Friday, September 12, 2014

FridayCutFacts: How to Use a Router to Cut Aluminum for Sign Letter Fabrication.

If you are looking to prevail in the sign industry where flexibility and versatility are necessary for a business to succeed, then adding a reliable CNC router to your workflow is a no-brainer.

Whether you are working with wood, foam, or acrylic a CNC router can help generate the superior products that customers envision. But one question we are frequently asked by manufacturers is "Can your routers cut aluminum as well?" Our answer is always a resounding, "Yes! As long as you do it correctly."

There are a few things know about cutting aluminum on a router before you begin. First, like all materials, there is a "Sweet Spot" for the best feeds and speeds. When cutting aluminum, the "Sweet Spot" is much smaller, and the chances for breaking a bit and outputting a poor surface finish are increased. Secondly, aluminum heats up and becomes sticky when cutting, so if you venture outside of the "Sweet Spot" aluminum deposits will begin to weld themselves to your tooling or your cut piece.

To help you visualize the "Sweet Spot" for speeds and feeds of cutting aluminum, take a look at the chart below.

Here is a breakdown of the different zones in the graph.

High Chipload Feed: When your feedrate is too fast for a given spindle RPM, you're chances of breaking the bit are almost certain.
MRR: Running the spindle as fast as you can without burning the bit and feeding as fast as you can without breaking the bit is the "Sweet Spot" for Maximum Removal Rates.
Too Fast: Too much spindle speed will generate excess heat which softens the tool and dulls it faster. 
Best Tool Life: Slowing down the spindle a bit and feeding at slightly less than appropriate for maximum MRR gives the best tool life. 
Surface Finish: Reducing your feedrates while keeping the spindle speed up lightens the chipload and leads to a nicer surface finish. There are limits, the biggest of which is that you'll eventually lighten the feedrate too much, your tools will start to rub, and tool life will go way down due to the excess heat generated by the rubbing.
Older Machines: So your spindle speed has come way down, and in addition, so has your feedrate. You're probably on an older machine where you can't run the kind of speeds you need to take advantage of carbide tooling. You may need to switch to HSS. 
Feeding Too Slow: Feeding too slow leads to rubbing instead of cutting, which can radically shorten your tool life and is to be avoided.

PUTTING IT TO THE TEST:

When cutting 6061 1/8 inch aluminum for sign letter fabrication we used a 63620 Stub Nose 1/4 inch Up-Cut Bit at 22,000 RPM and at speed of 100 in./min.
Multicam Cutting Aluminum

Multicam_Aluminum1

 HELPFUL TIP: Be sure to use a lubricating mist to cut down on the tendency for the chips to stick to the cutting edges. The optional mister on thisMultiCam 3000 router provides both an air blast and a coolant mist.
Multicam_Aluminum2

Notice how these chips aren't too flaky! They are exactly what you want to see when cutting aluminum. Its a good sign that your feeds and speeds are in the "Sweet Spot". At 22,000 RPMs, the chips produced were hot enough to transfer the heat to the chips instead of the finished piece or the tooling.

multicam_aluminum3

Here is our finished piece. As you can see cutting aluminum is entirely possible with a CNC router. It's just a matter of matching your machines capabilities to the "Sweet Spot" feeds and speeds of the material. 

multicam_cnc_aluminum4

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2 comments:

  1. Fellas, would really appreciate you linking back to CNCCookbook where your sweet spot graphic originated: http://www.cnccookbook.com/CCCNCMillFeedsSpeedsBasics.htm

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