The guillotine or shearing machine has been used to cut materials ranging from paper to plastics and steel for decades. Over time they have evolved into specialised and advanced machines that can cut varying thicknesses of material very accurately and at high speeds, even adjusting cutting parameters automatically through CNC controls. In this article we are going to focus on guillotines designed for cutting sheet metal. We will discuss how the machines deliver their cutting action, the two main types of sheet metal shearing machines and their characteristics and finally the advantages of using either. Looking for guillotines? Browse new or used.
How do the guillotines or shears power the cutting action?
Before we get to the action, so to speak, we need to understand the methods by which the machines produce the force required to move the blades. Typically, guillotines use mechanical, pneumatic, servo motor or hydraulic systems. In a motorised system, an electric motor can drive a flywheel and rolling key arrangement, or provide direct drive using a gearbox and eccentric system. The latter is preferable, as it does not require the motor to be running constantly, and only starts the motor when the pedal is pressed to initiate a cut. In the case of servo motors the machine drives the movement of the top blade with powerful electric servo motors and a set of pulleys. These modern machines are known as e-shears and are very energy efficient and quiet, but initial cost is still high. Pneumatics and hydraulics are very similar to each other, in principle. By far the most popular method is hydraulic type machines, using a motor, pump, valve set, pistons and hydraulic oil to provide a relatively efficient and very powerful force to the blades.
What are the popular types of cutting action?
Firstly - whilst these machines are all lumped together and called ‘guillotines’ we should note that there are two predominant types and only one is a ‘true’ guillotine. Historically a guillotine was a machine that uses a blade that drops along a vertical track, the most well known of course being the one was used for beheadings in the bad old days. The same principle is used in a ‘variable rake guillotine’ to cut sheet metal. The beam of the machine runs in gibbs and ways, and will need a certain amount of minimum clearance because of this.
The other type is known as a ‘swing beam shear’ which differs primarily in its action. The blade does not drop vertically, but rather pivots around a fixed point on bearings, in an arc to meet the fixed bottom blade. This machine is of a ‘C-frame’ design, with a deep throat and the ram moves from a fulcrum point in the rear of the side frames providing the shear with a large amount of plate between it and the cutting edges.
So why choose one type of guillotine over the other?
As always, there are many considerations when deciding on the type of guillotine for your application, not least cost, material types, space and production parameters. We will focus on the the primary differences between the machines and the advantages and disadvantages of each.
In a hydraulic guillotine with variable rake, one of the primary advantages is the ability to change the rake angle of the blade, since it is vertically mounted in slideways. This allows for relatively greater shearing capacity and higher accuracy and less distortion of the material, particularly on heavier materials. However, because the machine must run the top beam in gibbs and slideways and needs a certain amount of clearance, this has a direct effect on the thinnest material that can be cut. Finally, it is important to consider that this machine frame is susceptible to deflection, and therefore deeper throats are either not offered, or are very heavily re-enforced whilst the top beam is heavily gusseted to keep the top and bottom blades parallel.
When considering a swing beam type shear it clearly offers advantages especially in lighter material cutting. At first, it is obvious that the rake cannot be adjusted and prevents changing of the angle at which the blade meets the material and negates the advantages of having this feature.However, since the machine is of C-frame design, with the fulcrum action of the blade on bearings, there should be absolutely no play whatsoever in the action. Another important development is that the backgauge is attached to the cutting column and moves as the blade goes down. This eliminates the problem of material getting stuck between the back gauge and the blades after cutting. Finally, the C-frame of the machine wraps completely around the entire ram as one solid gusset, and is much stronger than a gusseted ram in a hydraulic guillotine and this allows for a deep throat and cutting of very thick material even with a fixed rake angle.
Over the years innovation has resulted in a the best outcome for fabrication customers - that of choice. Each machine type offers advantages and disadvantages. Machine Tools Online is able to supply motorised and hydraulic guillotines, of type variable rake or swing beam. Contact us and we can assist in choosing the correct machine for your application and supplying a high quality new or used hydraulic guillotine, backed by great service.