Precision Sheet Metal Bending and the V grooving Machine for Sheet Metal
We have already represented the idea of the V-groove, an excellent alternative to create cosmetic bending featured with strong bending radius. Architectural panel bends featured with outer radii too close to the thicknesses of the materials and excellent appearance, with no cracks or crack traces provides evidence that it is a V-groove formation.
V groove sets bend lines and angles making use of groove cuts along bending lines. You can make V-shape cuts at the base of bending lines. As soon as the grooving has been accomplished, completion of bending can be carried out manually or through press brakes. Metals exposed to grooving can be formed into varied angular and shape bends making use of specially customed as well as commercially available tooling.
Previously we have distinguished the benefits, that involve simple formation and precise sizes, as well as drawbacks, including the weak force of V grooving. Herein we are going to give the description of V grooving and offer some ways of providing repeatability and reliability for the operation.
Grooving Machine and Cut Tooling
If you happen to make a work piece, keep in mind the task you are solving. V groove technique is suitable for a task requiring weak stress. The accomplished pieces will gain force equal to the thicknesses of materials remained at the time of bending. Thus, V-groove technique may not be suitable for some applications.
While producing work pieces through V-groove technique, consider the radii retraction when the sheet gets thinner at the bend. The contraction of the radii may be beneficial or not depending upon the part functions. For example, at the beginning of V-groove process the thickness of the sheet might be 0.080 inch at the base of bending crease then decrease to 0.030 inch. Commonly, V-groove technique decreases the material initial thicknesses while bending up to three times. It is obvious that this method does not appear applicable for situations requiring high bending force. Yet, it is possible to create acute angles with no crack traces upon the outer side of bends.
As the V-groove technique decreases thicknesses, fewer tonnages are required to finish bending. Consequently, materials of more thicknesses can be exposed to bending with lower formation tonnages.
Grooving is possible to produce with lateral shaping machine, that makes lineal motions to produce cuts upon plane areas, just as materials get removed off cylindrical objects by a lathe machine. Thus, the formation of excessively acute inner bending radii becomes possible with no cracks upon the bending outer side and with low tonnages for bottom and coin formation.
Long ago prior to the merging of V-grooves and innovative CNCs, the small V-groove applied the machine to process V-grooving, though without a suitable method of attaching sheets to the machine desk, controlling depths of the V-groove suggested difficulty and excessive inefficiency.
Currently, the advanced CNC groove equipment delivers precision, position features of 0.005 inch. The V-groove machines sets cuts accurately upon bending range, at precise angular points creating formation sizes. They can appear under different names: a CNC V-groove machine, V-groover, a CNC V-cutter and just a V-groove machine.
In case of CNC V-cutting lateral shape machines, sheets are placed right beneath the cutter. The controlling system makes use of the sheet specifications (thicknesses, quality and so on) to direct the deepness as well as position of cuts. This type of CNC V-cutters have much in common with advanced laser and plasma cutters.
The knife type inserted into the V-groover depends on your bending angles. To gain inner bending angles within 45-60 degrees, rhombic knives featured with cutting angles of 35 degrees will be required. In case of inner bending angles within 60-80 degrees, trigonous knives are required, 80-90-degree angular bending requires knives possessing the same extent of angularity. The main knife forms are shown in Fig. 1, though you may as well adjust cutting angles to gain the proper grooving angularity for your task.
It is essential to consider that the back spring needs compensation. This has to be taken into consideration concerning both the press brake tools and cutting angles. Commonly additional one or two degrees for grooving angles will solve the problem.
Yet, it may happen so that you encounter materials and bending angularity featured with considerable back spring. Then you have to produce bigger grooving angles to manage the task. Greater grooving angles make it possible for your cuts to avoid binding in the formation process. The correct punching tool angularity provides a little clearance in V-grooving between twin ridges.
The knife angle required for your task will be the same as that of the cut + a little additional cutting angle for the compensation of back spring. This is usually estimated as the half of your inner bending angles (for example V-grooving of 90 degrees provides cutting angularity of 45 degrees) + the half degree of the back spring, when needed.
Operation of the V-groover
Cutting depths and remained thicknesses of materials depend on the designs. Do not make V-grooving through single access. Depths of V-grooving cuts should be no more than 0.031 inches at each access. This will require many accesses to finish cutting and minimize burrs along its span.
Not to allow this it is advisable to set default regulation on your equipment. For the beginning cutting depths must not be more than 0.031 inches. The least thickness of sheets between the bottoms of V-grooving and the sheet has to be at least 0,011 inches. Making use of the following default regulations, depths of your cuts will be adjusted in accordance with the sizes and design of your workpiece.
Imagine you have to produce V-grooving with 0.036-inch depth on materials of 0.060-inch thickness. Produce an initial cutting of 0.02 inch, then repeat cutting by 0.020 inches till you gain the ultimate depths. Next, perform the ultimate finishing to extra depths of 0.008 inches. Having done this, you will achieve the required sizes of the remained thicknesses of your sheets. To finish the cutting a slight cut is needed, considering the knife sharpness, your grooving will be without burrs.
While fabricating sheet metals, heat generation appears one of the most basic factors. V-groove formation is no exception. Continuous V-grooving through the same cutters, excessively deep cutting will bring about improper V-groove look and burrs upon the cuts as the knives get extremely heated and softer.
Materials of 0.078 inch or of more thickness require more than one pass or access. Certain materials may need up to 8 passes to gain their eventual deepness.
It is recommended to apply numerous cutters for the purposes of increasing the number of products, reducing expenses, as well as prevent the overheat. To alleviate the generation of overheat, V-groovers might possess numerous cutters closely located in groups on the mounting head. In the case of 2 cutters, mounted to the head, 2 circles on the material will be equivalent to 8 circles. As every cutter circles over the sheet twice, the extent of overheat will not be the same as in the case of 8 circles carried out by one knife.
Development of Flat and Bending Computations
The development of the flat V-grooving goes on differently. Regardless of whether you design a flat surface by hand for prototypes or model it in CAD, to get accuracy for your flat work pieces, each bending deduction will require precise value. To make the right computations for V-grooving you have to consider the existing differences of the sheet thicknesses and depths of V-grooved cuts.
For instance, in the case of 0.090 inch thick materials and 0.060-inch removal of a grooved cutting, use the remained 0.030-inch thickness to estimate bending allowance and deductions. You will also perform computations with internal radii equal to the thickness of the sheet — “ideal” bending.
Principles To Operate.
V-grooving and conventional formation have similarities in operation. Keep in mind these principles and you will avoid difficulties in the V-groove bend process.
- Place the punch in the die properly. Otherwise, will encounter troubles related to dimensions, changes of angles as well as inappropriate appearance.
- Do not bottom or coin V-grooved workpieces, as you might face failure. Instead, use air formation.
- Keep the TX axle. It is the relation of the central part of punches, dies, and the back gauge.
- Keep the TY axles as well. It is the parallel relation of punching noses and formation dies.
- Consider the entire thickness of materials while selecting bottoming dies (use the 8X principle) not the radii or the fact of how thick the sheet is while being V-grooved.
- In case you bend across a range of holes in sheets, the materials are likely to move toward the weakest point — here, toward the central part of V-grooving. Should any problems happen with aligning, the workpieces will be bent incorrectly or inconsistently.
- It is recommended to apply sharp-profiled punches and dies of eighty-five◦ or at least no more than this. This allows avoiding the further tool wedge process.
Attracted by the V-Groove Technique?
Thus, in case you are going to V-groove, keep in mind that the required depths can be achieved in a certain duration of time. The V-groove technique might not be applicable to all tasks and applications. Bending force is crucial for certain parts, and the total thicknesses of materials as well as greater bending radius are necessary to achieve the desired force.
For a low-stressed application V-groove technique delivers certain alternatives:
- Creating a figurative groove or channel.
- Creating architectural shadows.
- Performing acute bends.
- Formation of a profile with firm and presses looks.
You may as well try out making use of various knives to produce a variety of grooved forms such as wide V, semi-circular and square ones. Thus, this makes it possible to produce various designs, the needs of which cannot be met by conventional bend techniques.