Dan Prodan

Modeling and Simulation of Closed-Loop Counterbalancing Hydraulic Units for Heavy-Duty Machine-Tools

In the case of vertical travels of large masses it is necessary to have counterbalancing systems, besides the kinematic chain of feed/positioning. These systems have a positive influence on machine accuracy. The counterbalancing systems are mechanic or hydraulic. In some cases, hydraulic systems containing one cylinder and one or several accumulators in a theoretically closed-loop are used. This paper presents mathematical models and simulation programs for closed-loop counterbalance systems.

Mathematical Models on the Closed Circuit Balancing Systems in Machine Tools

In this paper we make a comparison between the most common balancing systems used in heavy duty machine tools and especially in CNC type ones. We introduce the systems with reducing valves, pumps with pressure regulator and the systems with accumulators assembled in closed circuit. For the latter we present calculation models used during operation under adiabatic transformations (operating times of seconds) or under isothermal transformations (operating times of minutes). There are also presented applications of these models for a gantry type milling machine and an AF type machine.

Rotary Tables for Machine Tools

In this paper the authors present some theoretical and experimental research carried out during the manufacture of a rotary table for CNC machine-tools AF type. There are shown the calculation methods in static and dynamic conditions for the indexable rotary tables and also for those that operate as numerically controlled “B” axes. The calculation methods were tested by manufacturing several such tables intended for the machines belonging to AF(P)100-180 range.

Decrease in Power Consumption of Hydraulic Systems of Modern Machine Tools

This paper shows several issues related to decrease in electric power consumption for hydraulic systems of modern machine tools, especially CNCs. A core element in the structure of such systems is the pneumo-hydraulic accumulator. Here, examples are shown for hydraulic systems destined to locking and unlocking of skids and to opening of tool holders. This paper shows mathematical models, diagrams, simulations and certain experimental executions.

Using Hydro-Pneumatic Accumulators to Increase the Operation Safety of Heavy Duty Vertical Lathes

This paper presents the principle diagrams that can be used to manufacture hydraulic systems that can prevent the seizing of the circular hydrostatic guideways of the table in the case of heavy-duty vertical lathes, with over 4000 mm diameter. The proposed systems will provide the lubrication of the guideways of the table as long as this one rotates up to a possible stop caused by an accident. Lubrication is achieved even in the absence of the machine supply voltage because it is provided by systems that do not need electrical power to operate. The absence of hydrostatic pressure, even in only one of the hydrostatic pockets, caused by the breaking of a hose, can be detected and will trigger the safety system activation.

Research on the Possibility of Replacing Oil with Water in Hydrostatics Units of Machine Tools

This paper deals with the possibility to replace the mineral oil with water in the hydrostatic units of machine tools. With this aim in view we try to make a technical-economic comparison between the hydrostatic drive that uses mineral oil in the range H38 - H46 and the drive with untreated water. Two simple units were taken for comparison, in principle, which use as hydraulic energy source one constant flow pump (qP = 4 cm3) for the actuation of two consumers and one constant flow pump (qP = 20 cm3) for making the hydrostatic suspension of the saddle of an AFP type machine.

Theoretical and Experimental Researches on the Balancing Systems of Machine-Tools Feed Kinematic Chains

In this paper, the authors present some of the theoretical and experimental researches conducted in recent years in the field of large masses shifted vertically. The paper starts with a technical-economical comparative analysis of the hydraulic and mechanical balancing. The following are the most commonly used systems of hydraulic balancing for modern machine-tools, the CNC ones especially. Finally the paper presents some of the experimental achievements materialized in hydraulic balancing units for machine-tools.

The Auxiliary Equipments of the Machine-Tools. Pneumatic Systems

This paperwork presents the most frequent applications of the pneumatic drives on universal machine-tools, particularly on CNC machine-tools. It also presents modern calculation and verification methods with simulation software.

Hydraulic System of Braking Energy Recovery for Heavy-Duty Machine-Tools. Mathematical Models. Simulation

In this paper we try to study the opportunity of recovery the kinetic energy accumulated by the main kinematic chains of heavy-duty machine-tools in arresting stage. We recommend a unit that can shorten the arresting time of the main spindle, with or without semi-finished product, and that would allow the recovery and storage of the accumulated kinetic energy in order to use it for a new start. We give a principle diagram and the results of the first simulations.

Increasing the Operating Safety of the Machine-Tools by Using Hydro-pneumatic Accumulators. Modeling - Simulation

This paperwork presents the results of the theoretical and experimental research that has had as object of study the hydraulic installations with hydro-pneumatic accumulators. It presents simulations for determining the performance of some hydraulic safety systems designed for actuating brakes, for ensuring bearings lubrication when the circuit incorporating the pump fails and for lifting loads in emergency situation. A hydraulic installation designed for a grinding machine is presented at the end.