Safety Stock versus Minimum Stock

According to E10 help (10.1.400) help for the safety stock definition is that it adds Minimum stock quantity and safety stock quantity together to determine how much is needed.
The question was why not just up the minimum stock quantity??? There seems to be no purpose for the safety stock

Does anybody have a good reason to keep safety stock split out of Minimum onhand quantity?

They are exactly the same unless you have a value in both. Have a look in the MRP Technical Reference Guide (search for Stock Part with Safety Stock Example).

I usually instruct users to set the lead time for a part. Minimum qty is usually set as the number of pieces used during the lead time. Safety stock can be equal to minimum, giving you a buffer for peak usage.
MRP suggestions will also tell you if you are below minimum or below safety, indicating the urgency of the suggestion.
The min max recalc dashbaord uses the same logic. A great tool in Epicor.

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We’re looking to start using PO Suggestions, so I’m educating myself on all the parameters. This morning we’re testing “Allow Consumption of Minimum Qty” in Site Maintenance.

The example in the MRP Tech Ref states: When the projected On-Hand Quantity for a purchased part falls below the Safety Stock quantity or a 0 quantity, the Urgent Planning parameters are used to determine quantities on the PO suggestions that fall within the lead time window.

It looks like we’d use Safety Stock as a buffer to drive an Urgent Planning generated PO suggestion sooner than if it hit a zero quantity on hand.

We have minimum quantity set, but I’m guessing that urgent planning won’t kick out a PO Sug if it’s below minimum, but above zero when Allow Consume to Min is checked.

If we start using safety stock, should I decrease the min quantity by the new safety stock amount to keep the same re-order point for standard lead time PO suggestions?

Hi Andris,

I think you should. Here are a couple of examples of our timephase where we use MOH plus allow consumption of MOH, in case it is useful to see it in action. There’s a below reorder and below SS shown respectively.

Hope this helps!
Nancy

Nancy - Thanks! That does help.

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Note that Epicor does NOT treat Safety and Minimum the same… they are different values, and have different uses. The balance of this discussion is assuming that you have the “Allow Consumption of Minimum” set to true.
Safety level is treated like an emergency value. If you are below safety, no matter what, MRP will schedule the replacement suggestion to TODAY to correct your on-hand. EVEN IF you have some scheduled to arrive tomorrow, MRP will yell at you to get it here today.
MINIMUM is a level that will trigger you to order more. BUT it is not an emergency. If the item has a lead time of 30 days, and you have an order that will bring you above the Safety + Minimum (yes they are ADDED together), and that order is within the leadtime, then it will not suggest a change. This is because you “Allow consumption of minimum” during the leadtime of the resupply. If you ever go below the safety level, see the safety rule above.
My rule of thumb… Use MINIMUM for your reorder… use Safety sparingly for those items that need an extra measure of safety qty over your minimum.
ALSO, Remember that at the end of lifecycle of the product, when you no longer need a product, you will still have whatever safety/minimum you have specified because Epicor is predictive… it will always suggest to keep your inventory at or above Safety+Minimum. You need to remember to turn off these values when shutting down a part.

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I came up with this a while back, if you’re a visual person. It’s helped here.

MRP - Min max and safety in Epicor.pdf (540.4 KB)

(These are actual numbers form my “lunchbox” - aka Scion xB.)

In non-Epicor terms, low-fuel light is “time to find a cheap gas station” and the reserve amount of 2 gallons is for if you’re going from Tampa to Ft. Lauderdale on that highway with 30 miles between exits and your stubborn self decided to keep going after you passed the last gas station, holding out for a better price, not that I have ever done that in the pouring rain…

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Thanks @JasonMcD! That’s a GREAT way to explain it (one thing I’ve never been able to do very well).

I had a Scion xD once upon a time… we named him Doodlebug.

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Excellent illustration!

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Curiously there is actually a field called ConsumeSafety on the PartPlant record in which the field help suggests this is similar to the consume minimum. The field is not exposed in the UI and through testing it doesn’t appear to have any effect.

I think that when the initial “Consume Safety” feature was released back 10-12 years ago, it was simply a Site(plant) setting… but then it was moved to the PartPlant table so that it could be set at the part level. In my humble opinion, this should never have been a “setting”… Consume Minimum should be the default. :wink:

I thought this was an old setting, I presume the consume safety would have behaved similar to consume minimum?

I’m still debating to myself the pros and cons of consume minimum…

While the consume minimum setting is good for mitigating unnecessary suggestions demanding material for today, it also has an impact on new PO suggestion due dates. So for example, a part has a minimum stock level of 10 and safety of 5 with a 10 day lead time. The part breaches it’s re-order level in 10 days time.

With consume minimum set to true the new PO suggested due date will be in 20 days time which is 10 days after dropping below re-order level.

With consume minimum set to false the new PO suggested due date will be in 10 days time to ensure you do not drop below re-order level.

It seems to me that for new suggestions you would want to plan with the intent of not dropping below minimum but if demand does happen to exceed supply within the purchase lead time you would be content in consuming minimum and not having to deal with change suggestions.

When Consume Minimum was “invented” it was for a customer I was working with… The initial design of Epicor was built with the thought that orders would be placed and be on the books, schedule for a future date. But This particular customer shipped nearly 100% of their product “Same Day” as the order (as long as it was ordered before 2:00 PM). So… In the morning, they were above minimum, By Noon, they were below minimum, and Tonight, MRP was telling them to rush an order into stock because they were below Min… they would place the PO, and the NEXT day, the suggestion would come in to reschedule the PO to come in TODAY, even though they still were above safety. They would lock the PO (for 30 days out… which is the delivery time), and a new suggestion would be created to fill the Minimum. No matter what you did, MRP would suggest a change.
Allow consumption takes into account the LEADTIME for the part… so as long as there is a new PO/Job scheduled to get you above minimum BEFORE the leadtime, it will stop suggesting reschedules.In a way, this “Allow consumption” is sort of a moving Time Fence, making it so it stops suggestions as long as you are replenishing the inventory on time.

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I like the influence it has on change suggestions, i just don’t like how it moves out the order by and due date of a new suggestion.

In my opinion… Minimum should be the quantity required to keep you going during the LEAD TIME for the part… for example, if the lead time is 30 days, and you “normally” consume 100 every 30 days, then the Minimum should be 100.
the SAFETY qty is “extra” just in case you consume more than the 100 in 30 days, OR if the lead time is not consistent (sometimes it is 40 days)… then you need “extra safety” to get you past the inconsistency.
In any case, MRP will add the two numbers together (safety + minimum) and that is the target level.
as stated above, these two quantities are treated differently in how urgent the signaling is handled… if you are below safety, then it is an emergency. If you are below Safety + Minimum, and if you are within the leadtime of the demand, then it is treated as normal, and will not tell you to rush.

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Maybe a slightly better illustration of Safety vs Min (still using the Gas Tank):

  • Maximum Quantity: Pickup truck Fuel tank holds 20 gallons.
  • Minimum Quantity: Low fuel light goes on when tank is below 2 gallons.
  • Safety Stock: You carry a 2 gallon gas tank in the back of the truck “just in case” you run out.

When the Minimum light goes on, you go to the gas station when convenient.
When the engine stops running, you use the extra gas tank to get you to the next station.

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Well I guess it depends on how you real-life manage the safety stock.

So if the safety stock is HANDS OFF, where it is physically separated from the rest of the stock, then it’s like your little red gas container.

But if it’s like where I work, where all stock, safety or not, is all mixed together physically in the warehouse, then it’s exactly like the guy that runs past the low fuel light AND past E and then sputters to a halt on the highway with no reserves left at all.

Every good materials manager I know has a stash of critical parts somewhere, under her desk, in a cleaning closet, their garage at home… :wink:

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