I was asked to create this control valve mechanical test procedure for one of the world’s leading engineering companies.

1 Introduction
2 Location of tests in the manufacturing programme
3 Stem position error test
4 Deadband test
5 Hysteresis test
6 Hysteresis plus deadband test
7 Stroking time test
8 Operation instructions
9 Equipment specifications

1 Introduction

The company has the facility to provide a permanent record of an assembled valve’s performance, whilst undergoing mechanical operation tests. The results of these tests are recorded on A3 size paper using an XYT pen recorder.

2 Location of tests in the manufacturing programme

All tests are carried out on the assembled valve and actuator before hydrostatic and seat leakage testing. The packing box gland flange nuts are finger-tight and careful assembly of the valve ensures that the packing material is in an uncompressed state. A light lubricating oil is applied to the area of the stem that passes through the packing box.

3 Stem position error test

The purpose of the stem position error test is to verify that the desired and actual stem positions are within acceptable limits. The acceptable stem position error for the company’s range of control valves is ± 5% of the rated travel. The stem position should lie between the following upper and lower limits for an input signal of 3 to 15 psig:

INSTRUMENT	% OF RATED TRAVEL
AIR PRESSURE	LOWER	UPPER
(PSIG)	LIMIT	LIMIT
3		5.00
4	3.33	13.33
5	11.67	21.67
6	20.00	30.00
7	28.33	38.33
8	36.67	46.67
9	45.00	55.00
10	53.33	63.33
11	61.67	71.67
12	70.00	80.00
13	78.33	88.33
14	86.67	96.67
15	95.00

The equipment is connected to the valve and actuator as described in section 8.

4 Dead band test

Deadband is the range through which an input can be varied without initiating observable response. In a diaphragm actuated control valve, deadband is the amount that the instrument air signal can be changed without initiating valve stem movement.
The amount of deadband is determined by measuring the changeover pressure for a given stem position. The stem is taken up to a position of 25% of the rated travel. While stationary, the change in pressure which causes a change in stem movement is measured. The test is repeated at positions of 50% and 75%. This changeover pressure is known as the 'deadband' and it should not exceed the following values :

VALVE AND DIAPHRAGM ACTUATOR WITHOUT POSITIONER
SPRING RANGE	POINT	MAXIMUM CHANGEOVER
	OF TEST	PRESSURE
3 TO 15 PSIG	25%	0.20 PSI
	50%	0.25 PSI
	75%	0.35 PSI
6 TO 30 PSIG	25%	0.40 PSI
	50%	0.50 PSI
	75%	0.70 PSI

VALVE AND DIAPHRAGM ACTUATOR WITH POSITIONER
SPRING RANGE	POINT	MAXIMUM CHANGEOVER
	OF TEST	PRESSURE
3 TO 15 PSIG	25%	0.0056 PSI
	50%	0.0068 PSI
	75%	0.0096 PSI
6 TO 30 PSIG	25%	0.0112 PSI
	50%	0.0140 PSI
	75%	0.0192 PSI

The equipment is connected to the valve and actuator as described in section 8.

5 Hysteresis test

Hysteresis is a characteristic of a control valve that is the dependence of the stem position, for a given variation of the instrument signal, upon the history of previous variations and the direction of the varying instrument signal, i.e. increasing/decreasing. The amount of hysteresis is determined firstly by performing the deadband test, followed by stroking the control valve over its full travel and returning it to its starting point. The amount of hysteresis is calculated by deducting the deadband from the distance between the cyclic envelope at 25%, 50% and 75% travel. The hysteresis should not exceed the following :

POINT	MAXIMUM
OF TEST	HYSTERESIS
25%	0.40 PSI
50%	0.35 PSI
75%	0.25 PSI

The equipment is connected to the valve and actuator as described in section 8.

6 Hysteresis plus deadband test

Hysteresis plus deadband is the total dynamic friction present in a control valve and is the vertical or horizontal distance between the cyclic envelope obtained from the hysteresis test.  The acceptable hysteresis plus deadband for a control valve is ±5% of the rated travel.

The equipment is connected to the valve and actuator as described in section 8.0.











7 Stroking time test
The stroking time of a valve is the time taken for the valve to stroke over its entire travel. This may be from the fully open position to the fully closed position, or vice versa. The duration is measured from signal increase/ decrease to full travel.  As the stroking speed is dependant upon many factors, it is not practical to define acceptable limits. The influencing factors listed in order of priority are :

(a) Actuator size
(b) Actuator stroke
(c) Air supply
(d) Pressure
(e) Size of pipework connections
(f) Spring rate
(g) Air to open/close
(h) Type of positioner

The equipment is connected to the valve and actuator as described in section 8.

8 Operation of the test equipment

The plugs and sockets of the electrical equipment are individually numbered for ease of assembly and to eliminate the possibility of incorrect wiring. Plugs and sockets, having the same number, should be connected together - with careful consideration of the actuator fail position. There are two leads labelled 'R', and a further two labelled 'D'. When testing equipment having a reverse acting actuator, the leads labelled 'R' should be connected and when testing equipment having a direct acting actuator, the leads labelled 'D' should be connected.

The power supply for the pressure transducer is situated on the left of the cabinet and it is labelled 'PRESSURE TRANSDUCER'. The operating voltage of this power supply should be set at 10 VDC and this is achieved by careful adjustment of the coarse and fine potentiometers. In most cases, the pressure transducer power supply will already be set at exactly 10 VDC.

The power supply for the linear potentiometer is situated to the right of the pressure transducer power supply and it is labelled 'LINEAR POTENTIOMETER'. The operating voltage of this power supply should be set at 24 VDC and this is achieved by careful adjustment of the coarse and fine potentiometers. In most cases, the linear potentiometer power supply will already be set at exactly 24 volts VDC.

The scale setting for the instrument signal axis is situated on the left hand side of the pen recorder and it is labelled 'INSTRUMENT SIGNAL'. Three controls are required to be set and their positions are dependant upon the maximum instrument signal pressure used.

For a maximum instrument signal pressure of 15 psig, set the range knob to 2mV/cm, vernier to (approximately) 0.00 - 0.40, zero adjustment to (approximately) 4.90 - 5.10. The vernier and zero settings are approximate and may require fine adjustments to achieve full scale deflection.

For a maximum instrument signal pressure of 30 psig, set the range knob to 2 mV/cm, vernier to (approximately) 7.08, zero adjustment to (approximately) 4.19. The vernier and zero settings are approximate and may require fine adjustments to achieve full scale deflection.

The scale setting for the valve stroke axis is situated on the right hand side of the pen recorder and is labelled 'VALVE STROKE'. Three controls require setting and their positions are dependant upon the maximum valve travel.

For a maximum valve travel of 1.1/8", set the range knob to 0.1 V/cm, vernier to(approximately) 6.72, zero adjustment to (approximately) 5.20.
For a maximum valve travel of 1.1/2", set the range knob to 0.1 V/cm, vernier to (approximately) 7.63, zero adjustment to (approximately) 5.20.
For a maximum valve travel of 2.1/4", set the range knob to 0.2 V/cm, vernier to (approximately) 6.72, zero adjustment to (approximately) 5.20.
For a maximum valve travel of 3.1/2", set the range knob to 0.5 V/cm, vernier to (approximately) 1.76, zero adjustment to (approximately) 5.11.

All of the above settings for the vernier and zero adjustments are approximate only and may require fine adjustments to achieve full scale deflection.

9 Equipment specifications

Linearity of the linear potentiometer is better than 1%, as is the linearity of the pressure transducer.

EQUIPMENT	MODEL NUMBER	SERIAL NUMBER
Pen recorder - Farnell	RW101	F2058
Power supply (Potentiometer)	E30/1	005949
Power supply (Transducer)	E30/1	006189
Pressure transducer - Honeywell	136PC30G1
Linear potentiometer - Penny & Giles	LP26/200/6"/6K	108112B

This is a  design proposal that I was asked to carry out for a Swedish world leading manufacturer of compressors, generators, construction and mining equipment, industrial tools and assembly systems.  They required a magazine system to present end-pieces for the pre-assembly of pneumatic cylinders.

The second stage for the robot assembly of pneumatic cylinders involves the sub-assembly of end-pieces and half-pistons.  End-pieces need to be handled by a magazine system because they are too large for conventional vibratory feeders.  A magazine system is required at the pre-production facilities that is a scaled-down version of the future production system, within budget limitations.  The cost of the system is split between the fixed cost for the transfer of parts to the robot and the variable cost of end-piece storage.  The variable storage cost is proportional to the capacity of the magazine system. There is also an indirect labour cost for the filling and transport of magazines, in addition to the equipment material cost. The prototype can have the same transfer device as the production model, but with a smaller capacity.

MAGAZINE FILLING

The only economical method of magazine loading is to fill them at the point of final manufacture. This is because the time taken to insert a part into a magazine can approach the time taken to insert it into the part-built assembly.  Nevertheless, end-pieces have to be transported from manufacture to assembly and magazines are the best way of doing this, whilst also giving protection to the surface finish.

MAGAZINE CAPACITY

The capacity of the magazine is as large as possible to achieve the minimum number of journeys from manufacturing to assembly during the shift.  If demand for each cylinder diameter is equal then the magazine must contain in excess of sixty parts for a refill only once a shift.  A single vertical stack magazine would be in excess of three metres high. It is therefore proposed that a number of units should be combined to form one magazine. Three magazines of twenty end-pieces seems reasonable.

PROPOSED SYSTEM

The system shown is one method of end-piece distribution. The illustration shows one magazine to store one style of end-piece.  The production version for the Swedish manufacturing plant would have three magazines per end-piece, each behind the another.

I originally presented this article, "A Software Aid to Product Design for Robot Assembly", as a guest speaker at an I.Mech.E. Congress on Automotive Technology ...

INTRODUCTION

Original work by industrial researchers into classifying and coding parts for automatic parts handling, more than 30 years ago, led to considerations of good design features for automatic handling.  Further research work resulted in a classification and coding system for manual handling, manual insertion and automatic insertion.  This work culminated in the production of assembly system designer guidelines and these were later converted to computer software package to help product designers in the Design for Assembly process. With the increasing interest in the use of industrial robots for assembly, an obvious extension to the work on product design was the development of appropriate classification and coding systems for assembly robots and the translation of this into a user friendly computer based system.

PRODUCT DESIGN FEATURES FOR VARIOUS FORMS OF ASSEMBLY

There are inherent design rules for all forms of assembly and these are independent of the assembly process being used.  There are other rules which are process dependent.  The more important considerations are:

Number of Parts:- For all forms of assembly, reducing the part count, through considering the potential redundancy of every part, leads to a reduction in assembly and component manufacturing costs.
 
Parts Handling:- A further example of a common design requirement is for parts handling where, although manual handling is completely different to automatic handling, both benefit from an increase in the symmetry of a part.   Similarly, both methods cannot easily accommodate minor asymmetrical features, nesting and tangling parts, very small or large parts, etc. As a result of this commonality, features which allow a part to be automatically handled easily are invariably useful for manual assembly and, in general terms, unless there is a significant manufacturing cost penalty, parts can always be designed for automatic handling.

Parts Insertion:- The requirements for the various types of assembly vary significantly for some insertion operations. For manual handling, the emphasis is on access and sighting.  For automatic assembly, the main features are alignment, ease of insertion and stability after insertion.  An additional potential problem is the direction of insertion for robotic assembly.  For fastening operations, regardless of assembly method, the most economic operations use integral fasteners and the most expensive require threaded fasteners.

Parts Gripping:- In manual and automatic assembly (ignoring the features already mentioned related to size), gripping doesn’t create technological or economic problems. In robotic assembly, however, gripping features can be very significant and parts should be designed so that the least number of different grippers are required. This reduces costs and often reduces non-productive assembly time.

Assembly sequence:- The optimum sequence of assembly is very much dependent upon the type of assembly. For single worker assembly, the sequence of assembly is not important and it’s often determined by operator preference.  In manual line assembly, sequence is controlled by line balancing considerations.  In automatic assembly, sequence is related to the basic logic of the equipment and is controlled by the quality and, under some circumstances, the cost of the parts to be assembled.  The sequence of assembly is determined by gripper requirements in single station robotic assembly, where the emphasis is on reducing significant non-productive time, such as either gripper changing or turret indexing.

ASSEMBLY ALTERNATIVES

In manual assembly, the two categories are single worker and line, with many variations incorporating features of both methods. It is generally not too difficult to identify the most appropriate form of assembly.

For automatic assembly, the choice of equipment is limited  and selection is based on the number of parts, cost and component quality. Again, it is not difficult to identify the most appropriate equipment.

In single-station robotic assembly however, the selection of the most appropriate equipment is more difficult.  There are many assembly robot types with different characteristics.  Additionally, there are many parts handling possibilities and various gripper options.  Although basic design for robotic assembly is essentially independent of the particular assembly cell configuration, both the product designer and system designer need some help to evaluate the performance and economics of alternative systems. Software applications have been developed for robotic assembly to serve both these functions.

Firstly, the product design is analysed by investigating its operation sequence relationship, handling features, gripping features and its insertion features. The user is asked to configure a system by specifying the robot to be used.  The cost and performance specification for three popular assembly robots is built into a robot data file and these can be increased by the user at any time. The software application determines the most appropriate assembly sequence, based on interdependencies and the type of robot to be used.  It then evaluates various parts feeding options. These options are based on feeder characteristics built into the system and they can be increased to include new types of automatic feeders.

The software application offers re-design possibilities to reduce the handling cost, where only expensive feeding methods can be used or when only manual handling is possible.  If the robot type is unsuitable, due to lack of capability, then this is reported and the application user can either modify the robot data file, enhancing the robot specification, or select another robot.  If the number of grippers required is excessive then various re-designs for easier gripping are proposed.  The application also takes into account existing equipment utilisation.  This is important because greater utilisation reduces the assembly cost.

CONCLUSIONS

The product and system design software application is a useful tool for evaluating robotic assembly.  It can be modified and extended to reflect advancements in robots, feeders and grippers.  It gives a quick evaluation of the suitability of a product’s design and determines the effect of changing assembly system parameters. These tasks could be done manually, using data sheets, but it is time consuming because of the large number of permutations of the various equipment types.

I originally presented this article, "The Flexible Assembly of Automotive Components", as a guest speaker at an I.Mech.E. Congress on Automotive Technology ...

There is a requirement for a special kind of system to assemble products required in modest volumes with a degree of variety.  A system which is as cost effective and efficient as hard automation, whilst providing the flexibility of manual assembly, is called a flexible assembly system. Within such a system, certain product parts may be required at a different rate to other parts. Some operations may require the flexibility and dexterity of a robot, or even manual labour. The resultant system would be a hybrid of many methods of assembly. This article recommends a technique to be used for the design of such a system, with the aid of a case study.

INTRODUCTION

The factory cost of a product is the addition of the manufacturing cost (e.g. casting, moulding, turning) and the assembly cost (e.g. manual, automatic, robotic).  Industrial engineers continually seek new methods to reduce the factory cost of products. The current trend of exploiting cheap labour in developing nations, through “offshoring” creates a challenge for domestic manufacturers in the developed nations.  Between 40 and 60 percent of the factory cost for many products is associated with the labour content. The majority of this cost is incurred during assembly. There are three reasons for this uneven split between labour costs in manufacturing and assembly.

(i) Manufacturing operations are usually done by, or with the aid of, a machine, i.e. turning, milling, drilling, etc. The manufacturing systems designer does not have the wide choice of the assembly systems designer because some degree of mechanisation must be used. It is then a logical extension to further automate the manufacturing process to reduce labour costs.

(ii) New processes have been developed which eliminate many manufacturing operations. Powder metallurgy is an example of such a process.

(iii) Most products are designed to be assembled manually.  This often means that components are of such a design that they cannot be handled by automatic feeders.  Additionally, many assembly insertion operations are too complex to be automated.

THE DESIGN OF FLEXIBLE ASSEMBLY SYSTEMS

The assembly process has two constituent parts and these are; the handling of components and the insertion of components. The design features of a part must be examined to decide if it can be automatically handled automatically or if it must be handled manually or placed in magazines.  Similarly, the insertion process must be analysed to decide what type of workhead is required.

Various organisations have developed procedures that help the designer to estimate how easy it is to handle and orientate components by assigning a handling code to each part. The maximum feed rate and relative cost of the feeding method can then be estimated from this code. The parts which would require expensive automatic feeders or which could not be fed at the required feed rate can be identified.  These parts must then be handled manually or in magazines/pallets.  Additionally, certain parts cannot be handled automatically because they have other bad feeding qualities, e.g. they may be flexible or too light. The previously mentioned estimation systems also help the system designer to forecast the relative cost of the workhead required to insert a part into a part-built assembly. Those operations which require a complex path of insertion, or a large thrust, require more expensive workheads than for simpler operations. A list of parts (with their associated automated handling codes) and a list of operations (with their allocated automatic insertion codes) can be constructed from the preceding information.

If the product parts are listed in order of increasing handling difficulty levels then the most economical method of feeding a part to the workhead can be determined. Parts with low handling difficulty levels are fed by conventional vibratory feeders and, as the difficulty level increases, specially designed feeders/magazines/pallets/manual handling are used. The relationship between the handling difficulty level and the type of feeder to be used depends upon the required return on investment for the equipment.

The insertion operations can also be listed in order of insertion difficulty levels to determine the most economical method of insertion of a part into a part-built assembly. Greater difficulty levels can mean that the equipment is more expensive and, for assembly robots, more degrees of freedom are required for an insertion operation. If the difficulty level is too high then it’s necessary to employ manual workers for some operations.

When an assembly system is designed for a new product, the cost of parts handling and insertion can be reduced through re-design of the product. It’s usually not viable for an existing product to be re-designed, because of the tooling modification cost in the manufacture of the parts. Inevitably, therefore, the most economical method of assembly is limited to the existing product design, without design efficiency improvements.

The assembly handling and insertion codes determine which feeding method and insertion device are most appropriate for each part and operation. The part-built assembly has to be transported to each workstation between operations. This will either be synchronous or non-synchronous motion.  Synchronous machines are generally less expensive than non-synchronous types, but they are limited by how many parts can be assembled on one machine. This is due to downtime and the space available.

It is desirable to construct a product from as many sub-assemblies as possible to achieve a high overall efficiency of the assembly system. These sub-assemblies should be common to all product styles, within the family of products. The variety can then be created in the final assembly of the product. If this approach is adopted then sub-assemblies will be required at a rate which is enough to justify the use of automatic indexing machines having dedicated workheads. The output from these machines can then be sent to the final assembly line via free transfer lines, to create a buffer stock of sub-assemblies. The buffer stock is necessary to minimise the effect of any indexing machine downtime.

This is a manufacturing study that I was asked to carry out for a Swedish world leading manufacturer of compressors, generators, construction and mining equipment, industrial tools and assembly systems. The company wanted to create a database of observed operation times for robot assembly tasks.

INTRODUCTION

The robot assembly of the pneumatic cylinder has been analyzed using the video taken recently.  Activity times were related to the digital clock display on the video.  The object of analyzing the assembly process was to create a data base.  Information could be extracted from this database to evaluate the robot assembly of other products manufactured by the client.

PNEUMATIC CYLINDER ASSEMBLY

There are fifteen parts used in the assembly of the pneumatic cylinder and some of these are actually sub-assemblies.  All the parts are presented to the robot on a pallet, with the exception of the screws.  The cover screws and piston rod screws are automatically handled by vibratory linear feeders. The cycle time for the complete assembly is 166 seconds.  This is substantially longer than predicted by academic estimation methods.

The speed of the robot is set at 60 percent of the maximum.  An electric current in excess of that tolerated by the drive motor circuitry, at 100 percent, makes this action necessary. This high power consumption, at start-up, is caused by the mass of the turret being approximately five times that of a conventional gripper.  The robot manufacturer is replacing the relevant circuitry to allow full speed of the robot.  Additionally, they have modified the feedback circuit to compensate for the larger mass. The robot programmer estimates that an increase in speed, from 60 percent to 100 percent, would provide a reduction in the cycle time of no more than 20 percent.  The activity times obtained from the current analysis are used for the purpose of design for robotic assembly, and the evaluation of the client’s other products.

SYNTHESIS OF ROBOTIC ASSEMBLY TIMES

The time taken to assemble a part by the robot has four periods :

1) The movement of the gripper from the previous assembly position to above the current part to be assembled.

2) The picking up of the part.

3) The movement of the part to above the place of insertion.

4) The insertion, and subsequent release, of the part.

The above time periods, when added together, make up the basic operation time for a single activity.

RESULTS OF THE STUDY

The total assembly time for the pneumatic cylinder is broken down into 54 steps to quantify the 4 constituent periods in each activity.  The time study sheet is shown later in this article. From the time study sheet, a basic operation time of eight seconds is derived. It can be seen from the table that this basic operation time is equally divided between the four constituent periods.  Notable deviations from the basic operation time are :

End-piece - The end-piece is used to form a sub-assembly with the half -piston.  There is no insertion time for this part because it is integrated with the half-piston.

Cover Screw - There is a 50 percent increase in the basic operation time for this part.  It is caused by the extra time involved with screw fastening and the transportation distance between the linear feeder and the work fixture.

Piston Rod - A significant increase in the basic operation time for this part is due to the additional operation of 'knocking down' the piston rod after insertion. This is necessary because of the technique used to lift this part from the pallet.

Piston Rod Screw - A 50 percent increase in the basic operation time is caused by the screw fastening operation and the transportation time from the linear feeder to the work fixture.

Completed Cylinder - The gripper is in an adverse position from the previous operation and this increases the operation time.

PREDICTION OF CYCLE TIME FOR THE ROBOT ASSEMBLY OF THE PNEUMATIC CYLINDER

The cycle time for the robot assembly of the pneumatic cylinder is predicted by using a basic operation time, multiplied by a factor.

assembly time = basic operation time * assembly process factor
where,
basic operation time = 8 seconds
assembly process factor = 1.0 for straightforward insertion
                  1.5 for screw fastening operations
                  1.5 for long parts requiring two insertions

Using the above approximations, a cycle time of 164 seconds is predicted.  This is within one percent of the actual time of 166 seconds. It is not suggested that such a simple method could always achieve this accuracy.  However, in the present case, the predictions for 9 out of 10 parts are within plus/minus 1 sec.

PART            ACTUAL    PREDICTED    DEVIATION OUTSIDE
DESCRIPTION        TIME    TIME        1 SECOND
CYLINDER BARREL    7    8        NONE
END-PIECE        5    *4 *        NONE
HALF-PISTON        7    8        NONE
COVER SCREW        48    48        NONE
PISTON ROD        13    12        NONE
HALF-PISTON        8    8        NONE
PIN ROD SCREW        12    12        NONE
END-PIECE        8    8        NONE
COVER SCREW        12    12        NONE
COMPLETED CYLINDER    10    8        2 SECONDS
            166    164   
**NOTE**

The predicted time of 4 seconds for the end-piece allows for the fact that it is not inserted into the part-built assembly.  This part forms a sub-assembly with the half-piston.

There is a negligible amount of time lost due to gripper changing.  The turret is indexed during movement from one operation to the next.  A typical programming chart for a component is given at the end of this article and it shows that the basic assembly operation takes 8 program steps. Additional steps are required for screw fastening.

TIME STUDY FOR ROBOT ASSEMBLY OF PNEUMATIC CYLINDER

0:01 Gripper above cylinder barrel
0:02 Pick up cylinder barrel
0:05 Cylinder barrel above fixture
0:07 Release cylinder barrel
0:10 Gripper above end-piece
0:14 Gripper above half-piston
0:15 Insertion of end-pieces and half-piston completed
0:17 Half-piston and end-piece above barrel
0:19 Release half-piston
0:21 Arm 2 above cover screw
0:24 Pick up cover screw
0:26 Cover screw above barrel
0:34 Arm 2 above cover screw
0:36 Pick up cover screw
0:38 Cover screw above barrel
0:46 Arm 2 above cover screw
0:48 Pick up cover screw
0:50 Cover screw above barrel
0:58 Arm 2 above cover screw
1:00 Pick up cover screw
1:02 Cover screw above barrel
1:09 Gripper above piston rod
1:11 Pick up piston rod
1:14 Piston rod above fixture
1:20 Completion of piston rod assembly to cylinder
1:22 Gripper above half-piston
1:24 Pick up half-piston
1:26 Half-piston above fixture
1:28 Completion of half-piston assembly to barrel
1:30 Gripper above piston rod screw
1:32 Pick up piston rod screw
1:35 Piston rod screw above fixture
1:40 Completion of piston rod screw assembly to piston rod
1:42 Gripper above end-piece
1:44 Pick up end-piece
1:46 End-piece above fixture
1:48 Completion of end-piece assembly to barrel
1:50 Gripper above cover screw
1:52 Pick up cover screw
1:55 Cover screw above barrel
2:02 Gripper above cover screw
2:04 Pick up cover screw
2:07 Cover screw above barrel
2:15 Gripper above cover screw
2:17 Pick up cover screw
2:19 Cover screw above barrel
2:27 Gripper above cover screw
2:29 Pick up cover screw
2:32 Cover screw above barrel
2:36 All cover screws inserted
2:40 Gripper above barrel
2:42 Pick up completed cylinder
2:44 Completed cylinder above pallet
2:46 Completed pneumatic cylinder in pallet

BASIC OPERATION TIME OF THE ROBOT

            FROM PREVIOUS    PICK    MOVE TO    INSERTION    OPERATION
            OPERATION    UP    PLACE OF    AND        TIME
            TO ABOVE    PART    INSERTION    RELEASE    (SECONDS)
            PART               
10) CYLINDER BARREL    1        1    3        2        007
09) END-PIECE        3        2    0        0        005
08) HALF-PISTON        2        1    2        2        007
07) COVER SCREW    3        2    2        5        012
07) COVER SCREW    3        2    2        5        012
07) COVER SCREW    3        2    2        5        012
07) COVER SCREW    3        2    2        5        012
06) PISTON ROD        2        2    3        6        013
05) HALF-PISTON        2        2    2        2        008
04) PISTON ROD SCR    2        2    3        5        012
03) END-PIECE        2        2    2        2        008
02) COVER SCREW    3        2    2        5        012
02) COVER SCREW    3        2    2        5        012
02) COVER SCREW    3        2    2        5        012
02) COVER SCREW    3        2    2        5        012
01) COMPLETED CYLINDER    4        2    2        2        010
                                    TOTAL    166