Vector cut not linear

[badbert]

I am unable to achieve any form of accuracy using the cut path tool. In the picture shown notice how accurate the cuts are on the right side of the board, yet how far off they are on the left end. And it becomes progressively worse depending on the distance. This has become a pattern for this machine. The bluegill nose was much more accurate than his tail. The disciples carved the same, with the right disciple only requiring sanding, the left one needed filing. I understand the calibration might be off, but why wouldn't it be the same for raster as cut? Why is it unable to accurately cut what it just carved. Notice that the inside cuts, are all perfect. This is because they were pierced. Any ideas. There was only a bit change, in between. This is a two-sided carve by the way, and the raster carve has perfect correlation between the sides. I have not attempted a calibration yet, are there two calibrations? One for raster, one for vector?! All bearings and belts are tightly adjusted, and all bearings are smooth and tight. It hums like a well oiled machine.

54949 54948

[fwharris]

Bert,

As Al would say "it's all in the brass roller"! It looks like it could be just a tracking issue. Are you using masking tape on the board edge that rides on the brass roller? For the cut outs, one or multi pass cuts?

[badbert]

No I did not... So I won't get a tracking error? I will definitely try that. I stopped using masking tape when I started planing and jointing to make sure there were perfect edges. I haven't had any errors though, and this error is repeatable.

[bergerud]

If the carving is all good, it is not a calibration issue. When I have had cutting offsets like this it was because the board did not stay under the rollers. With carving, it does not matter so much as the board just slowly inches along as it carves. With cutting, however, the board moves back and forth and is more sensitive to board tracking errors. Having to push the rollers back up (or cut too deep) can cause b slippage. Even worse is when the front roller drops and the x measurement is taken over by the x drive encoder instead of the brass roller. When the brass roller comes back into action after the front roller goes back up, there can be an offset. It is very important to stay under the rollers and to restrict the max cut depth.

[badbert]

The board is an old shelf board. It is twenty inches longer than the pattern. And it is centered. There are ten inches on either side. It definitely stayed under the rollers. And this is a Repeatable problem. I have another identical set to cut tomorrow. We'll see if it does the same thing. Of course this time I will use masking tape! Keep 'em coming guys. Thanks for your help!

[bergerud]

Ok, what about the depth of cut? Are you doing multiple passes at 1/4" or one single cut?

[badbert]

I did not do multiple pass cuts this time. I figured maybe I was multiplying the problem, by having it cut three passes. SO SHOULD I try multipass the next cut? Or leave it alone to see if it cuts the same?

[Digitalwoodshop]

That's right.... It's all in the Brass Roller..... I did not open the .mpc but I would also turn OFF Perspective to keep Parallax from causing alignment problems.... With it ON only the Center of the Screen will Superimpose a Cut Path on top of the item correct.... Adjust the sides of the screen and it will be off.... Turning it OFF lets you move stuff on the edges of the screen and you will get what you SEE...

Burning the Midnight Oil.... Making FRP Plastic with Vinyl Letters and Numbers for a 4 x 8 foot Softball Score Board for a weekend game at a new local park. I am just doing the letters... 2 AM... Sleep...

AL

[bergerud]

I looked at the mpc Al. It looks ok. I think the 3/4" single pass cutting could be the problem. There are large forces and vibrations involved with that. I gave up those aggressive cuts since it seems that something always goes wrong.

[badbert]

All of the paths were created automatically, using outline pattern. The same thing happens when I use multiple passes. I will turn off perspective. Delete all paths. Recreate with outline pattern. At this point I would like to assign pierced to all paths. But when I apply pierced to the outer path, the inner pierces go away? Download the MPC and apply pierce to the outer path, and you will see what I mean. Thanks again for all of your help! And keep those ideas coming. I won't be able to start the next one until tomorrow afternoon.

[AskBud]

I am unable to achieve any form of accuracy using the cut path tool. In the picture shown notice how accurate the cuts are on the right side of the board, yet how far off they are on the left end. And it becomes progressively worse depending on the distance. This has become a pattern for this machine. The bluegill nose was much more accurate than his tail. The disciples carved the same, with the right disciple only requiring sanding, the left one needed filing. I understand the calibration might be off, but why wouldn't it be the same for raster as cut? Why is it unable to accurately cut what it just carved. Notice that the inside cuts, are all perfect. This is because they were pierced. Any ideas. There was only a bit change, in between. This is a two-sided carve by the way, and the raster carve has perfect correlation between the sides. I have not attempted a calibration yet, are there two calibrations? One for raster, one for vector?! All bearings and belts are tightly adjusted, and all bearings are smooth and tight. It hums like a well oiled machine.

54949 54948I think you will find/see that your carves and cuts are too close to the edge of the board, (on the keyboard side). You need at lease 1/2" of uncarver area at the top.

You may remedy this by attaching equal rails to the edge of your actual board. All that will change is "Scaling" prompt, at which time you will select "Keep original size", and "Center on board".
AskBud

[badbert]

The board is wider than the virtual board. Take a look at the pic.

[AskBud]

You, probably, did not properly apply the pierce to the outer edge!
You do not need the cut-paths. Instead, you draw a path a bit away from the hearts (at least 1/4", I go wider). Then you assign tabs and set your pierce to that outer path. The attachment, below, shows you the rough idea. I enlarged the design just to show how it works.
AskBud
54952

[AskBud]

I know/understand that you will want to re-design to allow for your triangle support, so you have that area as well. I just did not take the time for that.

If your actual board has a finish on it (or is just slick) you may need extra runs in various places along the board, to help the traction belts move the board properly.
AskBud

[eelamb]

Bert, it looks like the board is finished oak. The finish will create a smooth surface. I would use masking tape on both bottom edges and one down the middle for belt traction, and the brass roller.

[badbert]

Thank all of you for the great help! I didn't get to carve it yet, but I did get to play with designer. Bud you are a genius! It was as easy as adding 1/2" to each dimension of the path I was using for the cut tool. Like magic the pierce worked. I added some tabs to the pierce and I believe it will be perfect this time! There will be a lot less cut paths in my future! I am working on a test carve carve for accuracy. Considering adding tests to every carve to make sure tracking is perfect.

[liquidguitars]

the pierce worked. I added some tabs to the pierce and I believe it will be perfect this time! There will be a lot less cut paths in my future!
I don't use cut path much if at all, and if you have the new "offset path" this is nice way to add the extra piercing clearance.

[badbert]

So I finally got around to calibrate my machine... lo and behold, it was WAY OFF! The length measured out at 37.3 on a 40.165 board! I sat down to figure out the multiplier... when it hit me! As an Auto tech, I had to calibrate Speedometers in peoples cars. That far off would be at least 2 teeth... but what could have thrown it off that far? Things that effect speedo calibration; final drive ratio, gear sizes, and tire diameter.... THE O-RING!! After reading on here about the o-ring debate, I had installed a generic o-ring! Effectively increasing the diameter of the brass sensor! I took the O-ring off and it measured perfectly. I never had a tracking problem before or after the O-ring, so I assumed it was OK... it was not. And just to add to the debate... My factory calibration is precise (.02 variation over 40 inches) without the o-ring! Thanks for all your support!

[fwharris]

Bert,

Great find!!!

[Digitalwoodshop]

"O MY"..... Good Catch....