Pick Module Design Questions And Answers

Q.  What happens when you design your pick module for growth and then you wind up with a pick module size that is too big for the current operation or has too many pick faces than the amount of SKUs that you initially want stored in the pick module?

A.  This is a common situation, especially when the growth rates used in the calculations are fairly significant.  For example, if a distributor estimates 5% annual SKU growth, then after 5 years the warehouse will be receiving, storing, picking and shipping over 27% more products.  Therefore, in these circumstances, one of the critical factors when designing the pick module is flexibility and expandability.   As a systems integrator, our goal is to provide you with a solution that is functional and cost effective for today, but also adjustable for your future needs.  A pick module that provides the most bang for your buck is a little big now and gives you room to grow into it.  This can be done by placing significant thought in designing for ease of expansion both horizontally and vertically. In other words, by ensuring that the location and orientation of the pick module is such that adding length to it would not be prohibited by building constraints such as structural bracing or walls. Designing for vertical expansion can be done by using tall rack uprights in the initial design and ensuring that the underside clear height of the building would allow additional levels to be built on the pick module. This way, the support components are already in place and adding levels can be done without significant rework of the existing pick module, which would also allow for current operations to continue without major disturbance.

Q.  What is your experience with acquiring the proper data from customers?

A.  Usually this is the biggest hurdle to overcome when properly designing a pick module.  We have found that most companies, from large multinational public companies to small family owned businesses share in the struggle to understand their product velocities and dimensions over an extended period of time.  That being said, if our customers cannot supply the data in the format that we would like to see over a period of time that includes seasonal busy periods and normal operating periods, then we have to operate on assumptions and averages.  This is obviously not ideal and being prudent engineers, we use conservative assumptions and averages so that extreme conditions will be met.  Therefore, the major take away from this is that if you are currently not actively designing a pick module, then you should start collecting the data in the proper format now so that when the time is right to add a pick module to your operation, you will have extremely accurate information to use in the design process.        

Q.  What happens when you have all of the velocity information but you don’t have the dimensions and weights?

A.  This is also a very common situation.  A way to collect this information extremely easily and efficiently is by use of a Cubiscan, a scanner and some software.  Basically, by assigning a person at some point in the warehouse operation where all products flow through, whether receiving, put-away, or shipping, to place each box on the Cubiscan, the information will eventually be accurately captured. In doing so, by simply scanning the bar code, and punching a key on the computer, the length, height, width and weights are all recorded and assigned to the product with the bar code and stored in the database.  Eventually, after all products are recorded, the database can be exported in many different formats and conditioned to be imported in to the warehouse management system or inventory management system. 

If renting or purchasing a Cubiscan and assigning a person to dimension and weigh all boxes is not an option, then the last resort is to make assumptions by using minimums, maximums and averages for length, height, width and weight.  Again, this is not ideal and may end up with a design that is more conservative than needed, which typically translates into more expensive than needed, but if that is all that you have, it is better to be conservative and have a working system than use bad information which might result in a poorly designed system.

Q.  If an order includes items picked from the pick module but also items picked outside of the pick module, say in bulk storage, how do these items from different pick locations get married up prior to shipping?

A.  This happens a lot.  Typically, for items picked from a pick module all paths lead to an order consolidation point, whether they are full cases thrown onto a take away conveyor or each picks that are placed into a tote or box and then put on a take away conveyor.  Many times, this path to the consolidation point is through a shipping sorter with multiple divert lanes and each lane representing a consolidation point prior to the items being loaded into the truck. As the name implies, the consolidation point is where the order is reconciled and all items are verified present, many times through fixed or hand held scanners. Therefore, items from the pick module are automatically routed to this order consolidation point by way of conveyors and a shipping sorter.  Items pulled from other areas of the warehouse are also directed by the warehouse management system or warehouse control system to be dropped off at the order consolidation point, either manually by pallet jack or by lift truck or any other means.  Eventually, after all items in the order are accounted for, the order is released and placed into the truck for shipment.

Q.  What is the control or information system that tells order pickers what to pick and how much to pick while the order is being filled and also where the boxes and totes and the shipping sorter to divert?

A.  Usually these tasks are performed by the Warehouse Control System (WCS).  The WCS is often called “middle ware” in a warehouse because it acts as the information broker between the upper level Warehouse Management System (WMS) and the lower level material handling controls such as Programmable Logic Controllers (PLC), Human Machine Interfaces (HMI), and picking technology system such as pick to light or voice pick.   Typically, the WMS sends the WCS information in batches which is includes the order information.  The WCS takes that order information and determines the best way to fulfill all of the orders to include the optimal pick locations, pick sequence, consolidation point, etc.  Therefore, the WCS interfaces with the various real time material handling control systems and orchestrates the movement of product throughout the warehouse. 

Q.  Is there an industry standard for reslotting frequency for pick modules after they have been designed, installed and initially slotted?

A. No. We have seen many extremes with our customers.  One of our most efficient customers reslots after every month-end.  Then again, some of our not-so-diligent customers reslot once a year or even longer.  Obviously, if you can maintain a culture of discipline and reslot the pick module and the rest of the warehouse on periodic basis, the better and more efficient the picking operations will be.  That periodicity however is dependent on SKU growth, volume growth and seasonal changes in demand. 

Q. Is there an industry standard for replenishment frequency for pick modules?

A. No, but generally speaking it is not a good idea to plan on replenishing while the picking activity is occurring.  There are two reasons for this. First of all, if you plan on replenishing pick faces during the picking period, then that would indicate that there exists a likelihood that a slot would become empty and a picker would either have to wait for the replenishment to occur to fill the order or the picker would simply short the order. Both options are not very good.  Second, if the replenishment activity is going to occur at the same time as the picking activity, then the traffic in and around the pick module will increase, this may slow down productivity.  So the best idea would be to analyze the data enough so that slots do not become empty during the picking shift and to replenish either before or after the picking takes place.