[airbrush]

Hi all,

just getting my feet wet in bobcad(v26) i have simple 2d parts that i want to cut out. How do I add tabs to my profile cut?

thx

[mmoe]

In V26 you have to do it one of two ways. First, you can do it manually by breaking up the geometry where you want tabs, then programming each section. Not ideal, but can be done that way. The second way, which is more automated, is to use the Bobnest feature. Within Bobnest is the option to use tabs, which you can specify locations manually or automatically. If you don't have the Bobnest option, but you don't want to do this manually, you'll need to see if you can get the Bobnest module added to your license.

Tabs is a feature that we had requested for a very long time, but just finally got added in V28 to the regular profile function. Not sure why it took so long for them to add it, and I know it was one of their most requested features for a long time, but unless you have V28, you need to have Bobnest to do it (or be creative about doing it manually). Let me know if you don't have Bobnest and I'll post up a sample of how to do it without Bobnest, but it's a bit of a time consuming task if you plan to do this often, enough so that I'd suggest Bobnest or better yet updating to V28.

[airbrush]

i remember watching the nesting and tabs video when i was researching what cam package to buy....which is one of the reasons i went with bobcad...i have v26 4 axis standard build 1335. I thought this was part of the package. I bought it last year as i was hoping to have my home cnc up and running by then, as usual when its a hobby other things take priority.

I've contacted Bobcad about this, awaiting their response. I don't see a nesting option in mine...

...i'll be very sad about this if they want me to pay for a package again just to get something like this....its such a basic function i don't understand how this isnt in there by default...

There's no way i would want to do this manually...what a waste of time.

[airbrush]

are there addon scripts/plugins/macros for bobcad that users have created to do this??

[mmoe]

are there addon scripts/plugins/macros for bobcad that users have created to do this??

Can you post a sample file of what you are typically trying to cut? What kind of machine? To post a file, use the "Go Advanced" tab, the upload a ZIP version of the .bbcd file (right click on .bbcd file, the select "send to" and "compressed folder" to make ZIP).

If you're using a router, another option is to onion skin the part. This is equally effective in most cases and requires no extra features in Bobcad. In fact, I often prefer this to tabs for parts that are too small for my vacuum hold down. It's easier to pop them out (push down, not up so that you don't break the edge into the part), and they clean up pretty fast if you keep the skin thin enough. If you don't have any vacuum hold down, the skin might have to be a little thicker and then tabs would probably be faster to clean up.

I don't like cleaning things up too much, so I also often use a 2" wide double stick tape to hold material down when it's tricky. It's basically like the old beige masking tape, but with sticky on two sides. I buy this at golf pro shops, where they use it to re-grip clubs, but some have better tape than others, so you may have to experiment to find one that you like. Holds exceptionally well and comes off easy after you are done (assuming you can get the part off to remove the tape). To give an idea of how well it holds, I've machined 3" and 4" thick aluminum blocks 5"x5" with up to 1/2" roughing cuts on a 1/2" cutter and using misted coolant hand applied during machining. Even after several hours of cutting with misted coolant, the tape holds well enough to get a perfect part off the machine. The problem is usually getting the part off the machine without marring the part since it holds down so hard! I have made some high end aluminum clamping cauls this way that come out with a glassy smooth surface finish, with no need to use clamps or fixtures at all. That allows me to machine the entire part non-stop, where normally you'd have to move clamps around or have multiple fixtures. I can do the roughing, drilling and finishing operations all at once. It wouldn't work with flooding coolant, but if you have only misted coolant (light oil on Aluminum or alcohol on plastics) or no coolant (wood, etc.), then the tape is way more than strong enough. Too much coolant gets under the part and into the tape, which could break the tape down and make it come loose, but you'd really have to be flooding it before that would happen.

[airbrush]

no need to upload a file...just simple profile cuts.

I've seen people using doublside tape...not sure what kind. I have some carpet tape which thin and very tacky.

By onion skin you mean just don't cut all the way through the part? I would prefer just to cut through and clean up the tabs after.

[SBC Cycle]

are there addon scripts/plugins/macros for bobcad that users have created to do this??

Yes, by user stevespo. Here is a nice discussion about tabbing with scripting: http://www.cnczone.com/forums/bobcad...66-bobcad.html

Expect to do some work, the script is very old and if I recall it had some bugs or needed something worked out but it did work for the user.

Never had to tab parts before myself. I find the concept somewhat bizarre but I'm sure there is sound reasoning for it other than laser/waterjet cutting.

[airbrush]

Quite disappointed with bobcad at the moment as it was never explained to me when i bought the package that nesting is an addon that you have to pay for....i assumed it was part of bobcad and was one of the features i was looking for....

[airbrush]

Tabs is a feature that we had requested for a very long time, but just finally got added in V28 to the regular profile function. Not sure why it took so long for them to add it, and I know it was one of their most requested features for a long time, but unless you have V28, you need to have Bobnest to do it (or be creative about doing it manually). Let me know if you don't have Bobnest and I'll post up a sample of how to do it without Bobnest, but it's a bit of a time consuming task if you plan to do this often, enough so that I'd suggest Bobnest or better yet updating to V28.

sample would be appreciated as i'm guess i'm stuck now without tabbing as Bobcad wants me to shell out more dough for this...i thought is was part of bobcad and not and addon and it was never explained to me when i bought that this isn't an included feature...great.

[SBC Cycle]

It has never been a feature of BobCAD before V28 unless you had a separate product (BobNest) so I'm not sure how you would have assumed it was in there. Did you buy V27 after V28 was released?

[airbrush]

It has never been a feature of BobCAD before V28 unless you had a separate product (BobNest) so I'm not sure how you would have assumed it was in there. Did you buy V27 after V28 was released?

I have v26. I am a hobbyist user and newbie to cnc. When i was looking at which cam software to buy I watched through a good chunk of the bobcad videos, it showed nesting with tabbing...i thought great, that something i want to have. When i purchased i had no idea this was an addon, nor was it mentioned to me.

User error to blame...looks like i get to learn the hard way $$$

[mmoe]

Do you use Bobcad to do your CAD work or do you use something else and then import the CAD to Bobcad? Do you usually model the parts or just do 2d drawings? I'll put together a sample file later today, but this will help me make it more how you are doing it.

[airbrush]

Do you use Bobcad to do your CAD work or do you use something else and then import the CAD to Bobcad? Do you usually model the parts or just do 2d drawings? I'll put together a sample file later today, but this will help me make it more how you are doing it.

I use 3dmax and zbrush. for the parts Im doing now its 2d exported
dxf. will also be bringing in models as stl .

[mmoe]

I use 3dmax and zbrush. for the parts Im doing now its 2d exported
dxf. will also be bringing in models as stl .

I'll have to think about that. I don't know if the workflow could be any more difficult! So from what I gather, you have some 2d parts for now, but plan to have some 3d parts later on which also need tabs? It's easier to do in 3d for sure since that is just a matter of modeling a frame and some tabs (there is no other way to do this even with Bobnest, since that only deals with 2d).

[airbrush]

I found this video which is helpful...and fairly simple to setup. Just create breaks in my spline which is easy to do in 3dmax.

https://www.youtube.com/watch?v=OkhaMhH4Yfs

although I would probably just run a full profile around until 'x' depth and then do the tabs after...guess it doesn't really matter...in my mind it makes more sense to me that way...

[mmoe]

You pretty well described how I would approach it. Break up the geometry where you want the tabs first. Then run two profiles. The first profile is set to about 1-2mm above the bottom of the part with the entire chain selected. The second is set to full depth, but only the areas between the tabs are selected. Breaking up the geometry is really the only significant extra time, and it depends on how many parts you have to cut whether or not it will be a big problem. Also, you'll find that the tool has to rapid out of the material to the clearance height and then plunge back into the material every time it encounters a tab, which is a little clunky at the machining end. You can hand edit the code, but with the possibility of an error it's not worth it.

[airbrush]

yah its not big deal to me if it rapids out..yes a little clunky...as long as its works. Not going to be doing big production runs of anything. a little more setup involved.

[mmoe]

One other thing to remember. The finish pass will move the tool to exactly the end point of the selected line right before a tab, which means that half of the tool will be extending beyond that line. If you were to create a 1/2" long tab and you are cutting with a 1/2" cutter, you won't have a tab when you are done. Rule of thumb is to decide how long you want the tab, then add the diameter of the bit to determine how long the line needs to be to represent the tab.

[airbrush]

Right...thanks.

[LeWhite]

My fav non tab, tab strategy is to use the engrave strategy as a 0.005 finish pass. But you have to offset the geometry one tool radius. Set top of part at the bottom. Set rapid and feed both equal to tab height. And engrave depth to about 0.010. Easier done than said.

- - - Updated - - -

My fav non tab, tab strategy is to use the engrave strategy as a 0.005 finish pass. But you have to offset the geometry one tool radius. Set top of part at the bottom. Set rapid and feed both equal to tab height. And engrave depth to about 0.010. Easier done than said.