Friday, September 23, 2011

How slow can you go?


If you take a light and shallow enough cut or run the spindle speed slow enough you can minimize the effects of Machining Dynamics and avoid chatter. But how low? You can damage a lot of parts, break a lot of tools and waste a lot of time on the way down as well as trying to go up. The BlueSwarf Dashboard shows you exactly where a milling tool assembly wants to run in a machine and in a material. It shows you the fastest speeds, the highest depths and widths of cut, but also the slowest and lowest along with everything in between..

Wednesday, September 14, 2011

The new BlueSwarf Dashboard for Titanium



For this demo Dashboard, we added buttons at the bottom:
  1. Current Parameters show where the process was running before we got there.
  2. The Catalog Recommendations are just that, the speeds, feeds and depths of cut recommended by the cutting tool manufacturer.
  3. The Number Buttons work as follows: Press 1) to optimize the speed, 2) to increase the depth of cut, and 3) to increase the feed rate.

Introducing the BlueSwarf Dashboard Version 2.1




For this demo Dashboard, we added buttons at the bottom:
  1. Current Parameters show where the process was running before we got there.
  2. The Catalog Recommendations are just that, the speeds, feeds and depths of cut recommended by the cutting tool manufacturer.
  3. The Number Buttons work as follows: Press 1) to optimize the speed, 2) to increase the depth of cut, and 3) to increase the feed rate.

Monday, September 12, 2011

If its in "harmony" why would you want to break that up?

At BlueSwarf we chafe on the misuse of terms. We received a major exorcism with this blog post  from Mark Albert of Modern Machine Shop. However we are often seeing the following term use with cutting tools; "it breaks up harmonics."

Experienced end users can tell when a machine tool sounds right and when it doesn’t. Stable, chatter-free milling produces a clear tone—a single, dominant frequency. Chatter, on the other hand, produces a harsh tone, often with different frequencies mixed together. It seems that this is what is being referred to as "harmonics". That is not technically correct.

The definition of "harmonics" when applied to physics is "a wave whose frequency is a whole-number multiple of that of another"

Let’s start by considering the cutting sounds that are a normal part of milling. Often there is the sound of the tool’s teeth hitting the workpiece. That hitting causes a force at the tooth passing frequency, and that force causes the tool to vibrate, creating the sound. A tool with two teeth rotating at 15,000 rpm will have a tooth passing frequency of 500 Hz. Other frequencies may also be present in the sound. For example, tool runout causes a once-per-revolution force, or 250 Hz for the previously listed case. The runout frequency is exactly half of the tooth passing frequency. If the radial DOC is small, then the force is a series of sharp spikes appearing at the tooth passing frequency. This kind of force leads to other sound components at exact multiples of the tooth passing frequency, and these are called “harmonics.”

When milling with a two-toothed tool at 15,000 rpm and a small radial DOC, there will be sound frequency components at 250 Hz (runout), 500 Hz (teeth passing) and multiples of those (750 Hz, 1,000 Hz, 1,250 Hz and so on). Because the resulting sound waves line up exactly, the combination sound will still be clear and dominated by the tooth passing frequency. These are the "good" harmonic frequencies that result in a stable cut.

What if the cut is not stable (chattering)? All assemblies of tool, toolholder and spindle have one or several frequencies at which they would like to vibrate, and these are called “natural frequencies.” When chatter occurs in milling, a new frequency appears in the sound that is not the runout frequency or the tooth passing frequency, and not harmonics (integer multiples) of those two. It is the chatter frequency. The chatter frequency is close to, but not equal to, one of the natural frequencies, and it is not connected to the tooth passing frequency. The chatter frequency sound mixes with the pure sounds of the tooth passing and the runout frequencies, and the resulting sound is harsh because the frequencies are not aligned.

So they would be closer to correct if they said they try to break-up "non-harmonics".

Thursday, September 8, 2011

Shop Floor Vending Feature on CNBC

Skilled Labor Discussion on CNBC



Matt Tyler of Vickers is a member of the National Tooling & Machining Association.

What if you could give your programmers or operators the skills of a skilled set-up machinist that you can't find?  They could calculate fully optimized and stable speeds, feeds and cutting depths for every job, every time.

Sunday, September 4, 2011

A New Perspective on Tool Balancing


There are plenty of reasons to balance your tool assemblies, but we will give you one you may not have heard:

REPEATABILITY

When you preset tool assemblies to the same projection, torque the knobs and screws to the correct values and balance them you eliminate all variation. If you have stable speeds, feeds and cutting depth, using a BlueSwarf Dashboard for example,  the your process will remain stable.