Material Handling and Packaging IE-455 DR. DEEMA M. ALJUHANI LECTURE #06 Prepared by: DR ATIF SHAHZAD Edited by: DR DEEMA ALJUHANI Recap Material Handling equipment Taxonomy Today β’ From-to Chart From-to Chart A table that can be used to indicate material flow data and/or distances between multiple locations From-to Chart Flow rates and distances between five workstations in a manufacturing system. β¦ The left-hand vertical column lists the origination points (loading stations), while the horizontal row at the top identifies the destination locations (unloading stations). Network diagram From-to Chart Mathematical equations can be developed to describe the operation of vehicle-based material transport systems It is assumed that the vehicle moves at a constant velocity throughout its operation and that effects of acceleration, deceleration, and other speed differences are ignored From-to Chart The time for a typical delivery cycle in the operation of a vehicle-based transport system consists of : Loading at the pickup station, Travel time to the drop-off station, Unloading at the drop-off station, and Empty travel time of the vehicle between deliveries. From-to Chart ππΆ = delivery cycle time, min/del; ππΏ = time to load at load station, min; πΏπ = distance the vehicle travels between load and unload station, m (ft); π£πΆ = carrier velocity, m/min (ft/min); ππ = time to unload at unload station, min; πΏπ = distance the vehicle travels empty until the start of the next delivery cycle, m (ft). Loading at the pickup station, Travel time to the drop-off station, Unloading at the drop-off station, and Empty travel time of the vehicle between deliveries. Delivery cycle time The delivery cycle time ππΆ can be used to determine two values of interest in a vehicle-based transport system: Rate of deliveries per vehicle Number of vehicles required to satisfy a specified total delivery requirement Hourly rate of deliveries The hourly rate of deliveries per vehicle is 60 min divided by the delivery cycle time ππΆ Adjusting for any time losses during the hour Possible time losses β¦ The possible time losses include Availability Traffic congestion Efficiency of manual drivers in the case of manually operated trucks Availability The Availability ( A ) is defined as the proportion of total shift time that the vehicle is operational and not broken down or being repaired Traffic congestion Traffic factor πΉπ‘ is defined as a parameter for estimating the effect of losses on system performance Sources of inefficiency accounted for by the traffic factor include: • Waiting at intersections • Blocking of vehicles (as in an AGVS) • Waiting in a queue at load/unload stations Traffic congestion If these situations do not occur, then πΉπ‘ = 1.0 As blocking increases, the value of πΉπ‘ decreases πΉπ‘ is affected by the number of vehicles in the system relative to the size of the layout If there is only one vehicle in the system, no blocking should occur, and the traffic factor will be 1.0 β¦ For systems with many vehicles, there will be more instances of blocking and congestion, and the traffic factor will take a lower value β¦ Typical values of traffic factor for an AGVS range between 0.85 and 1.0 β¦ β¦ β¦ β¦ Worker efficiency Worker efficiency is defined as the actual work rate of the human operator relative to the work rate expected under standard or normal performance Let πΈπ€ symbolize worker efficiency Available time per hour The available time per hour per vehicle can now be expressed as 60 min adjusted by π΄, πΉπ‘ , and πΈπ . That is, π΄π = 60π΄πΉπ‘ πΈπ Rate of deliveries per vehicle π _ππ£ is the hourly delivery rate per vehicle, deliveries/hr per vehicle; Tc = delivery cycle time min/del AT = the available time in 1 hour, adjusted for time losses, min/hr π ππ£ π΄π = ππ Workload Workload is defined as the total amount of work, expressed in terms of time, that must be accomplished by the material transport system in 1 hr ππΏ = π π ππ WL = workload, min/hr; Rf = specified flow rate of total deliveries per hour for the system, deliveries/hr; and Tc = delivery cycle time, min/del Specified flow rate of total deliveries per hour The total number of vehicles needed to satisfy a specified total delivery schedule π π in the system can be estimated by: β¦ Calculating the total workload required β¦ Dividing by the available time per vehicle Number of vehicles Now the number of vehicles required to accomplish this workload can be written as ππΏ ππ = π΄π nc = number of carriers (vehicles) required, WL = workload, min/hr; and AT = available time per vehicle, min/hr per vehicle Thank you Any Questions?
