Drag Knife Gadget?

Post general information and questions relating to Cut2D in this Forum.
Post Reply
willower
Posts: 16
Joined: Fri Nov 13, 2009 8:06 am

Drag Knife Gadget?

Post by willower »

Have looked to find this gadget after reading :-

https://docs.vectric.com/docs/V9.0/VCar ... lpath.html

Have looked everwhere I can think of to find this gadget - with exactly nil success.
I know the page is dated 2018 and things have maybe moved on a bit, but it should be around somewhere surely?

If anyone has a copy of this, I sure would appreciate a copy - having just made a drag knife holder for a Roland Blade holder on my shapeoko 2, it would sure save me a whole lot of messing around trying to establish successful toolpaths by trial and error!.

Am I the only one who wants to make the odd vinyl sign using Cut2D desktop?

Many thanks to anyone who can help....

User avatar
gkas
Vectric Wizard
Posts: 1450
Joined: Sun Jan 01, 2017 3:39 am
Model of CNC Machine: Aspire, Axiom AR8 Pro+, Axiom 4.2W Laser
Location: Southern California

Re: Drag Knife Gadget?

Post by gkas »

Cut2D Pro supports Gadgets, Desktop does not. Compare Products https://www.vectric.com/products

willower
Posts: 16
Joined: Fri Nov 13, 2009 8:06 am

Re: Drag Knife Gadget?

Post by willower »

Don't see an expensive upgrade as a good cost effective way of gettig where I want to be, Ijust hope there are others who could maybe help me with the basic tool settings for using a drag knife using Cut2D. Its easy enough to add a tool and modify the settings, I just wonder if somebody has already done so and is willing to share their experience?

Working with what you already have (and know) is half of the pleasure of this hobby....

User avatar
Adrian
Vectric Archimage
Posts: 14504
Joined: Thu Nov 23, 2006 2:19 pm
Model of CNC Machine: ShopBot PRS Alpha 96x48
Location: Surrey, UK

Re: Drag Knife Gadget?

Post by Adrian »

At the end of the day it's just a very thin endmill as far as the software is concerned. The "trick" is creating vectors that have the correct loops for the corners etc. The Fillet tool is your friend here as it will create Plasma/Drag knife fillets.

Some drag knives need an offset in the vectors/toolpaths as the cutting point of the knife isn't aligned with the tool centre. That's basically what the gadget does. It automates the fillets and offsets.

User avatar
gkas
Vectric Wizard
Posts: 1450
Joined: Sun Jan 01, 2017 3:39 am
Model of CNC Machine: Aspire, Axiom AR8 Pro+, Axiom 4.2W Laser
Location: Southern California

Re: Drag Knife Gadget?

Post by gkas »

Donek Tools has some software utilities. https://donektools.com/

willower
Posts: 16
Joined: Fri Nov 13, 2009 8:06 am

Re: Drag Knife Gadget?

Post by willower »

This is my take on the making of a vinyl cutter head for my Eshapeoko CNC machine.
Image


I have looked at soooooo many different ways of doing this by others, but all seemed to have one or other areas that I wasn’t too keen on. The primary fault in most designs - as I saw things, was the inability to be able to control the pressure on the knife point – most designs relying on a spring of some unknown quantity (or rubber band!) to exert the requisite force on the knife blade without actually knowing what that force was!

Roland are quite specific in their recommendations when it comes to blade pressure and go to some lengths with their machines to allow users to set the required force via the control menus in their machine firmware.

One of the biggest benefits of using some kind of ‘spring’ operated drag knife, is that it overcomes any poor alignment between the cutter and the machine bed. Let’s just remember that we are trying to cut the vinyl and not the backing paper as well.

My vinyl (from Hobbycraft here in the UK) was measured using a micrometer and showed that the actual vinyl layer was only 0.09 mm thick (0.004”). So, there is not a lot of leeway there if you happen to have a slightly misaligned or uneven machine bed is there?

My Shapeoko clone (eShapeoko from Amber Spyglass here in the UK), properly trammed and using a machine levelled waste board, might, on a good day – be able to cope with this level of required accuracy, but I still doubt it would be able to handle it on a regular basis. As I have to remove my spindle and replace it with a drag knife setup, this alone could upset the applecart when it comes to that kind of tolerance level.

As a result, my design had to be a full ‘floating’ type drag knife which could cope with inaccuracies far higher than 0.1mm variation. It should also have the option to add or remove weights – depending on the type of vinyl being cut. Some of the more exotic vinyl’s like Flock for instance, require a much higher pressure.

As you can see from the photograph, I have used a small (40mm) linear slide to mount my cutter head. It is probably one of the more expensive ways of having a floating cutter head, but it is very smooth in its operation with virtually zero play in any axis other than the Z axis, - and I am very happy with the way it works. The whole thing is all mounted on a short length of 16mm diameter stainless steel curtain rail, nice and strong (and was something I had here laying around!)

The knife blade is set so that only approximately a quarter of a millimetre extends beyond the cutter head. This make zeroing of the Z axis easy, I use a 0.010” feeler gauge and probe down until contact is established with the underside of the cutter head. I then zero out my Z axis in my CAM software – (I use openCNCPilot, a really great piece of software).

Once all is set, I just add the weight box (with the appropriate amount of lead in it) on top of the Cutter Block and run my job. I usually set my cutting depth to 2 or 3 mm below Z Zero (just to make sure that the cutter block is off of its bottom stop) and let the software run its course. Remember to set the retraction height to something like 10mm to make sure the knife is not dragged across the vinyl between the areas being cut out.

I have to say that I am extremely impressed with the way this works. It cuts beautifully and is easy to weed out when done. No more worrying if the bed is flat or whether it will cut through the backing paper…Happy days…..
Image


Willower
Attachments
IMG_0697a.jpg
IMG_0689.jpg

Post Reply