Thursday, November 1, 2007

Working With ‘Air’; Routing and Trimming

Skippy: We seem to get a lot of inquiries about trimming and routing in small job shops. This last month on the road, it felt a lot like that scene from 'The Graduate'; although instead of hearing the word 'plastics' everywhere, it seemed like a lot of folks are thinking that they need to look at 'Robotics'.

Buzz: Well, let's back up a little bit - for plastics and composite materials, air trimming tools are often easy to assemble machines that can be used either by hand or in semi-automatic mode with a little shop engineering to produce good quality parts at a fraction of the cost of robotic trimming.

Skippy: Doesn't that fall into the category of just 'throwing people at a problem'?

Buzz: Easy now, like you, I believe in increasing the productivity of our shop associates using high technology, but not all shops have volumes to justify high dollar investments into Robotics early on. On the other hand, one important item to consider ergonomically about cutting and trimming items with hand operated air tools is that user fatigue can increase when trying to extend cutting tool life and this must be carefully considered during tool selection and implementation (along with labor per unit costs.) Trying to work too fast with 'single fluted' tools can take less time than with 'multi-fluted' tools but quality will suffer. On the flip side, higher quality finishs can be obtained by making multiple passes: one roughing pass and a second finishing pass, but here again you need to consider the additional work for the operator or the semi-automatic machine.

Skippy: What are the critical shop issues?

Buzz: Air Pressure is probably first of the the most two critical items to consider and like a few other essential shop items (electricity?) when the supply drops a ‘little’ the resultant performance and quality drops more precipitously. For instance, these devices often need 90 psi or more at 30 cfm or greater of dry, clean, lubricated air to operate. If in this example with a drop in supply, the tool is receiving less than 70 psi or 20 cfm, then its usable horsepower is cut in half, as well as exhibiting a drop in its rpms. This compounds the quality and time related problems because router bits cutting edge surface speeds are designed for specific feet or inches per minute or second based on their rpms and do not perform as well at the wrong speed; just like the saw blade discussion earlier – time, pressure and surface speed all work together with the tool cutting surface design to yield a ‘sweet spot’. Some times air losses happen during the most innocent of 'plant improvement opportunities'. In the ‘Leaning’ process, shops often add more quick disconnects at multiple work stations to reduce travel time. These changes should be considered carefully as too small a supply line or too many users on a line can cause these pressure problems.

Skippy: You mentioned two critical items -

Buzz: - ah yes, Supply of air as above was the first and the second most important item is a proper maintenance schedule. Air tools are most often hampered or destroyed by particulate damage coming from their operating environments in shops where regular maintenance is not performed often enough. So, with the correct tooling, a well thought out implementation plan and a well executed maintenance program, air routers can be a very cost effective solution in small job shop settings.

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