Vinyl Cutting Tip: How to fix lifting corners

Blog_Vinyl_Ears_60degree_290x121Can a sign maker design a graphic that is too big or too small to cut? According to emails we receive, the answer is yes. Some common problems encountered in vinyl cutting are self-inflicted and are caused by designing something beyond the parameters of your equipment. One such problem is edge lifting during plotting, also known as ” vinyl ears”.  As the plotter blade moves across the vinyl, it begins to lift the corners as it cuts. This is annoying and problematic. What causes it and how do you fix it?

Causes and Solutions

There are three primary causes of the ‘vinyl ears’ edge lifting problem. These are improper offset, a worn-out blade holder, or a character size that’s too small for the blade to articulate.

• Improper offset. When I consulted with our manufacturer experts from Roland and Graphtec, the first response I got was incorrect offset. The offset is important because it’s a measure of the effective width of the blade’s cutting edge. It’s the distance  between the vertical axis around which the blade spins and the cutting edge of the blade. The offset is an adjustable parameter that can be changed with the cutting conditions along with speed and force.  The offset value tells the cutter how far past the actual corner tangent it must move in order to drag the tip of the blade to the same point. If the offset is not correct, the plotter will not articulate corners correctly. The standard offset for a 45° Roland blade is .0250. Graphtec cutters have a default offset depending on the tool used. It can be adjusted by the end user to plus or minus 3 (± 3) If this value is not correct, it may be the cause of the problem. Reset it to the default and try again.

• Worn out or dirty blade holder. The other cause of vinyl edge lifting can be a worn out blade holder. As the blade holder ages, its grip on the spinning

blade can weaken. This degradation is gradual. Usually the first indication is a failure to complete the corners of rectangular characters. If the blade holder’s grip has weakened sufficiently, it can also cause the corners to lift as it spins the blade and changes direction because the blade is losing its vertical orientation as it pivots. It’s not standing up straight. Debris in the blade holder can have a similar effect. Pull the blade out and make sure there aren’t small bits of vinyl stuck in there gumming up the works.

• Graphic smaller than the blade arc. The most common reason for this problem has nothing to do with the offset or blade holder. It’s simple math. If the arc or corner on a finely detailed letter is small enough, it simply can’t be cut correctly with a standard 45° blade. It’s like trying to mow around a sapling with a standard riding mower when you need a “Zero Turn” tractor.   The 60° blade is the Zero Turn tractor of digital sign-making. Changing from a 45° to a 60° blade effectively shrinks the offset and tightens the turning radius, allowing you to carve a more finely detailed arc.

Fig 1: Changing from a 45 to 60 degree blade fixed the corner lifting on this detailed graphic

Fig 1: Changing from a 45 to 60 degree blade fixed the corner lifting on this detailed half-inch tall graphic

Fig 1 shows the edge lifting of this graphic with the standard 45° blade. It’s an elegant serif font cut at 1/2″. This was cut on a Vinyl EXPRESS Qe6000 which has a high quality digital servo motor and cuts fine detail with amazing precision. But a serif or filigree on a 1/2″ tall letter may only be 1/16″ of an inch tall. Depending on the font, that can be a problem, as seen here. The solution in this case was to switch to a 60° blade. The same job sent with the same cutting parameters with the more acute blade angle produced a finely cut graphic. It was almost too small to weed, but it was cut correctly.

That brings up another factor. Not every plotter can cut characters this small with such precision. If you’re using  a cutter with a stepper motor, changing the blade angle may not be enough. You may actually have to enlarge the graphic to a size your cutter can handle. Click here to read more about the difference in capabilities between stepper and servo driven vinyl cutters.

There are other self-inflicted wounds sign makers sustain. The vinyl ears problem is pretty easily remedied as long as you understand what’s going on. Make sure you’re plotting with the correct offset, you’re not using a worn-out blade holder, and change to a 60° ‘Zero Turn’ blade. If that doesn’t work, adjust your design to fit your cutter’s capabilities. Or upgrade your equipment to something capable of cutting your designs