V21 Pocketing Question

[Terry G]

I am using V21 with the DeskCNC post processor. I attempted to create a sprial pocket by selecting multiple objects. The toolpath was created sucessfully, and I generated the gcode. The pocketing involved many passes with a very small diameter end mill.

The problem with the gcode generated is that the tool never returns to the Z rapid plane setting when it needs to move to a different location to pocket.

The pocket is one continuous pocket but an odd shape with islands in the middle etc.. So when it finishes one pocket its goes G01 at my -Z setting to the next area then continues to pocket. What should happen is a G00 to my Z rapid plane setting, move to the new spot, then continue to pocket.

Any ideas? Thanks.

[sorincnc]

when creating the spiral pocket, make sure that the "connect" box is checked and also "connect rest with dotted lines" is checked as well as "mark start" When the tool path needs to go over islands, Bobcad creates fine dash lines witch later on it is the equivalent of G) rapid moves to whatever clearance you have set on the UD icon (cam side).
Did you download the videos from my web site yet???? If not, go to www.cadcamtrainer.com and download them for free.
hope this helps,
Sorin

[Terry G]

I double checked my settings, and I did not have the "connect rest with dotted lines" setting. I tried this, but still have the same problem. The G0 rapid works fine when the toolpath needs to go over an island. The problem is that when the tool needs to move to a different location within the same pocket, (and not crossing over any islands), it does not do a G0 rapid move. It just keeps cutting at my cutting depth as it traverses to the new location.

Sure, in the end it will machine just fine, but it just doesn't seem right to keep the cutter down while moving to a new location.

Let me know if their is anything else I can do or if this is normal operation.

Thanks.

[sorincnc]

Could you please post the file itself and let me know what boxes are checked in the "spiral pocket window"??? I will try to see what is going on because the spiral pocket routine works very well and gives a very efficient tool path. It must be one of your settings but I need to see the part since it might require some trials on my part..... Please advise also on tool size, step over and finish allowance.

[Terry G]

Attached are my .DXF file and Gcode I generated.

Operation Roughing is checked. Tool Diameter .020". Distance between lines .010" Stock Distance 0. Connect, Connect rest with dotted lines, mark start are all checked. There is no finish allowance since I am only taking off .0025" of copper from a PCB.

Thats it for the spiral pocket window.

My environment general tab is set for general accuracy .001 and chain gap .0005. I had to change the general accuracy from the inital .0001" setting because it was doing strange things with the toolpaths. It would leave a bunch of toolpaths out, and send the tool right through an island, and even overlap 3 to 4 times on almost the exact same toolpath.

You can try it and see what I mean. But with the .001" accuracy, the toolpaths look perfect. Still, when the tool needs to move to a new location without crossing over an island, it does not do a G0 rapid.

Also one other questions which you will see in the files, I change my UCS to the small marks I made on the lower left hand side of the drawing. But when the gcode is generated, it always wants to go back to the center of the drawing (old 0,0 setting), then start machining. Anything I can do to fix that?

Thanks for taking a look at this. It took me a little while to get back to you since I don't always have access to the machine with this software.

[tjones]

The UCS change is normal. The code is generated as if the new UCS is the home position and therefore the path will appear from the screen zero when shown.

The UCS change is simply a way to change the zero while generating the code not for a perminate system change. Otherwise then you should move your part to the zero and not the UCS. The UCS is usefull like the workpiece coordinate system is on the machine.

As for the moving I am not sure that can be optimized without some manual editing. Otherwsie you could simply pocket the different areas then profile the entire contour afterwards. Bobcad simply does not know where there is air in your setup and when there is material for continuing the cut with stepover values. You really need to be careful in editing manually even so as not to rapid into solid stock. Maybe raise Z before rapid moving and then feed back down. (I never like rapid moves inside a pocket myself...raise Z first then lower afterward.)

[Terry G]

I still don't see why bobcad needs to move my tool to the old UCS 0,0, then start machining.

If you open the attachment you can see what I am talking about. The toolpath starts at my new UCS 0,0 then moves to the old 0,0 then starts machining. This can be a huge problem especially if I am far away from the original UCS 0,0.

I would much rather just have the corner of my part at the actual 0,0 without having to generate a new UCS. But this seems to be fairly difficult to do accurately. I use Autocad, and it is not very realistic to create a part and move it to 0,0 just so it will line up with bobcad. Even when I change the UCS in Autocad, for some reason it does not save this info, or bobcad does not use this info. The part is offset as it was in autocad.

I have used deskcnc for a few years and they have a great command which lets you select the drawing and just move to origin or center on origin. It will but the lower left corner right at 0,0. I do not machine many complicated parts, but this feature has worked great for me over the years.

About the pocketing, also from the drawing I attached you can see that the dotted lines (G0 move) show up when crossing an island. But when the tool needs to move to a different location within the pocket, it does not raise up and do a rapid move. It keeps cutting at my -Z height.

This all may be normal for bobcad and I'm just not used to it since deskcnc would always lift the cutter when moving to a different location regardless if it was crossing an island or not. Just want to make sure I understand how it all works. And I know I still have a lot to learn.

Thanks.

[tjones]

Try using the translate feature. Make sure that the snaps are on in your settings. Now moving should be a simple few clicks.

[Terry G]

Originally Posted by tjones Try using the translate feature. Make sure that the snaps are on in your settings. Now moving should be a simple few clicks.

Thanks, that worked perfect.

[Terry G]

Originally Posted by sorincnc Could you please post the file itself and let me know what boxes are checked in the "spiral pocket window"??? I will try to see what is going on because the spiral pocket routine works very well and gives a very efficient tool path. It must be one of your settings but I need to see the part since it might require some trials on my part..... Please advise also on tool size, step over and finish allowance.

Hi Sorincnc,

Just wondering if you had a chance to look at the files I posted. I understand you must be very busy and if you have not had a chance, no rush at all.

Thanks.

[The One]

Terry,

It looks like the Tool Size, Step Over and Finish Allowance are causing the issues. There are Clearance moves in the program, but the system is also making paths in the small around the outside of the part. I think these are the paths you are having trouble with. The max distance I found in these smaller areas was 0.04" and the system generated paths in this area.

What is the Tool Diameter you are trying to use?

Regards