What must be paid attention to when purchasing stainless steel Press brake?

Jun 07,2023

1、 Workpiece: An important consideration is the parts you want to produce, and the key is to purchase a machine that can complete processing tasks with a short workbench and a small tonnage. Carefully consider the material grade, processing thickness, and length. If most of the work is done on 16 gauge thick, 10 foot long mild steel, then the free bending force does not need to exceed 50 tons. However, if engaged in a large number of bottomed die forming, perhaps a 160 ton machine tool should be considered.

Okay, assuming the thickness of the material is 1/4 inch, a free bending of 10 feet requires 200 tons, and a bottom die bending (corrected bending) requires at least 600 tons. If most of the workpieces are 5 feet or shorter, the tonnage will be roughly halved, greatly reducing the purchase cost. The length of parts is crucial for determining the specifications of a new machine.

2、 Deflection: Under the same load, the deflection of the 10 foot machine workbench and slider is four times that of the 5 foot machine. This means that shorter machines require less gasket adjustment to produce qualified parts. Reducing gasket adjustment also shortens preparation time.

The material grade is also a key factor. Compared to low-carbon steel, stainless steel typically requires a load increase of about 50%, while most grades of soft aluminum reduce it by about 50%. You can get the tonnage table of the machine from the Press brake manufacturer at any time, which shows the estimated tonnage required per foot length under different thicknesses and materials.

3、 Bending radius of parts: When using free bending, the bending radius is 0.156 times the opening distance of the concave mold. During the free bending process, the opening distance of the concave mold should be 8 times the thickness of the metal material. For example, when forming 16 gauge mild steel with a 1/2 inch opening distance, the bending radius of the part is approximately 0.078 inches. If the bending radius is almost small enough to reach the material thickness, a bottomed concave die must be used for forming. However, the pressure required for forming a concave die with a bottom is about four times greater than that required for free bending.

If the bending radius is less than the material thickness, a punch with a front fillet radius less than the material thickness must be used, and the stamping bending method must be sought. In this way, 10 times the pressure required for free bending is required. In terms of free bending, the convex and concave molds are machined at 85 ° or less (smaller points are better). When using this set of molds, pay attention to the gap between the convex and concave molds at the bottom of the stroke, as well as excessive bending that is sufficient to compensate for rebound and maintain the material at around 90 °. Generally, the springback angle generated by the free bending die on the new Press brake is ≤ 2 °, and the bending radius is equal to 0.156 times of the opening distance of the die. For the bending of bottomed concave molds, the mold angle is generally 86~90 °. At the bottom of the stroke, there should be a gap slightly larger than the material thickness between the convex and concave molds. The forming angle can be changed because the tonnage of the bottom concave die bending is relatively large (about 4 times that of free bending), reducing the stress that usually causes rebound within the bending radius range.

Stamping bending is the same as bending with a concave die, except that the front end of the convex die is machined to the required bending radius, and the gap between the convex and concave dies at the bottom of the stroke is less than the material thickness. Due to the application of sufficient pressure (approximately 10 times that of free bending)