jjdennon

Poor cuts: Jagged and rounded cuts on MH 871-MK2

26 posts in this topic

Hey everyone. I am trying to figure out why I am gettng such crappy cuts. The plotting is OK, but the cutting is less than awful. I am pretty sure I am doing something wrong, so I appreciate the help.

Here's what I've done:

I've set the blade depth so there is just a smidge sticking out. Less than a credit card. Feed rate is 50cm/s and pressure is 110g. For what it's worh, the test print of a star is coming out OK. The points are sharp.

Images, see matt for scale:

KglaR.jpg

SYJQr.png

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Less than a credit card is too much blade. The only way you can set the blade depth is to take the blade holder out of the machine and in your hand cut firmly across a piece of scrap vinyl, You should only be cutting the vinyl, and barely a mark in the wax paper backing, Adjust to get there, Then put the blade holder back in your machine, make the same adjustment with force to get the same results. After getting the blade depth correct, then make adjusts with the blade offset. Change with + or - .05 adjustments to get smooth cuts.

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Skeeter,

Thanks for the help. I am not convinced there is too much blade. I did try your test, and it makes light marks on the wax paper, but the lines do not show through on the back. By your description, it sounds like it's already perfect.

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Check your offset.

Jay, how do I check the offset? I can jog the machine round, and there are feed rate and cutting for params that I can change, but that's the size of it, so it seems.

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I think on the MH machines, it's in the software. Look in the cutter setup in SignBlazer.

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Ok, so I've fiddled around with the blade and tried it a bunch of different ways

Blade barely visible - blade will cut through vinyl but not backing material when pressed firmly against material

Result: I can cut out a shape w/out going through the vinyl. I've tried running the machine between 100g and 250g and it will not cut through the vinyl.

More blade showing - blade will cut through entire first layer of vinyl, but not scratch second layer

Result: Shapes fully cut, no marks on wax paper, poor quality cut though.

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but did you adjust the blade offset like we suggested? If using Signblazer, it would be in your setup page.

Make sure the carriage head is firmly in the track. Make sure there are no vinyl pieces stuck in the blade holder.

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Skeeter,

Thanks for the tips, I did end up ajdusting the offsets and now the cuts I am getting now are pretty square. I also talked to Kevin as US Cutter who was very helpful. He suggested the same thing with the offsets and explained where to modify them in software.

The lines are still a little jagged, but it may be good enough for my purposes. Any way to clean up the jaggies? Is it because the blade itself is vibrating?

5TE5M.pngDc5pP.jpg

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Blade should be nice smooth cutting, not vibrating.. Have you tried a drop of 3-1 oil or same as, in the blade holder?

What kind of vinyl are you cutting there?

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Skeeter,

Just cutting regular 2 or 3 mil vinyl. Can't remember the thickness. I don't know that the blade is vibrating, it's just a guess. I get jagged lines on the straights too, which makes me think it's a hardware problem and not a software problem. This may well be the nature of the machine I got. Below I've attached an image of a horizontal cut plotted on the Y axis I did lubricate the blade with graphite so everything is smooth as butter as far as the mechanism itself goes.

JJ

~1" wide

3sa1b.png

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what driver are you using in Signblazer? If using on USB, try it on a keyspan adapter or serial cable, better connection.

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Yes, I am using the USB. Poor communication is an instruinging thought, but it was my understanding that the plotter itself was evaluating the HPGL. My assumption is that the driver sends a bunch of data over to the plotter until it's memory buffer is full, and then asks for more data. now I could be wrong here.

In short, if the software sends a command like PD X100 I would expect the plotter to try to draw a striahgt line w/out intteruption until recieving the next command.

I'll do some testing a bit later.

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If it's doing that on a straight line, I would agree. Check the blade to make sure that it is spinning freely in the holder. Like Skeeter said, put a drop of 3 in 1 or spary some WD-40 on the blade to make sure it not binding.

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Blade is not spinning? Look in the blade holder really good for vinyl pieces, maybe stuck in there,, Order a new blade holder, If you think that is the problem.

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Jay/Skeeter,

I increased the depth of the blade slightly and decreased blade pressure, this seemed to make some difference. Maybe it's my imagination though ;) FWIW, I've been trying this on the test cut pattern to completely remove software from the question.

Maybe this is just the nature of the machine. I took a look at some professional cuts that were done for me and some were definitely better than others. I have two other thoughts.

1. When I move the tip of the blade outside the holder, there is some lateral play in the blade, does this happen with your Graphtec holders too?

2. The mechanism that the blade holder clips into is made of plastic

Thanks,

JJ

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I started having a similar problem with my SC cutter. It's just a month old now. It use to cut nice straight lines. About a week ago I noticed the sound of the machine changed slightly. Then I noticed the wavy lines. At first it was just diagonal lines, but now I'm starting to see it on straight lines. It's more noticable on lines and diagonals in the x axis.

Sorry not trying to steal your thread.

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Doug,

Sounds to me like a belt or roller problem. Maybe there is some grime in the V-Groove, on the rollers, or maybe the belt needs to be tightened. I wouldn't go tinerking around with the belt unless you know what you're doing though!

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