their assembly in parallel to the lateral faces of  the  machine  body (Fig. 12).

2.4. Results

Based on the initial conditions and all work done, the holding system can be moved as  follows:

• Solution 1 - conventional cylinders;

• Solution 2 - servo-pneumatic  cylinders;

• Solution 3 - mixed  version.

2.4.1. Option 1 - conventional cylinders

This version consists of using four groups of two pneumatic cylinders assembled with “Multi-Position Kit”. The operation principle is the following: when the system is activated, all cylinders are extended to put the platform in the upper position, allowing achieves the correct plate placement (Fig.   13).

Starting the cutting process, the cylinders of the side where the blade starts to cut begin to retract (Fig.    14).

In order to accurately monitor the slope of the blade, the cylinders on the other side also retract, but slowly, allowing that the Z position of the holding system is in line with the point where the blade is cutting the sheet metal at each moment. At the end of the cutting process, the platform assumes a horizontal position and each cylinder assembly is retracted  (Fig. 15).

If it is necessary to continue to cut plates with a smaller thickness than 5 mm, the cylinders that support the front part of the dynamic holding system retract, causing the platform tilting and discharging the cut plate  (Fig. 16).

Fig. 5. Dynamic holding system evolution: (a) First and (b) final design.

Fig. 6. Intended freedom degrees and restricted movements on the system. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article).

Fig. 7. First approach of the guiding system.

Fig. 8. (a) Second approach of the guiding system and (b) final concept.

After a few seconds, all cylinders are actuated again putting the holding system in the upper position. Otherwise, all cylinders recede to put the holding system in the rest position (Fig. 17).

The  great  advantage  of  this  option  is  that  it  uses   conventional

cylinders that are easily found in the market at reasonable prices. As disadvantages, they present a very limited operation, since they only consent two positions, extended or retracted, not allowing control intermediate positions. In this case, a careful adjustment is also needed

Fig. 9. (a) Assembly of two cylinders with multi-position kit and (b) possible assembly positions [23].

Fig. 10. Servo-pneumatic cylinder DNCI/DDPC provided by FESTO [24].

Fig. 11. Pneumatic servo cylinders positioning.

Fig. 12. Conventional cylinders positioning.

Fig. 13. Conventional cylinder – upper position.

Fig. 14. Conventional cylinder – intermediate position.

Fig. 15. Conventional cylinder – final cutting stage.

in order to match the cylinders’ movement and the holder position with the descending blade and the cutting  point.

2.4.2. Option 2 – servo-pneumatic  cylinders

The operation principle is similar to that described in option 1. However, this option uses four servo-pneumatic cylinders. In the upper position, all cylinders are extended (Fig.   18).

Starting the cutting process, the cylinders at the cutting side start to retract, following the angle of the blade (Fig.    19).

At the end of the sheet metal cutting process, cylinders put the holding system in a horizontal  position,  slightly  below  the  blade (Fig. 20).