Drag knife gadget swivels

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mjuliana
Posts: 2
Joined: Wed Oct 19, 2016 2:21 pm
Model of CNC Machine: Shopbot PRS Alpha

Drag knife gadget swivels

Post by mjuliana »

Hi All,

My first post here.

I work at the Center for Furniture Craftsmanship up in Maine and we just bought a drag knife for our Shopbot CNC. I'm having an issue using the gadget to generate cutting paths. If I try generating a tool path on a rectangle, the corner swivels that result leave the rectangle still attached at the corners. It's not at all what I was expecting.

Please see the attached image to see the generate tool path.

Any thoughts or suggestions would be much appreciated.

Thanks,

Mark
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Screen Shot 2016-10-20 at 2.19.30 PM.png

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Adrian
Vectric Archimage
Posts: 14544
Joined: Thu Nov 23, 2006 2:19 pm
Model of CNC Machine: ShopBot PRS Alpha 96x48
Location: Surrey, UK

Re: Drag knife gadget swivels

Post by Adrian »

Run the preview and you'll see how it works.

mjuliana
Posts: 2
Joined: Wed Oct 19, 2016 2:21 pm
Model of CNC Machine: Shopbot PRS Alpha

Re: Drag knife gadget swivels

Post by mjuliana »

Thanks for the reply Adrian. The preview and actual cut both do the same odd thing to the corners. Here it is pictured below.

Thanks again!

-mj
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Screen Shot 2016-10-20 at 3.50.19 PM.png

kzeyus
Vectric Wizard
Posts: 346
Joined: Wed Sep 27, 2006 4:05 pm
Location: Rogers, AR

Re: Drag knife gadget swivels

Post by kzeyus »

The odd corners are to orient the drag knife to the new cut direction. The size of the corners is dependent on the blade offset you enter when setting up the toolpath. If the offset entered is correct for the knife you are using, it should cut a square corner.
Ken Zey
Rogers, AR
http://www.CedarSlabSigns.com
http://www.lookoutmercantile.com
Shopbot PRS Alpha 72x144

CosmosK
Vectric Craftsman
Posts: 151
Joined: Thu Jan 22, 2015 4:01 pm
Model of CNC Machine: multiple

Re: Drag knife gadget swivels

Post by CosmosK »

those patterns are correct. The cutting point trails behind the toolpoint, so the toolpath overshoots the corner (actually brining the knife point to the corner), then the swivel should pivot the spindle around the blade point (blade turns about its point). There is an option to lift Z during this pivot which can reduce tearing, but the blade point has to be in something to hold it is position during the pivot. Thickness of material can play into this. What are you cutting?
Pen Marking Tools from www.cosmos-industrial.com also>> CNC Drag Knife is back!

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