Rogue Cuts

[JustinCooper]

Hi
Ill start this off by saying I am new to all things related to CNC. I picked up a Millright Mega V and I am trying to start off with some simple things - such as yard decorations for Halloween.

The cut I am getting is far off from what I am seeing in the Easel app. Here are a few things I’ve noticed:

• Cut Depth - the board is 3/4" thick. I’ve measure it several times. I have set the board to be .26" in Easel and have also set the cut path to add .05", yet it still does not cut all the way through the board.
• Rogue Cut - As you can see near the lower right of the mouth on the ghost, it did a phantom cut extending beyond the circle
• The eyes and mouth are not a perfect oval/circle - you can see in the top left and bottom right corners of both there is a bit of a squared edge.
• The CNC tends to do “phantom cuts” where it will randomly just start cutting in a different area on the work piece or it will finish a cut and then shift over and start doing another cut of the same design.
  Ghost.zip (8.1 KB)
  
  
  
  
  

[RonCairns]

• Cut Depth - the board is 3/4" thick. I’ve measure it several times. I have set the board to be .26" in Easel and have also set the cut path to add .05", yet it still does not cut all the way through the board.**

Cut depth should be .26" and the material thickness set to 0.75. Set the Z axis so that the cutter is just touching the material surface and be sure to choose new position button for Z axis. It should be 0 when the cutter is just touching the material. The depth of cut must be the same as the material thickness to cut thru the work piece. Easel will offer to add tabs if you set to cut thru the material.

*** Rogue Cut - As you can see near the lower right of the mouth on the ghost, it did a phantom cut extending beyond the circle**

Click on 1 of the ghost shapes and see what is selected. If everything is selected then try exploding the drawing and delete unwanted lines. You may have to explode it a couple of timed to get to the line segments

Repeat above for the other unwanted items.**

If this doesn’t address the issues pls send the easel drawing file and not the svg.**
Ron**

[JustinCooper]

Thank you, Ron!

When you say to select the ghost and “explode” it, what do you mean by that? Is that just zooming in? Attached is the Gcode.
Ghost.nc (62.5 KB)

[RonCairns]

I mean the shape that is a “ghost” shape. I don’t know enough of G code to be of use it for this issue. I am quite comfortable with Easel and am so if you post a higher contrast .jpg I will guide you thru the process in easel or you could check my earlier post on basic Easel use. It is a simple process to import an image, Then use an app to import a jpg into the sketch. and you’ll be cutting them out quickly.
Ron

[JustinCooper]

Got it. The image I am using is from the Pro Design Library in Easel.

Here is a link to it, if that helps any?

Ghost

Also, I made a mis-statement earlier. The material is .25" and I had it set .26 in the project, and the .01 added dept, yet it still doesnt cut through.

[JordanLee1]

Hi Justin, just wanted to add my two cents - if you are American, I can do that, but if you are Canadian, it’s gonna have to be five cents. lol.

Thank you for confirming that the material is actually only 1/4" thick (0.25) and that you are trying to cut at 0.26

It would be helpful to know a few things:

What is your machine? A cheap 3018 from China will not cut this in one pass… but it can do it. We need to know what you are working with?

What is your Feed Rate and Depth Per Pass?

What size bit are you using, and what type?

Thank you for posting the pictures, they are helpful. You have some black marks which indicates burning, so you are either too deep, or too slow.

The offsets on the cuts (the rogue cuts) are very likely because the machine is skipping cogs on the belts, or following the grain of the wood and the machine isn’t strong enough to resist the pull at speed, so it goes off course. When it does, the software has no idea that it happened, so it just keeps going, but it can be off by a lot as you have seen.

I remember making a LOT of mistakes when I first started out with these machines, and it is easy to think that it should be able to do it quickly and easily. I have learned the hard way that it is different for every material, and that you may need to adjust some things on the fly, or do things over.

Patience is my best advice, and ask questions like you are doing, and try again. One more good piece of advice is to watch the machine and listen to the sounds that the bit is making in the wood. If it sounds chattery or screechy or uneven, look at what the bit is doing. If it is deflecting (moving a little bit), you are either too deep or too fast, or both.

I would suggest you try again with really conservative values to see if you can get a successful cut, and then slowly increase DPP and/or FR. For example, most cheap machines should be able to cut that at 1/16" per pass, and 12" per minute. - I hope I converted this right because I use metric for the carve, I find it to be much more accurate and easy. Basically, 0.5mm depth per pass, and 300mm/m.

Yes, this is terribly slow, but it should show you if the machine is accurate and working properly. You can slowly speed it up if you watch and listen. If it doesn’t look or sound right, slow it back down a bit.

Looking forward to seeing your results! Have fun, and again, have a lot of patience! It will reward you.

[RonCairns]

I suspect that your Z is not zero’d to top of the material. Is it offering you to use tabs?
Attached is the drawing with the changes needed to make these parts. Don’t forget to fasten the cutout pieces to the base. Suggest tape and CA glue.

[JustinCooper]

Thank you - what cut settings did you set for this?

[JustinCooper]

Appreciate the reply!

I’m using a Millright MegaV

I have a Jiiolioa 1/4” spiral upcut
DeWalt DWP611
Cut settings are as follows:
Router speed: 9
FR: 10 in/min
PR: 9 in/min
depth per pass: .15 in

[RonCairns]

It depends what material that I am cutting. I am sure that my settings won’t help you much as my machine is anon stock Genmitsu 3030 router. Back when I started in the hobby, I usually started with automatic settings. Then on a test piece of similar material I made cuts doubling the feed until it sounded like it was working too hard and then backed it off a bit.

My two most used bits are a 0.1 v 20 degree V bit and a 2 flute 1/8 upcut endmill.
I usually run the spindle as fast as I can without chattering. Surface finish is usually the controlling factor.

I do a bunch of engraving on machinery tags and cutouts and 1/4" acrylic. My favourite trick to to allow the router to cut the part out and then recut the same part drawing as this clears out any melted bits. BUT there is no substitute for practice and experience.

Yes I am in Canada so sense it is.

[JordanLee1]

Hi Justin, thanks for the info on your machine. That gives a better picture.

The Millwright Mega V is not a cheap little machine, it is a much better unit with bigger stepper motors and linear rails, which means that you are not likely losing steps or getting off track. So my original thought is not likely to be the problem.

So now I’m thinking that either your material is not fastened down properly and is moving with the router at some point during the cut. The other possibility is that it is something doubled up in the design perhaps? If you share your project here, we can take a look at it.

As for your settings, I have a couple of suggestions. I have a machine that also uses a DeWalt DWP611, and I typically run it at much lower speeds. White woods and softer woods I run at 1 (which is about 16,000rpm). Doing 10 ipm at 6 (which is max, there is no 9) is 27,000rpm, so that is why you are getting burn marks. Slow the router down. When using a 1/4" bit, you should be running no higher than 3. Like I say, I keep mine around 1. Another important thing to know about the DeWalt and running at high rpms is that it will burn out the brushes pretty quickly. I was burning them out in less than three months. Running at 1, I have been on the same set of brushes for a year now. Big difference.

10ipm is quite conservative, which is good to start. You can always increase this later, once you get a successful cut.

A depth of 0.15 ipp is pretty aggressive. My machine can’t do that. Maybe yours can, but I would suggest you reduce that and see if you can get a clean cut. Try doing a depth per pass of around 1mm, which converts to 0.0394 inches. Again, your machine can probably do more, but try it like this and then increase a bit at a time on your future projects to see where it starts to struggle and then back it off a bit.

I’m also going to add the idea that you should work in metric. It is much more accurate and easy to do the math on. Easel has a toggle switch that I use often, because I want to know the dimensions of my project and material in inches, but I cut in millimeters. You can switch back and forth as much as you want and it will not affect your project. Most CNC stuff is designed for metric, and the majority of the world uses metric.

How are you mounting your workpiece to the spoilboard, and are you certain that it is not moving?