Drag Knife

[donek]

I built my first drag knife in 2000. It was developed for die cutting (inlayed) snowboard base graphics. Over the course of about a year and a half, I developed 2 different holders that were very effective in different circumstances. I set myself the goal of creating a new knife holder this summer that could do both jobs.

My new knife holder uses a standard irwin utility blade rather than an expensive custom blade. Having spent a bit of time looking for a commercial product, it came to my attention that there is a potential market for such a device. Tangential cutters are great, but far more expensive and not always necessary. I put together a second one that can be used for materials up to 1/8in (like cardboard and leather). Both holders can be used to cut a variety of substrates. I have used drag knives for cutting gaskets, snowboard graphics, leather, flexible magnet material and probably others. I have also used them to score ABS plastic to later be broken apart.

I am curious if others would be interested in such a device and what they might be willing to pay for one.

http://donek.smugmug.com/photos/i-bJPSzcp/0/XL/i-bJPSzcp-XL.jpg

[VanIslanddan]

Looks like a brilliant idea. Does it have a spring? Having the ability to adjust spring tension may alow you adjust for different material.

[donek]

Looks like a brilliant idea. Does it have a spring? Having the ability to adjust spring tension may alow you adjust for different material.

A knife like this is not intended for thin materials like sign vinyl. If you surface your vacuum table frequently enough, there is no need for a spring, just accurate zeroing of the knife. You can quite easily set it to just cut through your material without cutting into the table.

[knight_toolworks]

looks really good.I made one for 1/2" cardboard. I used the spindle to swivel it. but I had to have the knife have a lot of tilt backward about 1/2" or so. if I had it like yours the knife would not turn and would just bend going around a corner. 90 degree cuts I had to manually line up the blade and cut all of the cuts in one direction.

[curtiss]

Seems like the commercial one I saw somewhere was $150.. which would be ok if one used it all the time.

Does one need a spring ? Seems a cushion or a pad under the material to be cut would provide the nearly same function.

[donek]

looks really good.I made one for 1/2" cardboard. I used the spindle to swivel it. but I had to have the knife have a lot of tilt backward about 1/2" or so. if I had it like yours the knife would not turn and would just bend going around a corner. 90 degree cuts I had to manually line up the blade and cut all of the cuts in one direction.

That's some thick cardboard. The typical technique for making sharp corners is to raise the cutter to the surface of the material and move the cnc through a circle/arc with a radius equivalent to the offset, then lower the cutter into the material and resume cutting. Minimum cut radius is usually equivalent to the offset of the tip of the blade.


Seems like the commercial one I saw somewhere was $150.. which would be ok if one used it all the time.

Does one need a spring ? Seems a cushion or a pad under the material to be cut would provide the nearly same function.

The $150 cutter requires a $14 replacement blade and can only cut up to 1/32" thick material. I'd be surprised if it could really do that as the blade is similar to my vinyl plotter blade, and they wouldn't last long in such an application. They are very very small. Most gasket material is thicker than 1/32, as is leather, snowboard base material, and (I think) the flexible magnet I've cut. Perhaps the applications are too specialized to make production affordable. I could never produce them for $150. You could easily spend that on 10 blades for the other device. A pack of 50 blades for my holders costs $15. When you are cutting thicker material, there's really no need for a spring or cushion. Materials like ABS can be cut partial depth and then broken much like you score glass and break it. Some materials are forgiving of an almost complete cut, but as I said earlier, setup is quite simple as long as your table is surfaced periodically. We just skim off .005 to .010in once a month and we're good.

[Mayo]

It looks like a well made tool. But if you need to get more than $150.00 for it, I think you will have a limited market and the companies already in that market probably have expensive flat bed plotters that can handle thick materials. I'm just making assumptions here...

If you want to sell these to the occasional user, I think something between $50.00 and $100.00 would be an affordable price for a tool that saves time manually cutting various materials.

Have you tried using an Exacto blade with more of an angle on them?
They might allow cutting of thicker material if you have the cornering issue figured out.

Is your knife holder is a swivel holder which allows the blade to turn the corner because of the blade off set?

[knight_toolworks]

That's some thick cardboard. The typical technique for making sharp corners is to raise the cutter to the surface of the material and move the cnc through a circle/arc with a radius equivalent to the offset, then lower the cutter into the material and resume cutting. Minimum cut radius is usually equivalent to the offset of the tip of the blade.

I thought of that too but it was a hassle. I finally just drew everything straight cuts with just single lines and all x cuts and y cuts had the same start points. so I would cut all of the x cuts rotate the knife 90 and cut the y's
the cutting I did was fairly limited so it was ok and it did not change.
his is what I tried like yours but this would not work well it needed a lot more trail. I ended up having about 1/2" or so trail. once I had it I could cut these parts with little problem.
http://i154.photobucket.com/albums/s266/knighttoolworks/cnc%20videos/knife-1.jpg
http://i154.photobucket.com/albums/s266/knighttoolworks/boothster/IMG_0264.jpg

[donek]

I thought of that too but it was a hassle. I finally just drew everything straight cuts with just single lines and all x cuts and y cuts had the same start points. so I would cut all of the x cuts rotate the knife 90 and cut the y's
the cutting I did was fairly limited so it was ok and it did not change.
his is what I tried like yours but this would not work well it needed a lot more trail. I ended up having about 1/2" or so trail. once I had it I could cut these parts with little problem.


I see no bearings in your cutter Steve. You have to have bearings. The spindle or router has way too much mass to be turned by the tip of a knife blade. Minimal inertia and freely spinning bearings are critical.

[donek]

Just a quick video of the motion on the knife. I'll try to put together some video of the knife in action this week.

Looks like I can't embed, so here's a link:
http://youtu.be/_9G2IZlW0gY

[knight_toolworks]

I see no bearings in your cutter Steve. You have to have bearings. The spindle or router has way too much mass to be turned by the tip of a knife blade. Minimal inertia and freely spinning bearings are critical.
Hey why did you not tell me that 4 years ago?? (G)
I just needed to cut that 1/2" cardboard cleanly and this was the only way I could do it. so I hacked it out after several tries. but I wonder if it is just the bearings. I can't remember but it seemed I had problems cutting straight too until I added the trail. but I can't remember for sure.

[donek]

Hey why did you not tell me that 4 years ago?? (G)
I just needed to cut that 1/2" cardboard cleanly and this was the only way I could do it. so I hacked it out after several tries. but I wonder if it is just the bearings. I can't remember but it seemed I had problems cutting straight too until I added the trail. but I can't remember for sure.

There are a number of things to consider. That's why I didn't get it right the first time. I've produced a number of prototypes on these things over the years. Some were successful and others were not. Unfortunately, it's not something you can just go and produce and have it work right away. I started thinking about this particular knife design about 6 months ago. I finally began work on the first prototype last Monday. I believe I have produced about 8 versions of it in the last week. The cutters in the picture will endergo one last version tomorrow. At that point, I believe, the design and prototype phase will be complete. I'll have a functional tool for next seasons production and I would imagine some of the board/ski manufacturers who purchased my previous knife holder will purchase this one. The inexpensive blades will pay for the new holder pretty rapidly. The question is if other cnc users will find it to be a good addition to their tool kit. It has the potential to open new avenues that are not open to the typical cnc router machinist.

[knight_toolworks]

it is complex for something so simple. thinking about it I doubt a bearing would have helped on the 1/2" cardboard it took almost all of my prtalpha power to cut it in one pass. but thinner material of course is a whole other ballgame. I would be interested though I don't usually need a knife anymore. But I od have a ski manufacturer I make parts for.

[donek]

2 1/2 weeks on development of this thing. I finally have it dialed.

http://youtu.be/r88r3prPhjc

[larry_r]

Very impressive!

[beacon14]

That is very cool!

[steve_g]

Sean

Where do I sign?

SG

[donek]

Sean

Where do I sign?

SG

Just give me a call and I'll get you one.

[cnc_works]

Very cool...would it cut hide leather, maybe 1/16" to 1/8" thick?

[donek]

Yes. The knife offset is .060, but it protrudes .150in. If you cut something thicker than 0.060, you're best off making two passes at it. I will likely produce a version with a 1/8in offset and a bit more protrusion. You loose a bit of fine detail and your tightest possible corner/turn increases. You typically don't want to cut a radius smaller than the offset. Sharp corners are performed by raising the cutter so the tip is just in contact with the surface, and then moving the machine through a circle (radius close to offset) and then lowering the cutter back into the material and continue cutting.



Very cool...would it cut hide leather, maybe 1/16" to 1/8" thick?

[paul_z]

Sean,

You have a PM.

Paul Z

[sawkerf]

I'm interested too, would artcam insignia software be suitable for this?

[danhamm]

I was interested to, till I found out the price...I'll keep on using my modified "cricuts"

[sawkerf]

What's the cost?

[David Iannone]

Yeah, what is the cost? I would like to cut shipping boxes out of 1/4" thick cardboard.

[gundog]

Yeah, what is the cost? I would like to cut shipping boxes out of 1/4" thick cardboard.

I am also interested both in cost and whether or not it can cut 1/4 box material.

[donek]

I'm interested too, would artcam insignia software be suitable for this?

I'm not familiar with that software. All you really need to be able to do is generate a tool path, specify the order and direction of cut and cut along the path.


I was interested to, till I found out the price...I'll keep on using my modified "cricuts"

I am attempting to eliminate the major price difficulty. I am investigating a number of issues to correct the issue. If I can, the price will drop significantly. There is a fairly high tolerance operation that follows the primary cutting of the parts. It has generated a significant amount of waste parts. If it can be corrected, the price will come down.


What's the cost?

I'm working on bringing it down. If you PM or e-mail me, I will update when I have that information.


Yeah, what is the cost? I would like to cut shipping boxes out of 1/4" thick cardboard.


I am also interested both in cost and whether or not it can cut 1/4 box material.

The present holder can not accommodate 1/4in cardboard, but could be relatively easily adjusted to do so. It will result in loss of detail on small parts. Most cardboard I am familiar with is 1/8in thick. Are you certain on the thickness?

[gene]

I would be interested also

[nightmare_dev]

sent pm, stoked to work with this.

[donek]

A friend of mine asked me today if the drag knife was capable of cutting veneer for inlay. I told him I didn't know, but I had a few veneer samples so I'd give it a shot. With a little experimenting it worked out great. The inlays are just as tight as those in plastic.

Here's a video of the procedure:
http://youtu.be/csk0QrvMHwM

and a photo of the end result:
http://donek.smugmug.com/photos/i-f739C4x/0/XL/i-f739C4x-XL.jpg

[gundog]

The knife changes direction with just the movement of the spindle correct? It does not have to have spindle orientation does it?

PS I got your email but I have been out of town I will get back to you soon.

Thanks Mike

[donek]

The knife changes direction with just the movement of the spindle correct? It does not have to have spindle orientation does it?

PS I got your email but I have been out of town I will get back to you soon.

Thanks Mike

Just as it says in the video, you do not supply any power to the spindle. The tip of the blade is slightly behind center and the holder incorporates bearings that allow it to swivel to the necessary orientation.

[Rick W]

OK Sean,

I'm interested as well!!

Thanks

Rik

[donek]

e-mail sent


OK Sean,

I'm interested as well!!

Thanks

Rik

[gundog]

The present holder can not accommodate 1/4in cardboard, but could be relatively easily adjusted to do so. It will result in loss of detail on small parts. Most cardboard I am familiar with is 1/8in thick. Are you certain on the thickness? http://www.talkshopbot.com/forum/images/buttons/quote.gif (http://www.talkshopbot.com/forum/newreply.php?do=newreply&p=131047)

No I am not sure I am just wanting to cut cardboard for making shipping boxes I thought they were 1/4" but you are probably right they might be 1/8"

Mike

[jerry_stanek]

there are different types of cardboard. the standard is 1/8 but there also is double wall that is 1/4 thick. we use both for boxing products depending on what we are shipping.

[donek]

No I am not sure I am just wanting to cut cardboard for making shipping boxes I thought they were 1/4" but you are probably right they might be 1/8"

Mike


there are different types of cardboard. the standard is 1/8 but there also is double wall that is 1/4 thick. we use both for boxing products depending on what we are shipping.

The current knife is capable of cutting up to 1/16in deep. Some semi rigid plastics can be scored to this depth and broken the rest of the way. Most softer materials, such as cardboard and leather allow the cutter to wander. This issue can be corrected, but I need clarification on some of the limits.

The question becomes, Would you be willing to have a knife that could cut these materials, but could not cut a tight corner or would have a minimum cutting diameter of 1/4in or 3/8in?

[gundog]

The current knife is capable of cutting up to 1/16in deep. Some semi rigid plastics can be scored to this depth and broken the rest of the way. Most softer materials, such as cardboard and leather allow the cutter to wander. This issue can be corrected, but I need clarification on some of the limits.

The question becomes, Would you be willing to have a knife that could cut these materials, but could not cut a tight corner or would have a minimum cutting diameter of 1/4in or 3/8in?

For my use I do not need to cut inlays just cardboard for boxes I have vacuum hold down for the material.

Mike

[donek]

For my use I do not need to cut inlays just cardboard for boxes I have vacuum hold down for the material.

Mike

I'm testing a second model right now. Programming boxes is challenging, but I almost have it.

[gundog]

The boxes I plan to make will be this style http://www.uline.com/BL_1304/Jumbo-Kraft-Easy-Fold-Mailers

Unfortunately they do not make the sizes I need. The products I need the boxes for are not very tall 2.5" high but up to 40" x 16" and as small as 10" x 6" I need about 6 different sizes having them custom made requires me to stock a huge number of boxes and I do not have room to store them.

You can see designing the type box above is pretty straight forward. I plan to make a spring loaded roller to make the creases for folding the boxes. I could make the cutter too but time is something I am short of and if your cutter will work for me I would choose to buy one rather than making my own.

Mike

[donek]

I have developed a second model for cutting thicker materials. It can definitely cut material that is 0.150in thick. It should be possible to cut up to 1/4in thick materials as well, but I have not tested that yet. Here are a couple of sample videos showing it in action.

http://youtu.be/P8jbtRTV6uw
http://youtu.be/bMoRUZnvbXw

[donek]

I did a quick test this morning in some 1/4in cardboard. It's actually 0.290in thick material. I just used spray adhesive to laminate two standard layers. It worked fine, but did not seem to want to cut a circle smaller than 2in diameter. Corners would be no problem if programmed correctly.

http://donek.smugmug.com/photos/i-kgRTDTr/0/XL/i-kgRTDTr-XL.jpg

[geneb]

So what's the asking price for this gadget?

g.

[evan]

Inquiring minds want to know.

[donek]

So what's the asking price for this gadget?

g.


Inquiring minds want to know.

PMs sent to both of you.

[gene]

Hi , send me a pm with a # in it

[donek]

The price for the tool is $189.

[evan]

Thank you.

[knight_toolworks]

well got the knife today and only spent a bit of time with it. but it cut some .03 sintra with no problems and I had a little bit of veneer to try. There will be some tricks on the inlay to get great results like rounding corners and such maybe mirroring the inlay part so the bevel is facing down.

[gundog]

I got mine also is there any programing strategies I should know? How much offset does the blade tip have from center line? I am going to design a small cardboard box and see how it comes out.

Mike

[donek]

I got mine also is there any programing strategies I should know? How much offset does the blade tip have from center line? I am going to design a small cardboard box and see how it comes out.

Mike

The thick material knife has an offset of 0.160in. I am working on a video explaining the programming strategies this weekend. I will post a link by the end of the weekend.

[gundog]

I just drew this up what do you think? I extended each vector by .250" to make sure my cuts intersect. The small pieces in the inside corners are to fold in so there is not gap in the corner of the boxes. How fast should I feed the cutter I was thinking like 6" a second?

[donek]

I just drew this up what do you think? I extended each vector by .250" to make sure my cuts intersect. The small pieces in the inside corners are to fold in so there is not gap in the corner of the boxes. How fast should I feed the cutter I was thinking like 6" a second?

It looks like it will work. Test your feeds on some scrap. 6ips should work, but you can sometimes get speed wobbles if you go too fast.

[jim_ludi]

Sean, you mentioned a video, "...I am working on a video explaining the programming strategies this weekend. I will post a link by the end of the weekend.", and I'm wondering if you ever posted it?

I'm interested in your drag knife and am curious about the programming required.

[donek]

Sean, you mentioned a video, "...I am working on a video explaining the programming strategies this weekend. I will post a link by the end of the weekend.", and I'm wondering if you ever posted it?

I'm interested in your drag knife and am curious about the programming required.

Unfortunately I have not had the time to finish that project yet. It is coming though. Basic programming is as simple as generating a tool path and telling your cad cam software to cut on the vector. More advanced stuff that involves swiveling the blade at the corners rather than crossing an existing too path is a bit trickier. That is what is intended in that video. I am leaving on vacation tomorrow, so it will be a bit longer. Sorry for the delay.

[terryjones]

The price for the tool is $189.
Sean,
I am thinking about doing veneer inlay. Would you suggest the D1 or D2 for an all around work including veneer inlay. I would like to purchase.:)
Terry

[donek]

Sean,
I am thinking about doing veneer inlay. Would you suggest the D1 or D2 for an all around work including veneer inlay. I would like to purchase.:)
Terry

I did all my veneer demos at IWF with a D2 and a safety blade. A safety blade reduces the offset in a D2 to about .090in. You get almost the same detail as a D1. If versatility is your goal, the D2 is the right choice. If all you wish to do is veneer, than the D1.

[terryjones]

I did all my veneer demos at IWF with a D2 and a safety blade. A safety blade reduces the offset in a D2 to about .090in. You get almost the same detail as a D1. If versatility is your goal, the D2 is the right choice. If all you wish to do is veneer, than the D1.

I never want to close a door to potential oportunities, so the D2 sounds like a winner. Are they both the same price at $189.00? Send me an email to process. tljrns@cableone.net.

[donek]

I never want to close a door to potential oportunities, so the D2 sounds like a winner. Are they both the same price at $189.00? Send me an email to process. tljrns@cableone.net.

You can go to donektools.com or call shopbot to purchase.

[terryjones]

You can go to donektools.com or call shopbot to purchase.

Thank you for the information.

[frank134]

sean what happen to the price of 189.00 ? If you get both is it less. Please pm me and let me know. the price on your web site seen a bit high.
Thank
Frank

[donek]

sean what happen to the price of 189.00 ? If you get both is it less. Please pm me and let me know. the price on your web site seen a bit high.
Thank
Frank

The introductory price of $189 ended shortly after IWF. I'm sorry, but it is often necessary to make adjustments when starting a new venture.

[zandeauto]

So I am ready to purchase a drag knife this week. I am very interested in your Donek Knife, but I need some help on getting past the price. I have found three brands of drag knives online and the price spread is huge. Maybe some of you can help me with this.

I will be cutting thermoplastic laminate sheeting .030 thick.

Here is what I have found.

http://www.rockcliffmachine.com/products-page/cnc/cnc-drag-knife/

This rockcliff drag knife is the least expensive for only $85 and that makes trying it almost my first choice. The two downsides I could possibly see is that the blade looks to be cutting on center and not behind the spindle. Would this make decent turns? Also the price of replacement blades is 3 for $29. Does anybody know how much longer these blades could last since they are carbide? Other positive note is they will accept a return on this knife if I am unsatisfied with it performance.

Next is the widgetworks knife.

http://www.widgetworksunlimited.com/CNC_Sign_Vinyl_Drag_Knife_Bit_p/cnc-vinyl_knife.htm

This one is $149.99 and has its limitations to 1/32" thick. Replacement blades are $13.99 and the blade also seems to be on center. I'm not sure that I am really even considering this one because of its limitation on thickness.

And of course the Donek Drag Knife.

http://donektools.com/

This one appeals to me most for a few reasons. Blades are cheap to replace, it seems to have better rotating action with the blade behind the spindle a bit, has the software for adding corner actions to tool path, and will cut thicker material. I just am having a hard time getting by the price.

[jerry_stanek]

Do you have to use a lead in cut to start at the proper point

[zandeauto]

Do you have to use a lead in cut to start at the proper point

In my case it wouldn't matter, but if the tools doesn't require it I would not.

[donek]

So I am ready to purchase a drag knife this week. I am very interested in your Donek Knife, but I need some help on getting past the price. I have found three brands of drag knives online and the price spread is huge. Maybe some of you can help me with this.

I will be cutting thermoplastic laminate sheeting .030 thick.

Here is what I have found.

http://www.rockcliffmachine.com/products-page/cnc/cnc-drag-knife/

This rockcliff drag knife is the least expensive for only $85 and that makes trying it almost my first choice. The two downsides I could possibly see is that the blade looks to be cutting on center and not behind the spindle. Would this make decent turns? Also the price of replacement blades is 3 for $29. Does anybody know how much longer these blades could last since they are carbide? Other positive note is they will accept a return on this knife if I am unsatisfied with it performance.

Next is the widgetworks knife.

http://www.widgetworksunlimited.com/CNC_Sign_Vinyl_Drag_Knife_Bit_p/cnc-vinyl_knife.htm

This one is $149.99 and has its limitations to 1/32" thick. Replacement blades are $13.99 and the blade also seems to be on center. I'm not sure that I am really even considering this one because of its limitation on thickness.

And of course the Donek Drag Knife.

http://donektools.com/

This one appeals to me most for a few reasons. Blades are cheap to replace, it seems to have better rotating action with the blade behind the spindle a bit, has the software for adding corner actions to tool path, and will cut thicker material. I just am having a hard time getting by the price.

Everything comes down to thickness in my opinion. The other two devices will cut vinyl and sandblast material. Anything thicker and you're going to struggle. Our tool is designed for cutting materials other than vinyl. In reality, I have never tried cutting vinyl with it as I have a vinyl plotter for that purpose. If you just need to cut sign vinyl, then look at the other two devices or something like this:
http://www.amazon.com/USCutter-Vinyl-Cutter-Plotter-Stand/dp/B003D22H26/ref=sr_1_1?ie=UTF8&qid=1354568455&sr=8-1&keywords=vinyl+plotter
If you wish to perform veneer inlays, cut cardboard, gaskets, some plastics, leather, (the list is extensive), then our tool is the only one I know of capable of doing so for less than a $5000 investment.