ECO-FRIENDLY LINEAR MODULE THROUGH HYDROSTATIC ECO-FRIENDLY LINEAR MODULE THROUGH HYDROSTATIC BEARING CONFIGURATIONBEARING CONFIGURATION

Experimental Procedure & SetupExperimental Procedure & SetupVertical displacement measurement of Bearings A, B C and D

IntroductionIntroduction

The objective of this project is to design and manufacture a hydrostatic module suitable for micro-machining purposes. The module will consist of a hydrostatic guideway with a suitable hydraulic power pack. The characteristics of the module will have to be evaluated, firstly with a common hydraulic fluid and then with a more environmentally friendly fluid. The module will be used in the development of a micro-lathe and a micro-EDM machines in the future.

ObjectiveObjective

Author : B. Janse van RensburgSupervisor : Associate Professor R. Kuppuswamy

Theoretical Performance AnalysisTheoretical Performance Analysis

1High pressure fluid is distributed by manifold to each bearing pad inlet passage.

2 Fluid flows through inlet passage to the bearing pad.

3 Fluid flows outwards from the bearing pad land into the sump.

4The “used” fluid is collected from the sump and extracted via the return lines back to the tank.

# Part

1 Base

2 Guide

3 Rail

4 Manifold

5 End Plate

# Function Actual Part

1 Sealed tank Glass Jar

2 Hydraulic pump 12V Bosch fuel injector pump

3 Relief valve Bosch fuel pressure relief valve

4 Variable resistor with a ball valve

FESTO pneumatic variable resistor

5 Pressure gauge Bourdon-tube gauge

6 Inlet restrictors M6 set screw

7 Bearing pad resistance Bearing pad

8 Sump Guideway base

Hydraulic Power Pack DesignHydraulic Power Pack Design

Hydraulic Circuit

PM

1

2 3

4

5

6 7

8

2

11

23

5

5

4

8

Hydrostatic Guideway Design and ConceptHydrostatic Guideway Design and Concept

Guideway Elements

Guideway Concept

12

3

4

Experimental ResultsExperimental Results

ConclusionsConclusionsTheoretical trendsDeflection over stroke (flatness)Due to the nature of this design the bearing gap will change over the stroke of the guideway. It is show that in order to overcome this disadvantage the supply pressure must be at around 5bar.Guideway stiffnessFrom the mathematical model it can be seen that the stiffness of the linear module is influenced by the payload. However the stiffness increases as the supply pressure increases.

Experimental trendsFluid film thicknessThe fluid film thickness for bearings A and C are greater than that of bearings B and D. It is suggested that this can be attributed to the mismatch between the bearing pad resistance and the restrictor resistance.Deflection over stroke (flatness)The deflection over the stroke decreases with the increase in supply pressure. In other words the flatness of the guide improves as the supply pressure increases.It can be seen that the hydraulic fluid (AWS32 specification) performs better than Baby oil. This is attributed to the better damping properties associated with the hydraulic fluid.StiffnessThe stiffness of the guide improves as the supply pressure increases. This trend applies for both fluids. However the baby oil has better stiffness results compared to the hydraulic oil.

Project number 522009

Force Analysis

Deflection Analysis

Stiffness Analysis

PADSBASE

LINEAR MOTOR : FORCER

PAYLOAD: SPINDLE /

WORKPIECE / TOOL HOLDER

RAIL

LINEAR MOTOR : MAGNETIC TRACK

RAIL

PADS

GUIDE

BEARING A BEARING C

BEARING B BEARING D

RAIL

BASE

GUIDE

O-RING

INLET PASSAGE

RESTRICTOR

PAD

Return of fluid back to tank

Pressurized fluid inlet from hydraulic

power pack

Test Rig

Proximity Sensor

Parallel Block

A deflection of the guide will result in a deflection of the

parallel block. This deflection will be observed by a

proximity sensor.

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2

3

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