Knowing Matra


By Mario Beaupain

Characteristics of the program

The program works on IOS platform and runs on the following devices:iPhone5, iPhoneSE,  iPhone6, iPhone6S, iPhone7, iphone7Plus, iPhone8, iPhone 8Plus, iPhoneX, iPadMini, iPad Air,iPadPro

The program calculates the drawing diagram of Carbon and Stainless Steel wires, Bronze, Aluminium, Copper and Zinc wires. For Aluminium and Bronze, we considered the analysis more popular and with the higher tensile strength. For Zinc we considered the material with 99% of base material.

Matra suggests the needing die number in function of the material and of  total reduction. In the underneath field you can insert a different die number. Aside the medium reduction is indicated.

It calculates the diameter sequence and the relative reduction per pass, the material tensile strength, the needing drawing force, the speed and the power for each pass.

It is possible to work with constant or with decreasing reductions, to set the reduction of the last block and, in the case of external skinpass, to set the value of it.

It foresees the final tensile strength of the material basing its calculation on practical values obtained from real experience.

It calculates the draw per pass using the advanced formulas of the Homogeneous Work, as inside specified.


It calculates also the productivity of the machine with possibility to set the efficiency of it.

The program works with International  Unit Measure (SI) or with  United States Customary Units (USC).


Setting of the  Measure Unit

S.I. (International Unit System): the diameters are in mm, the speed in m/sec, the drawing force  in Newton, the tensile Strength of the material in N/mm2 e power in kW. Productivity is given in kg/h.

USC (United States Customary Units): the diameters are in inches, the speed in ft./min,  the drawing force in Pounds and the tensile Strength of the material in p.s.i.. The productivity is given in Pounds/hour.


 Annealed Diameter

It is the diameter of the wire receiving the last annealing  before the drawing.  The annealed diameter can be same as the Inlet Diameter, but cannot be less than it. The tensile strength of the material is calculated in function of the total reduction from the Annealed Diameter

Inlet Diameter

It is the real diameter entering into the drawing machine.

Outlet Diameter

It is the final diameter, after the last die.

Number of dies

It is the number of drawing blocks.  In case of final skinpass after the drawing machine, this number includes  the skinpass die.


The program works with Carbon Steel, Stainless Steel, Aluminium,  Bronze, Zinc and Other wires.

In the Carbon Steel wires the Carbon content can vary from 0% to 1%, continuously. Enter directly the value of the Carbon content. For Carbon 0,47% enter directly the value “0,47”.

Last reduction

The program calculates the reductions using the logarithmic progressive sequence. To obtain these reductions you must fix the last reduction %.  In case this value is left empty the program introduces the value of medium reduction/pass minus 2 points. In case even reductions are requested is sufficient to enter the mean reduction per pass (calculated on the right).


After the drawing machine there is the possibility to have a final skinpass (for instance with an external block after a surface treatment). In this case it is possible to enter the skinpass value requested. If empty the program doesn’t consider this extra reduction.


This is the speed after the last die.  The program calculates the speed for each block.

 Machine Efficiency

It considers the production loss due to the machine  stops, the change of the spool or the coil, wire breakage and the threading of the machine. The efficiency normally ranges from 75% to 95%. If this value is left empty the program assumes 85% value.

 Wire Tensile calculation

The wire tensile is calculated using the standard  strength increasing table used from many years to dimension the drawing machines. These results can be also used to predict with a certain tolerance the final tensile after drawing. In effect many others parameters can modify the final result (alloy elements,  drawing speed, wire temperature, dies shape). The used data are prudent and have the purpose to dimension/verify the machine motors.

 Draw force calculation

The drawing force is calculated with the Siebel’s  formula integrated with the Friction Force in the cone and in the cylinder of the die. In detail the formula used is:

T = FH + FI + FA + FC

T = Drawing force

FH= Homogeneous Force

FI= In-Homogeneous Force

FA= Friction Force

FC= Friction Force on the bearing of the die

d(i)= exit diameter

d(i-1)= inlet diameter

TS(d)= Wire tensile at the exit of the die

Ts(d-1)= Wire Tensile at the inlet of the die


B(%) = Bearing length of the die/Die Diameter

The approach angle of the die has been considered in the following way:

 Reduction 25%÷30% 2alfa = 14

Reduction 20%÷25% 2alfa = 12

Reduction 15%÷20% 2alfa = 11

Reduction 5%÷15%  2alfa = 8

The friction coefficient was assumed = 0,038. It is valid for dies lubricated with soap. For dies lubricated with oil or emulsion the friction coefficient should be 0,1 and then the drawing force results increased of 20/30%.

The length of the die bearing is assumed = 0,03 % (Bearing length/Die Diameter).