I am getting these swirl marks during my pocketing operations. It looks like it is where the bit changes direction. What are the causes of this?
Research has not given a clear answer. Is this due to a misaligned z axis?
Even with a well trammed spindle & tool, wood fibers do not cut the same in all directions & will tend to bend/flex instead of being cut cleanly off. Thus, you’ll see some tool marking which can usually be lightly sanded out.
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I suppose you mean that double ended Y shape? If that is what you are talking about then increase the IPM and the decrease depth of cut. Usually when you get those circles the bit is moving too slowly and large bits will be more pronounced than smaller bits. It looks like you are using a large diameter bit to remove the stock in the pocket.
Typically when you are out of tram the pocket is cut in a sort of square router. That produces ridges in either X or Y directions but they go from side to side and front to back. If the ridges are only on the front to back then your router needs to move left or right. If the ridges are accross the front and back from side to side then you need to shim the router to shift the router axis front to back.
The resolution is not high enough for me to see very well what you are talking about except for the double ended Y shape.
I was talking about the double Y. Thank you for the info. I am glad I don’t need to tram! It doesn’t seem like that is the issue here.
Those marks were made during a finish operation, so it was a very small depth of cut and the speeds were pretty high already 110ipm.
For the future if anyone runs across this issue, I ran some more tests. I am fairly certain that these marks are related to the jerk of the machine. In other words, when the machine changes direction there is a lot of momentum and that causes some movement that leads to these gouges. Turning the feed rate down helps–the gouging seems to be proportional to the feed rate.
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Okay, another update for posterity.
I played around a lot with fusion 360 and surface finish. Some loose learnings for the Shapeoko 5 Pro 4x4.
For surface finish, it is best to use a “3d Flat” with parallel selected toolpath after roughing or pocket. But, this will still leave marks. It just changes the location. Every parallel pass is linked by a rapid movement at the start of the pass…At this point, the gouging occurs.
The default acceleration for the machine is too high.
Using $120,$121,$122 = 250, I was able to pretty much remove the gouging from the Flat’s parallel. Surface speed doesn’t matter since the gouging occurs between passes.
For surface finish using a pocketing operation, much better results can be achieved in fusion 360, using smoothing deviation and a reduced machine acceleration.
Fusion’s smoothing deviation is how sharp the corners are for pocketing. Less sharp corners means less abrupt acceleration (jerk). This has a large impact on surface finish. For pocketing, I increased smoothing deviation to .05 to .1 (inches), and this greatly improved surface finish. But, it will still require sanding.
Could be caused by a flexible table that the machine is on.
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This very informative! thank you. You have given me another reason to start learning f360…any more experient results or details with some more info?
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