Optimizing operations on a manual crosscut saw.The crosscut saw can be a vital component to a shop's part optimization optimization
Field of applied mathematics whose principles and methods are used to solve quantitative problems in disciplines including physics, biology, engineering, and economics. . The decisions made by the cutoff sawyer will affect a company's production and profitability. It is the responsibility of the rough mill supervisor, however, to ensure that the cutoff saw operator has been given part grade specifications and understands the allowable characteristics and requirements of each product. The cutoff saw operator must know whether the part grade requirements are Clear-One-Face, Clear-Two-Faces, Sound, and so on. In addition, supervisory personnel must instruct in·struct
v. in·struct·ed, in·struct·ing, in·structs
1. To provide with knowledge, especially in a methodical way. See Synonyms at teach.
2. To give orders to; direct.
v. the operators whether it is appropriate to cut parts to maximize yield or to maximize value.
Design of the Workstation
Workstation design can play an important role in determining the productivity and yield that can be achieved. Mirrors should be used at each crosscut saw to allow the operator to easily inspect the freshly sawn end for drying checks. Sufficient lighting must be provided so defects can be seen and the correct sawing decision can be made.
The crosscut saw operator should not have to expend ex·pend
tr.v. ex·pend·ed, ex·pend·ing, ex·pends
1. To lay out; spend: expending tax revenues on government operations. See Synonyms at spend.
2. a lot of effort in bringing full size lumber lumber, term for timber that has been cut into boards for use as a building material. The major steps in producing lumber involve logging (the felling and preparation of timber for shipment to sawmills), sawing the logs into boards, grading the boards according to to the workstation. The operator's main job is to properly cut the lumber, which, by itself, can be very demanding. Preferably pref·er·a·ble
More desirable or worthy than another; preferred: Coffee is preferable to tea, I think.
pref each piece of lumber is conveyed to the workstation by a material handling system or another worker. If the lumber is manually fed, the use of a scissors scissors
Cutting instrument or tool consisting of a pair of opposed metal blades that meet and cut when the handles at their ends are brought together. Modern scissors are of two types: the more usual pivoted blades have a rivet or screw connection between the cutting ends lift to raise the lumber package to the workstation level will facilitate the job by reducing material handling time and effort and reduce the risk of injury.
Board Inspection and First Cut
Prior to cutting, the crosscut sawyer should inspect both sides of the board and consider what parts can be obtained at the ripping (1) Converting an audio CD from its native CD-DA format to MP3, AAC or some other compressed audio format. When the term was coined, it had a perverse meaning. Many loved the idea they were "ripping off" the music industry by making copyrighted works available in a compact format and salvage operations 1. The recovery, evacuation, and reclamation of damaged, discarded, condemned, or abandoned allied or enemy materiel, ships, craft, and floating equipment for reuse, repair, refabrication, or scrapping.
2. . Clear-One-Face specifications require cutting with the better face of the lumber visible to the operator. Clear-Two-Face grade parts should be cut with the worse face up. It is important to keep in mind that the crosscut saw is not an island, but must work in consideration and cooperation with the other operations. Operator cross training is useful in helping operators better understand product requirements.
The first cut to square the end should remove end checks (if present). The end trim should be as small as possible, only 1 inch, and perhaps as small as 1/2-inch for well-dried stock containing only minor end checking. Using mirrors as described above, the operator should inspect the freshly cut end for drying checks and make an additional end trim cut if needed. However, the crosscut saw operator should not take an exceptionally long end trim in order to remove a single, long end check or spilt spilt
A past tense and a past participle of spill1. .
When round logs are sawn into rectangular rec·tan·gu·lar
1. Having the shape of a rectangle.
2. Having one or more right angles.
3. Designating a geometric coordinate system with mutually perpendicular axes. boards, wane (the lack of wood on edges) allowed by the lumber grading rules is left on the board. in addition, natural wood characteristics such as knots are included in the sawn boards. The rough mill must remove those characteristics that do not meet product criteria.
How much defect removal should the crosscutting cross·cut·ting
A technique used especially in filmmaking in which shots of two or more separate, usually concurrent scenes are interwoven. Also called intercutting. saw perform? Certainly the crosscut saw should not try to remove all defects. Coordination with downstream From the provider to the customer. Downloading files and Web pages from the Internet is the downstream side. The upstream is from the customer to the provider (requesting a Web page, sending e-mail, etc.). operations will allow wane, pith pith, in botany, core of the stem of most plants. Pith is composed of large, loosely packed food-storage cells. As the stem grows older the pith usually dries out, and in some it disintegrates and the stem becomes hollow. , and many knots to be removed at the ripsaw or at the salvage salvage, in maritime law, the compensation that the owner must pay for having his vessel or cargo saved from peril, such as shipwreck, fire, or capture by an enemy. Salvage is awarded only when the party making the rescue was under no legal obligation to do so. saw operations. Defects running lengthwise length·wise
adv. & adj.
Of, along, or in reference to the direction of the length; longitudinally.
Adj. 1. lengthwise , such as long splits, can be ripped RiPPED are an alternative rock band from Burlington, Ontario, Canada on Sextant Records/EMI Distribution. The band formed in 1994, and were originally called "Ripped Emotions". out with less waste. Those defects that run across the width of the board should be considered for removal at the crosscut saw. A few rules of thumb coupled with examples may help you develop defecting guidelines guidelines,
n.pl a set of standards, criteria, or specifications to be used or followed in the performance of certain tasks. at your crosscut saw.
One rule of thumb used by some rough mills is for the crosscut saw operator to remove defects that extend over 50 percent of the board width. Saddle wane extending across the full width of the board should be removed at the crosscut saw. Spike knots and multiple knot knot
In cording, the interlacement of parts of one or more ropes, cords, or other pliable materials, commonly used to bind objects together. Knots have existed from the time humans first used vines and cordlike fibers to bind stone heads to wood in primitive axes, and were clusters, including the distorted grain around the knots, also should be removed at the crosscut saw. Distorted or sloping grain around knots may lead to torn grain or fuzzy fuzz·y
adj. fuzz·i·er, fuzz·i·est
1. Covered with fuzz.
2. Of or resembling fuzz.
3. Not clear; indistinct: a fuzzy recollection of past events.
4. grain in later machining.
Those operations with experienced crosscut saw operators and a strong yield orientation are able to use a more rigorous rule: if a strip of clear lumber is available between the defect and opposite side of the board that is at least equal in width to the narrowest "solid" width on the cutting bill, then the defect will not be removed at the cutoff-saw. Instead these defects will be left and removed later by the rip or salvage saws in order to recover a part.
If the crosscut saw operator determines that a defect should not be removed at his or her operation, the question becomes, "Into which length should the defect be placed?" If the defect is placed in the shortest length section, the crosscut sawyer eliminates most options for recovering a part at either the ripsaw or the salvage saw. It is often better for the crosscut operator to place the defect into an intermediate length, thereby providing the opportunity for the salvage saw to squeeze out a required shorter part.
Although it may seem to have a minor impact on yield, it is important for the operator to maximize the available clear wood by running the saw blade into the defect and removing only wood containing the defect. Doing this four times on an 8-foot board with a typical crosscut blade kerf kerf
1. A groove or notch made by a cutting tool, such as a saw or an ax.
2. The width of a groove made by a cutting tool. of 1/4 inch can boost yield as much as 1%.
Cutting to Length
The cut list used at the crosscut saw should have between five and nine different part lengths representing short, medium, and long lengths. Each length available represents an option for the crosscut saw operator. As part requirements are met and a part length is removed from the crosscut saw stops, a new length should be added to maintain as many lengths and combinations as possible for the operator.
For each board, the most difficult-to-find sizes should be looked for first. Of course, flexibility must be maintained in the decision making process to prevent excessive yield losses within aboard. For example, if taking the longest part results in excessive yield loss, it might be better to cut an intermediate and a short length.
Use a Backgauge
End trim is the leftover wood at the trailing end of the board that is too short to produce a part of required length and thus is wasted. Using a backgauge will help reduce end trim loss. The backgauge (Figure 1) is a simple device that can be located above the infeed table of any crosscut saw. Each cutting length set on the "stops" is also marked on the backgauge. in addition, combinations that represent multiple lengths are also marked on the backgauge. Use of the backgauge allows the operator to plan and place cuts between defects.
An example will illustrate the use of a backgauge. Figure 2 shows an 11-foot board. The operator examines the board for defects to be removed at the crosscut saw and decides to first cut a clear 36-inch piece, designated as the red stop. The next choice to cut another 36-inch piece assumes that the defect will be removed at the ripsaw. Note the future ripping of the 36-inch piece containing the defect will yield a narrower 36-inch piece and later at the salvage operation either one 24-inch or two 15-inch pieces.
At this point, the operator has removed 6 feet from the original 11-foot board as shown in Figure 3. Guided by the backgauge, the operator sees that the end of the board falls just beyond the mark that indicates the red and yellow combination (RY). The operator knows that a 36-inch (red) and a 24-inch (yellow) section can be cut with a small amount of end trim waste. Use of this system allows lumber to be defected strategically and end trim to be minimized, resulting in improved utilization of the wood.
Electronic backgauges with colored lights automatically calculate and display the location of backgauge marks. A manual system consisting of a channel bar with drilled holes, colored taper pins Taper pins are tools used for enlarging holes usually for mechanical, Machine Tapers or body modification purposes. They are typically designed as long metal rods with one end having a slightly larger diameter than the other. (golf tees, for example) to set the backgauge marks, used in conjunction with a spreadsheet spreadsheet
Computer software that allows the user to enter columns and rows of numbers in a ledgerlike format. Any cell of the ledger may contain either data or a formula that describes the value that should be inserted therein based on the values in other cells. program to calculate backgauge mark locations, also will work well.
Determining backgauge combinations must be done while balancing conflicting needs. The goal should be to minimize gaps between pegs on the backgauge. However, the operator must be careful when combining lengths to avoid cluttering cluttering Speech pathology A condition characterized by an excessive rate of speech with an irregular rhythm, collapsing of sounds and words, and loss of syllables; cluttering can range in severity from garbled, but generally intelligible, to virtually the backgauge and complicating com·pli·cate
tr. & intr.v. com·pli·cat·ed, com·pli·cat·ing, com·pli·cates
1. To make or become complex or perplexing.
2. To twist or become twisted together.
1. its use. When introducing the use of the backgauge, one approach to simplify its use is to use only two combinations of part lengths. Some combinations that include low-priority parts can be excluded even though their inclusion would more completely fill in the backgauge. The most needed lengths should be paired with each other first to make them appear more frequently on the backgauge.
Determining the Overage Overage
Apples mainly to convertible securities. Difference between how much common stock one party must sell and the other wishes to buy for the same amount of convertible in a swap. Allowance
The overage allowance -- the extra number of parts manufactured to replace the defective defective adj. not being capable of fulfilling its function, ranging from a deed of land to a piece of equipment. (See: defect, defective title) parts created in the normal sequence of machining operations -- should be carefully examined.
One of the major causes of part loss is that parts are needed to test machine setups at the beginning of new runs. Using defective parts as set-up pieces can boost rough mill yield significantly. A second major cause of part loss is rejected parts where machining operations expose hidden defects, cause breakage or torn grain, or produce mismachined profiles, faces or edges.
More rejections occur when higher numbers of parts are needed and when more complex machining is required. End use also will affect the definition of what is defective, since hidden frame parts located on the inside of furniture can contain defects that cannot be tolerated in an exposed part that will receive a high gloss finish. Taking all these into consideration, overage allowance must consider set-up, quantity, complexity, and end-use.
Based on these factors, it is easy to see that using a fixed percentage to determine overage is wasteful. The "Yard, Kiln kiln (kĭl, kĭln), furnace for firing pottery and enamels, for making brick, charcoal, lime, and cement, for roasting ores, and for drying various substances (e.g., lumber, chemicals). & Rough Machine Standard Practice Manual," prepared by Ross Associates for the Hardwood hardwood: see wood.
Timber obtained from broad-leaved, flower-bearing trees. Hardwood trees are deciduous trees, except in the warmest regions. Dimension Manufacturers Assn. (now the Wood Component Manufacturers Assn.) recommended preliminary overage allowances grouped according to according to
1. As stated or indicated by; on the authority of: according to historians.
2. In keeping with: according to instructions.
3. end use and complexity. Three different types of parts are identified: simple interior parts; simple exterior parts; and complex exterior parts.
* Simple interior parts are those in which five or less straightforward operations are performed on wood that is easily machined, and where minor defects may be tolerated. An example would be interior frame parts.
* Simple exterior parts also have only a few straightforward operations to be performed on wood that is easily machined. Minor defects are not tolerated, however, and defects are likely to occur in the machining operations. An example would be mouldings.
* Complex exterior parts are those in which a larger number of operations are to be performed and/or where part design results in fragility of the part or difficulty of machiming, or where the species used is difficult to machine. An example would be a sash or a complicated crown moulding with a check-prone wood.
These groupings are used to calculate an initial estimate of the overage allowance, as shown in Table 1. It is expected that manufacturers will adjust these values to fit their general production needs, and to fit specific situations that periodically arise.
The size of the overage allowance required is greatly impacted by the quantity of parts required by the production run, as shown in Table 2. For small run sizes the overage allowance becomes a large percentage of the total production run. This illustrates the reason that many manufacturers are using computer technology to reduce the number of parts required for machine setups.
Crosscut saw operators have an oversight
Oversight may refer to:
Bottlenecks may occur downstream from the crosscut saw such as at the straight-line ripsaws and the salvage saws. It may be tempting to control the bottleneck A lessening of throughput. It often refers to networks that are overloaded, which is caused by the inability of the hardware and transmission lines to support the traffic. It can also refer to a mismatch inside the computer where slower-speed peripheral buses and devices prevent the CPU by having the crosscut saw operator cease production of certain parts until the bottleneck eases, but that approach will likely hurt yield. A better approach is for the rough mill foreman to smooth flow by adjusting cutting bills, lumber grade brought to the mill, lumber length and width of lumber brought to the mill. These adjustments will have a less drastic negative Impact on yield.
This abridged article has discussed many of the details that can impact yield at the crosscut saw. Other considerations that should be examined can be found in the complete article available online at www.ces.ncsu.edu/nreos/wood/ and looking under "Rough Mill Operators Guide."
Table 1 Proposed method of calculating preliminary overage allowance Part Type Set-Up Production Production Allowance First 100 Parts First 900 Parts Simple Interior Parts 3 Pieces + 3% of 1st 100 + 2% of next 900 Simple Exterior Parts 3 Pieces + 3% of 1st 100 + 3% of next 900 Complex Exterior Parts 5 Pieces + 5% of 1st 100 + 4% of next 900 Part Type Production First 1000 Parts Simple Interior Parts + 1% over 1000 Simple Exterior Parts + 2% over 1000 Complex Exterior Parts + 3% over 1000 Source: Yord, Kiln & Rough Machine Standard Practice Manual Table 2 Calculated overage allowance for simple exterior parts as a function of production run size. Production Overage Percentage Run Quality Allowance Allowance 10 3+0.3=3 * 30% 100 3+3=6 6% 1000 3+3+27=33 3.3% 10000 3+3+27+180=213 2.1% * Overage allowance was rounded to nearest whole number.
Phil Mitchell is associate professor and extension specialist, Department of Wood and Paper Science, North Carolina State University History