Takt time is the maximum time allowed to produce a product in order to meet customer demand, or the pace at which the process must run to successfully meet customer demand.
The iGrafx Lean VSM diagram calculates Takt time as "Available Time/Customer Demand".
The Available Time and Customer demand are 'Based on Diagram settings', which means that the numbers you enter into the Lean Properties dialog box for a diagram (e.g. by going to the Lean menu and choosing Value Stream Map Properties) are used. For "Available Work Time", the numbers you enter for 'Hours Per Shift', 'Break Minutes Per Shift', 'Shifts Per Day', 'Days Per Week', and 'Days Per Month' are used. For "Customer Demand", the number you use for 'Customer Demand' per time unit (e.g. 100 / Month) is used.
Note that if you know the 'Takt' or current pace that your process can produce each piece of work at, you can enter a Takt time directly, and based on the "Available Work Time" settings iGrafx will then calculate the Customer Demand. However, it's more typical to enter Available Work Time and average Customer Demand over some reasonably long amount of time, and calculate Takt time from that.
Once a Takt time is set, it will affect Inventory Time (which in turn affects Lead Time) calculations by default. This assumes you have the Lean Properties set to calculate "Inventory Lead Time" to be "Based on Takt Time". If you change the Inventory Lead Time setting to be "Based on Activity Capacity", then Takt is no longer used and the actual capacity of the activity following the inventory step is used; see the Lean Data Reference in the iGrafx Help for how Capacity is calculated.
Setting a Takt time will also show the Takt time goal, or line, on the Work Balancing Graph. The Work Balancing Graph may be displayed by enabling the 'Show Work Balancing Graph' option on the Graph tab of the Lean Properties dialog box.
On a related note, remember that 'ideal' or customer Takt time is the maximum time allowed to produce a product in order to meet customer demand. Said another way, Takt time is customer demand normalized for your available time or work schedule. The calculation of ideal or customer Takt time assumes that production will occur during the full (every second of) the scheduled time. In reality, people do not tend to maintain 100% efficiency, and there may be work stoppages for other reasons, so allowances will need to be made for this probability. You will probably want to set up your process to run at a proportionally faster rate than ideal Takt, to account for any work slowdown or stoppage that may occur. Otherwise, overtime is the other way to handle not producing to demand.
Assuming that overtime is undesirable, a faster pace than ideal customer Takt can be used, so that there is a small degree of time built into the work day to make up for interruptions. That way, if there are delays the production process can still meet demand. If all expected production is complete without significant delays, the line can be stopped (otherwise it would be overproducing), and the extra time used for organized 'Kaizen' or continuous improvement to create more value with less waste.
So when Takt is discussed you may hear "Customer Takt" to represent the pure or ideal calculation of Takt time (the pace normalized to your schedule and assuming 100% efficiency during that schedule), and "Actual Takt" or "Operating Takt" to represent the actual (faster) pace of the process to meet customer demand in the real world.
There are calculations that iGrafx performs that can help you understand the actual operating takt or efficiency of your process. In particular, the Work Balancing Graph displays a graph of Takt Time of the process in relation to Production Time at each activity or step. In addition, you can add Production Time to the timeline if you would like to.
Production Time at a step is the actual time (on average) between each piece of work being produced. Production Time is calculated based on data you enter into an activity based on the following formula:
Production Time = Processing Time / ((100 - Defect%) * (Operators * Availability%))
Production Time, then, is affected by Processing Time and any 'Defect%', number of 'Operators', and 'Availability%' of those operators that you enter into the Lean Data for a shape. By default (in the iGrafx Lean VSM diagram template), "Processing Time" is labeled as 'Total C/T' in the Lean Data Properties, and is composed of VA and NVA time. Production time will decrease as your availability percentage and number of operators increase, and as your defect percentage decreases. Production time will also decrease as Processing Time decreases.
You can show Production Time on each activity shape and on the Timeline data. See the Knowledge Base article on how to show more data on the Lean VSM timeline, or the iGrafx Help for more information on how to show more data on the Timeline. If you show Production Time on each shape and/or the Timeline, you can get a better sense of what your actual "Production Time" (or Production Takt) is, and that may help set what your "Operating Takt" might need to be to meet ideal or Customer Takt.