That Dratted Frog. It is getting to me.

[ElderlyGent]

Hello all.

I want to try my hand at 3d xarving the FROG in the clip art to make a garden ornament possibly a family of them as I have just remoddelled the whole garden,

I set it all up and went out to start carving it. The roughing cut finished just as it shoulf, so I changed the bit from the end mill to the ball nose, reset the touch off to the same place ie the home postion, and hit the start . A pausewhile it thought about it then off it went. The immediate problem was that it plunged straight down into the wood and then the whole thing went berserk. Frantic stopping saved the CNC from coming apart,

So when I looked back at the set up on the computer I saw that the roughing toolpath was smaller than the finishing one. So now I could see that the BN bit was starting to cut at the original height but was suposed to start cutting at the bottom. So this meant that it was impossible for the bit to cut sideways through 1.25 inch thick of wood to get to the right place. I then thought that possibly it should have done a series of layers until it reached the correct depth, Lord knows I have done this many times on past projects.

So I looked at the selected bit in the list and all seemed ok until I saw thatthe PLUNGE RATE was set at 50 inches. Did this mean that the bit was trying to plunge into the piece at that rate? If so then it was no wonder it all went pear shaped, and at that depth the whole bit was in the wood, not just the tip .

When milling out a pocket you can set the depth of cut for each pass, so how do I do this when as I say the start positon for the BN is outside the already done roughing cut.

Any help to understans where I ahe gone wrong will ne mouch appreciated.

Sta y safe.

EG...... aka Drew.

[dealguy11]

It's hard to say exactly what's going on, but my guess would be that the roughing bit was a little too large to hit all the areas of the model, and the point where it started the finishing path was one of the areas that wasn't roughed. The finish path will always cut directly on the surface of the model so there is no way for that type of toolpath to work its way down to the depth.

Possible solutions include:

1. Provide an offset to the roughing pass so it covers the entire model, including the areas near the edge where (I assume) the finishing bit is starting. This will mean that the roughing bit will go beyond the boundary of the model, if that works for your application
2. Use a smaller roughing bit to cover more of the model.
3. Use the finishing bit in the roughing toolpath - this will essentially do the same thing as you're suggesting you want to happen. Then follow it with the finishing toolpath.

I'm sure there are others.

[ElderlyGent]

Good morning Dealguy11

Many thanks or your help. I have now set it up in the computer so that the frog is in a square so that the roughing pass goes to a selected boundary, I then offset that square inwards to give me a cleared part for the finishing tool to go straight to the cleared lowest part and it goes from there, It tracks along the Y axis moving across on the X axis doing nothing until it starts to meet the frog. It then follows the Z as well and so completes the shape, Well it does in the preview, so I now will try to put theory into practice.

EG