general engineering manual bearing design guidehydratech.net.au/acmbearings/pdfs/general engineering...

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General Engineering Manual

BEARING DESIGN GUIDE

CONTENTS

1. Introduction

2. Bearing Design, Machining

3. Installation Fitting Procedure

4. Recommended Interference Fits

5. Running Clearances

6. Typical Stress Strain Curve

7. Typical PV Graphs

8. Material Data Sheets

CONTACT DETAILS

Australasian Agent

Address:- HYDRATECH PTY, LTD, Building ‘C’ Phoenix Estate 210 Evans Rd., Salisbury. Queensland 4107

Telephone:- (0)7 32768819 Fax:- (0)7 32768233 E-Mail:- [email protected] Web:- Hydratech ACM Bearings; www.acmbearings.co.uk

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ACM Bearings Ltd

Company History

Established since 1988, Advanced Composite Materials Limited,

Rotherham, England.

ACM designs and manufactures synthetic composite bearings and

materials.

Supplying World Wide markets from Construction Equipment to

Power Generation, Food Processing to Pharmaceutical, Structural to

Rail, and Hydraulic Cylinders to Marine Bearings.

Under new management from 2002, ACM supplies bearing materials

and components direct to customers as well as through appointed

Agents, Distributors and other Bearing suppliers.

ACM is an ISO 9001/2008 approved manufacturer with a

comprehensive range of material grades to meet any challenging

application, and replacing many traditional bearing materials.

The ACM Engineering Department is here to help.

ACM also has an approved Bearing Test Rig facility at its UK Factory

location.

4

BEARING DESIGN

The purpose of this manual is to offer a guide to the design of composite

bearings manufactured from ACM materials, and to outline the

importance of establishing the correct data required to ensure optimum

performance of such bearings.

Essential information to establish

Housing diameter and tolerance

Shaft diameter and tolerance

Shaft material and hardness

Maximum operating speed

Maximum operating load

Maximum operating temperature

Minimum operating temperature

Operating environment

Lubrication medium

The above information is essential not only for the design of the bearings

but also to ensure the correct grade of material is selected.

5

Bearing Design Method

To calculate bearing od for machining purposes

1, Housing id max + interference fit = Bearing od min

2, Bearing od min + M/C tolerance = Bearing od max

Subtract min bearing housing dia from max bearing od, this will give the

maximum interference fit value.

This value is necessary when calculating machining dimensions for the

bearing id due to transfer of interference fit in ACM composite bearings.

To calculate bearing id for machining purposes

3, Shaft dia max + “Running clearance” + % transfer value of max

interference fit from chart on page 5 (relevant to the wall thickness of the

bearing and shaft diameter) = Min bearing id

4, Min bearing id + M/C tolerance = Max bearing id.

A Microsoft xl spread sheet containing a comprehensive version of this

calculation is available.

6

Machining

The material is readily machined using conventional machine tooling. It

is advisable that the material is machined in a dry condition using the

suggested feeds and speeds, Surface speed 300 to 350 m/min with a feed

of 0.1 mm/rev for finishing cuts. 0.25mm feed can be used for roughing

cuts.

Tungsten Carbide tipped tools with positive rake geometry of between 3

& 5 degrees top, side and front have been found to give best results.

MACHINING SPEEDS AND FEEDS

Dia 0 – 50 50 – 100 100 – 150 150 – 200 200 – 300 300 – 400mm

RPM. 2100 1000 700 550 350 250

Dia400 – 500 500 – 600 600 – 700 700 – 800 800 – 900 900 –1000mm

RPM 200 175 150 130 120 100

Positive rake tool geometry is required, with the tools having 3 – 5

degrees of front side rake, and a top rake between 5 and up to 20 degrees

can be used.

A tool point radius of minimum 0.8 up to 2 mm is suggested for good

surface finishes.

Boring tools should have 10 degrees side rake and 15 degrees front rake

7

FEED RATES

TURNING Roughing 0,7 Finishing 0.25 mm per rev

BORING 0.5 0.20 mm per rev

PARTING 0.4 0.20 mm per rev

GROOVING

ACM can be readily grooved on a lathe, shaping, milling or boring

machine with a 90 degree machining head.

For most situations a lathe will be adequate. A sharp tool made from high

speed steel ground to the correct form should be clamped to a boring bar

with at least 3 degrees clearance ground on the sides of the tool. No top

clearance is required

The chuck should be marked with the correctly spaced number of

grooves, each groove should be shaped in turn.

A depth of 0.2mm should be used for each subsequent cut until the

recommended groove depth is reached, the machines fast traverse with

the spindle locked should be used for the power. Linear speeds of up to

20 metres per minute can be achieved.

For long bearings a steady may be required.

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DRILLING

ACM is easily drilled using either high speed steel or Carbide tipped

drills.

The following feeds and speeds are suggested

DRILL DIA SPEED RPM FEED MM/MIN

5 1000 300

10 800 400

15 600 400

20 400 400

25 350 400

30 300 400

No asbestos is used in the manufacture of ACM material, the material is

completely non toxic, the material should be machined dry no cutting or

cooling fluids should be used.

Dust extraction is recommended when machining ACM material, if not

available them it is suggested the operator should wear a non toxic

particle mask to avoid inhalation of dust particles.

9

Installation

The bearings can either be pressed into the housing or freeze-fitted.

Recommendations for freeze fitting, see the relevant data sheet.

Care must be taken at all times not to damage the bush during the fitting

process. The use of lead in chamfers on the bearing and housing are

recommended.

Bore sizes must be checked along all axes at ambient temperature to

ensure the minimum bearing running clearance has been achieved.

Bearings can also be bonded into housings with the use of a number of

adhesives possible, typically toughened acrylic adhesives have been

found to give the best results. Consult our technical department for

recommendations on this procedure.

10

RUNNING CLEARANCE

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 100 200 300 400 500 600 700 800 900 1000

SHAFT DIAMETER (mm)

RU

NN

ING

CL

EA

RA

NC

E(m

m)

Slow Speed Dry

High Speed Lubricated

Slow Speed Lubricated

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Recommended Interference Fit

0

0.5

1

1.5

2

2.5

3

0 50 100 200 300 400 500 600 700 800 900 1000

Housing Diameter

Inte

rfere

nce F

it

Interference Fit

16

L7/G PV DRY RUNNING (140)

1

10

100

1000

0.1 1 10 100 1000

Velocity (m/min)

Lo

ad

(K

g/c

m2̂)

L7/G PV GREASED RUNNING (340)

1

10

100

1000

0.1 1 10 100 1000

Velocity (m/min)

Lo

ad

(K

g/c

m^2)

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PV Correction Factor

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 50 100 150 200

Temperature C

Corr

ection F

acto

r

18

ACM GRADE L1 Scope L1 is intended for use as a bearing material. It is available in the form of tube, plate or fully machined parts. Material L1 is a high load composite bearing material made from synthetic fabric reinforcement, which is impregnated with a thermosetting resin system. Friction modifiers can be added to reduce friction (graphite for general engineering applications (L1/G) or MoS2 for marine application, (L1/M) also PTFE can be added to further improved frictional properties. The material is off white when unfilled or grey in colour when filled with either graphite or MoS

2.

Property Value Units

Tensile Strength 55 N/mm

2

Tensile Modulus 3200 N/mm2

Ultimate Flatwise compressive strength 345 N/mm

2

Compressive Modulus 2400 N/mm2

Ultimate Edgewise compressive strength 97 N/mm

2

Hardness 100 Rockwell M Density 1.25 / 1.30 gms/cc Static Coefficient of friction (dry) at 15 N mm

-2 0.15 - 0.2

Linear expansion coefficients 20 -100

oC

Parallel to laminations 5 - 6 10-5 o

C Normal to laminations 10 - 12 10

-5 oC

The above values are typical Method of manufacture The material is manufactured to documented procedures and propriety standards. Certificates of conformance can be issued and full traceability is kept for 5 years.

19

ACM GRADE L2 MARINE Scope L2 Marine bearing material has been specially developed for use in marine applications. It is available as finish machined components to customer or ACM drawings and also in tube or sheet form Material L2 Marine is a high load composite bearing material made of synthetic fabric reinforcement which is impregnated with a thermosetting resin and solid lubricant fillers, (Molybdenum Disulphide & P.T.F.E ). The product is grey in colour.

Property Value Unit

Flatwise compressive strength Maximum 414 N/mm

2

Minimum 360 N/mm

2

Compressive modulus 0.25 N/mm2 x 10

4

Maximum edgewise compressive strength 166 N/mm

2

Flatwise impact strength >0.534 Nm/mm Ultimate tensile strength 60 N/mm

2

Elongation (min) 10 % Modulus of elasticity (tensile) 0.34 N/mm

2 x10

4

Shear strength 137 N/mm

2

Crosswise flexural strength 72 N/mm2

Lengthwise flexural strength 72 N/mm2

Flexural Modulus (3 point bend) .18 N/mm2 x 10

4

Specific gravity 1.3 / 1.32 g/cc Hardness 100 Rockwell M

43 Matrix Barcol Coefficient of friction (dry) 0.15 / 0.18 (Typical dry sliding on 316 Stainless Steel) Usable temperature range cryogenic to + 120

oC

Thermal conductivity 0.293 W/mK Specific heat 1.005 J/kgK Linear expansion coefficients Parallel to laminations 5 10

-5 oC

Normal to laminations 10 10-5

oC

Water adsorption to saturation <0.1 % Water absorption in 24 hours <0.1 % Material Testing is carried out in accordance with BSEN 2782 methods of testing plastics THE ABOVE VALUES ARE TYPICAL

Method of manufacture The material is manufactured to documented procedures and propriety standards. Certificates of conformance can be issued and full traceability is kept for 5 years.

20

ACM GRADE L3/G Scope L3/G is intended for use as a bearing material in the form of bushes, bearings and wear pads. It is also available in the form of tube or sheet. Material L3/G is a high load composite bearing material made from a synthetic non-woven fabric reinforcement, which is impregnated with a thermosetting resin system. Graphite solid lubricant is added to improve the dry running friction. The composite is grey in colour.

Property Unit Value

Tensile Strength 45 N/mm

2


2

Ultimate Edgewise compressive strength 105 N/mm

2

Hardness 95 Rockwell M Density 1.35 gms/cc Static Coefficient of friction (dry) at 15 N/mm

2 0.15 - 0.20

Linear expansion coefficients 20 -100

oC

Parallel to laminations 5 - 6 10

-5 oC

Normal to laminations 10 - 11 10-5 o

C

The above values are typical


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ACM GRADE L4

Scope L4 is intended for use as a bearing material in the form of tube, plate or finished parts. The material ( L4 ) complies with the EEC Plastics Materials Directive No. 90/128 for contact with food stuffs. Material The material is a high load composite bearing material made of synthetic fabric reinforcement which is impregnated with a thermosetting resin. The material is off white in colour.

Property Value Unit

Ultimate tensile strength 55 N/mm

2

Maximum flatwise compressive strength 414 N/mm

2

Compressive Modulus (Flatwise) 0.2800 N/mm2 x10

4

Maximum edgewise compressive strength 166 N/mm2

Elongation (min) 10 % Shear strength 137 N/mm

2

Modulus of elasticity (Tensile) 0.3350 N/mm2 x10

4

Crosswise flexural strength 72 N/mm2

Lengthwise flexural strength 72 N/mm2

Flexural Modulus (3 Point Bend) 0.18 N/mm2 x10

4

Specific gravity 1.20 g/cc Hardness 100 Rockwell M Coefficient of friction (dry) 0.15/.18 Linear expansion coefficients Parallel to laminations 5-6 10

-5 per

oC

Normal to laminations 9-10 10-5

per oC

Max working temperature (Intermittent) 140 0C

Water adsorption to saturation <0.15 % Water absorption in 24 hours <0.15 % THE ABOVE VALUES ARE TYPICAL


22

ACM GRADE L7 Scope L7 is intended for use as bushings bearings etc, and other high load bearing applications. Material L7 is a high load, composite bearing material made of synthetic fabric reinforcement, which is impregnated with thermosetting resins. The product is off white in colour.

Properties Value Units


2

Modulus of Elasticity (Tensile) .3400 N/mm2x10

4


2

Compressive Modulus (Flatwise) 0.2900 N/mm2x10

4

Ultimate Edgewise compressive strength 186 N/mm2

Flexural Strength 69 N/mm

2

Flexural Modulus (3 Point Bend) 0.1880 N/mm2x10

4

Ultimate shear strength 100 N/mm2

Impact strength (flatwise) >20 ft/lbs IZOD Poisson’s Ratio 0.12 Matrix Hardness Barcol 46 Specific gravity 1.3 gms/cc Coefficient of friction (dry) 0.18 / 0.21 Water absorption 24 hours <0.15% Water adsorption to saturation <0.15% Temperature range cryogenic to +130

oC.

Linear expansion coefficients Parallel to laminate 5-6 10

-5 per

oC

Normal to laminate 9-10 10-5

per oC

THE ABOVE VALUES ARE TYPICAL Method of manufacture The material is manufactured to documented procedures and propriety standards. Full traceability is kept for 5 years. Certificates Certificates of conformity can be issued that material supplied conforms to ACM grade standard for a particular order.

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ACM GRADE L7/G Scope L7/G is intended for use as bushings, wear rings and other high load bearing applications. It is available in tube, sheet or finish machined components. Material L7/G is a high load composite bearing material, manufactured from synthetic fabric reinforcement, which is impregnated with a thermosetting resin system incorporating graphite solid lubricant filler. The product is grey in colour.

Properties Value Unit


2

Modulus of Elasticity (Tensile) 0.3400 N/mm2x10

4

Ultimate flatwise compressive strength 442 N/mm2

Compressive Modulus (Flatwise) 0.2400 N/mm2x10

4

Ultimate edgewise compressive strength 186 N/mm2


2

Flexural Modulus (3 Point Bend) 0.1880 N/mm

2x10

4


Impact strength (Flatwise) >20 IZOD Poisson’s Ratio 0.12 Matrix Hardness 46 Barcol Specific gravity 1.3 g/cc Coefficient of friction (dry) 0.13 /0.15 Water absorption in 24hrs <0.15% Water absorption to saturation <0.15% Maximum temperature range cryogenic to +130

oC

. Linear expansion coefficients Parallel to laminate 5 10

-5 per

oC

Normal to laminate 10 10

-5 per

oC

(Thermal Contraction in Liquid Nitrogen) 3 – 3.5 10

-5 per

0C

Elongation to break Tensile (min) 10% THE ABOVE VALUES ARE TYPICAL Method of manufacture The material is manufactured to documented procedures and propriety standards. Full traceability is kept for 5 years. Certificates Certificates of conformity can be issued that material supplied conforms to ACM grade standard for a particular order.

24

ACM GRADE L10 Scope L10 is intended for use as a bearing material where good heat resistance is required. It is also extremely good for use as a thermal block. Material L10 is a high load composite bearing material made from Aramid fabric reinforcement, which is impregnated with a thermosetting resin system. Solid lubricant fillers such as graphite, MoS2 or PTFE can be added to assist to the dry running capability. The material is off white in colour unless graphite or MoS2 are added which colours the composite grey.

Property Unit Value

Ultimate tensile Strength 60 N/mm

2

Ultimate compressive strength 442 N/mm2

Flexural strength 186 N/mm2


Impact strength >20 IZOD Matrix hardness 46 Barcol Specific gravity 1.30 g/cc Coefficient of friction (dry) ~0.2 Water absorption 0.5 % Maximum Intermittent temperature 200

oC

(For applications above 150

oC consult ACM technical department).

Melting point N/A (thermoset system) Elongation (min) 4 % Linear expansion coefficients 20-100

oC

Parallel to laminations 3.7 10-5

per oC

Normal to laminations 4.6 10-5

per oC

Thermal conductivity 0.185 W/m/oK

THE ABOVE VALUES ARE TYPICAL

Method of manufacture The material is manufactured to documented procedures and propriety standards. Full traceability is kept for 5 years. Certificate of conformity can be issued that material conforms to ACM Grade Standard for a particular order.

25

ACM GRADE L14 Scope L14 is intended for use as wear strip within hydraulic cylinders. Material L14 is a high load composite bearing material made from synthetic fabric reinforcement which is impregnated with a thermosetting resin. Typically graphite is added to improve the dry running friction coefficient. Other fillers such as PTFE or MoS2 can be added dependant upon the application

Property Value Unit


2

Ultimate Flatwise compressive strength 413 (unbroken) N/mm

2

Ultimate Edgewise compressive strength 165 (unbroken) N/mm

2

Crosswise flexural strength N/A (Elastomeric matrix) Lengthwise flexural strength N/A (Elastomeric matrix) Shear strength 137 N/mm

2

Flatwise impact strength (IZOD notched) >0.534 Nm/mm

2

Hardness -resin matrix 43 Barcol -composite 67-77 shore D Specific gravity 1.3 g/cc Coefficient of friction (dry) 0..15 / 0.20 Water adsorption to saturation <0.15 % Water absorption in 24 hours <0.15 % Thermal Expansion Coefficient Parallel to Laminations 5-6 10

-5 0C

Normal to Laminations 10-12 10-5 0

C Usable temperature range -197 to + 120

oC

Elongation (min) 10 % THE ABOVE VALUES ARE TYPICAL


26

ACM GRADE L15 Scope L15 is intended for use as low friction / dry running, bushings, wear pads and other bearing applications. Material L15 is a high load composite bearing material. L15 is manufactured from a special composite synthetic fabric reinforcement which is impregnated with a thermosetting resin. Additional solid lubricant fillers can be added to the grade to help to improve its dry running friction coefficient.

Properties Value Units


2

Flatwise compressive strength 428 N/mm

2

Edgewise compressive strength 173 N/mm

2


2

Ultimate shear strength 100 N/mm

2

Impact strength (flatwise) >20 IZOD Hardness 95 / 100 Rockwell M Specific gravity 1.3 g/cc Coefficient of friction (dry running on 316 st/steel) 0.07 / 0.12 Water absorption <0.1% Water adsorption to saturation <0.1% Maximum temperature range cryogenic to 130

oC

NB. For applications >130 oC consult ACM technical department.

Melting point NA (Thermoset system) Linear expansion coefficients Parallel to laminate 5 10

-5 per

oC

Normal to laminate 10 10-5

per oC

Elongation to break Tensile (min) 10% THE ABOVE VALUES ARE TYPICAL Method of manufacture The material is manufactured to documented procedures and propriety standards. Full traceability is kept for 5 years. Certificates Certificates of conformity can be issued that material supplied conforms to ACM grade standard for a particular order.

27

BEARING FREEZE FITTING PROCEDURE

Most ACM composite bearing materials are capable of being freeze fitted using

Liquid Nitrogen, the procedure for this process is as follows.

1. Select or manufacture a thin wall steel container which can be clad with insulating

material around its outside diameter the container should be just large enough to hold

the bearing and allow it to be completely immersed in the liquid nitrogen.

2. Place the bearing into the container then start to pour in the nitrogen. For the first

few moments the nitrogen will boil off as soon as it contacts the steel surface. Once

the steel surface has cooled sufficiently the nitrogen will start to fill the container.

3. Due to the extreme temperature differential the liquid nitrogen will continue to boil

off for some time during this period it will be necessary to keep topping up the

container ensuring the bearing is completely covered by the nitrogen.

4. When the boiling has subsided, the bearing should be left to stand in the nitrogen

for a further period of time. This will be dependant upon the bearing size and can vary

from a minimum of 10 minutes for small bearings, up to 45 minutes for large

bearings.

HANDLING AND SAFETY

When working with liquid nitrogen operators should ensure they are fully conversant

with the necessary precautions for its handling and use, as prescribed by the liquid

nitrogen supplier. The correct protective clothing and eye protection should be used at

all times.

Liquid nitrogen is oxygen depleting and should not be used in

confined spaces.

Thermal contraction coefficient of most ACM materials is 3.5 x 10-5

/ 0C.

It should be noted that Dry Ice typically will not give sufficient shrinkage of the

bearing to facilitate freeze fitting additional mechanical force to press fit may also be

required. Consult our technical department for guidance when using dry ice

28

ACM GRADE L10/KG10 Scope L10/KG10 is intended for use as a bearing material where high compressive strength, enhanced hoop strength and or good heat resistance is required. Material L10/KG10 is manufactured from a unique composite aramid fabric reinforcement which is impregnated with a thermosetting resin system. Graphite solid lubricant is added to the material to improve its dry running ability. L10/KG10 is non toxic and non carcinogenic. The material is grey in colour.

Property Unit Value

Ultimate tensile Strength 88 N/mm

2


2

Impact strength >20 IZOD Maximum Static Pressure 300 N/mm

2

Maximum Dynamic Pressure 220 / 250 N/mm

2

Hardness Rockwell M 95 Density 1.30/1.35 g/cc Coefficient of friction (dry) 0.13 / 0.15 Compatible pH range 3 – 12 Water absorption (Saturation) 0.5 % Working temperature range -40 to + 150

0C

Maximum working temperature 200 oC

(Intermittent) . Elongation (typical) < 3 % Linear expansion coefficients 20-100

oC

Parallel to laminations 2 - 3 10-5

per oC

Normal to laminations 3 - 4 10-5

per oC

THE ABOVE VALUES ARE TYPICAL

Method of manufacture The material is manufactured to documented procedures and propriety standards. Full traceability is kept for 5 years. Certificate of conformity can be issued that material conforms to ACM Grade Standard for a particular order.

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