BobCad 21 circles corrupted?

[Tristar500]

I've noticed a problem reoccurring with BobCad 21 (21.5.3)

When machining a circle I've had the finished result very far from what I initially designed.

The resulting toolpath is distorted and usually if not always resembles two half circles one above the other but not concentric.

Any ideas?

I'm outputting to Mach 3 and the messed up file is visible on the Mach toolpath screen.

Note, the attached file was a perfect circle drawn in BC 21 then used the offset feature to create another series with the same center line.

Notice how the "circle" is no longer a circle and now a series of arcs and the center is no longer at "0,0,0"

What's up with this?

Frustrated!

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[machinehop5]

...it looks like the outer Ring is drawn in incorrectly....its not a circle. The file you posted shows up with my BC23 as two radius with Y offset .010 on the bottom radius....maybe a typing error was entered.

Note: have to add the .dxf file ext when saving file

[Tristar500]

This is the problem. I simply used the arc tool to create a circle around X0, Y0, Z0. Then used the offset tool was using a 3/16th endmill so 09375 inch offset. Then Change/Translate .007 to give me a shallow pocket.

Been using BobCad for 20 years so I'm pretty familiar with the CAD and the CAM side of the software.

I'm stumped!

[machinehop5]

...unfixed bugs with BC21 possible..... sometimes using a Number value that ends Odd numbered or to many decimals places can cause problems with software. Try rounding up or down .09375 to .0938 or 6.

[Tristar500]

I'll keep that in mind while drawing some parts over the next couple of days and see if that makes a difference,

Thanks!

[Tristar500]

So today I set out to bore a .52 inch hole through a piece of .375 6061 T6 Aluminum.

Simple right?

I start out and use the arc tool to create a circle with a radius of .26.

Then drop it down in Z to a depth of .38 (enough to bore the hole and a touch more)

I'm using a ,25 endmill do I do an offset of .125

Still simple stuff right?

Now I take it to the CAM side and set up auto roughing to drop down .02 increments.

I hit the 3D button and then "Cut Auto"

This is the code I get.

It's a mess.

While watching the mill I noticed the DRO would occasionally pull up a few thousands and then return to slowly dropping down to bore the hole.

What's up with that?

Then, upon recreating the geometry from the NC code I get a less than perfect circle and when viewed from the side you can see where it doesn't drop down evenly but it erratic at times.

Again Stumped!! I'm losing total faith in the software as I have to chase behind everything I do to make sure some phantom errors haven't "magically appeared".

Really don't want to have to learn new software at my age and the frustration is killing me.
Ugh!!

Any ideas gladly appreciated.

[machinehop5]

...I was just looking around today for V21 information and found the manual.
https://bobcad.com/wp-content/media/...ad-cam-v21.pdf

On page 152 there is Note about turning Off the COMP function in Cam Mode.
I'm not sure how V21 exactly works putting in Data but, I see something about using the "Other" function then selecting Pocket. Page 149
hope this helps

[the_gentlegiant]

Go into FILE/ENVIRONMENT/GENERAL and make sure you have your General Accuracy and Chain Gap set fine enough. If they somehow got set too course you can get problems, like the one your code shows giving you R0.26100. You might also be able to fix the extra trailing zero (in Attributes) that you don't need, as it's doubtful that the control has the resolution to make use of it anyway.

[Tristar500]

Go into FILE/ENVIRONMENT/GENERAL and make sure you have your General Accuracy and Chain Gap set fine enough. If they somehow got set too course you can get problems, like the one your code shows giving you R0.26100. You might also be able to fix the extra trailing zero (in Attributes) that you don't need, as it's doubtful that the control has the resolution to make use of it anyway.

Both General accuracy and chain gap at set at .0005

[the_gentlegiant]

I'd say that's too course. My General is at 0.000002 and Chain Gab is 0.00002. Even then I get the occasional errant 0.0001 added or subtracted for something that's been sized or stepped or mirrored or offset or what have you. Those numbers in my settings (V20) I think are the defaults. If not I seem to remember the defaults were pretty effing small. You could write down all your settings and hit the DEFAULT button and see what the software gives.

BTW - are you working on a machine without a tool changer? I can't imagine why you wouldn't drill a 1/2" hole first and then bring it to size at full depth in one pass with your end mill. No tool changer would explain that to some degree. (I'd get tired of changing tools that's for sure)

More BTW - I see you control your field width (resolution) and decimal digits in the CAM side under SETUP/COORDINATES. I knew it was somewhere.

[Tristar500]

I'd say that's too course. My General is at 0.000002 and Chain Gab is 0.00002. Even then I get the occasional errant 0.0001 added or subtracted for something that's been sized or stepped or mirrored or offset or what have you. Those numbers in my settings (V20) I think are the defaults. If not I seem to remember the defaults were pretty effing small. You could write down all your settings and hit the DEFAULT button and see what the software gives.

BTW - are you working on a machine without a tool changer? I can't imagine why you wouldn't drill a 1/2" hole first and then bring it to size at full depth in one pass with your end mill. No tool changer would explain that to some degree. (I'd get tired of changing tools that's for sure)

More BTW - I see you control your field width (resolution) and decimal digits in the CAM side under SETUP/COORDINATES. I knew it was somewhere.

Thanks!, I'll give that a look and see if it makes a difference.

[Tristar500]

Go into FILE/ENVIRONMENT/GENERAL and make sure you have your General Accuracy and Chain Gap set fine enough. If they somehow got set too course you can get problems, like the one your code shows giving you R0.26100. You might also be able to fix the extra trailing zero (in Attributes) that you don't need, as it's doubtful that the control has the resolution to make use of it anyway.

My field with value is 0
Decimal digits 4

Not sure what this means?

[the_gentlegiant]

I believe it means: (concerning CAM output)

Field width = maximum characters in a coordinate (If you were running a giant machine with travels over 100" you might need this at 7. I use 6.)
Decimal Digits = number of places filled after the decimal point. If "trailing Zeros" is off it will truncate to the least needed increment. Meaning it will make 2.1000 be 2.1

I leave trailing zeros off, but personally I like leading zeros as in 0.21 I find it easier to read then .21 Especially when it's crammed in with a bunch of other coordinates.

[machinehop5]

I believe it means: (concerning CAM output)

...good point gent....try MM vs Inch? input output? with Part settings in v21?

the number 3.141 has problem in machines that do numbers

[BNR_RANDY]

Been a long time since I looked at these setting. I am set to 0 field width. Per BobCad's help :

Leading Zeroes: When this option is checked BobCAD-CAM will create enough zeroes on the left hand side of a coordinate value to reach the specified Field width.

And Zero has worked for me for years.

[Tristar500]

This shows my settings. Don't believe I've every changed any of it in 15+ years?

[the_gentlegiant]

Did you ever change your chain gap and general accuracy settings to much finer values as I suggested earlier?

Also, I'd turn off 3D unless you're drawing in 3D. I get weird things going on even if I have a 3D file hidden and am working in 2d in the same file.

[Tristar500]

I made the suggested changes so now I'll wait and see if it continues to behave itself.

Thanks all!

Now if I could just get my drill routines back. They disapeared when I did a reset to factory. Don't know how to get them back. really used the G83 a lot. Still works on my laptop but gone on the desktop.

[the_gentlegiant]

You probably have to go over to your CAM side and go to SETUP, Configuration and also Cycle. Configuration is the script file it uses to create your code. Look in your BobCAD Program files on your hard drive and find the Configuration and Script files you used to use. It may auto load the Drilling cycles. If not you just install each one via the SETUP - Cycle menus.

I think the manual talks all about this stuff somewhere.

You might also have better luck using I and J instead of R.