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The manufacturing of tensile specimens with tensile specimen punches and tensile specimen grinding machine PSM2000 is a standard in sheet metal industry. Actual this technique is approved hundreds times and in highest quality market.

Especially in steel service centre’s for sheet metal plates (pre cut in longitudinal / traversal belts / plates) and small companies in sheet metal industry this type of specimen preparation is the most helpful and economic method to prepare specimens: If a high quality specimens has to prepared within 3 minutes to perform an urgent tensile test you can’t find a replacement that will be quicker in this application
(ready to test…)

For the specimen preparation we recommend in first step to cut the specimen plate with a blanking tool that is special designed for this application. From the sheet metal plate to the tensile specimen shaped as bone type / dumbbell is takes only 10 seconds (without changing the tool for different thickness ranges).

After this the blanked specimen (of course a batch) should be fixed into a specimen holder. Within 30 – 60 seconds you will receive ready to test tensile specimen in absolute highest quality.

There is no other method to receive a better quality than with the S+L – System.

But of course there are some limits in this system:        
Starting at a thickness of 6.0 - 7.0 mm the blanked specimen will have a big area which is damaged by punching. The flank of the specimen shows rough breaks and cracks and there might be a big burr. The area which is damaged by punching is at the limit to be removed with the specimen grinding machine. For this it is necessary to make a first rough removing with a rough grinding belt. So for thickness range of 6.0 – 8.0 mm it is recommended to use a belt with grain 60. After removing 0.6 mm each side you should change the belt (needs 30 seconds) and to finish the grinding process with belt grain 80 (standard). Only with this rough grinding the very thick specimens won’t be influenced with heating effect by grinding.
Below 6.0 mm there is no problem for grinding the specimens. Researches for this problem found out that the max. temperature while grinding does not exceed 80 – 90° C. So only starting from 120° C or more there might be an effect that the microstructure will change.        

Hundreds of customers and a several researches showed that an abrasion of about 0.8 each side (10 % of thickness range) will be enough to remove the cold hardened edge (damaged edge of the specimen). Several time we made temperature measuring while grinding process is running and we never measured temperatures more than
50 – 70° C.   

But also when the specimen is thicker than 6.0 – 8.0 mm is makes sense to pre cut the tensile specimen:

• It doesn’t need to pre cut strips (for milling machine) of 300 x 50 mm on a shear, the rough specimen can easily stack up to a package to be milled

• access time for milling will be reduced because of reduction of milling volume

Following combinations of machines are common:

• tensile specimen punch and specimen grinding machine
  (specimen quantity of 300 - 500 per day / shift)

• tensile specimen punch and CNC – milling machine
  (specimen quantity of 500 – 1,000 per day / shift)

Very often the interested companies ask also which competitive system is suitable / common in the market for to prepare specimens:
For to help you in your decision as follows we are mention some arguments (positive and negative) for different methods:

High pressure jet cutting machines

     Advantage  

• processing sheet steel with high tensile strength > 1.700 MPa

     Disadvantage

• High investment – approx. 200.000,00 €  (assumed)

• Log term to prepare a single specimen (waiting time to the test)

• You have to finishing the surface because the enlargement of the

• High pressure jet will course a conic cross section

• Specialist for machine operating necessary

• Operating expenses

    Laser cutting

     Advantage  

• processing sheet steel with high tensile strength > 1.700 MPa

     Disadvantage

• High investment – approx. 200.000,00 €  (assumed)

• delay time to prepare a single specimen (waiting time ready to test)

• You have to finishing the surface because the hot laser will damage the edge zone of the specimen and will influence the results

• Operating expenses; Specialist for machine operating necessary

    Conventional milling machine
     Advantage  

• small investment so it can be used second hand machines

• flexible using the machine different specimen shapes or other job

     Disadvantage

• The Advantage of the small investment will be consumed by the high labour costs

• delay time to prepare a single specimen (waiting time ready to test)

• High quality specimens need a very accuracy working...

• Operating expenses, wear out of cutter; Specialist for machine operating necessary

    CNC - controlled milling machine
     Advantage  

• processing sheet steel with high tensile strength > 1.700 MPa

• flexible using the machine different specimen shapes or other job

     Disadvantage

• High investment – approx. 150.000,00 €  (assumed)

• Ldelay time to prepare a single specimen (waiting time ready to test)

• Operating expenses, wear out of cutter...

• Specialist for machine operating necessary

    Nibbling machine
     Advantage  

• fast specimen preparation (one specimen shape - has to be ground / milled

     Disadvantage

• Very high investment < 300.000,00 € (assumed)

• Edges not ready for test – has to be milled after nibbling

• Depending on thickness of material the sheet metal starts to flutter

   Tensile specimen punch, blanking tool + specimen grinding machine
     Advantage  

• Very quick specimen preparation - also instead of a single specimen - within only three minutes ready for test

• Cheap producing of a high number of specimens within a short time ( up to 1000 a day...depending on thickness and max. tensile strength

• Specimen with a high quality: without cold hardened edge, with a parallelism of 0,02 mm, with s surface grinded and finished in longitudinal direction...without rupture marks – in most of the test you will get higher elongation

• Low operating expenses:
  punch 4 - 7,5 kW
  grinding machine 1,1 kW
  grinding belt approx. 0,03 € / specimen

• accessing by not skilled workers – no expensive specialist needed

     Disadvantage

• medium investment – complete equipment from approx. € 50.000
  (punch 50 t, tool, grinding machine

• Tools have to be sharpened every 6 - 36 month depending an tensile strength and numbers of samples (no. of samples 10,000 - 100,000)

• Wear out of the grinding belts (approx. 8,00 € each, depending on tensile strength and thickness for         100 – 600 specimens

• Limit of punching for hard specimens at
  - 1.200 MPa (standard tool)
  - 1.700 MPa (special alloyed tool)

• Max. thickness of sheet metal plates to be punched at approx. 8 mm (2.900 kN)

Limit to use the grinding machine for sheet metal plates with a thickness of more than 6 mm, above this limit you have to use a rough grain grinding belt (grain 50) otherwise specimen will get to hot, this will influence the texture of metal