Saturday, July 4, 2015

Tool Related Methods Efficiency Analysis


Questions on Tool Equipment. The tool  and equipment used to perform the operation needs to analysed logically. The following questions are the sort that will lead to suggested improvements:

1. Is the machine tool best suited to the performance of the operation of all tools available?

2. Would the purchase of a better machine be justified?

3. Can the work be held in the machine by other means to better advantage?

4. Should a vise be used?

5. Should a jig be used?

6. Should clamps be used?

7. Is the jig design good from a motion-economy standpoint?

8. Can the part be inserted and removed quickly from the jig?

9. Would quick-acting cam-actuated tightening mechanisms be desirable on vise, jig, or clamps?

10. Can ejectors for automatically removing part when vise or jig is opened be installed?

11. Is chuck of best type for the purpose?

12. Would special jaws be better?

13. Should a multiple fixture be provided?

14. Should duplicate holding means be provided so that one may be loaded while machine is making a cut on a part held in the other?

15. Are the cutters proper?

16. Should high-seed steel or cemented carbide be used?

17. Are tools properly ground?

18. Is the necessary accuracy readily obtainable with tool and fixture equipment available?

10. Are hand tools pre-positioned ?

20. Are hand tools best suited to purpose?

21. Will ratchet, spiral, or power-driven tools save time?

22. Are all operators provided with the same tools?

23. Can a special tool be made to improve the operation?

24. If accurate work is necessary, are proper gages or other measuring instruments provided?

25. Are gages or other measuring instruments checked for accuracy from time to time?

Because of the wide variety of tools available for different kinds of work, this list could be extended almost indefinitely with specific questions. Foundries, forge shops, processing industries, assembly plants, and so on all have different kinds of tools, and different questions might be asked in each case. The list given above, drawn up principally and by no means completely for machine work, will indicate the kind of searching, suggestive questions that should be asked. A special list might well be drawn up by each individual plant to cover the kind of tools that might be advantageously applied upon its own work.

Tool Design. The matter of tools is one that has received a good deal of attention, because a good tool is necessary to do a good job. Therefore, tools that function properly are found on the majority of operations that the methods efficiency engineer studies. If the tool did not function properly, it would not be used. Of course, in some shops where the matter of tools does not receive the proper attention, operations are encountered on which the operator is turning out passable work in spite of his tools rather than because of them.

For the most part, however, it may be said that the tools do function properly from the standpoint of the finished job. Whether or not they function properly from a motion-economy standpoint is another matter. The tool designer is usually more concerned with making a tool that will do a certain job than he is with the motions that will be required to operate it. Therefore, unless he has made a study of the principles of methods engineering or has had the importance of motion economy impressed upon him in some other way, it is probably safe to say that the motions required to operate the tool are the last thing he thinks of.

As a result, tools are designed and built that require much more time to use than they should. The common machine vise is a good example. The quick-acting vise is far superior. On machining operations where the cutting time is short, it will save 20 to 40 per cent of the total operation time. The jaws of the vise are cam-actuated. They are tightened by moving the two levers in opposite directions which conforms to the principles of motion economy. They hold securely without hammering on the levers. They are adjustable to a variety, of sizes of work. In short, they possess many real advantages over the standard vise.

Suggestions that will improve the quickness of operation of tools should be made to tool designers as they are conceived. If they are presented with a summary of the yearly saving in dollars and cents that they will effect, interest in better tool design from a use-time standpoint will be aroused. This is very desirable, for tool designers as a group are clever arid ingenious, and if the importance of reducing the time required to operate tools Is clearly demonstrated, they will be able to assist materially toward this end by producing more suitable designs.

Hand Tools. There is a tendency to pay too little attention to the hand tools used upon even the more repetitive operations. To many, a screw driver is a screw driver, and if it fits the slot in the screw to be driven, it is considered satisfactory. This is far from being the case, however. Screw drivers vary widely in design, and some are more suitable than others. Screw drivers come in a number of different styles. There are the solid screw drivers, the ratchet screw drivers, the spiral screw drivers, and the various types of power-driven screw driyers. Even the variation among screw drivers of a given type is tremendous. They vary in size, of course, but in addition they vary in about every other way imaginable. The handles vary in diameter, length, cross section, shape, and nature of gripping surface. Points are wide, narrow, blunt, sharp, taper toward the point like a wedge, or are narrower right above the point than at the point. A lately introduced type has a special point to fit a special screwhead which offers many advantages.

When all these factors are considered, the wide variation in even such a simple tool as a screw driver becomes apparent.

There is, of course, one screw driver that is better for a given application than any other. For medium work with the conventional screwhead if a solid screw driver is to be used, the one with the largest cylindrical handle which can be comfortably grasped by the operator should be chosen. The handle should, of course, be fluted to prevent slipping. The diameter of the handle will vary with the size of the operator's hand, but two or three standard sizes are sufficient for most hands. The diameter of the handle should be large, because the larger the handle within the limits of the human hand, the more easily can a given torque be applied. To prevent slipping, the point should not be wedge-shaped but should be slightly larger at the point than just above it. Few screw drivers commonly encountered in industry meet these simple specifications.

If many screws have to be driven, a ratchet, spiral, or power-driven screw driver can often be used to good advantage. If many screws of the same size are to be driven, a piece of hardened tubing slipped over the end of the screw-driver point will make it much easier to locate the screw driver in the slot.

The same sort of searching analysis can be made for every type of hand tool used. Wrenches, hammers, chisels, saws, scissors, knives, pliers, and drills all come in a great variety of styles. Standardization on a limited number of the better styles within a plant will tend to prevent the use of the more inefficient tools. Tests must be made to determine which styles are actually the most efficient, however, for the judgment of the operators cannot be relied upon. A man will prefer a certain tool because of its apparent strength, the color of its handle, its pleasing appearance, or its familiarity. Unbiased tests are much more reliable.

Judgment must be used, of course, in determining the amount of time that can economically be spent in analyzing the tools used on any one job. Unless a job is highly repetitive, it will not pay to try to discover the best screw driver for that particular job. Instead, the whole subject of hand tools including screw drivers may be investigated in a general way, and good tools may be adopted for standard use. The tool supply should be plentiful, for it is not uncommon to see operators not only using the wrong size of tool, but also using a chisel for a hammer or a screw driver for a crude chisel merely because the proper tool is not available. An insufficient supply of proper tools may reduce the amount expended for tools, but it will prove costly in the long run.

Source: Operation Analysis by Maynard
Full Knol Book - Method Study: Methods Efficiency Engineering - Knol Book

Modern Developments in Tools

2001

Duraspin Screw Fastening System increases productivity by 31%.
https://www.rsmeans.com/consulting/Senco.pdf


Updated 4 July 2015
First published 23 Nov 2011

No comments:

Post a Comment