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Hi folks, I'm hoping someone can help me solve this little mystery....

My EH721 plotter is great, except it keeps making little cuts outside the lines as you can see in the photo below:

vinyl-cut.png

I've tried adjusting the blade height and cut speed, neither help. I'm using SignCut, if that makes any difference. The cutter appears to be on the track and moves smoothly, any advice greatly appreciated!

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Do you happen to have your tangential emulation check marked? If so check the setting for lead in. That feature is designed to set the blade down a little early and allow it to turn on the way into a cut so it is pointed the correct way when it starts cutting. It should only be set for about what your blade offset is. Possibly it set WAY to far and coming down too early. The feature is misleading because it only does it at the start of a line and not in every corner like you would think. If it's not that then it's likely a file issue. You can post the working file here if it's under 1000 kb and someone can take a look. Your letters look very rounded. That is usually a sign that your blade offset is too low.

I know you said you checked your blade depth but I would make double or triple sure that you don't have too much out. Most new users have way too much out. I am not saying that this is the cause of your problem but if there were too much out it would be dragging early on its way to the letter. You should almost to be able to see the blade with the naked eye. If you pull the holder out of the cutter and cut a piece of vinyl by hand with moderate pressure it should not be able to cut clear through the vinyl and backing. 

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That star provides a clue. What I'm seeing is 'wobble' overall.

The blade holder itself sits inside a clamp, and those have been known to break with overtightening. Look closely and check if there is a hairline crack on the plastic arm. I've busted two of those suckers over the years.

http://www.uscutter.com/US-Cutter-MH-Carriage-Arm

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3 hours ago, Wildgoose said:

Do you happen to have your tangential emulation check marked? If so check the setting for lead in. That feature is designed to set the blade down a little early and allow it to turn on the way into a cut so it is pointed the correct way when it starts cutting. It should only be set for about what your blade offset is. Possibly it set WAY to far and coming down too early. The feature is misleading because it only does it at the start of a line and not in every corner like you would think. If it's not that then it's likely a file issue. You can post the working file here if it's under 1000 kb and someone can take a look. Your letters look very rounded. That is usually a sign that your blade offset is too low.

I know you said you checked your blade depth but I would make double or triple sure that you don't have too much out. Most new users have way too much out. I am not saying that this is the cause of your problem but if there were too much out it would be dragging early on its way to the letter. You should almost to be able to see the blade with the naked eye. If you pull the holder out of the cutter and cut a piece of vinyl by hand with moderate pressure it should not be able to cut clear through the vinyl and backing. 

Thanks Wildgoose for your advice, I've had a look and the "tangential emulation" is not checked. I had wondered what that was for!

I've attached the SVG (created in Inkscape) I'm working from, the image in my original post is cutting just the dark green layer and the size was reduced to 55mm in Signcut before cutting (that might explain the rounded corners?). 

As for the blade length - I previously had waaaay too much protruding (as most newbies!), but these days it's just the tiniest amount and I even tested putting it in so far that it was just scratching the vinyl and it still makes those marks. Do you think it's the file causing the problem? It seems intermittent, which might suggest some bad files?

2 hours ago, slice&dice said:

That star provides a clue. What I'm seeing is 'wobble' overall.

The blade holder itself sits inside a clamp, and those have been known to break with overtightening. Look closely and check if there is a hairline crack on the plastic arm. I've busted two of those suckers over the years.

http://www.uscutter.com/US-Cutter-MH-Carriage-Arm

Thanks slide&dice, it's a new machine (well, couple of months with very little use). I checked the clamp and there are no cracks or damage I can see. Worth checking though, that's for the suggestion.

Logo.svg

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The file looks fine to me and has decent quality text. Your cut text is rounded and looks like a mess. Have you checked blade offset?

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On 2017-6-24 at 10:50 AM, KYSIGN said:

The file looks fine to me and has decent quality text. Your cut text is rounded and looks like a mess. Have you checked blade offset?

Hi kysign, it doesn't look great does it :/

The offset is set to 0.0, any idea what it should be set to? Sorry for being such a newbie! 

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  I am not kysign, but start blade offset at 0.25MM.   Then adjust at .05    + or minus until it looks good.   Use the test feature on your vinyl cutter.  Corners should be sharp.    FIRST make sure your blade is set correctly,  This is how. below.   I know you said you did,  but retry on the vinyl you are cutting at the time. Blade depth has to be set correctly first. 

To start with, you should set your blade depth correctly, by taking the blade holder out of the machine, and firmly cut across a piece of scrap vinyl, you will be cutting. You should only be cutting the vinyl and barely a mark on wax paper backing, Adjust blade to get there, Then put the blade holder back in machine, and use the force of the machine to get there, same results, only cutting the vinyl and barely a mark in wax paper backing.  You should just barely see or feel the blade tip out of the blade holder....

 

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On 6/25/2017 at 5:40 PM, MZ SKEETER said:

  I am not kysign, but start blade offset at 0.25MM.   Then adjust at .05    + or minus until it looks good.   Use the test feature on your vinyl cutter.  Corners should be sharp.    FIRST make sure your blade is set correctly,  This is how. below.   I know you said you did,  but retry on the vinyl you are cutting at the time. Blade depth has to be set correctly first....

Thanks MZ SKEETER, all help is massively appreciated! So I took your advice and adjusted the blade height again, thanks for the useful method. Unfortunately that had no affect the problem though. I also tried adjusting the offset in the "cutter options" in SignCut Pro, anything other than 0.0 just makes a mess, so I assume the EH721 is already compensating for the blade offset?

23 hours ago, Dakotagrafx said:

also how tall are those letters?

About 4mm tall. 

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I've just done a cut preview in SignCut and it appears the extra cuts are happening right at the entry point of the blade for each shape. Is this at all helpful to any of you cutting gurus?

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So,for those of us in the past s that us 15/100 of and inch . . . That explains a lot. These cutters drag the blade and the blade is dropping in an orientation different than what you want.  You are trying to do that with the lowest end course stepper motor whan the only real way to get anywhere near that small would be with. A true machine that orients the blade by mechanical means ( summa might make one) . . . The cutter though is going to cost over $2000 compared to the $250 one you are trying to accomplish this with.  At least that is my take on it, other opinions may vary.   My first clue was the width of the pressure roller tracks in the picture to give some scale.

 

actually at just over .15 " that machine did a great job for what it is

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3 minutes ago, Dakotagrafx said:

So,for those of us in the past s that us 15/100 of and inch . . . That explains a lot. These cutters drag the blade and the blade is dropping in an orientation different than what you want.  You are trying to do that with the lowest end course stepper motor whan the only real way to get anywhere near that small would be with. A true machine that orients the blade by mechanical means ( summa might make one) . . . The cutter though is going to cost over $2000 compared to the $250 one you are trying to accomplish this with.  At least that is my take on it, other opinions may vary.   My first clue was the width of the pressure roller tracks in the picture to give some scale.

 

actually at just over .15 " that machine did a great job for what it is

This is actually quite reassuring! I'm happier having a machine that is working correctly but just has less accuracy than I expected, rather than a broken machine! These marks exist at all sizes, though they don't scale up, so I guess my original image is somewhat misleading :/ Sorry about that.
So if you're confident it's not a fault, but a limitation of the cutter, I'll take that. Thank you!

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That was my take also, when you stated 4 MM   .    Now go back to  larger sizes and try the blade offset again at 0.25mm.   Blade offset is not set into those value cutters.   EH721 is just another name for the Refine MH 721 here. 

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12 hours ago, MZ SKEETER said:

That was my take also, when you stated 4 MM   .    Now go back to a larger sizes and try the blade offset again at 0.25mm.   Blade offset is not set into those value cutters.   EH721 is just another name for the Refine MH 721 here. 

Will do, I've also made minor adjustments on overlap which helps a little. I'll report back after I've cut a larger sample. Thanks Skeeter.

6 hours ago, Wildgoose said:

Here is a good study guide from Roland. Not your machine brand but the overall concepts are exactly the same. 

ra_cutter blade knowledge.pdf

This is a great guide, going straight into the keep file! Thanks Wildgoose. 

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