Modern Machine Shop

NOV 2018

Modern Machine Shop is focused on all aspects of metalworking technology - Providing the new product technologies; process solutions; supplier listings; business management; networking; and event information that companies need to be competitive.

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Lights-Out Machining Modern Machine Shop 91 • Chip conveyor. Not all chip conveyors are the same. Custom Tool's first Y-axis turning center has a conventional unit, but the second one features a Hennig unit with teeth on the conveyor. The Young brothers say this conveyor more effectively removes long, stringy chips commonly produced when machining aluminum, so they are more likely to run aluminum jobs overnight on this machine rather than the other. This eliminates chip "bird nesting," which can interfere with the parts collection system. • Parts collection. Initially, the chip hopper also ser ved as the parts collector. Now, each turning center has an integrated parts collector. The size of the collectors must be able to accommodate overnight production volume. If the capacity is too small, then the number of large parts that can be produced overnight is limited. In addition, coolant comes out with each part that is collected, so some means of draining the coolant out of the parts collector and back to the machine's sump is needed. • Bar feeder. If parts for a job are sizeable, a bar feeder's capacity might limit how many parts can be machined overnight. On the other hand, if cycle times are very fast, it is possible to consume all the loaded barstock, meaning someone would have to come to the shop to replenish the material so that overnight part production is not reduced. • Redundant tooling. The fuel fitting part with two types of threads shown on page 89 was the first job that Custom Tool set up to run overnight using redundant tools. When this job ran with an operator standing by, that operator could tell when an offset change might be needed due to tool wear. However, the shop found that it initially could only run that job lights-out for four hours, because it was at that point in which offset adjustments were needed for the two threading tools. Recognizing that necessity, the shop started using redundant threading tools, calling for a tool change at a certain part count just prior to when tool wear became an issue. Although the shop does not get all the potential life out of its threading tool inserts, the addi- tional time the machine can run unattended justifies this. • Load monitoring. None of the turning centers have broken-tool-detection devices, but they do have spindle-load-monitoring capability. When the load goes to zero, that means a tool has broken. Part programs are written so that the machine stops at that point rather than continuing to run the job and risking breaking subsequent tools. • Measurement capacity. It is nice that when hundreds of parts can be machined overnight, but that unattended production has changed what some Custom Tool shopf loor employees do to start each day. Time must be set aside for part segregation, inspection, machine evalu- ation and setup for the next job. In fact, part inspection became a bottleneck when the shop first implemented lights-out production. To speed inspection routines, Custom Tool added a Keyence IM series image dimension measure- ment system, which can automatically measure and record numerous external part features on one or more parts set up on the device. It is important to consider chip management when developing a lights-out machining process. This unit features conveyor teeth that enable it to better handle long, stringy aluminum chips when the turning center runs unattended overnight.

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