[cismontguy]

I have a 3D CNC wood router, running BobCAM V24. I have created a 2D wing airfoil rib shape with lightening holes that I want to cut out of 1/4" plywood. The airfoil shape was drawn in AutoCAD and imported into BobCAM as a DWG file. I selected the geometry (outline) I want to cut, but for some reason BobCAM is missing some of my selected line segments and cuts the entire shape with in no logical order of cuts? It cuts here, then goes over there, on the profile, then comes back and cuts over here?

I do not understand what is going on ?

Is there a way to tell BobCAM to ignore tiny distances between line segments, too? Its a kind of complicated airfoil outline, and it would seem, not all the hundreds of line segments are snapped to one another.

Thanks in advance for any constructive help you can give.

[jrmach]

Sounds like some Geometry issues.A file would be most helpful.



This probably will not resolve all your issues,but the very first thing you should do,always,when importing a CAD file is go to utilities/reorganize/clean-up and optimize.RAF,I just edited this in as you posted that,ha.

When all the geometry is good,"Contours"will be powerful in helping with control of tool path.

[RAF.]

Have you tried using Utilities/Reorganize/Erase doubles/Clean up and Optimize

It might just be bad geom thru the translation

[cismontguy]

Thank you jrmach and RAF.. I really appreciate the help. I did not know about these features until just now. Will try this tomorrow and report back.

[tlharris]

Ditto what RAF and JR said... I'll just add a couple of comments, as we import a ton from various sources :

- with all due respect.... the Garbage-In/Garbage-Out rule does apply. I'm not sure of the source of the AutoCAD files. If they're yours, and you create clean geometry, then that will make for easier translations. If they're from a vendor, who actually created them in some non-ADesk product, and supplied you with 'AutoCAD files', then there can be a little more cleanup required. Even if they actually used AutoCAD, let's just say that the quality of the geometry is dependent on the operator.
- Make it a religious habit.... EVERY time you import, run through the Erase Doubles/CleanUp routine FIRST. It saves lots of time.
- As JR said, contours become your friend when you want more control, and in fact, can help troubleshoot things that sneak by Erase Doubles & CleanUp. Once you've done the optimizing routine, then try to create contours. If you can't get a contiguous contour (or you get multiple segments) for each rib/individual part, then zoom in on endpoints and fix minor problems. You might have to add a line segment here or there, or trim/extend something. The CleanUp routines are good, but they're not infallible.

[cismontguy]

I checked my original AutoCAD drawing imported into BobCAD and there are some breaks in the outline It was drawn in AutoDesk AutoCAD 2006, by yours truley, but never intended for CNC. So I will be more careful in the future for sure. But we have switched to SolidWorks 2013 for most things. This is a legacy drawing.

I do not see the "Clean up and Optimizing" command doing anything? Also I have a problem with the tool path changing which side of the outline it is on? I know how to change this (left or right) in the tool path set up, but I do not want it to changing by itself. The shape will be cut out wrong but I do not know why it is switching sides in a single Feature Profile ? Any ideas?

[tlharris]

Re: ACAD files.... we've all been there and done it. Just a reminder that shortcuts upstream will almost always cost you downstream... but that's not your current issue

Clean Up / Optimize might not fix everything. In my experience, it does help, especially when trying to sort out duplicate or overlapping entities that were created on different layers. Vector files created by graphic designers in Adobe Illustrator are especially prone to this, but we see it in ACAD files sometimes, too. SO - here are a couple of thoughts -
- make sure your geometry isn't picking up duplicates underneath. One way to confirm this is by shift-click-selecting, (not window-selecting) then deleting the selection, to see if there was anything left underneath it. If not, just UNDO and restore it. (You could Blank things out if you wanted, but it's more steps) If there are hidden entities beneath the ones you think you're toolpathing, you'll rip your hair out trying to figure out what's going on.
- The toolpath will reset back to default if you RESELECT it. It shouldn't 'change on its own'. If one part paths clockwise, and the next counter, it might be that they were created in different UCS's in ACAD, or maybe they were created as blocks, mirrored, or some other function that might have given them different normal vectors. In any event, maybe there's a better workaround, but I'll usually just create another feature for the problem parts, and toolpath them separately. While I generally try to clean up every file 100%, sometimes you just need to get the parts cut. So, to be clear, if you have 10 parts on the sheet, and 8 go the right way, with 2 weird ones that just want to path the other way, the simple solution is create a separate feature for just those two parts. Post it and cut

[RAF.]

I think that if you have breaks in the contour line it will do what ever it wants. You will most likely will have to join all of the lines or select each line so you can keep the chain in the same direction.

[Trotline]

If you've converted the geometry to contours, BobCAD will assume you want it to cut in the direction that the contour is pointed. [Utilities] <Reverse Contour> can change that direction. If you haven't converted, then you can do something similar by selecting the parts of the geometry in your preferred order.

Man, I wish Sorin's videos were still up. He really explained all of that so well. Almost makes me want to "clean room" them, and cover the same topics in some Youtube videos...

Luke

[jrmach]

Show us a file,we will show you what is wrong,that is if you can.
FWIW bobcad v24 videos - YouTube

[SBC Cycle]

Is there a way to tell BobCAM to ignore tiny distances between line segments, too? Its a kind of complicated airfoil outline, and it would seem, not all the hundreds of line segments are snapped to one another.

Try tweaking the Preferences-Settings Part-System-Chain setting. I've only used this once previously and had mild success. I assumed that if the endpoints were within the range of this setting, BobCAD would assume that they are "Chained".

[jrmach]

If you've converted the geometry to contours, BobCAD will assume you want it to cut in the direction that the contour is pointed. [Utilities] <Reverse Contour> can change that direction. If you haven't converted, then you can do something similar by selecting the parts of the geometry in your preferred order.

Man, I wish Sorin's videos were still up. He really explained all of that so well. Almost makes me want to "clean room" them, and cover the same topics in some Youtube videos...

Luke

Luke,I went to a seminar in Reno and met Sorin.He did not disappoint.Even though I knew most,I learned some things,and I learned his workflow.Really knows how to explain things so you understand.He actually owns and operates many CNC's.Machinist by trade.
I have all his video's and they are required viewing as far as I think.There is many hours worth.He gives a DVD at class.It is too bad some little punks were hacking his site,he just closed it down.
Maybe he will make available another way??They sure are all that.

[Trotline]

Yep, his videos gave me SUCH a leg up when I was first figuring out the basics. In fact, I ought to watch them again, since I know there was stuff that went by me back then. I have the full set for V24. If I did this stuff for a living, instead of fun and side money, I think I might spring for the seminar, too. As it is, though, I don't have any way to justify it, even if I did have the cash.

Given that he does training as a big source of income, it was great of him to ever put the videos up for free in the first place, so I have a hard time faulting him for not making them available again, given the hacking problems with his forum. It's sure a shame, though.

Luke

[cismontguy]

Hello Forum Members,

Well today was much more productive than yesterday. After several trials at closing all the line segments in my AutoCAD file and then importing that file into BobCAM (never have figured out their commands for trim, extend etc) I was able to get a good part CNC routed out. One helpful trick I came up with for myself, was to install a spring loaded pencil in the collet and run the program with a fresh sheet of plywood. This found any problems without wasting an expensive piece of aircraft grade materials. See pictures attached. Thanks for everyones help. Will report back when I get some more parts made. Attachment 209510Attachment 209512

[MAS]

My two & half cents worth, try drawing your parts with Bobcad. I use V23 for plasma cutting and I have similar issue also.
If I use BobCad to draw my parts then I get excellent toolpaths.

[mmoe]

My two & half cents worth, try drawing your parts with Bobcad. I use V23 for plasma cutting and I have similar issue also.
If I use BobCad to draw my parts then I get excellent toolpaths.

If it was drawn correctly in Autocad, it would still produce excellent toolpaths as well. That said, the tangent to two circles function in Bobcad is probably the fastest and best implementation of that specific task I've ever used in any CAD system.

For the OP, Not sure if you were just eyeballing things or how you ended up with gaps, but here's just a couple small tips. You can create those cutouts in the middle by using the tangent drawing function in Autocad and it will pretty well guarantee that you'll end up with good geometry. You would start by drawing and locating the circle at each end of those cutouts, then switch to line and type "TAN" followed by clicking on the circle near where you want the line to start from. Then type "TAN" again and click on the other circle where you want it to intersect. This should create a line that is perfectly tangent to both circles. Do the same for the other side, then use the trim tool to trim out the segments of circles left inside. Also, be sure you're starting a line/arc from a snap by looking for the snap indicator. Don't assume that if you are close to the end of a line that it actually snapped to it. Depending on how you have your snaps setup, it may not be snapped. Another tip is to use the close function at the end of a polyline to be sure that the geometry is properly closed. When you get to your last line, just type "C" and enter. This will automatically connect a line from the last point to the start point.

[jrmach]

Geez,a lot of work it sounds like to do something simple in ACAD.

[mmoe]

Geez,a lot of work it sounds like to do something simple in ACAD.

I find Bobcad and Autocad to be similar in terms of the level of difficulty to use or learn. Bobcad has more input boxes and buttons to deal with and fewer snap options, but it also has more "shortcuts" built in to make some tasks easier, like the line tangent to two circles function. If you used 20 different CAD systems, you'd discover that this feature is never as easy as it is in Bobcad. This is because Bobcad created a dedicated shortcut for accomplishing the task where other products typically rely on the user to know how to use the existing tools to accomplish the job. To be totally fair, a skilled Autocad user could do the task I described in seconds. It is less "easy", but perhaps just as fast as going to a menu and clicking on the tangent line function in Bobcad. Autocad is best when you know the commands and don't use the mouse as much. It does usually take less time to type something than it does to move the mouse over to a menu and back. For example, you can click on the "line" tool in Autocad, or you can just type "L" (upper or lowercase) and hit enter to start a line. If you want it to start at X0Y0, you can either hunt for the snap with the mouse, or just type "0,0" and enter. Once you are good with Autocad, typing is usually faster than using the mouse, and you also get good at typing with one hand so you can use the mouse simultaneously to entering these commands.

If you just want to try "Autocad" and fool around with it, you could use Draftsight, which is a free Acad clone that is developed by Dassault (Solidworks). It's not quite as full featured as full on Autocad, but I'm very impressed with how similar it is overall. I have not yet found a command that works in Acad that doesn't work exactly the same in Draftsight. There are very slight visual differences, but it's pretty darned close.

[jrmach]

Worlds fastest mouse driver here,but slower than a slug typing.I better stay with BoB for now.