Sunday, December 10, 2017

Jobs vs Research

30-second Challenge

Most people with milling machines are in the business of taking jobs and cutting them. However, once in a while, there is a question asked, or a challenge to be met, as is the case with our latest blog.

A company in particular, which we can not name, needs to face mill samples of material, which are then used for metallurgical testing. Depth of cut needs to be enough to get to get all the scale off and show clean metal. The question was; can this process be done on a small CNC, like the Tormach PCNC 440? Also, can the process be automated, and most importantly, can the cycle time be reduced to under 30 seconds?

In this case, tooling was provided by the tooling supplier, as well as two of the sample pieces. While the material is proprietary, we did learn the hardness was around 54-55 on the Rockwell C scale. 

The cutting tool supplied for the testing was a four-flute 1/2" dia cutter, with a 0.03" corner radius. Since we only had two samples available to us, we would not be able to perform dozens of speed/feed cut combinations.

We used HSM Advisor, with a downloaded power profile for the PCNC 440. After inputting some data, and doing some calculations, we were able to get the cycle time down to 23 seconds, as shown in the video below. You can hear the spindle draw as the cut starts, but it mills the pieces completely, and in 23% less time than requested.

Moving forward, the mill is large enough to hold several test samples. Either a custom fixture could be made, or they could simply use a self-centering vise, such as a 5th Axis Deuce, to hold multiple parts.

Other tooling to try

With this project, the tooling was provided. However, we would like to try inserted tooling to see if additional speed benefits could be obtained. Cutters like these toroidal cutters with round inserts may allow for additional chip thinning, and faster feed rates.

However, the project was definitely a success. We are able to get a more than acceptable cycle time, we can automate the process, and it can be done on an affordable, compact, CNC mill.

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