Flycutting Acrylic 2

[kaizad]

Hi,

We are attempting to flycut an acrylic billet on a 3axis CNC high speed router (max rpm = 18000, max feed = 800ipm). So far we have used PCD inserts at different feed rates. The issue is the tool marks and also ridges at tool stepover. The feed rates were dropped to 50ipm and the tool marks were reduced, however not the ridges. Optical quality is very important for our application. I would appreciate it if someone can answer the following:

1. Is there a specific tool/insert that works best in this operation?
2. How can the toolmarks and ridges be minimized with a greater feed rate since time is a major factor?


Please let me know if you need further information. Any suggestions/advice will be highly appreciated.

Thanks.

 

[looslib]

Use a large nose radius insert.
Use a slower feed rate to control the stepover ridges.
I suspect you may have to polish the surface to really get optical quality.


"Wildfires are dangerous, hard to control, and economically catastrophic."
"Fixed in the next release" should replace "Product First" as the PTC slogan.

Ben Loosli
CAD/CAM System Analyst
Ingersoll-Rand

 

[jbel]

Acrylic has a high associated cutting speed. The use of PCD inserts will make the cutting speed values go through the roof. You probably cannot generate the correct cutting speed on your machine. The result being the material rubs and smears instead of shearing cleanly. We have cut this material sucessfully using Shear Hog end mills fron AB Tools. Information is available here:

http://www.abtoolsinc.com/shearhog.html

We did this in a machining center using coolant. Only a light diamond polish afterward was required to achieve optical quality. You may be able to do this with no coolant if you get your cutting conditions just right, i.e. all the heat from cutting to the chip and not built up in the work piece.

The previous suggestion to

Use a large nose radius insert.

is an excellent idea. Use the largest nose radius cutter possible as this will greatly improve your surface finish. When you cut this thing you should really be crusing with your feedrate. Use a good air blow so that you do not recut existing chips.

Consult with the material supplier to get a starting point for speeds and feeds for cutting the material.

 

[unclesyd]

Reading post ignited a spark about cooling. We machined a lot of various plastic parts
and one of the methods of cooling was with the Vortec Spot Coolers. This was predominate method for cooling while machining plastics.

http://www.vortec.com/solutions_cooling.php

 

[jbel]

The above mantioned cold air gus work well when cutting many plastics. Others benefit from the use of coolants. Both have their places. That being said, in the proper applications, the cold air guns are are excellent. They also work well when grinding very small steel parts.

 

[TVP]

I just wanted to add another concurrence with the suggestions already mentioned. The feed rate should be very high-- you do not want any dwell. The air blast is very helpful for clearing everything out of the way. My experience is that the air blast is better than use a liquid coolant/lubricant.