HD 4 clearance pass lines... HELP

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HD 4 clearance pass lines... HELP

Postby jaces » Mon Oct 30, 2017 11:47 am

Having problems running clearance path on a shark HD4. It started with just lines across the piece of material. (Which I assume is the z axis out of square and needs shimmed). But then it started to leave deeper cutting marks in the material as can be seen in the picture. But it is not consistent it only does it sporadically from start to finish... any help would be appreciated thanks.
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Re: HD 4 clearance pass lines... HELP

Postby Kayvon » Mon Oct 30, 2017 12:45 pm

Most of that will be caused by the router being out of square with the material. See http://www.cncsharktalk.com/viewtopic.php?f=7&t=4684 for some ideas on how to address that or some of the recent posts for more discussion.

You said it gets worse sporadically. I'm betting that's caused by feed rate variables. The bit rotation may cause the spindle to "prefer" a slight tilt depending on how fast it's going, both rotationally and linearly. I'll let someone with more experience chime in here.

You should post a full picture of that sign. It looks beautiful!
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Re: HD 4 clearance pass lines... HELP

Postby Rando » Mon Oct 30, 2017 4:54 pm

jaces:

When I see those rings where it's not a nice smooth pattern, to me it says "juttering". The head gets stuck, then lunges free, then stuck, and oscillates, bucking up and down. That's caused by much too great a depth of cut, and/or moving too fast through it by maybe as much as 40-50% (too fast).

Plus all the out-of-alignment stuff, but the plunging to bad depths is almost always because of taking too much, too fast, and in the wrong direction. The sharks HATE pushing the bit deeply into most materials. Pushing in the sense of movement in the direction along the t-track beds, where if you're standing with the gantry back-plate facing you, the gantry is moving away from you. When a normal bit gets pushed into a significant amount of material that it causes a spike in torque, the shark will deflect, and that moves the bit. You really do have to be gentle with the cutting parameters on these things. My advice would be stop imagining sizable chips are going to fly, and assume until you get it dialed in, cuts are going to be more conservative and take long, but with greater success.

Hope that helps clean up the mess.

Oh...and if you haven't already, add a finishing pass...and I recommend radiused endmills :D.

Regards,

Thom
Last edited by Rando on Tue Oct 31, 2017 10:20 am, edited 1 time in total.
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Re: HD 4 clearance pass lines... HELP

Postby Kayvon » Mon Oct 30, 2017 5:15 pm

Rando wrote:Oh...and if you haven't already, add a finishing pass :D.

VCarve makes this easy when you create a toolpath. You can manually specify the number of passes and make the final pass very shallow.
Last edited by Kayvon on Tue Oct 31, 2017 9:31 am, edited 1 time in total.
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Re: HD 4 clearance pass lines... HELP

Postby SteveM » Mon Oct 30, 2017 5:22 pm

Rando is correct.

Try slowing down your feed rate. If you go to fast, the head on the HD4 will bounce up and down and cause those marks.
There is far too much flex in the design of the HD4 router mount in my opinion. I had the same problems with mine.
I was never able to cut faster than 50-60 ipm. Any faster, causes the jitter in the router mount, which makes those marks.
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