In this article we go deeper into the knowledge of the slipping in the wet drawing machines and how it is possible to manage it with the program Matra.
Slipping machines: How to use the new functionality of Matra
Matra is a program calculating the drawing diagram for the dry drawing machines and wet slipping drawing machines. The slipping machines are included in the version 2.0 of the program. In this article the instructions to work with the wet slipping drawing machines. The instructions for the use of the program for the dry drawing machine are in another article of this site.The program can be downloaded from Apple Store and is working on iPhone 6S, 7, 7S, 8, 8Plus, X,XS,XSMax, 11, 11Pro, 11 ProMax, all types of iPad.
After the choice of the language and of the Measure Unit (Metric or Imperial), press the Button Slipping Machines.
With the button “CA” it is possible to clear all the page and start the data cleaning up all the fields. Pressing the button “List” you can see the data of the preloaded machines.
If your machine is one of them included in the List you can enter in the green field the number of the machine chosen. In this way all the data defining the property of the machine will be populated automatically. If your machine is not included in this list you can enter manually all the data defining the properties of the machine.
“Total Die Number” is the maximum dies number of the machine. This number, after entering the dies/group, must be the same indicated in the grey field aside.
“I° group of elong/reduct”. In the following photo you can see what is the meaning of group. In this machine of four shafts we have two groups of reductions. In many machines the reductions are the same in the first and in the second group, but sometime in the first group the reductions are bigger. In this case we can say the groups are two and we can specify for each group the relative elongations per pass. If the reductions are equal then you can consider only one group. In a six shaft machine some time the groups are three with different reductions.
In the machine n. 1 of the list in the following photo there is another situation. The groups are still 2 but the reduction of the die in the passage from the first to the second section is different from the other. In this situation we have to use all the three groups of elong/reduct as indicated in the machine n.1 of the List.
In correspondence of the first group, then, you can enter the elongations or the reductions of the relative dies. You can enter either because the program is calculating the other automatically.
“Last Die elong/reduct”. After filling all the data of the three groups you have to enter the elongation/reduction of the last die that normally is different from the others. Check now if the “Total die number” is the same value of the grey field and, if you want, you can check all the parameters of the wet drawing machine pressing the button “Check Machine Data”. Here following what you can see:
Now it is possible to enter the data to define the drawing diagram: after the insertion of the inlet and outlet diameter you must enter the slip you want per each pass of the machine. The slip is the amount of elongation we have to add to the wire respect the elongation of the machine in order to have the possibility to work. Pressing the push button “Slip Setting” we have the following window explaining in short the slip meaning.
In the column P you can insert the slipping you want considering the first number the slip for all the capstans (except the last) inside the bath. With the second number there is the possibility to give to the last pass a different slip.
“Suggested Dies”. After entering the slip, in this row are appearing the suggested dies needing to effect the drawing diagram from the inlet to the outlet diameter and in the following row are appearing the correspondent inlet reduction “Max Inlet Reduction”.
At this point you can effect the choice of the number of dies trying to choose a compatible reduction with the type of material of the wire.
After this choice the red button “Drawing Diagram” is enabled and you can see the result of your job: The green numbers are the machine data with the machine elongation, the red data are representing the drawing diagram with the relative elongation%, reduction % and the resulting slip% per pass.
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).
| DUTY OF MATRA
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.
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
It is the real diameter entering into the drawing machine.
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”.
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.
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).