MH 721 changes speed & downforce during cuts!!

[plotski 0]

Got my MH 721 on eBay and it was delivered Jan 11, 2007.  My problem is: I change my speed settings to 8 inches and force settings to 30g for optimum premium vinyl plots but, in the course of the cut (especially longer ones of 4 feet or more), the settings will invariably move up in speed and downforce.  The result is that many times the plotter cuts through the paper backing in the middle of the plot.  I also think it strange that I have to ratchet the speed and force down to such low settings to make a successful plot (at least, at the start).

Please help, as I have ruined lots of premium vinyl!

I have grounded the stand to the plotter, I'm using a serial connection on Comm1, and I'm running Signcut X2 PE on XP.

[thredz 1]

I think when you get into the longer lengths,the curve of the vinyl is what causes the depth.If the roll is a partial roll,or a roll with a lightwieght core,it doesn't hold thebackside down,causing it to arc a little bit.On the speed,it's probably going faster on a small area or a long single line.When it goes in to the corners and complex curves is when the 8 would be taking effect.And if you check your blade depth,it should be barely sticking where you can barely see it.If you have it out farther,you have to compensate with lower g's on the cutter.That would also explain the depth of the cut problem.If you have the blade out farther,it gives more room between the blade holder and the vinyl,allowing it to arc up against the bottom of the blade holder.At least that's what I have found through my own use.

[Beardown 0]

is it changing the speed and down force in the screen as well ...or does the screen settings stay the same and you hear it speed up and slow down ?..If the settings on the screen change on their own you just might want to contact Marcel and ask him what he thinks about the situation.....

GO BEARS

[plotski 0]

is it changing the speed and down force in the screen as well ...

Yes, the force and speed settings actually change on the display.  They start out lower, then I hear a difference in the "music" the plotter plays, I look and see that the settings have changed on the screen in mid-cut (and sometimes there are some strange "hieroglyphics" on the display, too -- like parts of letters).

[MarcelC 5]

It does seem in this case that there is something wrong with the motherboard. I'm working with plotski to get a replacement out.