Help for open a pocket on a cylinder

[David Colin]

This is a common machining i have to do: To open a pocket on a cylinder. I would like to optimize toolpaths because stock isn't a box but cylinder. So if i use a standard 2d pocket function, tool is gonna loose too much time. I usually manage this with contour toolpath+2d pocket but i'm pretty sure there are better and quickier ways to make it. Probably with surfaces machining functions. Any advices ?

 

I uploaded a file on Cadcam FTP (Directory: MC9 / Filename: POCKET-OPENING.MC9)

[Toolfab]

What about just drilling thru then sending an endmill around the edge and just dropping that chunk into the cavity.

 

or maybe I am just

 

[David Colin]

Nice idea. I will advise the guy who prepare machining job.

 

However, if i still must remove all chips. Best known method ?

[Guest CNC Apps Guy 1]

David,

 

Have you tried using two boundaries for your pocket???

[ricky_fire]

Hi David

 

What Toolfab has suggested is the fastest & best way

I would like to add that instead of drilling u could ramp and then move the endmill around the edge.

That avoids the drilling cycle

I would recommend using a round insert bull cutter with a shank of a lesser diameter to avoid rubbing against the wall.

 

Hope this makes sense

So dont give me

[Camdude®]

+1 to James, inner / outer boundary will solve problem.

[Müřlıń®]

+1 to James.

 

I always draw a boundary that is a little bigger than the tool dia around my box or cylinder.

 

Then when you run a pocket on the 2-d lines, the tool will plunge OFF the workpiece.

 

Using a Zig-Zag path with the finish outer boundary unchecked and KEEP the tool down checked. Finish boundary after each pass.

 

 

Murlin

[Mgrenier]

Hello all,

 

quote:

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So if i use a standard 2d pocket function, tool is gonna loose too much time

---

I am also having this problem

 

 

quote:

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What about just drilling thru then sending an endmill around the edge and just dropping that chunk into the cavity.

---

That is what I do for small pockets. But what would you do if you had a 20"Ø pocket to open on the diameter of a 100"Ø cylinder?

 

Have a nice day,

[cadist]

In such case we prefer helix under circle toolpaths with the help of a bull tool with dia a little more than radius of hole.

[Fig sign]

David .

I can do it in a lot of ways .

If it is a through pocket the simplest way to do is a 3d contour .

It can be a problem if you are taking more then one cut ,because if you have fillets and pocket is angled ,keeping tangency draws to the tool jumping too deep in some places .

If it not a prob ,that`s the simplest way .

My part before a couple of days I did in this manner .

You can always also make the contour toolpath and project it on a cylinder .

the same for a pocket .

You can also make a regular poket and trim the toolpath after that too .

A bit dirty but works .

The best is to project ,IMHO

You want some example ?!?

[David Colin]

You want some example ?!?

 

Sure!

 

Thanks for your help.

[Fig sign]

I will put in the Dirty tricks thread soon .

Stay tuned ,David

[Fig sign]

David .

Look in ftp in Mc9 folder at file :

 

LAZYCYLPOCKET.zip .

 

I will explain later .

Just say is this is what you looking for ??!!??

 

HTH

ITHH

[David Colin]

Yes, this is fine for finish!

But what i really would like is to rough with constant z-depth (tool/material) and let Mcam to stop contours according to stock boundaries(surface cylinder).

 

A stuff we didn't talk here about opening pockets that way (contour and let middle part) is vibrations at the end of contour...

[Fig sign]

What i do is this cut through countour with offset value 2-3 mm and then finish like I showed .

BTW in project make faked pocket and point surface project operation to it and you will get nice pocket .

But the best is contour - less vibrations ,if you set your depth right (checked ) IMHO .

And very fast

The last cut enter deeper 3-5 millimeters with depth take off 1 mm and less RPM you will not have big vibrations .

I do it in steel with success always

You can leave on the contour tab like in wire EDm ,put MO ,broke all tabs by hand and make finish cut .All is possible .

But I prefer simple things ,I would go with contour ,and remember I run my machines ,I would never write something not good for me

HTH

[Jean-Simon]

Hi David, I've done a trim on your toolpath, it helps a little but I'd like to have some peoples help on 2 boundaries for trimming, has anyone succeed with 2 boundaries? Look at the file POCKET-OPENING-SIMON and try to select the 2 cyan (color 11) boundaries, would be nice if it'd work. HTH!

 

Simon

[Jean-Simon]

Sorry file name is pocket-opening-trimmed.

 

 

+1 on post count!

[David Colin]

That's pretty fine. I just invert your chains and it trimmed correctly with 2 boundaries. However there are glitches remaining (Z-clearance)

[Fig sign]

I changed your file to my taste .

See the file POCKET-OPENINGISK.zip

 

 

Waiting for the answer

[David Colin]

Hi Iskander.

I tried your file and should work fine to first roughing but i hope this won't take too much time. I will then use common contour roughing.

[Fig sign]

So I understand it is Ok ?

Check pocket offsets I have not added them and all the other nessasary things

Good luck

[David Colin]

Yes, it will be