March 2008 Edition

FROM THE SHOP FLOOR

Test Anxiety

Testing tools is a way to keep up with technology,
but be judicious about it

Keeping current with new tools is hard. Harder still is figuring out which tools are worth testing. In my shop, new parts give me the opportunity to test tools that I couldn't in a strict production environment.

Sometimes a new tool goes in, and I wonder how we ever ran our shop without it. Sometimes we try the tool, and it takes a bit of tweaking. Sometimes the results are less than stellar.

Before I authorize a new tool test, I ask myself: Does it do something we cannot currently do? Does it do something we currently do, but faster? Is it less expensive?

If the tool meets one or more of these criteria, I'll give it a whirl. I limit my tests to tools I believe will solve a problem. Conducting too many tests, especially failures, can give you a bad reputation with the guys on the floor: Here comes another crazy idea.

Failures Are the Most Exciting

The most successful tests are the most boring. I've had tools that run exactly as advertised. Our most interesting test was one that went awry. We were testing a long-length carbide drill. We had a 0.5" diameter hole that had to go 12" deep.

We were crawling through our pieces using an extended high-speed steel drill, and were pecking to keep the chips from causing problems.
A solid carbide drill seemed to be the solution.

A sales engineer brought us a test drill. The test started out fine. The first hole made too much noise for our taste, but the drill remained intact and the test continued. After a few more holes, we had our feeds and speeds tweaked so that we were confident in the process.

After we drilled three holes at this speed and feed, the sales engineer second-guessed himself, and called his applications engineer to optimize the drilling for tool life. We plugged in the feeds and speeds the engineer suggested. The drill snapped off an inch into the material.

This was the only test drill. By the time another arrived, we could have completed the job using the slower peck process.

The lesson learned? Trust the guy who is standing at the machine, not the guy on the phone with just the catalog.

Sometimes the test starts out poorly, but after some work, provides the expected results.

We tested a face mill for use on a repeat job. We'd been using a 45° face mill and facing at 15 ipm. We were promised this new mill would double our feed rate, and the inserts would have eight cutting edges per insert, compared to the four on the the one we were using.

Less Is More

At first, the cutter made the entire machine shake, then stalled the machine. Our mill foreman was ready to pull the cutter, until we could get someone from the factory. The first thing that helped was something I never would have thought to do: remove three of the inserts.

This tool had 12 evenly-spaced teeth. By removing three inserts, this balanced the cutting load, and therefore reduced vibration. This seemed to work on one operation, but as the tool came back to do more work on the part, the vibration started again. This wasn't working as planned, and frustration set in. Again a factory representative arrived to diagnose
the problem.

Unlike the conventional 45° cutter, this face mill design required a higher chip load to work optimally. After slowing down our spindle speed, and increasing our feed rate, we achieved the 30 ipm promised and the vibration was under control. Inserts lasted longer, and with eight cutting edges per insert instead of four, the tool would pay for itself.

Tool tests aren't always going to be smooth. Sometimes they just plain fail. Some may take perseverance and effort. From what I have learned, the right tests can pay off big.

Dave is responsible for programming, tool selection, and fixture design for Ansco Machine's 20 CNC machines in Peninsula, OH.

What do you think?
Will the information in this article increase efficiency or save time, money, or effort? Let us know by e-mail from our website at www.ModernApplicationsNews.com or e-mail the editor at pnofel@nelsonpub.com.