Mechanical and plant engineering

Presses and more – Dieffenbacher wooden board and forming technology

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The Dieffenbacher group of companies is one of the leading international manufacturers of press systems and complete production systems for the wooden board industry. Also in the field of forming presses, e.g. for glass fibre reinforced plastics for the automobile and supply industry, the hydraulic presses, with their short cycle times, are at the forefront.

The family business founded in 1873 has more than 1,600 employees worldwide. In accordance with the slogan „presses and more“, Dieffenbacher delivers everything from a single source. Over 70% of production is exported. With a worldwide distribution and service network, Dieffenbacher is always accessible to its customers.
For the wood processing industry, complete production lines are delivered for the manufacture of chipboard, MDF, OSB and LVL boards, as well as for wood fibre insulation boards and door leaves. In manufacturing, the basic material, for chipboard, e.g. wood in the form of chips, wetted with glue and processed in single opening presses or in continuous operation CPS endless presses into plates.

In the CPS, the glued chips are scattered in three different layers onto a continuous belt. This transports the so-called chip cake into the press, which is heated to over 200°C. Here, the wood chips are pressed to the desired thickness between an upper and lower steel belt and hardened. At the end of the CPS, the plates, which are up to 2.5 m wide, are sawn and frequently also laminated immediately. For the lubrication of the complex high-tech machines, only high-quality lubricants authorised by Dieffenbacher may be used. A synthetic hightemperature oil, which protects the roller bars continuously moving through the press at temperatures of over 200°C and their guide chains against wear, is important for the CPS presses. High demands are also made on the greasing of the slow-moving spherical roller bearings in the return pulleys. The filterability of the hydraulic fluid in the presses, which run in a very dusty environment, can be key to achieving optimised production.

With fully automated presses for the manufacture of fibre-reinforced plastic components, e.g. whole vehicle floor plates are produced in a single operation in the automobile and auto supplier industries. With an active servo-controlled parallel motion system as a high-precision press and the corresponding heating of moulds and blanks, it is possible to manufacture fibre-reinforced plastic components suitable for the outer shell of vehicles.

Dieffenbacher only permits a number of zinc-free hydraulic oils of HLP46 type for use in the presses during the guarantee period, pursuant to DIN 51524-2. One of these presses can contain up to 10,000 litres of hydraulic oil. With consistent care and maintenance, it achieves lifetimes of up to 40,000 hours or over 5 years of operation. By way of preventive maintenance, the service experts of the company recommend the following to operators of installations:

  • Only pour oil into the installations through one filter, including new oil.
  • Carry out an analysis of the oil of the newly filled installation during commissioning as a starting sample. In this way, any impurities can be recognised in advance and suitable elimination measures taken.
  • Carry out hydraulic oil analyses at recurrent intervals, for a normal 3-shift operation, every 2,000 hours.
  • For a necessary oil change, flush the hydraulic system and clean the tank thoroughly.

By regular monitoring of hydraulic fluid, the optimal time for an oil change can be planned. In the long term, oil analyses have a cost reducing effect on the overall amount of hydraulic oil and the work load. But the analyses also help avoid production disruptions to the press hydraulics. Impure, oxidised hydraulic oil or hydraulic oil with insufficient additives can ultimately lead, after a short period, to disturbances in one of the many installed control valves and thereby lead to the halting of the entire line. If the causes of sticky deposits are unknown and corresponding replacement components are not immediately available, extremely high costs will be incurred.

Among other things, the oil analyses consider oil purity, aging and the condition of the additives. The oil purity indicated in the purity classes is important for undisturbed functioning of the hydraulics and of the large number of servo- and control valves. During production of chipboard, the surrounding air is often polluted with fine wood particles. Both the ventilation filters for the hydraulic oil tank and the main and bypass filters of the installation are designed correspondingly. If dirt particles nevertheless get into the oil, they can also be deposited on the control edges of the valves or cause sticking. Fine wear particles may also pollute the oil and lead to leakages within the valves, causing increased losses and higher oil temperatures. When subjected to the shearing forces arising in a leakage split, important additives become sheared and ineffective. On the basis of the IR spectrum, of the increase in the AN or the NN and the change in viscosity, the oxidation and condition of the oil are observed. In this way, depending on the oil deployment time, an indication of the oil change extension can be given.

In addition to the operators of the Dieffenbacher installations, its own construction and service experts use OELCHECK‘s lubricant analyses, albeit in general only when a cause of damage has to be clarified. As a rule, it transpires here that zinc-free hydraulic oil has been mixed with hydraulic oil containing zinc. The accompanying zinc soap formation then leads to gummed up control valves, leakages on cylinders, thermal problems or disturbances to piston accumulators. With the results of the analyses, Dieffenbacher can support customers with targeted recommendations for the necessary maintenance actions. In addition, these are a valuable aid in testing the effectiveness of the filter design or even for gauging possibilities for improving the assembly and commissioning of the installations. 

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