Sage X3 自动计算 安全库存、 经济批量 等参数的功能

numberandnet

一直关注，请你讲讲服务比率和安全存货因素之间的关系，哈哈

icetea_cn

1.        Types of service level
For inventory models we often refer to two types of service level:
Type I - The service level is defined as the probability of stocking out when there is an order event in the lead time. (Equivalently we can define it as the probability of not stocking out when there is an order event in the lead time).
Type II - The service level is defined as the percentage of demand that is not met from inventory, or equivalently, the percentage of demand that is met from inventory (also known as the Fill Rate).

Example
The example in the following table illustrates the interpretation of the service level:
Period        1        2        3        4        5        6        7        8        9        10
Expected demand        100        100        100        100        100        100        100        100        100        100
Units Short quantity        0        0        0        0        0        1        0        0        0        19
Units Short event        -        -        -        -        -        X        -        -        -        X
●     Total of Unit Short events:  2 -> Type I service =1 – (2 / 10) = 80%
●     Total of Unit Short quantities:  20 -> Type II service level =1 – (20 / 1000) = 98%


2.        Why we should select the Type II as the service level
A Type I service objective is appropriate when a shortage occurrence has the same consequence independent of its time or amount. One example would be where a production line is stopped whether 1 unit or 100 units are short. The presupposition of this service, i.e., the same consequence ignoring the time or amount of a shortage occurrence, is not satisfied for most business scenarios. Also, as different items have different cycle lengths, this measure will not be consistent among different products, making the proper choice of this type difficult.

The term Fill Rate is often used to describe Type II service level, and is generally what most managers mean by service level. And the type is applied in most supply chain planning and inventory management products.


3.        How to calculate the Safety Factor based on Type II Service Level (i.e., Fill Rate)



Using the above formula, you can get the L(z) via the Fill rate, and then get the Safety Factor z from the normal distribution table based on the calculated L(z).

[ 本帖最后由 icetea_cn 于 2008-8-20 14:57 编辑 ]

numberandnet

看不懂这文字啊，还是麻烦把他搞成中文吧！谢谢

龙特ERP

说一说我的意见吧。

就安全库存而言，我们认为，是指在正常情况下不会使用到，但为了预防意外情况下而设置的那一部分库存。
意外的情况下，包括由于意外原因，供应商不能准时交货，或者质量出现问题的情况。

因此，安全库存的设置要考虑的是库存成本以及缺货成本。
所谓库存成本是指保持这个安全库存量的成本。比如占用仓库的成本、保险费成本、损耗成本，等等；
所谓缺货成本是指当需要用到这个物料，而这个物料没有而造成的紧急采购、用别的物料替换的成本。
de
设置安全库存就是要找出一个数字，在这两者中找到一个平衡点，或者说找出 min(库存成本+缺货成本)对应的那个值。

说实话，要进行精确设置安全库存是很麻烦的，这也就是为什么我们对库存进行ABC管理的原因，抓大放小，管好了A类物品，就能起到事半功倍的效果。

国人很多把安全库存和订货点混淆了（包括某大名顶顶的X友软件，也把这两个字段视为同一个）。呵呵

楼上的分析，我认为确定订货点可能更加合适。但是，用订货点管理的物料，通常都不会是A类物料。
A类物料，我们应该用MRP管理，不是吗？

lacamus

传说中的SAGE X3,呵呵!