Material flow time

Above the fraction line write down the sum of all times measured on your stop watch which had a value-added effect on the purchased part during this material flow time span. 

Inventory also has a significant impact on the material flow time in a supply chain. Material flow time is the time that elapses between the point at which material enters the supply chain to the point at which it exits. For a supply chain, throughput is the rate at which sales occur. If inventory is represented by /, flow time by T, and throughput by >, the three can be related using Little s law as follows ... 

The preceding example emphasizes the impact of lead lime variability on safety inventory requirements (and thus material flow time) and the large potential benefits from reducing lead time variability or improving on-time deliveries. Often, safety inventory calculations in practice do not include any measure of supply uncertainty, resulting in levels that may be lower than required. This hurts product availability. 

Reinforced Thermoplastic Sheet. This process uses precombined sheets of thermoplastic resin and glass fiber reinforcement, cut into blanks to fit the weight and size requirements of the part to be molded. The blanks, preheated to a specified temperature, are loaded into the metal mold and the material flows under mol ding pressure to fiU the mold. The mold is kept closed under pressure until the temperature of the part has been reduced, the resin solidified, and demolding is possible. Cycle time, as with thermosetting resins, depends on the thickness of the part and the heat distortion temperature of the resin. Mol ding pressures are similar to SMC, 10—21 MPa (1500—3000 psi), depending on the size and complexity of the part. 

Preferential Removal of Crystals. Crystal size distributions produced ia a perfectiy mixed continuous crystallizer are highly constraiaed the form of the CSD ia such systems is determined entirely by the residence time distribution of a perfectly mixed crystallizer. Greater flexibiUty can be obtained through iatroduction of selective removal devices that alter the residence time distribution of materials flowing from the crystallizer. The... 

Composite Samples Obtained by Multiple Sample Extractions Material flow streams are sampled in practice by combining extractions taken at successive time intei vals into a composite sample. Multiple increment collection to obtain representative composite sampfes for specified bulk-material flows is performed according to a... 

Selection of appropriate time intei vals for increment extractions relates to property variation (inhomogeneity) within material flow streams. Ten minute extraction intei vals are generally adequate to obtain suitably representative samples from material flows under practical circumstances. Precise determination of extraction intei vals consistent with individual apphcations can be calculatedthrough autocorrelation of historical sampling data, a statistical method described in references (Gy, Pitard). 

Example 5 Solids Sampling by Linear Traversing Trajectory Cutter lucremeut weight S hy a linear traversing cutter from hulk material flow of fine powder B expressed in unit weight per unit time is calculated hy... 

A filter removes particulate matter from the carrying gas stream because the particulate impinges on and then adheres to the filter material. As time passes, the deposit of particulate matter becomes greater and the deposit itself then acts as a filtering medium. When the deposit becomes so heavy that the pressure necessary to force the gas through the filter becomes excessive, or the flow reduction severely impairs the process, the filter must either be replaced or cleaned. 

There is no entirely satisfactory way of measuring flow. In the BS 2782 flow cup test an amount of moulding powder is added to the mould to provide between 2 and 2.5 g of flash. The press is closed at a fixed initial rate and at a fixed temperature and pressure. The time between the onset of recorded pressure and the cessation of flash (i.e. the time at which the mould has closed) is noted. This time is thus the time required to move a given mass of material a fixed distance and is thus a measure of viscosity. It is not a measure of the time available for flow. This property, or rather the more important length of flow or extent of flow, must be measured by some other device such as the flow disc or by the Rossi-Peakes flow test, neither of which are entirely satisfactory. Cup flow times are normally of the order of 10-25 seconds if measured by the BS specification. Moulding powders are frequently classified as being of stiff flow if the cup flow time exceeds 20 seconds, medium flow for times of 13-19 seconds and soft flow or free flow if under 12 seconds. 

As previously discussed, many, if not most, cases of particles adhering to substrates involve at least one of the contacting materials deforming plastically, rather than elastically. Under such circumstances, it would be expected that the extent of the contact should increase with time and, with it, the force needed to detach a particle from a substrate. Moreover, material flow can occur, resulting in the engulfment or encapsulation of the particles. 

Tlie average time spent by material flowing at volumeUie rate u tlirough a volume V is known as the mean residenee time f, expressed as... 

Strength and Stiffness. Thermoplastic materials are viscoelastic which means that their mechanical properties reflect the characteristics of both viscous liquids and elastic solids. Thus when a thermoplastic is stressed it responds by exhibiting viscous flow (which dissipates energy) and by elastic displacement (which stores energy). The properties of viscoelastic materials are time, temperature and strain rate dependent. Nevertheless the conventional stress-strain test is frequently used to describe the (short-term) mechanical properties of plastics. It must be remembered, however, that as described in detail in Chapter 2 the information obtained from such tests may only be used for an initial sorting of materials. It is not suitable, or intended, to provide design data which must usually be obtained from long term tests. 

Is a multiple-cavity tooling approach possible to reduce piece costs Yes Yes. Depends on size and configuration, although rapid cycle time may eliminate the need. Not necessarily. Secondary operations may be too costly and material flow too difficult... 

Materials handling applications can be made wherever materials are transported, positioned, or.stored, the most extensive use being in mahufg. Manufg involves elements of motion, time, quantity, and space motion to transport materials between work stations, time to process and handle materials, quantity to establish work schedules and.material flow rates, and space to house materials, machines, and employees. The... 

Material flowing at a position less than r has a residence time less than t because the velocity will be higher closer to the centerline. Thus, F(r) = F t) gives the fraction of material leaving the reactor with a residence time less that t where Equation (15.31) relates to r to t. F i) satisfies the definition. Equation (15.3), of a cumulative distribution function. Integrate Equation (15.30) to get F r). Then solve Equation (15.31) for r and substitute the result to replace r with t. When the velocity profile is parabolic, the equations become... 

The time required for a batch of material to pass through the entire process is called the residence time or flow time tm for product i. The residence time is defined by ... 

Brunner and Rechberger [13] consider material flow analysis (MFA) to be a valuable tool for the tracing of stocks and flows of materials in a system defined in time and extension. Therefore the related SFA is supposed to be a valuable tool... 

Such a supply chain network easily adds up to tens of thousands of nodes and edges with which the product relations are described, whereby a node can represent raw material, an intermediary product or a final product. An edge represents the relationship between two products. As there are usually predecessor/successor relations, the relation network can be interpreted as a directed graph. The material flow is modelled in form of an edge, material factors and offset times are stored as attributes [3,10, 23, 25, 33]. 

A process order is a request asking production to produce a specific quantity of a material on a specific date. Creation of a process order uses a master recipe that is valid for the specific material and quantity as a template to determine the specific timing and component quantities (material flow). 

Figure 12.5 depicts an abstraction of the production schedule for the sample plant, expressed by process order steps allocated to resources over the time scale. The small arrows represent the receipt and issue elements that are directly related to the process order. The large arrows represent material flows that cross the balance area (i.e., they have either a source or a target outside of the organizational unit considered, e.g., purchase orders and sales orders). 

---