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Cutting Cardboard - Drag Knifes

Cutting Cardboard - Drag Knifes

Postby evillarr » Sat Mar 15, 2014 1:08 am

Hi, has anyone attempted to use their buildyour CNC to cut cardboard using a drag knife?

Form what little I know from this art, the router or spindle is constantly rotating.
Can the rotation be controlled to direct the orientation of a drag knife to cut cardboard?
Is it a matter of the software I use or/and if it is a router or spindle?

I am looking into purchasing a green bull to work with cardboard sheets and paper prototypes that need to be cut not routed.
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Re: Cutting Cardboard - Drag Knifes

Postby Awesomeness » Sun Mar 16, 2014 2:00 am

1. Do you mean cardstock, as in thick paper, or corrugated cardboard? Corrugated cardboard will be very difficult to cut, because of the extreme thickness's impact on how a drag knife works. Cardstock isn't a big problem.
2. Yes, the spindle is normally constantly rotating, when used as a router. However, with a drag knife, you turn it off, and let it free-turn as the machine drags the knife around, literally as the name implies.
3. No, the rotation of the router/spindle can not be indexed to a specific position. Since you don't need the router/spindle though, you could always take it out, and put in another stepper motor that could do this.
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Re: Cutting Cardboard - Drag Knifes

Postby keith » Fri Mar 28, 2014 7:46 pm

If you take a look here:
http://donektools.com/
I think all your questions will be answered :D

If I can figure out a way I am going to order one :D
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Re: Cutting Cardboard - Drag Knifes

Postby Awesomeness » Fri Mar 28, 2014 8:23 pm

Yeah, that guy is here in Colorado! I saw him a few months ago at the Maker Faire Mini. It looked like it worked pretty well.
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Re: Cutting Cardboard - Drag Knifes

Postby keith » Tue Apr 08, 2014 8:26 pm

Awesomeness this is a longshot I know but you know how you managed to get us all a FANTASTIC deal on the BobCad software......

Any chance on a deal for us for the Donek Dragknife.... ;)

If you don't ask you don't get, right ;)
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Re: Cutting Cardboard - Drag Knifes

Postby Awesomeness » Tue Apr 08, 2014 9:23 pm

You never know. I could contact him and see.

I'm still really curious to know why it costs $240. Even if he's making 100% profit, $120 seems way too much. It's a CNC'd/laser-cut aluminum blade holder, and a CNC lathed arbor. Nothing about it is especially extravagant in the machined-part world.
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Re: Cutting Cardboard - Drag Knifes

Postby kevinl » Wed Apr 09, 2014 2:28 pm

wonder how hard it would be to make one, his price probably has quiet a bit of R&D time..

in designing, you would have to experiment on how far off center the cutting tip would need to be for the pivoting acting of the drag knife, which i believe would control or limit your cutting radius...

parts: two bearing, a spring, 2" x 1" round stock & maybe a 3" x 4" x 1/2" flat stock.. your flat stock replacement would be the main cost.. the hardest part to me would be figuring out how to turn the stem that fits in the bearing once the flat stock part was machined..
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Re: Cutting Cardboard - Drag Knifes

Postby Awesomeness » Wed Apr 09, 2014 2:36 pm

We have a Denver Mini Maker Faire coming up next month. I wonder if he'll be there, and I can take a look at one close up?

There may be R&D time in the price, but how much, and why? It's not some kind of super-complicated piece of equipment. It's a knife blade holder, that spins.

It also comes in a custom machined and laser engraved wooden box. Will he take $25 off the price if I don't want that thing wasting space in my garage?
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Re: Cutting Cardboard - Drag Knifes

Postby keith » Wed Apr 09, 2014 8:26 pm

PLEASE don't anyone think I am saying anything at all negative about DonekTools, however you are right I do think that it is VERY expensive. :(

Why he wants so much I have no idea. I do know that Brian Oltrogge of Grunblau fame wanted one and went ahead and designed and built one himself, see here on CNCZOne

http://www.cnczone.com/forums/diy-cnc-r ... og-12.html

I know his has a larger visible bearing but is is essentially the same. If you do manage to see him Awesomeness perhaps he might be interested in making some sort of deal.

Good Luck :D
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Re: Cutting Cardboard - Drag Knifes

Postby Awesomeness » Wed Apr 09, 2014 9:00 pm

kevinl wrote:wonder how hard it would be to make one... the hardest part to me would be figuring out how to turn the stem that fits in the bearing once the flat stock part was machined..


keith wrote:Why he wants so much I have no idea. I do know that Brian Oltrogge of Grunblau fame wanted one and went ahead and designed and built one himself, see here on CNCZOne

http://www.cnczone.com/forums/diy-cnc-r ... og-12.html

I know his has a larger visible bearing but is is essentially the same.


From the looks of Grunblau's parts, I think it should be fairly easy to make. Don't go buying one yet. I'm going to talk to Donek if he's at Maker Faire, and then I'll design something similar/better up and see if I can get a decent quote to get them produced by a local machine shop.
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