Determination of band saw feeding speed

Abstract

In a method and a system for determining the feeding sped when bandsaw cutting a workpiece, the tough pitch TP of the bandsaw blade is determined in a first unit ( 6 ) depending on the shape and dimensions of the workpiece. In a second unit ( 12 ) feeding depth per tooth is determined depending on properties of the workpiece material and the width of the bandsaw blade. The bandsaw blade velocity BS is determined in a third unit ( 22 ) from the width W of the workpiece and the hardness of the workpiece material, whereafter the cutting time T is determined in a first calculating unit ( 30 ) from the height H of the workpiece, the feeding depth per tooth, the tooth pitch TP and the blade velocity BS. In a second calculating unit ( 32 ) the feeding speed MH for the bandsaw blade is then determined by the equation MH=H/T. A computer program, when executed on a computer, performs this determination of the feeding speed when cutting a workpiece with a bandsaw from supplied input data.

1 . Method for determining the feeding speed when cutting a workpiece with a bandsaw, characterized in that the tooth pitch TAP of the bandsaw blade is determined depending on the shape and dimensions of the workpiece, in that feeding per tooth is determined depending on workpiece material properties and shape and size of the workpiece as well as the sawblade width, in that the bandsaw blade velocity BS is determined from the width and material hardness of the workpiece material, whereafter a cutting time T is determined from the height H of the workpiece, the feeding per tooth, the hardness of the workpiece material, the tooth pitch and the handsaw blade velocity BS and in that the feeding speed MH of the bandsaw blad is then determined by the equation  
       
         MH=H/T  
       
     
     
         2 . Method according to  claim 1 , characterized by the cutting time T being determined by the equation:  
         T =( H·K   2 /(39,7 ·S·HF·TP·BS·K   1 )  
       where the tooth pitch TP is stated as tooth per inch, K 1  is a tooth pitch factor and K 2  is an empirically determined factor for compensation for different values of the bandsaw width.  
     
     
         3 . Method according to  claim 1  or  2 , characterized by the tooth pitch being determined from a predetermined table of suitable tooth pitch TP for workpieces of different widths W.  
     
     
         4 . Method according to  claim 1  or  2 , said workpiece being tube shaped, characterized by an average value W med  of the length of contact between the bandsaw blade and the workpiece being determined by the equation  
       W med =(2 WT+k )/2  
       where WT denotes the wall thickness of the tube and k the length of the chord at the inner wall of the tube, whereafter the tooth pitch TP is determined from a predetermined table of suitable tooth pitch for different average values W med .  
     
     
         5 . Method according to  claim 3  and  4 , characterized by the same table being used for solid and tube shaped workpieces, said average value W med  of the length of contact between the bandsaw blade and the workpiece being used as workpiece width W for tube shaped workpieces.  
     
     
         6 . Method according to any of the preceding claims, characterized by the velocity BS of the handsaw blade being determined by the equation:  
       
         BS=EXP 
         L−KW 
         ·HF·SD  
       
       where L and K are constants, W is the width of the workpiece, HF is a factor determined by the equation:  
         HF =(( Y   3   /Y ) ·x )/(1 +x )  
       where Y is the nominal hardness of the workpiece material and Y 3  denotes the actual hardness, x is a constant empirically determined for each type of material, and SD a factor compensating for surface defects of the workpiece.  
     
     
         7 . System for determination of the feeding speed when cutting a workpiece with a bandsaw, characterized by a first unit ( 6 ) provided for determining a tooth pitch TP for the handsaw blade from data about size and shape of the workpiece, a second unit ( 12 ) provided for determining nominal feed per tooth S from data about properties of the material of the workpiece and a compensation factor K 2  from data about the width of the bandsaw blade, and a third unit ( 22 ) provided for determining a bandsaw blade velocity BS from data about the width W of the workpiece and a factor HF depending on the hardness of the workpiece material, and by a first calculating unit ( 30 ) provided to calculate a time T for cutting through the actual workpiece from data obtained from said first, second and third units, a second calculating unit ( 32 ) being provided to calculate the feeding speed MH from data about the height H of the workpiece and said cutting time T.  
     
     
         8 . System according to  claim 7 , characterized by the first unit comprising a memory in which is stored a table of suitable tooth pitch TP for different widths W of the workpiece.  
     
     
         9 . System according to  claim 8 , characterized by the first unit comprising a first calculating unit, provided to calculate in case of a tube shaped workpiece, an average value W med  of the length of contact between the handsaw bled and the material according to the equation:  
         W   med =(2 WT+k )/2  
       where WT denotes the wall thickness of the tube and k denotes the length of the chord at the inner wall of the tube, to be used for determining from said table a suitable tooth pitch TP for the workpiece.  
     
     
         10 . System according to any of claims  7 - 9 , characterized by the third unit comprising a second calculating unit for determining the factor HF by the equation:  
         HF =(( Y   3   /Y )· x )/(1 +x )  
       where Y is the nominal hardness of the workpiece material and Y 3  denotes the actual hardness for the material, and x is an empirically determined constant specific for each material.  11 . Computer program which when executed on a computer, from supplied input data, determines a value of the feeding speed of a handsaw when cutting a workpiece according to the method according to any of claims  1 - 6 .