Area clear avoiding an island?

[dlenardu]

I was wondering if there is a way to clear a block away avoiding an island where the tool cuts from the outside of the block toward the island?

For instance say I have a 12"x6" block with an irregular island in the center of the block. I want to get rid of everything except the irregular island. I'm trying to avoid having the endmill doing a full slot width cut. The only way I have been able to do this is to increase the XY finish and then decrease it each time until I get to the final dimension of my irregular part. Doing this though has a lot of wasted travel not cutting anything. Any suggestions?

[John S.]

I don't fully understand the problem.

If you are doing a pocket at some point, usually the first cut you will have the end mill doing a full width pass otherwise how can you get it into the pocket ?

Once in the pocket you can adjust the step over to determine how much is cut per pass.

Ramping down will help use the cutting forces. can you post a CAM drawing so we can advise better ?

John S.

[dlenardu]

John,

What I am wanting to do is like chip away at the block so that my endmill is not doing a full slot cut. I am machining aluminum and I do not have coolant only air, so I would like to avoid full slots as much as possible. Currently the only way I have found to do what I want is the have the xy finish on a goround large and then decrease it each pass. Doing this however creates wasted time as the cutter is cutting air on the first few passes. I am attaching a .dra and a .cnc of an example for you to look at test1.zip

[andre-dolphin]

Use Area Clear instead of Goround.

Set the outside contour as "block" and "part" as an island.

Under the Options tab you will see a whole bunch of options about strategy and so on. One of the things you may want to change is the "Swathe" value this the amount of overlap between passes.

If you don't want to cut the full width of the tool when the tool starts you could draw the "block" as being the tool radius bigger, this will mean that the tool is only cutting 50% of tool dia on the first pass runs the outside of the block.

Hope this is clear.

ATB
Andre

[John S.]

I did what Andre said earlier and was going to post it but had problems.
Just tried it again but still have a problem that should not be there.

I have attached the file, basically I have drawn a new box round the job to form the outer and called the part as the island, as Andre says I have reduced the swathe to 20% to cut down on how much per pass it cuts.

In this example I have also clicked "Ignore cut depth " so it only does one pass for clarity.

Now the problem, Dolphin has been told to bi- directional machine with limited overlap to reduce cutting forces which is what the OP wants, however watch the simulation with animate tool it starts off Ok and does as requested until at 4 minutes 50 seconds it starts to area clear the top part of the shape and at this point it contours the outside of the island using the full width of the tool instead of working from the outside in.

Can anyone from Dolphin explain why please ?

John S.

[dlenardu]

ok, I made the outer box around the entire block and set it up to area clear. Even with the 20% swathe, I get a completely different tool path than what John S got in his example. I am still getting full cutter engagement. Is there a way for it to cut from the outside in?

[John S.]

It all depends on the cutter swathe change that value and you get all sorts of cutter toolpaths.

I can't see an easy way other that how you did it to start with to ensure it does what you want.
A pity really as it's a nice program but lacking detail which really needs to be addressed.

John s.

[andre-dolphin]

If you set the machining angle to 45 degress the result is pretty much what is required.

There are no hard and fast rules about what is the value optimum for this, it depends entirely on the shapes involved.

Setting to 0,90 or 45 produces different results depending on what outcome is required.

ATB
Andre

[John S.]

Andre, but in all the examples you are still getting the tool going in at full width somewhere even though the shape will allow it to be nibbled away from the outside in.

When this happens it ignores the swathe width.

John S

[dlenardu]

I have tried eveything possible, different angles, cutting swathe, etc but still at some point will get full cutter engagement. I really wish there was a way for it to machine from outside in, this would save me a lot of wasted cutting time.

[dlenardu]

I have tried everything I can think of. Different angles, different swathe passes, etc. I still get full cutter engagement at some point. I would really like to find a way around this. It would save me a lot of wasted cutting time.

[andre-dolphin]

The is no absolutely guaranteed way to avoid full tool cutting, there are various method to minimise this such as changing the swathe and angle parameters.

One other method that reduces it "virtually" no full cutting is uni-directional linear machining (only mcahines in one direction). However this results in a lot of rapid movement between the end of one pass and the beginning of the next, this really needs a tool that can plunge cut, althought you can use the Ramp option with Zig-Zag and a shallow angle for tools that can't plunge.

We are aware of the above issues and are looking into them.

ATB
Andre