By Tom Voges, Hartwig Applications Engineer

There is nothing quite like having your brand new lathe setting on your floor ready to provide years of reliability and quality parts. The stress of justification, financing requirements, and choosing the right brand of equipment for your shop is over, and now you are ready to start on the backlog of work waiting for this machine.

After a period of time, you begin to notice that the machine isn't as productive as you thought it would be. Yes, it's working just fine with no service issues, the operators are at the machine and the work is getting done, just not quite as fast as you were expecting. There is something missing but you can't pinpoint it. We are continually asked to look at improving customers processes, and the old saying, "The devil is in the details" is where we start. Here are some specific areas to consider.

Chip Control
Chip control on a lathe is generally thought of as a short curled chip in the shape of a 6 or 9. Not all tools and processes can generate this style of chip, but a chip that always ends up in the conveyor could be considered controllable because there is no other action required to handle it.

This issue generally gets brushed off as "We can work on that later, we need to get the part running now," which in a lot of cases is very true. It is this detail that starts to decrease the process efficiency from the beginning. If "later" is never pinpointed to a specific time, the chances of it getting done decrease. It is then left up to the operator to deal with, which he does with the machine not running a part, thereby adding cycle time to the process. Because the machine is running good parts at the expected cycle time, the loss in productivity becomes more difficult to find.

There are four main areas that influence chip control.
The first is material selection or type. Chip control should be considered when we have a choice in material because of the direct effect it has on the cutting process. The second is cutting tool selection. Insert manufactures have a wide range of choices and selecting the correct insert for your application can be challenging. Your insert representative will be more than happy to work with you and can generally bring in sample inserts to test in your application. The third is general cutting parameters. This works hand in hand with the cutting tool selection. Again your insert representative can help recommend the correct feeds, speeds and depths of cut to optimize chip control. The fourth is coolant system performance and in particular high pressure coolant which is defined as 1000psi or above. Coolant delivered at this pressure breaks through the vapor barrier between the cutting tool and the chip being formed cooling it closer to the cutting edge and curling it faster causing it to break.

Change Over
Another area that is typically doesn't see enough attention is change over time. Today's lot sizes are smaller than they have ever been, which decreases the amount of parts that we can amortize the change over time across. Any non-productive time can greatly affect the total part process time.

The areas that we look at to reduce the change over time are tool changes and work holding changes. Fortunately, there are quick change offerings in both categories that can be considered. Today's quick change tooling offers excellent repeatability, rigidity, and flexibility. These holders also have the benefit of directed coolant flow - some of which can be used with high pressure coolant systems - eliminating the need to make up and continually adjust coolant nozzles or pipes. Quick change work holding systems offer the same qualities of repeatability, rigidity, and flexibility and can drastically reduce the changeover time.

All of the details I have outlined require some sort of investment to improve. It may be as simple as taking the time to watch the machine run and identify problem areas, or it may be to purchase process improving accessories. All of these improvements are best done at the beginning of the project. This gives you the maximum amount of parts to spread the cost over and the most amount of time to maximize the productivity of the machine. If you wait until the project is half over, you can only apply the savings to half of the parts, thereby reducing the overall efficiency of the equipment.

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