Drag Knife / Vinyl Cutting Holder

Projects and Source files that are created to extend the Zen Toolworks DIY CNC machines.
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Drag Knife / Vinyl Cutting Holder

Postby sensor » Thu Oct 18, 2012 3:59 pm

Here is a vinyl cutting / drag knife holder. There are many ways to build this, and better ways as well. Cost is ~$40 or less.

UPDATED: 10/22/2012
Please note, this is not a tutorial on how to cut vinyl, but how I made a blade holder. I added notes about vinyl cutting, however.

PARTS
- Roland compatible vinyl blade cutter (e bay) 12mm clamp x 56mm long - $12
- Vinyl cutting blades (45 and 60 degree) (e bay) - $10
- 12mm linear bearing and holder SC12UU (e bay) - $7
- hobby wood strip
- one long screw
- one soft spring
- one small collar to fit the screw
- optional thumbwheel
- some other wood scrap for a screw holder
- other screws to hold the bearing block to the wood strip (3mm will work)

ASSEMBLY
Blade holder:
-Remove the bearing from the block, and CA it (just a drop) about half way out of the block
-Attach the bearing block to the wood strip (as shown)
-Insert the blade holder in the bearing

Blade pressure mechanism: (not to be confused with blade holder extension adjustment)
-Attach a soft spring to a collar with CA
-Thread a long narrow screw through another block of wood, tighten the collar/spring assy to a screw, CA to the wood strip
-The spring should rest on the top of the blade holder, down in the linear bearing, lightly, maybe about 120 grams

-Affix this whole assembly to your spindle.

Tool Chain Options:
-CAMBAM Text -> MACH
-Inkscape -> CAMBAM -> MACH
-CAD Text -> CAMBAM -> MACH
You really just need a graphics path converted to GCODE with minimal setup

CAM:
Set most everything to zero for the tool path, use an engrave and V-cutter tool. I set a safe Z to some safe amount. I don't cut fast but many vinyl cutters move pretty quickly. No hurry here.

Vinyl Cutting Notes:
I'm not an expert by any means but have cut finely detailed graphics with this rig. The Zen is accurate enough, but vinyl, as a material, has its limits. A sheet of cutting vinyl contains a wax backing layer and the adhesive vinyl itself. The vinyl is mils thick. The cutting blade is a 'drag knife'. The holder can adjust the extension of the cutting blade and has a button (opposite the blade) to release the tiny blade. The blade rotates in the holder (the purple item in the images) as it is 'dragged' along. As the machine guides the blade through the graphic paths to be drawn/cut, the blade rotates in the holder, being 'dragged along' making the cut. The blade follows the cutting line (tool path) like a trailer follows a truck. The blade tip is tiny. The holder mechanism needs to float along the path vertically, hence the linear bearing, in conjunction with the blade adjusted pressure, hence the spring, so it cuts through the vinyl to the wax backing layer only. The spring is for pressure and the linear bearing for vertical movement. The holder handles the blade rotation. The bearing and spring keep the purple blade holder from crashing. The amount the blade protrudes from the holder is about half the thickness of a USA state drivers' license. So, very little blade is needed and little pressure is needed (120 grams I believe). This is the typical easy setup. A typical CnC machine can't move long swaths of vinyl though a machine like a pen plotter does, since there are no rollers or tractor mechanisms. It is limited to the table size or less depending on where/how you mount the blade holder. If you need to cut larger sizes, a $200 dedicated machine is probably a better solution. For little stuff and $40 it works well enough. Getting the CnC machine to follow the cut path on the line is the other CAM challenge. An engrave function can work, well enough.

Setup:
I simply set my zero to just touch the vinyl, and apply a touch of spring pressure so it pushes through. The spring and linear bearing allow the knife holder to float and not crash. You will have to experiment and learn about vinyl cutting. Don't cut through the vinyl paper backing. If so, you are cutting too deeply.

Fixturing:
I used a 12x12 ceramic tile from HomeDepot I bought for $1. I apply Krylon Easy Tack to the tile and clamp the tile down. The vinyl piece is simply stuck to the tacky adhesive on the tile. This is the same concept as a Cricut-style sticky mat used for paper cutting.

Thanks to all previous posters on other forums, and my vinyl cutting friend/expert, for the help and advice.
Attachments
blade_holder.jpg
blade_holder.jpg (5.96 KiB) Viewed 9454 times
vinyl_cutter_end_v1.jpg
vinyl_blade_holder_v1_rdc.jpg
Last edited by sensor on Mon Oct 22, 2012 12:12 pm, edited 2 times in total.
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sensor
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Re: Drag Knife / Vinyl Cutting Holder

Postby rawkstar320 » Fri Oct 19, 2012 2:19 pm

This is very cool, I like the idea of putting it next to the spindle (makes your machine dual use). A quick release mechanism would be sweet, so you could just pop that guy on and off for the two different projects.

Anyways, good job!
Check out my Etsy store: http://www.etsy.com/shop/WondrousWidgets

Interested in making your own machinable wax? Check out: http://www.instructables.com/id/Machinable-Wax/
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Re: Drag Knife / Vinyl Cutting Holder

Postby johntech » Fri Oct 19, 2012 3:52 pm

sensor wrote:Setup:
I simply set my zero to just touch the vinyl, and apply a touch of spring pressure so it pushes through. The spring and linear bearing allow the knife holder to float and not crash. You will have to experiment and learn about vinyl cutting. Don't cut through the vinyl paper backing. If so, you are cutting too deeply.


I guess I'm a little fuzzy about the setup instructions??? What keeps the knife from cutting through the backing? I guess it has something to do with the blade holder?? Maybe if there was a fine adjustment between the blade and what is holding the blade.......... I think I get the idea, but a drawing of the holder and the round silver part with the black band around it in your picture would be more help.

Thanks

John
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Re: Drag Knife / Vinyl Cutting Holder

Postby sensor » Mon Oct 22, 2012 10:32 am

johntech wrote:
sensor wrote:Setup:
I'm a little fuzzy about the setup instructions??? What keeps the knife from cutting through the backing?


I added some background on the vinyl cutting concepts and another image.
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