Re: [CAD_CAM_EDM_DRO] BobCad-Cam / What am I doing????

Paul,

I used Bobcad v17 for about 2 years or so . Started w/ V14 (1995?),
stayed with it through V17, moved away from it as soon as I could. (2001)
I still have it loaded on an older laptop of mine.

> program,version 17 for creating my parts. I'm trying to teach myself
> the basic's, however I'm running into problems. I'm looking for an
> individual that uses this program so that I can bounce some questions
> off him/her.

I've attached some clips from a couple posts of mine in the past. Perhaps
they'll help.
If you aren't too set on using BobCAD v17, I'd strongly suggest looking
at something else, like Dolphin or Vector. You may find it easier to do your
wire frame drawing in one of those two's CAD only module (Dolphin's is free,
Vector's is low cost), and then import them via DXF or IGES into BobCAD.

Regards,

Keith




<<Start old posts:>>

***Dec 3, 2001, part 1***

Subject: Re: [CAD_CAM_EDM_DRO] BobCad??

> My next goal is to be able to get BobCad to do a complex 3D surface. I
> expected this to be straightforward when I bought the software, but now I
> think otherwise. I want to import a 3D model and generate g-code, not
> redraw my 3D model in BobCad.

James,

As far as importing models into BobCAD v17, most will need to be
modified by you. On anything beyond wireframe is often a long, tedious, or
non-feasible task. Wireframes almost invariably need to be tweaked for
'skin'-ing. (intersections, inside curves, entity count between 'rungs'...)
Solids and surfaces have to be imported (IGES) as edges in BobCAD. Each
surface 'patch' having a line perimeter means two entities of almost the
exact same position and size wherever surface patches meet. A real pain to
clean up. Then you've still the tweaking process.
For business use, I'd recommend moving up to a CAD/CAM program that
handles surfaces and solids, and can import current IGES files.

- Keith Rumley

Now, if you've more time than money, which includes most :)...
To make 3D complex items, I found that it worked best to manually create
a new wireframe offset from the original model by the cutter center
distance*. Next, use the skin tool with an 'end radius' of zero and a
constant stepover to create the toolpath, the stepover amount determining
surface smoothness. ('distance between lines' = stepover)
Not only does this simplify dealing with double entities and
less-than-perfect models, but you can modify the wireframe in another CAD
program, say a legacy version of ACAD, or IntelliCad, which has better view
and entity manipulation.
Certain details, such as steep walls and multiple sharp corners, usually
need a separate toolpath.
If you use the original model, BobCAD's offsetting tend to result in
gouges, wierd tangents, and the like. With a zero tool diameter, BobCAD
won't do the goofy offsetting tricks, and your toolpath will fit your
boundaries exactly.

* A good way to get a start on the new offset wireframe is to use the skin
tool with a large distance between lines, then from the newly created
offsets you can 'chain' select the edge lines you need.

'Copy' them to clipboard, 'Undo' back past the skin command, 'paste'
from clipboard. Wa-La! Do it once in each of the two perpendicular
directions of the surface 'patch'.
In the skin tool under the 'Connect' heading select 'None', otherwise
it's near impossible to select the contour edges you want without getting
unwanted extra entities.
To get just the two offset edges, use a 'distance between lines' greater
than the distance between your surface boundaries. Use less distance if you
need cross-sectional segments.


*** Dec 3, 2001, Part 2 ***

Subject: Things I wish someone had told me when I was using BobCAD
As I was writing out my angle on the CAD comparison post, I was reminded of
some of my initial frustrations with BobCAD v17. Particularly 3D toolpaths.
So, for what its worth, here's a strategy I've used for the development of
complex 3D toolpaths from wireframe models in BobCAD. Perhaps some of this
would be useful in Vector, as well.

OK, I also cheated at times and used ACAD for building the wire-frame
(better osnap and viewing, coordinate control). But, this is all BobCAD
below. :)

- Keith


* Note: This is for 'I've got more time than money' types, and for speeding
up odd fillet creation. Also assumed is a working knowledge of BobCAD v17

The main concept is using the 'skin' tool to create boundary control curves
which are offset the cutter center distance from the wireframe, then using a
cutter of zero radius to create a toolpath. Another way of looking at it is
creating toolpath 'skin' that doesn't require any cutter offset figuring by
BobCAD.
It seems that most of the problems with contours come from offsets
intersecting to form undercuts and wierd shapes.

1. Using the 'skin' tool, create a widely spaced toolpath, offset the
proper center-of-cutter to part distance. (ALT, 3, U, S in sequence) The
'Max distance between lines' should be set to a distance greater than
that between your section segments. The resulting boundary curves (the main
toolpath curves) are created only at each path/section intersection, and at
entity endpoints.
Use the 'ruled' (parallel to the path entities), 'zig-zag' (parallel to the
section entities), and side of surface check box to get the proper
orientation and side of wireframe.

2. Copy the boundary curves you need to the clipboard (CTRL-C), then 'undo'
(CTRL-Z) back to before the skin command. Usually the curves you want are
the beginning and ending ones of
the toolpath. (ALT, E, S, C in sequence - select chain..)

* Alternatively, If more control curves are needed, set the 'Max
distance between lines" to less than the distance between sections. By
creating more curves (denser toolpath) it is possible to create the upper
and lower bounds at the same time, too - using the point tool and 3-point
curve tool (or whatever). snapping to the toolpath curve endpoints. (so that
you have four sides...)

3. Paste the curves back in, and modify/divide if necessary to obtain the
prober entity counts, tie in to the paths/sections, etc. These curves
become your toolpath surface boundarys. As is good practice, keep path and
section entities on different layers and colors. Make sure the pasted
entities are assigned correctly, too.

It may be necessary to run the skin tool twice to create all four sides
* Note that you can still have many more than four paths and sections.
* BobCAD v17 allows sections to have non-matching entity counts. Useful
if you use splines for sections.

4. Run the skin tool again, this time using your offset control curves as
the paths and sections. Set the cutter to zero radius. For a 'ruled'
surface, stepover is set by the 'Max distance between lines' in the final
dialog box of the skin tool. For a 'zig-zag' toolpath, you need to catch the
first dialog box - 'Max length of division' - to set stepover.

This has the benefit of fitting exactly to your boundaries, allowing a
toolpath up over a fillet edge, etc.

Another strategy is to lay out the main model planes, and using the ruled
surface tool create quick roughing schemes. Then follow with finish, then
fillets.

Ruled surf is also good for any surface that can be 'extruded'. Rotate your
sectional curves (usually non-planar...) around to plan orientation (looking
down from Z) and 'move to Z' entities. Sometimes it's necessary to divide
arcs, put points on entity ends, and 'move to Z' the points, then recreate
the arcs using the 3-point arc tool or the spline tool. Then, with the new
'flat' profile, rotate back to desired angle, and position as needed. (May
need to leave some points suspended in Z, in order move flat up, then rotate
back....)

For non-orthogonal fillets, especially arcs in different planes...study a
book on plane and solid geometry. Basically you do the thinking, and use
BobCAD as a crutch. Much better than paper, IMO.

For a convoluted description....

I'd change the view into the plane of the arc I needed to create (ALT, V,
L, 'orient', in sequence) Select arc center first, then the two entity end
points, or points on the entity. (order of the second two not that
important) This is sometimes easier than finding and writing down 8 digits
of two angles. Sometimes it's faster to find the angle using construction
lines, and rotate the view to it.
Once in the object plane, an arc of known radius and included angle from
the center point can be made. I found that this makes for accurate trims and
entity creation, especially if the lines coming in aren't on the same plane
as the arc needs to be for your toolpath.
Or, create one in an orthogonal, and rotate it around. BobCAD creates
new entities at your viewing angle, and also reports line angles that way.
(Incorrectly, if you aren't in the object's plane)

BobCAD's IGES import of surfaces and models give the trim curves, usually
doubled on top of each other. They need a fair amount of cleanup.

'Copy to Clipboard' and 'UNDO' is a very useful process, because it cleans
up all stray construction entities (especially small spline and toolpath
entities, and those blanked out). If you missed copying something, you'll
remember to save the file before 'undo'-ing next time. :) On a 'big' file,
this cuts down on construction layer congestion (what were those 'surfaces'
for?)

'Divide' has the benefit of leaving arc entities as arcs, interpolate
converts arcs into lines. (Arcs give smoother 2D cuts)

I liked having my path layer named 'P' and section layer named 'S', as
BobCAD will go to the first listing of the keyboard key tapped when in the
select layer for path/section dialogs.

*** Dec 3, 2001, Part 3 ***

Subject: Re: [CAD_CAM_EDM_DRO] BobCad??

> BobCAD does all kinds of weird stuff.

Yup.

>The only solution I've found to
> prevent the machine from going all the way to the bottom is actually
> changing that first Z value manually in NCcam. You just have to checkevery
> time before you run a new program. I've broken more end mills than I'de
> like
> to admit due to this problem.

I ran into this one, too. Solution is to 'bring tool to clearance' before
starting the auto-cut.

> Another problem that I found is that on multiple passes sometimes BobCAD
> decides to bring the tool to clearence after every pass and then feed
> (very
> slowly) back to the new Z depth. Other than being time consuming it's not
> a
> big deal but the only solution for it (as far as I know) is deleting those
> lines of code or replacing those Z values for the correct ones. Very time
> consuming, especially on long programs. If anybody knows why it does this
> and how to fix it ....please let me know.

The reason is to make sure the cutter clears clamps, islands, etc. Of
course, it does it on clean circle, too. No setting that I know of to change
it.

A work-around is to drill/cut your entrance point hole to just above
z-depth, then run the roughing passes with the plunge set to a higher speed.
You can then ramp to your start point and use a finish toolpath. (Or the
same one, as you see fit) Run the finishing pass with the plunge speed set
slower and automatic-roughing off.

HTH

- Keith


*** Jan 25, 2002 ***

Subject: BobCAD cut repetition, was Re: [CAD_CAM_EDM_DRO] BobCAD users

> I ran in to a similar problem last night. This time it wasn't a pocket
> function, just an "auto cut" that went out of control and repeated some 20
> times (the previous 3 cuts worked fine).
>
> No explanation or fix that I know of other than manually deleting extra
> code - a real pain.

I think you'll find it is relatively easy to fix it when it happens by
'undo'-ing the NC code just generated, auto-cut again, but manually select
the ending entity.

If you are using 'cut-all' or press "]" to auto-complete your path, BobCAD
needs a small gap or overlap (preferred) at the point on the drawn toolpath
where the finish pass comes around to the start. Have to do that manually if
it does the loop trick. Changing the end entity to a different color can
help with the 'picking'. Really only need to do this when your path ends
with a small, hard to pick entity.

Quick fix is to fillet the two entities where the path enters the O.S. loop.
A quick lead in/out is to offset the entity that "T's into the finish pass.
Offset by the amount of overlap you need, then fillet them to the outer loop
entities. (fillet tool extends entities automatically, as long as they
intersect somewhere in the same plane)

BobCAD runs over a previous path when your CAD chain has no end (a node with
no entities within chain gap tolerance distance), and also when you have an
doubled entity (one on top of another, a common problem for imported IGES
files, accidentally unblanked layers, etc) In the first case BobCAD doesn't
realize where the chain ends when it meets itself again. (No 'tag' for the
used entities to avoid repeats.) In the second, the draftsman didn't realize
the multiple entities existed.

- Keith

After using BobCAD v17 a number of years...:)
N00 ;(A little redundant on the last paragraph there! Ahh, its starting to
control my mind!)
N10 ;(A little redundant on the last paragraph there! Ahh, its starting to
control my mind!)
N20 ;(A little redundant on the last paragraph there! Ahh, its starting to
control my mind!)
N30 ;(A little redundant on the last paragraph there! Ahh, its starting to
control my mind!)
N40 ;(A little redundant on the last paragraph there! Ahh, its starting to
control my mind!)
N50 ;(A little redundant on the last paragraph there! Ahh, its starting to
control my mind!)
....
<UNDO>