Alfa Main Catalogue Strana 197
Nabídka komerčních zákazníků **Nejlépe prodávané z ALFRA
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PUNCHING UNITS APS 70/120 – USAGE INSTRUCTIONS From the field, questions continue to be asked about the material thickness / hole diameter ratio (S/D = Ø ratio). Minimal punch die Ø with existing material thickness Intermediate material thickness and the smallest hole or punch diameter must be a certain ratio. With Chart 2, the smallest hole punch Ø can be easily determined. Three varieties of material with different strength options are specified. A specific ratio must exist between material thickness and the lowest hole or punch die Ø. An old rule of thumb is that the punch die must be as big or even bigger than the thickness of the material to be cut. The material thickness must be but never be greater than the punch die Ø. This rule no longer applies to our hydraulic punching units. They are still used with fast-working, mechanical presses because the process takes place abruptly and the punch is loaded to the utmost. For our ALFRA APS punching units, the punching process is carried out slowly and gently. Another example: Holes to be punched in a steel plate with a thickness of 20 mm made of S235. How large may the smallest punch die Ø be? On the horizontal scale for material thickness, move vertically upward at 20 mm to the full line of S235. Then horizontally to the left up to the scale of the punch die Ø. Result: = 15 mm Ø. To get the breaking point of the stamp, move up to the second line. It is therefore advisable only to proceed according to the first method. In this case, holes can also be punched the diameter of which is less than the thickness of the material to be cut. Chart 1 clarifies the right thickness/diameter ratio. This is based on trials such as.: Holes are to be punched in a steel plate made of S235. What is the recommended ratio? The shear strength of S235 is about 30 kg/mm2. At 30, move vertically upwards in the chart to line A, from there to the left to the S/D diameter ratio scale. ALFRA punch dies and matrices are made from high quality material. Nevertheless, it may happen that a stamp breaks. This is caused by: 1. S/D diameter ratio is not correct. 2. The material to be punched is not lying straight but wedged on the matrix. 3. The punching unit or the material is moved greatly during the punching process. Result: The recommended ratio is 1:1.3. The upper limit of the ratio is the dotted line B which specifies a ratio of 1:1.7. This would mean that the thickness of the material to be cut may be 1.7 times larger than the diameter of the punch die. It goes without saying that the life expectancy of a punch with this diameter ratio should be considerably shorter than one with a ratio of 1: 1.3. We therefore recommend only working to line A so that sufficient reliability exists. 4. If the scraper is damaged or not properly set to the height, the material can be wedged when the punch die retracts. 5. The scraper is located too far from the punch die so that thin sheet metal bulges when scraping. In this case, the punch die breaks in flakes at the cutting edge. In this case, we recommend providing the scraper with a bridge or possibly using a special change guide. We hope that you work easily and reliably with the ALFRA Press punch units with these usage instructions. Diameter of the punched holes/material thickness 1 S/D Ø ratio 2 Punch die diameter Shear strenght Material strength 197
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