More on item safety stock in AX 2012

Regular readers of this blog (hello you two) will know that I’ve got a bit of a bee in my bonnet about Dynamics AX Master planning, and safety stock / re-order point in particular. You’ll also know that these blog posts come out of my day-to-day work, and currently I’m working with a small manufacturing company here in New Zealand that have been running Dynamics AX 2009 for about five years, but up to now haven’t run master planning – so we’re working through the setup with them.

Obviously the old chestnut of item coverage minimum stock soon became a topic of conversation.

The classic interpretation of safety stock goes something like “it’s the buffer stock that you use to cover your supply lead time” – forgive the over simplification I want to get to classic picture of your inventory over time following this classic ‘saw-tooth’ pattern:

Many New Zealand manufacturers import raw materials, and we obviously have to cope with long lead times. Let’s assume a 60 day lead time and an average demand of about 800 per month. We could setup master planning to give us this classic pattern by using min/max planning, and a minimum stock of 1,600 (to give us enough stock for 2 months). Our net requirements would look like this:

But we can do better than this because Dynamics AX master planning uses the item coverage minimum stock on all three of its planning methods (min/max; requirement (a.k.a. ‘make-to-order’), and period). And it uses the item coverage minimum stock even if you are forecasting your demand. It doesn’t actually matter whether the forecast is entered on the specific item you’re planning (like a finished goods item) – to represent independent demand – or whether the item you are planning inherits that forecast demand because it’s a component or a raw material which has dependant demand. The point is that we have both an item coverage minimum stock and a forecast. Like this:

For the first couple of months everything is hunky-dory, and then the planning goes wild and we end up holding far more stock than our safety stock – because master planning reacts to each demand forecast by recommending a planned purchase order – and that’s the other thing that we typically see in New Zealand manufacturers who are importing raw materials: a regular supply pattern. A purchase order is going to arrive every couple of weeks or so, on a cycle that isn’t directly related to the long, overall purchase lead time. So a more realistic example would be that we’d already have a couple of open purchase order lines (based on the planning we did in the previous months) and now we see:

Even worse.

Obviously my mistake was to set the item coverage minimum quantity based on the simplistic re-order point logic assuming a replenishment period equal to the full purchase order lead time. When you’ve supplies arriving more frequently than your full replenishment lead time, you only need enough stock to cover you until the next supply arrives. Also, when you’re forecasting demand, the safety stock is used to cover un-forecasted demand. Or to put it another way, the safety stock represents your confidence in the accuracy of your forecast. If your forecast was 100% accurate, you wouldn’t need any safety stock. Maybe I’ve been looking in the wrong place – but I haven’t seen anywhere near as much discussion about setting safety stocks like this – but the discussions I have seen relate to buffer stocks and Kanban sizes. In the toy-town example I’m presenting we can reduce the buffer stock dramatically and still plan never to go below 2 weeks stock:

And this screen shows another Dynamics AX master planning subtlety: the implicit safety stock that is hiding in my supply order minimum quantity.

Easy to over egg this particular pudding.

Project forecasts for items and hours in AX 2012

Projects in Dynamics AX have come a long way – especially in the assignment of workers to projects. That’s not the topic of this post, but if you’re interested checkout the Technet Identify and assign qualified workers to projects [AX 2012] documentation, or download the two whitepapers: Microsoft Dynamics AX 2012 R2 – Resource scheduling in Project management and accounting and Worker resource scheduling in Microsoft Dynamics AX 2012 R3.

But we’re travelling back in time, to a simpler, earlier age, and we’re going to look at how we can use project forecasts for items and work centre (resource) hours.

I’ve looked at some of the various ways we can issue inventory to projects in an earlier post: Project production orders in AX 2012 R3. Forecasting the items that you’re going to issue to a project is simplicity itself. As in that earlier post I’m working in the Dynamics AX 2012 R3 CU9 demo Hyper-V image. In the USMF company I’ve gone to Project management and accounting > Common > Projects > All projects, and created an ‘Internal’ project


As you can see, on the Plan tab we can create forecasts for Hours, Project expenses, Items, Fees and On account transactions. Incidentally, changing the size and order of these buttons is really easy – see this post. Click on the item forecast button and the familiar (well familiar to me anyway) Item forecast form opens. Click on the New button to create a new forecast:

The system immediately fills in the Forecast model and the Project ID. The default forecast model comes from the Project management and accounting parameters form. You define the default forecast model on the Forecast tab. All forecasts have to be entered into a forecast model. One forecast model is linked to a master plan, and that’s the one that will trigger ordering based upon your project forecast. Forecast models are setup at Inventory management > Setup > Forecast > Forecast models:

Here, I’m using a Sub-model to identify my project item forecasts (and keep them separate from my inventory forecasts). Master planning includes all sub-model forecasts in its calculations, but you can only have one level of parent forecast model and sub-model.

Back on the project item forecast form before I try to enter any forecast lines I’ll use the Inventory > Dimension display form to show Site and warehouse on the Overview grid. All forecasts have to be entered with respect to a warehouse. Now I enter my forecast model, a date (the date I expect to issue the item to the project) and an item number. When you enter the item number the system will fill in the default sales site and warehouse. Finally enter the quantity you plan to issue to the project. Then the system asks me to specify a project category:

Although it’s tempting to click on the Project tab on the forecast and enter the category, it’s smarter to go to the item and set the default category on the item:

This isn’t a mandatory field when you create the item, but well worth setting if you plan to issue items to projects.

Now we’ve got our item forecast – which we can also see at Project management and accounting > Common > Transactions > All project forecasts:

When I run master planning the Item Net requirements form shows the planned demand from the project:

This is all good, except that nothing really identifies this as a project item forecast (as opposed to an inventory sales/demand forecast).

The project Hours forecast form looks slightly different. When I click on the New button I again get the default project model and project ID, so I can enter a date and a category and a number of hours:

Next I’ll click on the Resource requirements tab and define a resource that will provide the hours:

Again this form looks familiar to me – I’m used to setting up the resource requirements on production order route operations like this. There are now (in Dynamics AX 2012) a lot of options for defining how the system can select resources during scheduling – but I’ll stick to the simplest, and assign a single resource (a work centre in old money):

Unlike the item forecast (which is processed by master planning as soon as it’s created) you don’t see the Hour forecast as a capacity reservation on the resource until you schedule the hour forecast. Click on the Scheduling > Resource scheduling button and the Scheduling form appears:

The ‘Scheduling’ parameters look a bit odd, but there are some familiar elements (if you’re used to scheduling production orders), the In/Out options are Forwards and Backwards, the familiar scheduling directions.

However one odd feature here is that the Scheduling date on the Scheduling form is used to schedule the hours forecast – even though the project date is mandatory when you enter the project hours forecast it isn’t used. I’m setting my scheduling date to 14/03/16 and clicking OK. The scheduling tab now shows that capacity reservations have been created by the scheduling:

You can see these on the Scheduling > Capacity reservations form:

Another form that looks familiar to me, from the resource you can see the same display:

And on the References tab you can see that these are Project capacity reservations:

You may have noticed that we’re in the Dynamic master plan – these capacity reservations are copied into the Static master plan the next time you run master scheduling and regenerate the master plan.

Two more things and then we’re done. Firstly, there’s a Line number on the General tab of the Project Hours forecast:

If you have more than one resource to reserve (and of course in a real example you might have) the reservations are made in Line number sequence.

The other thing is that the Edit button displays options for copy, update and delete:

There’s a similar form for the project item forecasts. Use the select button to select the forecast; select the update you want to perform; and OK to process.

There is of course another way to generate capacity reservations for your project and that it simply create an item forecast for a production item with a route – but this option (adding an hours forecast to your project and generating capacity reservations directly for the project) works well for project activities not directly related to production items (for instance plant maintenance, or new product development).

A master planning setup checklist for Dynamics AX 2009

Well I’ve put is off a long as I could – but I’ve just been asked to setup Dynamics AX 2009 master planning for a small manufacturing company so I’ve added an AX 2009 category to the blog.

One of the intriguing oddities about Dynamics AX master planning is the number of different places in the system involved in setting up master planning. I got tired of forgetting a setup step, so for the past few years I’ve been collecting the steps I go through into a check-list.

Here is the Dynamics AX 2009 version (I’m not certain how tables format on blog posts so I hope this is readable):

Module / Menu path Setup Comment
Basic > Setup > Calendar Working times template
Basic > Common forms Calendar Define working times using the Working times template
Master planning > Setup Master planning parameters You’ll have to re-visit the parameters after setting up a forecast plan, master plans, and coverage groups.
Master planning > Setup > Plans Forecast plans For Forecast scheduling
Inventory management > Setup > Forecast Forecast models
Inventory management > Setup > Forecast Item allocation keys Optional
Inventory management > Setup > Forecast Period keys Optional
Master planning > Setup > Plans Master plans
Master planning > Setup > Coverage Reduction keys
Master planning > Setup > Coverage Coverage groups
Master planning > Setup > Coverage Min/max keys Not used that often
Inventory management > Setup > Dimensions Dimension groups Coverage by item dimension (enable coverage by warehouse)
Inventory management > Setup > Inventory breakdown Warehouses Manual warehouses
Refilling warehouses

Transport lead times

For finished goods items:
Inventory management > Inquires > Forecast Sales forecast By item and warehouse
For BOM items: Item master coverage group
Active Bill of material version

Active route version or production lead time

Production order minimum, multiple, and possibly maximum quantities

For purchased items: Item master coverage group
Primary vendor

Purchase lead time

Purchase order minimum and multiple quantities

For all items: Item coverage records for minimum stock (by warehouse)
Item coverage records to over-ride default re-filling warehouses

Transfer order (inventory) quantities

Stay tuned for the Dynamics AX 2012 version – it’s coming soon.