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Calculations and Results Display.

(Covers: Calculation of stacks, Container loading plan, Results on Standard and Custom sizes, Types of pattern, Optimal solution, Graphical display, Custom pallet designs.

Summary of Calculations Performed.

SLIPSHEET MANAGER uses the data provided on the input screen to carry out the following calculations:

Firstly the given product is loaded onto standard slipsheet / pallet sizes (e.g. Metric: 1200*1000 / 1200*800 or Imperial: 48"*40" / 42"*42") in an optimal way. Then these stacks are loaded in the best way into the container / trailer and the total amount of cargo loaded recorded. The Custom Stack Size (1100*1100) is also examined in a similar way.

Second the software determines what other custom stack sizes might be used for the given product. These sizes are derived from the case size input on the above screen. Each custom stack size will have associated with it one or more patterns which might be used to create the load stack. Once again these stacks are loaded in the best way into the container / trailer and the total amount of cargo loaded recorded. 

4.1 Calculating the possible custom stack sizes.

For the given case dimensions the software calculates all possible stack sizes which might potentially be created using the case as a basis. The simplest possible arrangements might involve just cases arranged as a 'simple block' such as the plan view shown below:

Given the above picture shows a block formed by 11*3 cases there are clearly a large number of other potential stacks of this form (11*2; 11*1; 10*3 etc etc). However in addition the software calculates a complete range of far more sophisticated patterns, many of which would provide interlock within any stack which might be created, and which therefore might be more stable as a load stack. These more complex arrangements, such as the one below:

might well prove more suitable when considering effective utilisation of the container space.

Having determined all possible stacking plans for the given case those that meet the size limits imposed by the restrictions on the data entry screen are then each packed into the given container size in the best possible way.

4.2 Calculating the container load plan.

In the second phase the software calculates how effectively each of the standard and non-standard stack sizes fit into the stated container size.

If a Slipsheet/Block Stack has been specified on the input screen then the value of Slipsheet Lip (if set as non-zero) is considered when performing the loading of the container / trailer:

A slip sheet will normally project on 2 adjacent edges of the stack. A value of 50mm was specified on the input screen thus for a 1200*1000 stack the slipsheet size will be 1250*1050 in size. However in practice it will not be necessary to make the 50mm allowance on each stack loaded into the container for the following reason:

When placing a number of loaded slip sheets across the container, the operator will normally either work from one side of the container towards the other or work from both sides towards the centre. In placing each stack the lip will normally be bent up (by using a side shift) - e.g. against the container size or against the side of another stack). When viewing any loaded section across the container, whilst there will normally be one slip sheet stack where the lip is flat on the container floor (and thus is a gap between stacks), on the remaining stacks the lip will be vertical and not require any additional allowance to be made.

Thus any load plan produced by SLIPSHEET MANAGER will (at the extreme) include room for one lip allowance on width and one along the container length. Normally the dimension of the case will ensure that extra space is indeed available, but given the desire to maximise space utilisation the software will not add any extra allowances.

If a Pallet Based Load is stipulated on the Input Screen then no account will be taken of any lip size (as it clearly does not apply), BUT in loading pallets we clearly need to account for the height of the pallet platform itself. Thus the Container Internal Loading Height will be reduced by the pallet height specified on the Data Input screen. Also, on diagrams, the pallet will be drawn.




4.3 The Results.

SLIPSHEET MANAGER uses the data provided on the input screen to carry out the following calculations:

Firstly the given product is loaded onto standard sizes (e.g. 1200*1000 / 1200*800 or 48"*40" as appropriate) in an optimal way. This will eventually provide the user with a range of loading plans for the creation of the these stacks. Then the stacks are loaded into the container / trailer (once again in an optimal manner) and the performance obtained recorded.

1100*918 (Entry 6 in table overleaf)

1112*912 (Entry 4 in table overleaf)

Second, the software determines what other custom sizes might be used for the given product. These sizes are derived from case size input on the above screen. For a given case there may be several hundred potential sizes but SLIPSHEET MANAGER will reduce this down by taking account of the size constraints entered on the data input screen.

Each custom size will have associated with it one or more patterns which might be used to create the load stack. Two examples of possible patterns are shown below. In some instances there may only be a single pattern which might be used, but in other instances there may be several dozen possible optimal patterns. In many cases it will be possible to produce a highly stable stack by rotating alternate layers as shown in the 2nd example below. SLIPSHEET MANAGER provides you with powerful graphics facilities to achieve this.

In the next stage of the analysis SLIPSHEET MANAGER examines the efficiency with which each of the given stacks can be loaded into the stated container size. As you might expect the efficiency varies greatly with the best solution to the above problem fitting 9504 cases / container whilst the worst solution (a 1400*912 stack) loads just 7040 cases / container.

The first screen of results (top 11 of 79 solutions) for this analysis is shown below:

Below this a scrollable window lists all those solutions which SLIPSHEET MANAGER has evaluated. Each line represents a different stack size and associated with each is information about the performance achieved. The top 2 lines always report the performance of the most popular sizes (here the 2 standard European sizes) when used to load the given case size. When first displayed the topmost of these is highlighted (as shown). Line 3 contains the solution for the Custom Size which the user can edit on the Data Input Screen. 

The lines which follow these 3 sizes report (in ranked order) the performance of other custom sizes. We will firstly explain the results for the standard sizes:

(a) 1200*1000 / 1200*800 Results.

The first 2 lines of the results always present the results for standard slipsheet / pallet sizes when loaded with product of the size input. In the above screen 36 cases each 306*100 fit on each layer of a 1200*1000 stack and a total of 8712 cases fit into the container. In practice the case does not fit especially well onto the slipsheet / pallet (wasted space), and as discussed earlier the 1200*1000 dimensions do not fit very well into the container. In fact there is over 20% wasted space - AIR - in this container.

Lines 2 and 3 of the results repeat the analysis for the 1200*800 and (custom) 1100*1100 slipsheet / pallet sizes. These prove even worse, and allow far less cargo to be loaded into each container.

With the 1200 *1000 line still highlighted the user can select the StackView button to view the possible ways in which the cases could be optimally loaded onto the load area. There are a number of different solutions offered (each of which fits 36/layer), one of which is shown overleaf, but given the (difficult) 306 length dimension of the case there will always be wasted space on the 1200*1000 base.

The Contview button can be used to display two and three dimensional views of how the given stacks can be loaded into the given container. The 3D load picture for the 1200*1000 stacks is also shown overleaf.


1200*1000 stack, 306*100 case.

This arrangement is one of four possible patterns which provide this optimal solution. The software allows users to display and manipulate the stack arrangement to produce stable stacking plans.


1200*1000 stacks in given container.

The software initially displays the load plan in 2D and gives numerical values for the free lengthwise and widthwise space. The user can then select 3D display to produce this picture.

For palletised loads the container loading height specified on the input screen must be reduced to allow for the height of the pallet itself. Thus when comparing a pallet and a slipsheet of the same size, slipsheets will typically perform better as they allow an extra layer or two of product to be loaded on each stack. However as we illustrate below, the use of non-standard stack sizes (on pallet, slipsheet or as a free standing stack) will almost always allow more cargo to be packed into the container - often a 10%-15% improvement.

(b) Other Slip Sheet / Custom Pallet Sizes.

Following the results for the standard sizes, the main set of tabulated results tabulate the load performance achieved when custom stack sizes are used. Each line represents a different stack size and the performance achieved when using this in the given container size. The results are ranked in order of efficiency. The screen shows just the first 11 of the 79 possible stack sizes. Information output includes:

The results of using the two standard sizes can be bettered using any of the top 33 calculated sizes listed in the remainder of the table, with the best of these achieving 9504 cases / container - a further 9% improvement.

You will also note that each line is numbered and following this number there is quite often a T code. Whilst all the results calculated can be successfully packed into the given container size, some solutions (those with a T coding- 'Tight Fit') have a limited amount of additional free space. SLIPSHEET MANAGER examines the free space in the load and if this is less than 2% of width or length then a T coding is given. Those without any T coding are therefore a relatively easy cargo to load.

As might be expected those sizes which provide the highest load quantities are more likely to be a tight fit, though there are examples in the above table (e.g. entry 10, a 1224*1000 stack) which are relatively easy to load (no T coding), are just marginally bigger than standard (by just 24mm) and yet fit over 700 more cases / container than that achieved using a 1200*1000 stack (> 8%).

4.4 Types of Pattern:

Each stack size which is presented has associated with this a pattern code (e.g. NC, C1 etc). In many environments specialist slip-sheet loading equipment will be available, in which case the exact load plan forming the stack will be of limited interest. However as will be illustrated later the software includes powerful graphics facilities which can be used to display available stacking plans.

In other situations some form of clamp truck may be used to transport the load and, in these instances, it will be important to know whether a stack of the given size can be successfully transported using such equipment. The pattern code allows users to see at a glance whether a clamp truck could be used for a given stack size.

A code C1, C2, C3 and C4 indicate that a clampable arrangement can be achieved. A code of NC indicates that a stack of this size cannot be transported by clamp truck on both of the stack sides. The number following the 'C' in any such coding indicates the complexity of the load pattern - the higher the number the more complex the arrangement.

4.5 The Optimum Solution.

The results table presented above is listed according to the efficiency with which the container base is utilised. This would still be so if the container weight limit had come into play, but in such situations the number of layers fitted would be adjusted to meet the container load limit.

Users can naturally print out any or all of the table of results and, as illustrated above, it may well be that there are a number of potential slip-sheet sizes which could be used to provide significant improvements in load efficiency. In addition the user can also appreciate how well standard slip sheets sizes perform compared with any existing palletised solutions, and compare standard slip sheet size performance with any of the custom sizes proposed. 

SLIPSHEET MANAGER does in addition display graphics of both the way(s) in which the slipsheet stack might be constructed, and the way in which stacks on these slipsheets could be loaded into the container.

The mouse (or up/down arrow keys) can be used to highlight any of the entries in the results table, and following this StackView or ContView selected to display in both two and 3 dimensions the Stack Plan or Container Load Plan.

From a numerical viewpoint the best solution uses a 1118*1000 stack, fitting 36 / stack layer and with 24 such stacks sitting into the container. This fits 9504 cases / container, and given that a 'T' follows the rank number (column 1) we know that it is a somewhat tight fit in the container.

Stackview allows us to view the 2D patterns which might be used to create such a stack (3 in total) and to select one of these (and space out cases) to form a 3D stack as shown below:









The ContView button allows you to view the container load plan in both 2D and 3D. The result for this problem is shown below: 

As can (just) be seen on the 2D diagram (a dark border at the top and right of the diagram) there is a very limited amount of space available within the container - as detailed in the text just 35mm on the container length and 64mm is unused - hence the 'T' coding in column 1 of the results.

It should be noted that the unused space on the width of the container DOES take account of the 50mm slipsheet allowance input for this problem. Thus a total widthwise space of 114mm applies for this solution, with 50mm of this being allowance for the slipsheet lip. 

As discussed earlier, should you feel that this container load is too tight then you can quickly display the results for any other of the stack sizes. For example result 2  does not have a T coding, and whilst losing out a little in total load, has free space of 257mm and 64mm on length and width in the container.

Printing Results:

This release provides a standard print button which allows you to print out part or all of the set of tabular results. In addition, any of the 2D / 3D graphics displayed on screen can be cut and pasted via the Windows Clipboard to other windows applications (e.g. Word). To do this: 

"Position the mouse at one corner of the required region, depress the left mouse button and move the mouse to 'rubber-band' the area required. Then release the mouse and you will be informed that the region has been copied to the clipboard".

Also, once you have displayed on screen the 2D/3D arrangement of either the pallet load plan or the container stacking plan you can then select the Print option.

This allows you to carry out a variety of tasks: 

4.7 Custom Pallet Designs.

Whilst the emphasis throughout has been on producing solutions for the loading of slip sheets on standard or custom slip sheets SLIPSHEET MANAGER can of course be used to examine what sizes of custom pallet might be used. As described earlier one of the limitations of loading standard pallets into shipping containers is the poor utilisation these sizes provide of the container floor space. The use of pallet sizes which are customised to suit both the product and the container size can be very effective in increasing loads, though naturally one will still suffer some loss of space as you would still need to allow for the pallet base height in your calculations.

When applying SLIPSHEET MANAGER in this way the following would be recommended:

Enter the case details in the standard way.

Select the 'Loading a Pallet' option on the data entry screen and ensure that the height of the pallet base is set appropriately (162mm is a standard CHEP pallet).

The Results display will state (in the summary at the top) that the loading height has been reduced by the amount entered for the pallet base height.




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