Whether you are using ‘Min/Max’ or ‘reorder point’ and ‘order quantity’ to determine when and how much to restock, your approach might deliver or deny huge efficiencies. Key mistakes to avoid:

1. Not recalibrating regularly
2. Only reviewing Min/Max when there is a problem
3. Using Forecasting methods not up to the task
4. Assuming data is too slow moving or unpredictable for it to matter

“We have over 150,000 SKU x Location combinations. Our demand is intermittent. Since it’s slow moving, we don’t need to recalculate our reorder points often. We do so maybe once annually but review the reorder points whenever there is a problem.” – Materials Manager.

This reactive approach will lead to millions in excess stock, stock outs, and lots of wasted time reviewing data when “something goes wrong.” Yet, I’ve heard this same refrain from so many inventory professionals over the years. Clearly, we need to do more to share why this thinking is so problematic.

It is true that for many parts, a recalculation of the reorder points with up-to-date historical data and lead times might not change much, especially if patterns such as trend or seasonality aren’t present. However, many parts will benefit from a recalculation, especially if lead times or recent demand has changed. Plus, the likelihood of significant change that necessitates a recalculation increases the longer you wait. Finally, those months with zero demands also influence the probabilities and shouldn’t be ignored outright. The key point though is that it is impossible to know what will change or won’t change in your forecast, so it’s better to recalibrate regularly.

This standout case from real world data illustrates a scenario where regular and automated recalibration shines—the benefits from quick responses to changing demand patterns like these add up quickly. In the above example, the X axis represents days, and the Y axis represents demand. If you were to wait several months between recalibrating your reorder points, you’d undoubtedly order far too soon. By recalibrating your reorder point far more often, you’ll catch the change in demand enabling much more accurate orders.

Rather than wait until you have a problem, recalibrate all parts every planning cycle at least once monthly. Doing so takes advantage of the latest data and proactively adjusts the stocking policy, thus avoiding problems that would cause manual reviews and inventory shortages or excess.

The nature of your (potentially varied) data also needs to be matched with the right forecasting tools. If records for some parts show trend or seasonal patterns, using targeting forecasting methods to accommodate these patterns can make a big difference. Similarly, if the data show frequent zero values (intermittent demand), forecasting methods not built around this special case can easily deliver unreliable results.

Automate, recalibrate and review exceptions. Purpose built software will do this automatically. Think of it another way: is it better to dump a bunch of money into your 401K once per year or “dollar cost average” by depositing smaller, equally sized amounts throughout the year. Recalibrating policies regularly will yield maximized returns over time, just as dollar cost averaging will do for your investment portfolio.

How often do you recalibrate your stocking policies? Why?

Microsoft Dynamics 365 BC and NAV can manage replenishment by suggesting what to order and when via reorder point-based inventory policies. The problem is that the ERP system requires that the user manually specify these reorder points and/or forecasts. As a result, most organizations end up forecasting and generating inventory policies by hand in Excel spreadsheets or using other ad hoc approaches. Given poor inputs, automatic order suggestions will be inaccurate, and in turn the organization will end up with excess inventory, unnecessary shortages, and a general mistrust of their software systems.  In this article, we will review the inventory ordering functionality in BC & NAV, explain its limitations, and summarize how Smart Inventory Planning & Optimization can help reduce inventory, minimize stockouts and restore your organization’s trust in your ERP by providing the robust predictive functionality that is missing in Dynamics 365.

Microsoft Dynamics 365 BC and NAV Replenishment Policies

In the inventory management module of NAV and BC, users can manually enter planning parameters for every stock item. These parameters include reorder points, safety stock lead times, safety stock quantities, reorder cycles, and order modifiers such as supplier imposed minimum and maximum order quantities and order multiples.  Once entered, the ERP system will reconcile incoming supply, current on hand, outgoing demand, and the user defined forecasts and stocking policies to net out the supply plan or order schedule (i.e., what to order and when).

There are 4 replenishment policy choices in NAV & BC:  Fixed Reorder Quantity, Maximum Quantity, Lot-For-Lot and Order.

• Fixed Reorder Quantity and Max are reorder point-based replenishment methods. Both suggest orders when on hand inventory hits the reorder point.  With fixed ROQ, the order size is specified and will not vary until changed.  With Max, order sizes will vary based on stock position at time of order with orders being placed up to the Max.
• Lot-for Lot is a forecasted based replenishment method that pools total demand forecasted over a user defined time frame (the “lot accumulation period”) and generates an order suggestion totaling the forecasted quantity. So, if your total forecasted demand is 100 units per month and the lot accumulation period is 3 months, then your order suggestion would equal 300 units.
• Order is a make to order based replenishment method. It doesn’t utilize reorder points or forecasts. Think of it as a “sell one, buy one” logic that only places orders after demand is entered.

Limitations

Every one of BC and NAVs replenishment settings must be entered manually or imported from external sources.  There simply isn’t any way for users to natively generate any inputs (especially not optimal ones). The lack of credible functionality for forecasting and inventory optimization within the ERP system is why so many NAV and BC users are forced to rely on spreadsheets.  Planners must manually set demand forecasts and reordering parameters.  They often rely on user defined rule of thumb methods or outdated and overly simplified statistical models.  Once calculated, they must input the information back into their system, often via cumbersome file imports or even manual entry.  Companies infrequently compute their policies because it is time consuming and error prone. We have even encountered situations where the reorder points haven’t been updated in years. Many organizations also tend to employ a reactive “set it and forget it” approach, where the only time a buyer/planner reviews inventory policy is at the time of order–after the order point is already breached.

If the order point is deemed too high, it requires manual interrogation to review history, calculate forecasts, assess buffer positions, and to recalibrate.  Most of the time, the sheer magnitude of orders means that buyers will just release it creating significant excess stock.  And if the reorder point is too low, well, it’s already too late. An expedite is required to avoid a stockout and if you can’t expedite, you’ll lose sales.

Get Smarter

Wouldn’t it be better to simply leverage a best of breed add-on for demand planning and inventory optimization that has an API based bidirectional integration? This way, you could automatically recalibrate policies every single planning cycle using field proven, cutting edge statistical models.  You would be able to calculate demand forecasts that account for seasonality, trend, and cyclical patterns.  Safety stocks would account for demand and supply variability, business conditions, and priorities.  You’d be able to target specific service levels so you have just enough stock.  You could even leverage optimization methods that prescribe the most profitable stocking policies and service levels that consider the real costs of carrying inventory. With a few mouse-clicks you could update NAV and BC’s replenishment policies on-demand. This means better order execution in NAV and BC, maximizing your existing investment in your ERP system.

Smart IP&O customers routinely helps customers realize 7 figure annual returns from reduced expedites, increased sales, and less excess stock, all the while gaining a competitive edge by differentiating themselves on improved customer service.

To see a recording of the Dynamics Communities Webinar showcasing Smart IP&O, register here:

https://smartcorp.com/inventory-planning-with-microsoft-dynamics-nav/

1. Blaming Shortages on Lead Time Variability
Suppliers will often be late, sometimes by a lot. Lead time delays and supply variability are supply chain facts of life, yet inventory carrying organizations are often caught by surprise when a supplier is late.  An effective inventory planning process embraces these facts of life and develops policies that effectively account for this uncertainty.  Sure, there will be times when lead time delays come out of nowhere.  But most often the stocking policies like reorder points, safety stocks, and Min/Max levels aren’t recalibrated often enough to catch changes in the lead time over time.  Many companies only review the reorder point after it has been breached, instead of recalibrating after each new lead time receipt.  We’ve observed situations where the Min/Max settings are only recalibrated annually or are even entirely manual.  If you have a mountain of parts using old Min/Max levels and associated lead times that were relevant a year ago, it should be no surprise that you don’t have enough inventory to hold you until the next order arrives.

2. Blaming Excess on Bad Sales/Customer Forecasts
Forecasts from your customers or your sales team are often intentionally over-estimated to ensure supply, in response to past inventory shortages where they were left out to dry. Or, the demand forecasts are inaccurate simply because the sales team doesn’t really know what their customer demand is going to be but are forced to give a number. Demand Variability is another supply chain fact of life, so planning processes need to do a better job account for it.  Why should rely on sales teams to forecast when they best serve the company by selling? Why bother playing the game of feigning acceptance of customer forecasts when both sides know it is often nothing more than a WAG?  A better way is to accept the uncertainty and agree on a degree of stockout risk that is acceptable across groups of items.  Once the stockout risk is agreed to, you can generate an accurate estimate of the safety stock needed to counter the demand variability.  The catch is getting buy-in, since you may not be able to afford super high service levels across all items.  Customers must be willing to pay a higher price per unit for you to deliver extremely high service levels.  Sales people must accept that certain items are more likely to have backorders if they prioritize inventory investment on other items.  Using a consensus safety stock process ensures you are properly buffering and setting the right expectations.  When you do this, you free all parties from having to play the prediction game they were not equipped to play in the first place.

3. Blaming Problems on Bad Data
“Garbage In/Garbage Out” is a common excuse for why now is not the right time to invest in planning software. Of course, it is true that if you feed bad data into a model, you won’t get good results, but here’s the thing:  someone, somewhere in the organization is planning inventory, building a forecast, and making decisions on what to purchase. Are they doing this blindly, or are they using data they have curated in a spreadsheet to help them make inventory planning decisions? Hopefully, the latter.  Combine that internal knowledge with software, automating data import from the ERP, and data cleansing.  Once harmonized, your planning software will provide continually updated, well-structured demand and lead time signals that now make effective demand forecasting and inventory optimization possible.  Smart Software cofounder Tom Willemain wrote in an IBF newsletter that “many data problems derive from data having been neglected until a forecasting project made them important.” So, start that forecasting project, because step one is making sure that “what goes in” is a pristine, documented, and accurate demand signal.

Extend Epicor Kinetic’s Forecasting & Min/Max Planning with Smart IP&O  
Epicor Kinetic can manage replenishment by suggesting what to order and when via reorder point-based inventory policies. Users can either manually specify these reorder points or use a daily average of demand to dynamically compute the policies.  If the policies aren’t correct then the automatic order suggestions will be inaccurate, and in turn the organization will end up with excess inventory, unnecessary shortages, and a general mistrust of their software systems.  In this article, we will review the inventory ordering functionality in Epicor Kinetic, explain its limitations, and summarize how Smart Inventory Planning & Optimization (Smart IP&O) can help reduce inventory, minimize stockouts and restore your organization’s trust in your ERP by providing the robust predictive functionality that is missing from ERP systems.

Epicor Kinetic (and Epicor ERP 10) Replenishment Policies
In the item maintenance screen of Epicor Kinetic, users can enter planning parameters for every stock item. These include Min On-Hand, Max On-Hand, Safety Stock lead times, and order modifiers such as supplier imposed minimum and maximum order quantities and order multiples.  Kinetic will reconcile incoming supply, current on hand, outgoing demand, stocking policies, and demand forecasts (that must be imported) to net out the supply plan.   Epicor’s time-phased replenishment inquiry details what is up for order and when while the Buyers Workbench enables users to assemble purchase orders.

Epicor’s Min/Max/Safety logic and forecasts that are entered into the “forecast entry” screen drives replenishment.  Here is how it works:

• The reorder point is equal to Min + Safety. This means whenever on hand inventory drops below the reorder point an order suggestion will be created. If demand forecasts are imported via Epicor’s “forecast entry” screen the reorder point will account for the forecasted demand over the lead time and is equal to Min + Safety + Lead time forecast
• If “reorder to Max” is selected, Epicor will generate an order quantity up to the Max. If not selected, Epicor will order the “Min Order Qty” if MOQ is less than the forecasted quantity over the time fence. Otherwise, it will order the forecasted demand over the time-period specified.  In the buyer’s workbench, the buyer can modify the actual order quantity if desired.

Limitations
Epicor’s Min/Max/Safety relies on an average of daily demand. It is easy to set up and understand.  It can also be effective when you don’t have lots of demand history. However, you’ll have to create forecasts and adjust for seasonality, trend, and other patterns externally.  Finally, multiples of averages also ignore the important role of demand or supply variability and this can result in misallocated stock as illustrated in the graphic below: 

In this example, two equally important items have the same average demand (2,000 per month) and safety stock is determined by doubling the lead time demand resulting in a reorder point of 4,000. Because the multiple ignores the role of demand variability, Item A results in a significant overstock and Item B results in significant stockouts.

As designed, Min should hold expected demand over lead time and Safety should hold a buffer. However, these fields are often used very differently across items without a uniform policy; sometimes users even enter a Min and Safety Stock even though the item is being forecasted, effectively over estimating demand! This will generate order suggestions before it is needed, resulting in overstocks.  

Spreadsheet Planning
Many companies turn to spreadsheets when they face challenges setting policies in their ERP system.  These spreadsheets often rely on user defined rule of thumb methods that often do more harm than good.  Once calculated, they must input the information back into Epicor,  via manual file imports or even manual entry.  The time consuming nature of the process leads companies to infrequently compute their inventory policies – Many months of even years go by in between mass updates leading to a “set it and forget it” reactive approach, where the only time a buyer/planner reviews inventory policy is at the time of order.  When policies are reviewed after the order point is already breached it is too late.  When the order point is deemed too high, manual interrogation is required to review history, calculate forecasts, assess buffer positions, and to recalibrate.  The sheer volume of orders means that buyers will just release orders rather than take the painstaking time to review everything leading to significant excess stock.  If the reorder point is too low, it’s already too late.  An expedite is now required driving up costs and even then you’ll still lose sales if the customer goes elsewhere.

Epicor is Smarter
Epicor has partnered with Smart Software and offers Smart IP&O as a cross platform add-on to Epicor Kinetic and Prophet 21 with API based integrations.  This enables Epicor customers to leverage built for purpose best of breed forecasting and inventory optimization applications.  With Epicor Smart IP&O you can automatically recalibrate policies every planning cycle using field proven, cutting-edge statistical and probabilistic models.  You can calculate demand forecasts that account for seasonality, trend, and cyclical patterns.  Safety stocks will account for demand and supply variability, business conditions, and priorities.  You can leverage service level driven planning so you have just enough stock or turn on optimization methods that prescribe the most profitable stocking policies and service levels that consider the real cost of carrying inventory. You can build consensus demand forecasts that blend business knowledge with statistics, better assess customer and sales forecasts, and confidently upload forecasts and stocking policies to Epicor within a few mouse-clicks.

Smart IP&O customers routinely realize 7 figure annual returns from reduced expedites, increased sales, and less excess stock, all the while gaining a competitive edge by differentiating themselves on improved customer service. To see a recorded webinar hosted by the Epicor Users Group that profiles Smart’s Demand Planning and Inventory Optimization platform, please register here: https://smartcorp.com/epicor-smart-inventory-planning-optimization/

Recently, I had an interesting conversation with an inventory manager and the VP Finance. We were discussing the benefits of being able to automatically optimize both reorder points and order quantities. The VP Finance was concerned that given their large supplier required minimum order quantities, they would not be able to benefit.  He said his suppliers held all the power, forcing him to accept massive minimum order quantities and tying his hands. While he felt bad about this, he saw a silver lining: He didn’t have to do any planning. He would accept a large inventory investment, but his customer service levels would be exceptional.  Perhaps the large inventory investment was assumed to be the cost of doing business.

I pushed back and pointed out that he was not as powerless as he felt. He still had control of the other half of the procurement process: while he couldn’t control how much to order, he could control when to order by adjusting the reorder point. In other words, there is always room for careful quantitative analysis in inventory management, even when you have one hand tied behind your back.

An Example

To put some numbers behind my argument, I created a scenario then analyzed it using our methodology to show how consequential it can be to use inventory optimization software even in constrained situations. In this scenario, item demand averages 2.2 units per day but varies significantly by day of week. Let’s say the imaginary supplier insists on a minimum order quantity of 500 units (way out of proportion to demand) and fills replenishment orders in either three days or ten days in equal proportions (quite inconsistent). To spread the blame around, let’s also suppose that the imaginary supplier’s imaginary customer uses a foolish rule that the reorder point should be 10% of the minimum order quantity. (Why this rule? Too many companies use simple/simplistic rules of thumb in lieu of proper analysis.)

So, we have a base case in which the order quantity is 500 units, and the reorder point is 50 units. In this case, the fill rate is 100%, but the average number of units on hand is a whopping 330. If the customer would simply lower the reorder point from 50 to 15, the fill rate would still be 99.5%, but the average stock on hand would drop by 11% to 295 units. Using the one hand not tied behind his back, the inventory manager could cut his inventory investment by more than 10%, which would be a noticeable win.

Incidentally, if the minimum order quantity were abolished, the customer would be free to arrive at a new and much better solution. Setting the order quantity to 45 and the reorder point to 25 would achieve a 99% fill rate at the cost of a daily on-hand level of only 35 units: nearly a 90% reduction in inventory investment: a major improvement over the status quo.

Postscript

These calculations are possible using our software, which can make visible the otherwise unknown relationships between inventory system design choices (e.g., order quantity and reorder point) and key performance indicators (e.g., average units on hand and fill rate).  Armed with this ability to conduct these calculations, alternative arrangements with the supplier may now be considered. For example, what if, in exchange for paying a higher price per unit, the supplier agreed to a lower MOQ. Using the software to conduct an analysis of the key performance indicators using the “what if” costs and MOQs would reveal the cost per unit and MOQ that would be needed to develop a more profitable deal.   Once identified, all parties stand to benefit.  The supplier now generates a better margin on sales of its products, and the buyer holds considerably less inventory yielding a holding cost reduction that dwarfs the added cost per unit.  Everyone wins.