BS 1983-4-1987 Chucks for machine tools and portable power tools - Specification of criteria to be stated affecting performance of power operated workholding chucks at speed《机床与便携电.pdf

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1、BRITISH STANDARD BS 1983-4: 1987 Chucks for machine tools and portable power tools Part 4: Specification of criteria to be stated affecting performance of power operated workholding chucks at speed UDC 621.9.022 229.323BS1983-4:1987 This British Standard, having been prepared under the directionof t

2、he Machine, Engineers and Hand Tools Standards Committee, was published under the authority ofthe Board of BSI and comesintoeffect on 29 May 1987 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference MTE/1 Draft for comment 84/77942 DC ISBN 0 580 15926 4 C

3、ommittees responsible for this British Standard The preparation of this British Standard was entrusted by the Machine, Engineers and Hand Tools Standards Committee (MTE/-) to Technical Committee MTE/1 upon which the following bodies were represented: Advanced Manufacturing Technology Research Instit

4、ute Cranfield Institute of Technology Department of Trade and Industry Mechanical Engineering and Manufacturing Technology Division (Mmt) Federation of British Engineers Tool Manufacturers Health and Safety Executive Institution of Production Engineers Ministry of Defence University of Aston in Birm

5、ingham The following body was also represented in the drafting of the standard, through subcommittees and panels: Portable Electric Tool Manufacturers Association Amendments issued since publication Amd. No. Date of issue CommentsBS1983-4:1987 BSI 09-1999 i Contents Page Committees responsible Insid

6、e front cover Foreword ii 0 Introduction 1 1 Scope 2 2 Definitions 3 3 Criteria to be stated concerning performance ofworkholdingchucksatspeed 3 Figure 1 Variation of gripping force with speed for atypical250mmscrollchuck 5 Figure 2 Variation of gripping force with speed for atypical250mmwedgetype p

7、ower chuck 6 Publications referred to Inside back coverBS1983-4:1987 ii BSI 09-1999 Foreword This Part of BS 1983 has been prepared under the direction of the Machine, Engineers and Hand Tools Standards Committee and is being published in advance of related ISO work which is based on a proposal subm

8、itted by the UK. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This do

9、cument comprises a front cover, an inside front cover, pagesiandii, pages1 to 6, an inside back cover andabackcover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS1983-4:1987 BSI

10、 09-1999 1 0 Introduction 0.1 General The safe grip performance of chucks is a problem which has been present ever since the chuck, in its current form, was developed. The problem has been accentuated in recent years due to the increased spindle speeds and power available on current types of machine

11、 tool. These factors are continuing to increase due to the improvements being brought about in cutting tool and machine tool technology. In order to highlight the problems and danger involved in using chucks at high rotational speed, this standard indicates the various influential factors and their

12、relative importance in an attempt to guide the user as well as the supplier. It is not possible to state categorically the safe maximum working speed of a workholding chuck. This is because the safe working speed varies and depends on the operating conditions, some of which are beyond the control of

13、 the chuck manufacturer. Even when these conditions are fully known an element of arbitrary assumption enters into the conclusion. To give a general set of maximum speed figures for any chuck or range of chucks is, therefore, impracticable. However, it is the duty of the manufacturer to provide some

14、 guidance to the user. Such figures would, however, be for guidance only and represent a certain set of qualified conditions which can be used as a yardstick. Some of the problems and considerations which have to be taken into account are as detailed in 0.2 to 0.8. NOTEThe terms used are defined in

15、clause 3. 0.2 Effect of high speed The high rotational speed of a chuck can create four basic problems: a) loss of gripping force in the chuck; b) breakage or excessive distortion of component parts of the chuck; c) excessive vibration; d) inertia problems (relative to the machine spindle and drive

16、and including the workpiece). 0.3 Loss of gripping force With conventional chucks, this is usually the most important consequence of high rotational speed. Loss of gripping force is a direct result of the effects of centrifugal force on various parts of the chuck and, in particular, the chuck jaws a

17、nd the chuck body. An appreciation of the centrifugal force law will highlight the influential factors as related by the following equation: Any increase in m or r will have a direct effect and, therefore, heavy component parts of the chuck situated at large distances from the centre of rotation wil

18、l cause larger centrifugal forces than if they were of smaller mass and situated closer to the centre of rotation. Chuck jaws are a particularly good example of a case where some control can be achieved by suitable design but the particular workpiece being handled will usually dictate the jaw config

19、uration to a substantial degree. By far the most important factor is the rotational speed since its effect is to the second power. Doubling the speed, for example, will quadruple the centrifugal force. Changes in speed, therefore, can be very significant. Care should be taken when applying this law,

20、 where values for the various factors such as jaw masses and gripping diameters are known, to calculate a theoretical loss of gripping force at appropriate speeds as there is often an appreciable difference between a theoretical loss of gripping force thus obtained and the actual loss. The actual lo

21、ss is often less severe than the theoretical loss due to the frictional effects within the assembly of the chuck and the relative stiffness of the chuck and the workpiece. Nevertheless, the use of this law is perhaps the best single guide to loss of grip when no other information is available since

22、it quantifies, in the majority of cases, the situation and gives figures which are generally more severe than those obtained in reality. The factor which ultimately dictates the speed at which a particular amount of grip loss is acceptable is the amount of gripping force actually required in the par

23、ticular application, i.e. the amount of grip which remains at a certain speed and its capability to withstand environmental forces such as gravitational, inertial and, particularly, the cutting forces involved. CF = mr 2 where CF is the centrifugal force (in N); m is the combined mass of all the bas

24、e jaws and top jaws (in kg); r is the radius of the centre of mass of the combined base and top jaw from the rotational centre (in mm); is the angular velocity (in rad/s) expressed as 2;N/60, where N is revolutionsperminute.BS1983-4:1987 2 BSI 09-1999 When this gripping force requirement for the app

25、lication is known by the user, an assessment can be made as to how much grip is available when the chuck is stationary and, following this, as to how much grip loss can be afforded and accordingly, the corresponding rotational speed that may be employed. Among the factors which affect the dynamic gr

26、ipping force actually required are the type of machine, the cutting conditions and performance required, whether wet or dry cutting is used, the condition of the gripping surfaces of chuck and workpiece, etc. These factors are known to the user and can be assessed to ascertain the amount of gripping

27、 force at the jaw. The next step is to apply the appropriate amount of input operating torque, pressure or drawtube/drawbar pull to the chuck to give the desired gripping force, taking into account the loss to be suffered at the appropriate speed and also inefficiency in the actuation device and in

28、the chuck itself. This input/output information is normally available from the chuck suppliers. Typical examples of gripping force/speed characteristics are shown in Figure 1 and Figure 2. These illustrate a set of qualified conditions and can be used only as a guide. Chucks of the same size and typ

29、e will not necessarily have identical characteristics. The foregoing comments apply only to the use of chucks for external gripping. If internal gripping is used a loss of gripping force will not occur. Instead an equivalent amount of increase in gripping force will be shown and, from a safety stand

30、point, this does not generally represent the same problem. 0.4 Breakage or excessive distortion of chuck A chuck is capable of being broken either in some minor way internally or, ultimately, by the complete body bursting if rotational speed is increased to excessive values. The contributory factor

31、is again centrifugal stress. However, in most instances, with conventional chucks in a sound condition, the speed at which this stress becomes serious is much greater than that at which complete loss of gripping force occurs. Therefore, centrifugal stress failure will not normally dictate maximum sa

32、fe operating speeds. Exceptions to this are, for example, when fracture prone bodies are involved and these have been cracked or damaged, or when the chuck or jaws have not been properly secured. When chucks are used at high speed, the importance of adequate guarding becomes even more acute since th

33、e velocity with which a broken piece of chuck mechanism or loosened workpiece is thrown outward is accordingly much greater. 0.5 Excessive vibration Excessive vibration occurs more readily at medium and high speeds but its reduction is basically a responsibility of the machine tool manufacturer in t

34、he design of the spindle and bearings. The chuck manufacturer can assist by providing a chuck with minimum overhang (width) and mass compatible with its function, and also by dynamically balancing the chuck. This does not exonerate the machine tool supplier from balancing the whole rotating assembly

35、 (including chuck driving buttons, etc.) on the machine spindle. 0.6 Inertia problems Mass and large diameter contribute most to chuck inertia and a problem arises when stopping from and starting up to high rotational speeds. Basically this is a machine design problem and is soluble from the outset

36、by the use of suitable clutches and drives. It rests with the chuck manufacturer to design as light a product as possible bearing in mind strength, wear and functional capability factors, and that the nature of the workpiece will, in addition, have an influence. 0.7 Workpiece The shape and size of t

37、he workpiece and the effect of the extra centrifugal and other forces, including balance, which it exerts on the chuck when the chuck is rotated at production speeds needs to be taken into account by the user, both under free running and cutting conditions. 0.8 Bursting speed If the bursting speed i

38、s lower than the speed at which loss of grip occurs then it is to be stated by the manufacturer. NOTEBursting speed is generally far higher than the speed at which loss of grip occurs providing the chuck is undamaged and is not constructed of a fracture prone material. 1 Scope This Part of BS 1983 s

39、pecifies the criteria which affect the performance at speed of power operated workholding chucks of machine tools, and which are to be stated by the manufacturer and supplied with each chuck to the supplier and user. In the introduction (see clause 0) various influential factors are presented concer

40、ning the problems and dangers involved in using workholding chucks at high rotational speed and the relative importance of the factors is indicated in order to guide suppliers and users. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover.BS1983-4:1987

41、 BSI 09-1999 3 2 Definitions For the purposes of this Part of BS 1983 the following definitions apply. 2.1 gripping force the algebraic sum of the radial forces imparted by all the chuck jaws on the workpiece 2.2 static gripping force the gripping force of the chuck before the chuck has been rotated

42、 2.3 maximum static gripping force the maximum actual total gripping force obtained when the maximum permissible input torque, pressure or drawtube/drawbar pull is applied to a chuck of particular design 2.4 dynamic gripping force the total gripping force of the chuck whilst it is rotating NOTEThe w

43、orkpiece may additionally influence this. 2.5 loss of gripping force the loss which occurs due to nett centrifugal effects on the chuck top jaws 2.6 input force the force actuating the chuck mechanism, applied from an external source 2.7 input torque the torque actuating the chuck mechanism, applied

44、 from an external source 2.8 input pressure the fluid pressure applied to the integral chuck cylinder 2.9 rotational balance the equilibrium of all the elements of mass about the axis of rotation NOTEAny radial difference between the axis of rotation and the centre of gravity will cause out-of-balan

45、ce conditions. For further information see BS 5265-1. 2.10 moment of inertia (second moment of mass) of a chuck about its axis of rotation the sum of each element of mass, m (in kg), multiplied by the square of the distance, r (in m), of each element of mass from the axis of rotation, i.e.C(mr 2 ) 2

46、.11 drawbar pull the axial force necessary to provide an input force to actuate a chuck or other workholding device NOTEThe drawbar (or drawtube) is normally sited co-axially with the machine spindle bore and is normally connected to a rear mounted actuator at one end and a chuck or workholding devi

47、ce at the other end. 3 Criteria to be stated concerning performance of workholding chucks at speed 3.1 Data to be stated and engraved on chucks 3.1.1 Maximum permissible input force, F max(inkN), input torque, C max(in Nm) or input pressure, P max(in bar). This data shall be stated by the manufactur

48、er and shall also be engraved on the chuck. 3.1.2 Maximum total measured static clamping force at maximum input, CS max(in kN), with the chuck as new and with lubrication as prescribed by the manufacturer. This data shall be stated by the manufacturer and shall also be engraved on the chuck. NOTEN m

49、ax(revolutions per minute) is not to be engraved on non-centrifugal compensated chucks at present pending a full assessment of the subject. 3.2 Data to be stated only 3.2.1 Dynamic gripping force. The manufacturer shall state all the data necessary to determine the decrease or increase of the dynamic gripping force for each chuck. NOTEThe dynamic gripping force is influenced by the following: a) the initial static gripping force; b) the decrease or increase of the gripping force due to the effect of a centrifugal force which is proportional to: 1) the square of rate