<?xml version="1.0" encoding="utf-8"?>
<ManualTopic ID="/baanerp/ti/onlinemanual/000332" xml:lang="en">
	<Header>
		<Title xmlns:ssa="http://www.ssaglobal.com" xmlns:HTML="http://www.w3.org/TR/REC-html40">Slack time and planning: time in days, planning method Backward</Title>
		<Keyword><Level1>Planning and slack: example 3</Level1>
		</Keyword>
		<Keyword><Level1>Slack and planning: example 3</Level1>
		</Keyword>
	</Header>
	<GeneralSection><GeneralSection><SectionTitle>Introduction</SectionTitle>
			<Paragraph>Planning backward is more difficult than planning forward if slack is defined in days. The operations are scheduled starting with the last operation, and calculated back based on the lead times. If slack is defined in days, these days are subtracted from the end date first. The first available moment of this calculated date is then taken as the start of the production order. To make sure there is enough time to carry out the whole operation and still have enough slack time left, the slack time is first subtracted from the end date, and then later later added again to the calculated start time.</Paragraph>
		</GeneralSection>
		<ExampleSection><SectionTitle>Example</SectionTitle>
			<Paragraph>Slack time is expressed in days; the planning method is Backward.</Paragraph>
			<List><ListItem>The work center has a calendar with five working days Monday through Friday, from 8 AM till 5 PM.</ListItem>
				<ListItem>One operation is planned for the production order. Operation time: 2 hours.</ListItem>
				<ListItem>Requested delivery date is Wednesday, 5 PM.</ListItem>
				<ListItem>Slack time: 1 day.</ListItem>
			</List>
			<List><ListIntro>Calculation:</ListIntro>
				<ListItem>Subtract from 5 PM the two hours that are necessary to carry out the operation: Wednesday 3 PM.</ListItem>
				<ListItem>Subtract the slack time and determine the first possible start time of the operation. That time is Wednesday 8 AM.</ListItem>
				<ListItem>Plan the operation forward again: Operation start date: Wednesday 8 AM. Earliest finish date: Wednesday 10 AM. Latest finish date: Wednesday 5 AM (slack time is between 10 AM and 5 PM).</ListItem>
			</List>
			<Formula><Paragraph UserLevel="Novice" UserType="Taskuser">

Wednesday:
| Production time                       Slack time                   |
|-----------------|--------------------------------------------------|
| 8 AM          10 AM                                             5PM|

</Paragraph>
			</Formula>
		</ExampleSection>
	</GeneralSection>
</ManualTopic>
