Parallel holding system with cutting shock damping

Improvement of press performance

Press requirements are becoming more and more demanding. Old hydraulic presses can no longer be used for precise work with new tools. New pressing tools make it necessary to make the presses more stable and to improve the parallelism of upper and lower tools. Even with off-center loads in the die, we can significantly improve the performance of old and new hydraulic presses with our parallel holding system. The loads on man and machine caused by the cutting impact during presses and punching must no longer be part of a hydraulic press, which is why our parallel holding system was also developed as cutting impact damping for presses.

How it works

The basis of this sys­tem is our lin­ear syn­chro­nised flow di­vider, which has proven it­self in many areas of in­dus­try for many years. With the syn­chro­nous cylin­ders, the cut­ting im­pact is re­moved in a con­trolled man­ner via a de­fined oil cush­ion and a par­al­lel po­si­tion is cre­ated. De­pend­ing on the ap­pli­ca­tion, it is man­u­fac­tured with or with­out an ex­ter­nal oil sup­ply. For presses with a low stroke fre­quency, we rec­om­mend units which are equipped with a pres­sure ac­cu­mu­la­tor and op­er­ate in­de­pen­dently. In the sim­plest case this can be done man­u­ally with­out con­trol. How­ever, a con­nec­tion to the press con­trol is prac­ti­cal. The syn­chro­nous cylin­ders and the lin­ear syn­chro­nised flow di­vider au­to­mat­i­cally re­turn to their ini­tial po­si­tion when the press is opened. An oil pres­sure of 60 bar via an ac­cu­mu­la­tor causes a force of 5kN per cylin­der to re­turn to the ex­tended po­si­tion. The cylin­ders then wait for the next ram stroke. Dur­ing the down­ward move­ment of the press the par­al­lel hold­ing sys­tem works as a dis­placer. The re­sult­ing flow rates can be eas­ily lim­ited. The en­ergy re­leased dur­ing the cut­ting im­pact in­creases the vol­ume flow; this in­crease is ab­sorbed and sig­nif­i­cantly re­duced by the se­lected com­po­nents right from the start. The par­al­lelism is also main­tained dur­ing the cut­ting stroke. The syn­chro­nous cylin­ders are al­ways de­signed for the full press force and are thus able to ab­sorb the com­plete press force even in the fully re­tracted po­si­tion (stop).

Im einfachsten Fall kann dies manuell ohne Steuerung geschehen. Praktikabler hierbei ist jedoch ein Anschluss an die Pressensteuerung. Die Gleichgangzylinder und der Linear-Gleichlauf-Mengenteiler fahren beim Öffnen der Presse selbsttätig in ihre Ausgangsposition zurück. Über einen Speicher bewirkt ein Öldruck von 60bar eine Kraft von 5kN pro Zylinder um wieder in die ausgefahrene Stellung zu fahren. Anschließend warten die Zylinder auf den nächsten Stößelhub. Während der Abwärtsbewegung der Presse  arbeitet das Parallelhaltesystem als Verdränger.

Die sich ergebenden Durchflussmengen lassen sich einfach begrenzen. Die beim Schnittschlag frei werdende Energie erhöht den Volumenstrom, diese Erhöhung wird schon im Ansatz durch die ausgewählten Komponenten aufgefangen und deutlich reduziert. Hierbei wird die Parallelität auch während des Schnittschlags gehalten. Die Gleichgangzylinder werden immer auf die volle Presskraft ausgelegt und sind somit in der Lage, auch in der voll
eingefahrenen Position (Anschlag) die komplette Presskraft aufzunehmen.

Structure or installation

DThe linear synchronised flow divider and the synchronous cylinders can be designed flexibly and to suit the machine incl. tool, depending on the required size and given possibilities. Normally, the flow divider is placed on the side of the press table and the synchronizing cylinders are placed on the press table in a non-slip manner. To ensure the greatest possible parallelism, the synchronous cylinders are connected to the LGM by tubes of the same length. The synchronous cylinders are manufactured to the highest precision and have the same heights. In order to compensate for mechanical inaccuracies of the machine, there are intermediate plates that can be adapted accordingly. Thus the parallelism of the system can be further improved.

Precision

We manufacture our systems ourselves, so that we can ensure a high accuracy of the components. The greatest deviations or tolerances are caused by the compressibility of the fluid used. With hydraulic oil, a volume loss of 0.7% can be assumed with a pressure difference of 100 bar. If a water-glycol mixture is used, this value is halved.