding along this iterative process, a combination of 2 board lengths in multiples of each length is arrived at that possesses the minimum drop. The computer is thus capable of determining the optimal pre-cut combination of different members from a truss to efficiently cut the proper number of boards from the various stock lengths.
Current batch 140 is shown in the upper right shows the batch number that is being cut. Designator 142 “×1” indicates that the batch is being cut one time for one building or truss application. In other situations, designator 142 may indicate “×2” or “×3” and so forth to show that the batch needs to be performed numerous times since the particular truss is used several times in the building for which the trusses are being constructed.
Pusher bar indicator 144 shows the position of the pusher bar as a means to indicate to the operator that the machine is in operation and lumber is being moved into the saw. The indicator shows inches of distance from the saw. In this example, the pusher is positioned at 175 inches from the saw. Waiting indicator 146 tells the operator that the machine is currently idle. This indicator changes to “working” when the lumber is being advanced and cut.
Cut display box 150 indicates how the stock length lumber will be cut. It displays the member name 152, length 154, and destination 156 for each pre-cut piece. Length 154 is measured in a three number sequence for feet, inches and sixteenths of an inch. Thus in length 154, the member length designation of “2-8-8” means a piece of lumber that is 2 feet, 8 inches and 8 sixteenths of an inch long. Storage 1 box 158 and Storage 2 box 160 will display the word “saw” when it is time for the operator to move lumber from their respective storage areas to the advancer and ultimately into the saw.
Grid 162 displays all the cuts for a batch and may change colors according to the legend where it states “uncut, partially cut and finished cutting” at the bottom of the screen to indicate the status of a particular cut. The operator can decide which cut to perform by using the arrow keys on the keyboard or other input devices to scroll up and down the grid.
While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
