SECTION 6 - PACKING OPTIONS.

Covers: suggested settings for specific practical situations; also complexity, effort, priorities, ranking, multiple drops, column packings, layered solutions and overhang)

CARGOMANAGER has been designed to deal with a huge range of possible problem types - from a single container holding just a few dozen identical items to a multiple container load containing many thousands of items of many different types. It is therefore not surprising that in order to meet the needs of a specific application some degree of 'tailoring' may be required. The Packing Options screen provides this facility. It should be noted that changes to these values are unlikely to be required on a regular basis, and once set they may well not require any subsequent change.

Following the display of the Summary of Input Data you may select to pack immediately the specified cargo or alternatively select Options to display the Packing Options Screen. The Options screen allows you to control the way in which packing is carried out. If you choose to move directly to Packing then the previous (or Default) option settings remain unchanged.

The settings on this screen are very important in obtaining solutions appropriate to your needs and the description below of the parameters and their effect should be read with some care. Once set they may well not require any subsequent change.

The Packing Options screen can be selected prior to the commencement of loading of each empty container. A default set of answers to the questions posed is provided, and the user may set up their own defaults

These questions and the effects they have on the packing process are discussed below, and a summary of suggested settings for some common situations is given at the end of the Section.

It should be noted that help is available on the Options screen in two forms - both through the Help option at the top of screen and through help text which will appear as the mouse pointer is moved to select options.

Acceptable Complexity - 0 = Simple / 4 = Complex.

This is by far the most important control available to the user in determining the type and complexity of layouts produced.

Depending upon the type of cargo and the manner in which the products are to be physically loaded it may be acceptable to you for CARGOMANAGER to utilise relatively complex packing arrangements. If this is the case then a value of 3 or 4 will allow CARGOMANAGER to experiment with both simple and more complex arrangements. In doing so CARGOMANAGER will still retain a preference for simple arrangements to be used if they are as efficient (in volume fill terms) as more complex forms. The highest value of 4 provides (for all cargo sets) the full range of solutions offered by level 3, but does in addition, for cargoes of just a single product type, include investigations of solutions using optimal layers of the product.

If offered a complexity value of 5 this should only be tried if solutions that firstly pack one SIDE of the container and then move progressively across towards the other side are a requirement.

You should also note that setting a complexity value greater than 2 may result in solutions which are easier to pack into an open-side / curtain-side container rather than a conventional closed shipping container. Thus if you wish to minimise the length of container used a maximum complexity value of 2 should be used.

If however only relatively simple arrangements are acceptable to you then a value of 1 should be specified. This will tend to provide slightly less volume efficient loadings and require a great deal less computing time. A value of 2 is likely to provide a reasonable compromise in many situations. Using a value of 3 may lead to solutions which require significantly increased loading effort.

A value of 0 is also available. This provides an even faster calculation phase but at the expense of some loss of quality. Thus solutions using a value zero, although always fully feasible, may have a volume utilisation that is significantly lower than is actually possible. It has been included so that very quick estimates of cargo fill may be obtained.

The Effort Once Packed value described below is also important if the time taken to pack cargo sets is found to be rather great.

Once all the cargo has been successfully packed, CARGOMANAGER may be instructed to strive to further improve the packing (pack in a shorter container length) with various levels of effort. If a value of 1 is specified then once a complete packing has been achieved little further effort will be applied. This would be most suitable if you simply wanted to determine whether or not a cargo would fit. If a value of 2 is given then some continued effort will be used to obtain a simpler packing using the same or a shorter length of container. A value of 3 will result in significant continued effort being used to improve the packing. If during further examination a solution is found which is as good but is simpler to pack then this simpler solution is retained.

When entering data pertaining to each case type, you have the opportunity to specify priority values in the range 1 to 99 (a larger range - say 1-9999 can be used if required but may impact on solution times). These values may be treated in CARGOMANAGER in two distinct ways which we term as Absolute and Relative priorities.

If an Absolute priority scheme is selected (the default negative response to this question), then cases with a higher priority (i.e. a lower numerical value, e.g. 1), are assumed to have higher 'value' and will always (space permitting) be packed in preference to those of a lower priority. Thus cases of priority 1 will be packed in preference to those of priority 2 and so on. The actual numerical values used for the different priority classes do not matter if an Absolute priority definition is used as long as they are different and are smaller for items of greater priority.

If a Relative priority scheme is selected then although the priorities specified indicate a preference for certain case types to be packed, these priorities are modified according to the volume of the case concerned. Thus a case of volume 1M³ and priority value 2 will have 'equal value' in the packing to a case of volume 0.5M³ and priority 1. Thus the priority value you specify is utilised in a way so as to represent value per unit volume. In this way some trade-off between the volume of a case and its priority is achieved in the packing.

It is suggested that you initially utilise the Absolute priority scheme to ascertain whether it achieves your objectives, and later examine the effect of selecting a relative scheme.

The response to this question, which is only meaningful in respect of Absolute Priorities (above), determines exactly how the packing carried out by CARGOMANAGER treats the priority values you have specified.

A response of No to this question indicates that although you have a preference for (say) priority 1 to be packed before priority 2 items this is not a binding rule. Thus, should there be insufficient space for all the priority 1 items to be fitted into a container, then any remaining spaces can be used for lower priority items.

By responding Yes to this question, no attempt will be made to load any lower priority items into a container until all the higher priority items have been placed.

The multi-drop loads option (discussed immediately below) can utilise priority codings to indicate the sequence of loading into a container, items with a higher priority coding being loaded first. If you choose to use the priority mechanism in this way then a Yes response to this question will clearly apply. It should be stressed however, that the quality of solution obtained (% fill) may well be lower than that obtained if intermixing of priorities were allowed.

If we had intended to load the container with the stated cargo for one destination, and then add a number of other items (using the End Packing option) which are to be unloaded at different (earlier) destinations, then we would need to ensure that the cargo for these earlier destinations is physically accessible without unloading the complete cargo.

In such instances a reply of Yes at this stage is likely to be required. However a reply N will enable CARGOMANAGER to use any spaces towards the rear during any subsequent 'End Packing'. This is likely to improve load efficiency but may cause cargo access problems.

A further situation in which a Yes answer should be given is where a single set of cargo items has been specified with priority values which reflect the sequence in which they are to be loaded into the container. As described below priority values can be used in this way and the resultant packing will ensure that the highest priority items are placed first into the container, and other items having a lower priority value are then packed in sequence in such a way that access (for unloading) to all items of the same priority value is maintained. A Yes response here ensures that this access is maintained. If a No response were given then cargo of differing priorities might be intermixed.

Restrict packings to Columns?

Normally the packing solutions provided by CARGOMANAGER take a wide variety of forms, though all of course take full account of the restrictions you stipulate for both individual case types and for the consignment as a whole. A small number of users have identified situations where they ONLY wish to obtain solutions in which cases on second and subsequent layers form perfect vertical columns with no overhang or underhang. Whilst this naturally places a major restriction on the type of patterns possible, by responding Y to this question such restrictions may be applied. We would normally recommend that a N response be made to this question.

As described earlier, special item types (those which have been specified as being either heavy or fragile) are subject to special packing rules. Normally if a number of different heavy item types have been specified then, even if such items may be placed several stacks high, NO intermixing of different item types will be attempted. Thus if both items A and B are defined as heavy, and both may be stacked 3 high, then no stacking of A on B or B on A will be attempted. The same rules are applied to groups of fragile items. If however such intermixing (within the heavy and fragile classes) is allowable, then a Yes response to this question should be given. A positive response to this question (thus partially removing a packing constraint) is likely to produce improved packings.

Two distinct methods of presenting the loading arrangement on screen are employed in CARGOMANAGER. One is based on the drawing of 'blocks' of identical cases (where these exist), whilst the other approach considers each box as an individual element and produces cross-sections along the width of the container. Although both approaches produce diagrams in which each case is individually drawn and labelled the 'block' approach does have a significant advantage in terms of drawing speed and is considered by many to provide a more effective visual impact. This does however depend upon the characteristics of the cargo (e.g. number of case types) and on individual preference.

The Sectional view can be selected by responding Y to this question. If there are a large number of cases then, for speed of response, an N selection is recommended.

It should be emphasized that the answer given will NOT change the actual packing arrangement calculated.

When loading, for example, mixed pallets, it may be a requirement that solutions are readily placed in layers on the pallet base, rather than in 'walls' at one edge. This option, when selected, will produce solutions of a layered form. Where layered solutions are desirable, then we would strongly recommend that not only should a positive response be made to this question, but also a value of 3 or ideally 4 be made to the 'Acceptable Complexity' option discussed above.

Once the loading of a container is complete then, either prior to display of the packing used, or following the screen display a levelled solution may be selected. This procedure attempts to spread the container load more evenly across the floor of the container, minimising the height used. CARGOMANAGER contains two procedures for doing this, one based upon building 'walls' from the back of the container, and the alternate approach of 'layered solutions' in which product of the similar type tends to be spread across the container floor in layers.

If a Yes response to this question is given then such layered solutions will be attempted. In the event of there not being a suitable layered solution (e.g. when the cargo contains many different item types), then the default 'wall' solutions will be provided. Once again, should layered solutions be more desirable in general, these may be produced for the single product situation (without the need to apply levelling at a later stage) by selecting a value of 4 for 'Acceptable Complexity’.

Maximum % Overhang ?

Although the use of overhang in packings will usually be undesirable, there may well be instances in which the characteristics of cargo and container are such that a significantly greater packing might be achieved if overhang is allowed. If overhang is to be allowed then, as described below, the percentage of a case which may be allowed to overhang another is specified. Should a packing not using overhang be found which is equally effective, then this solution will be used. Selecting overhang does increase the computation time.

The limit of 50% will obviously generate a very unstable load, and a figure of 10% or 15% is likely to be more realistic.

Having selected suitable values for these options three options are available.

Once these questions are answered, the user may select from the following options at the base of screen:

Pack to proceed to the packing of the cargo

Save to save the options on the current display. These will then form the default answers for all subsequent runs.

Back to return to the previous screens. On selecting Pack the Calculation phase will commence.

When distributed, CARGOMANAGER has default values set up for all the above parameters. For all Yes / No answers the default is No, and for numeric responses values of 4 and 3 are typically used. Ideal values for particular situations are best determined through experimentation. It should be stressed that once default values appropriate to a particular situation have been defined then little subsequent modification should be needed.

The suggestions given below are for changes you might wish to make to the distributed default values as a first basis for experimentation.

In such situations the calculation time required may be significant and a lower level of Acceptable Complexity might usefully be selected, perhaps a value of 2 or 1.

In a container load of a few dozen cases a fairly complex loading arrangement may be quite acceptable, but in a load of thousands of cases a similar degree of complexity may well not be suitable. Also, what one loader might consider as complex, another might consider as quite acceptable. Once again lowering the Acceptable Level of complexity to values of 2 or 1 should assist in obtaining suitable loading arrangements.

The 'Effort once packed' parameter determines what happens once a complete solution for the given cargo is found. Reducing this will speed things up as described above.

CARGOMANAGER has two mechanisms to achieve this, one known as 'End Packing' and the other utilising cargo priorities. These have been described elsewhere but a summary of each is given below together with suggested parameter values.

End Packing allows additional cargo to be added to a partly filled container. Using this mechanism the suggested procedure would be:

Input ALL the case descriptions / dimensions that you expect to form the complete container load. In each instance use the default ZERO quantity value. Once all the case descriptions have been input, modify the quantity entries to reflect the quantities to be 'dropped off' at the last drop-off point (i.e. to be loaded first). Once this has been done, select PackCalc and thus perform the loading of this initial set of cargo. Then select Add when the Tabular Packing results are displayed and modify the quantity values to reflect the quantities to be unloaded at the last but one drop-off point and continue with this process until all the required cargo has been packed.

When using End Packing for this multi-drop situation the following parameter values (changes from the distributed settings) are suggested:

Multi-drop load : Yes (If No is used access to later cargo may be a problem) 

Complexity: 2 or less

As described earlier priority values are primarily intended to indicate the 'value' of an item in the consignment so that CARGOMANAGER can (where the cargo cannot be completely loaded into a container) maximise the value packed.

It is, however, possible to use this parameter to indicate a strict order in which the consignment is to be loaded. This is achieved in the following manner.

Input details of the items required at each drop-off point together with the required quantities. Where an item is required at two locations then two separate entries will need to be made. For those items required at the last drop-off point give a priority value of 1, for the next to last a value of 2 and so on. Once all data has been input select EndEdit and then Options to set option values as given below:

When using Priority Values for this multi-drop situation the following parameter values are suggested:

Multi-drop Yes

Complexity 2 (or less)

Priorities as a strict ranking Yes