Troubleshooting Fuzzy Cut Edges on Plywood with CNC
Suggestions for programming tricks, climb cutting, bit choices, and sanding attachments for a CNC user who's getting fuzzy edges. August 22, 2013
Question (WOODWEB Member) :
I am having some issues with fuzzy edges left on 19mm. plywood on my CNC. I am cutting with 1/2" 2 flute chipbreaker compressions running about 18,000 rpm at a rate of 18 m./min. I have in the past just completed two cuts (one clockwise and the other counter clockwise). This then takes twice as long - any suggestions?
Forum Responses
(CNC Forum)
From Contributor G:
Are you climb cutting or cutting against the rotation?
From Contributor D:
With plywood you will get a much cleaner finish with a power cut as opposed to climb cut.
From the original questioner:
I have a two field CNC so one side cuts with rotation while the other cuts a mirror image therefore climb cutting (counter clockwise). I do notice a better finish when climb cutting. I suppose the best would be to climb cut in both fields but doing that in nesting could take some programming tricks.
From Contributor U:
It used to drive me crazy that the router reversed direction of travel around the part when using the right hand fields. I have since learned that I can use a conditional jump at the start of my program (Biesse Rover) to run two entirely different sub programs within the main. This has elevated a lot of problems for me, cut quality, sizing because of climb vs. conventional cutting, width of dados, etc. You still need to write two different router programs but they just run seamlessly within the main instead of needing to run two different programs in the work list. This may help for some of your jobs.
From the original questioner:
After talking to the tech at Biesse (I run a rover as well with Biesseworks) he showed me a trick on my piece variable to export the symmetry. I still get mirror cuts in both fields but now I get the same direction of cut. I simply program my millings in reverse therefore getting a climb cut in both fields - problem solved!
From contributor S:
I have customers that had the same problem and I switched them to a triple flute compression and it ran much better for them with longer tool life.
From contributor R:
To eliminate the fuzzing use a 3 flute compression with serrations. We have been doing this for years for our customers.
From contributor F:
Could you guys define your fuzzy plywood? The issue I have is with the plies that run perpendicular to the cut. I want the edges to be extremely smooth, as they do not get banded, but the plies that are cut as end grain don't look so hot. I'm using 3/4" birch Europly and the long grain parts are great, but the end grain parts are more pitted, like it's ripping out parts of those plies. Is this the fuzzy that you describe, because that's the issue I'm trying to solve.
Will the direction help this issue? Do chipbreakers address this? Do I just need to do an offset cut and a final pass where I shave off the final 1/32"? I would prefer an easy solution, like direction or different tooling, but the sanding required to deal with this issue unresolved is so time consuming, I'm happy to add an extra step if this is the way to go.
From contributor R:
A 3 flute compression chipbreaker will stop your issues. One pass and a perfect edge finish.
From contributor M:
Try putting a small Flex Trim head on a secondary holder and following the cut with a brush sanding. You will be amazed at what these heads can do for edges on a CNC machine.
