[FERNYER]

Hey guys,

We are building a custom 8x4 foot CNC. Our company has to cut various sized rectangles out of window tint... thin film. We have decided on a rack and pinion drive system... Nema 23 steppers... and everything else except for the actual cutting mechanism. It doesn't take a lot to cut the film, as long as it's a clean straight cut.

Would a laser be overkill? Do you think it would leave the edges curled/burnt looking?

Our other idea would be a circular knife. All of the cuts would be straight down the x or y... no curves. We are just cutting squares and rectangles so we thought we could use two arms, one with a circular blade for the x, one for the y, and they wouldn't have to rotate at all. Just move each arm up and down.

I've searched for off the shelf circular knife components but couldn't find any. Does anything exist that you know of? We have some hobby knives here that work well manually... maybe we could retrofit the hobby knives?

Do you guys have any recommendations on how you would do this build knowing you just need to cut rectangles out of film?

I've never built a CNC before and I want to make sure I make the right decision here. Any thoughts are appreciated.

Thanks in advance!

[jfong]

Look up Donek tangential knife. That's one version of a single blade cutter that seems to work really well. It's not circular but the blades are cheap to replace.

[FERNYER]

Thanks for the link! We'll look into that... might be the simplest solution. Simple is good

My first thought is there might be a problem with the drag though. I guess if the blade is real sharp it might not be a problem. Our hold down system was going to be with bars on the ends of the bed. A drag knife might move the material. Probably not on the first cut or two. But once the rectangle has a few sides cut it would become free. I could see a drag knife moving the material inside the rectangle... just thinking out loud.

[jfong]

Donek has a video making a simple vacuum hold down system. I guess you could do the vacuum holes at the both ends of the CNC and leave the center with no holes so the material can be cut.

Im not sure what type of plastic window tint is but some do give out dangerous gas when melted by a laser. Anyways it would smell pretty bad. Something to think about.

[FERNYER]

Look up Donek tangential knife. That's one version of a single blade cutter that seems to work really well. It's not circular but the blades are cheap to replace.

What type of head would you recommend for a drag knife like this? We could use a 2 head system and static mount one to cut X and on the other head to cut Y. (All of our cuts are straight lines down the X or Y) Or, we could use 1 head and have a dynamic collet of some sort that turns the drag knife. We would control it with Arduino. Sorry for the ignorance... I'm sure this would be common knowledge for most but we are new to CNC.

[OldEngraver]

The obvious question is why can you not use a vinyl cutter?

[FERNYER]

We have to cut all the way through the material. Would doing so damage the vinyl cutting blade because it will be dragging along the bed?

[fixtureman1]

I have one of these that works good. I use a piece of sintra as a bed when I need to cut through

Sign Vinyl Drag Knife Bit - Use Your CNC Machine to Cut Vinyl Stickers and Lettering, Paper, Cardboard, and Plastic - WidgetWorks Unlimited