Drawing around other 3d objects to create another object

[Dadgad]

I would look closely at the plates.

Go to a view parallel to a plate.

Are the cut edges perpendicular to the flat? (might be easiest to check in wireframe shademode - there should be only one boundary)

That is the way sheet metal is generally cut.

 

Another good point there JD, spoken like a true machinist, and clearly

they are not going to be as the projection is non rectilinear.

Be that as it may I still think it a very good introduction to the whole

subject of rather interesting 3D modeling.

Having never worked with CNC, despite a great interest in doing so,

I was under the impression that some CNC machines will accept

a 3D solid as the input method? Might one like that be capable

of including the modeled angles of those cuts?

[ReMark]

I elected to demonstrate one possible solution. Since I am not a machinist nor do I have any CNC experience I could not say if my method would produce the desired results. I'll leave that decision up to the OP and his machinist.

[JD Mather]

.... Might one like that be capable

of including the modeled angles of those cuts?

 

An expensive machine with multi-axis articulating head, (read - more expensive part).

Most machines that would cut a part like that from sheet metal using waterjet, plasma, laser .... whatever..... only move table on X and Y and head only on Z axis - so no angle rotation of the head. Cuts are perpendicular to the flat.

 

There would be an angled gap rather than parallel gap between plates and frame tubes, but I'm making the assumption that these will be welded joints - so not a bad thing.

 

Similar to ReMark/s solution - if I were doing this (in Inventor of course) I would pattern workplanes at desired offset distance. (I would have done the Loft as surface for simplicity.)

Start a sketch on each plane and Project Cut Edges (of the slicing plane through the loft surfaces). Then Extrude each plate. The extrude would ensure perpendicular edges. If I had to use AutoCAD, I would figure out some similar technique (perhaps using xedges or something), but I haven't really kept up with what functions in AutoCAD might be available to me.

[Dadgad]

An expensive machine with multi-axis articulating head, (read - more expensive part).

Most machines that would cut a part like that from sheet metal using waterjet, plasma, laser .... whatever..... only move table on X and Y and head only on Z axis - so no angle rotation of the head. Cuts are perpendicular to the flat.

 

There would be an angled gap rather than parallel gap between plates and frame tubes, but I'm making the assumption that these will be welded joints - so not a bad thing.

 

Similar to ReMark/s solution - if I were doing this (in Inventor of course) I would pattern workplanes at desired offset distance. (I would have done the Loft as surface for simplicity.)

Start a sketch on each plane and Project Cut Edges (of the slicing plane through the loft surfaces). Then Extrude each plate. The extrude would ensure perpendicular edges. If I had to use AutoCAD, I would figure out some similar technique (perhaps using xedges or something), but I haven't really kept up with what functions in AutoCAD might be available to me.

 

Given that the spacing of these plates is 4 feet, it certainly sounds like it will be welded.

Thanks for the feedback, I really need to get into a state of the art modern facility one

of these days, also fascinated by the water jet.

[Jimmy111]

"Also keep in mind that perfect parts cannot be manufactured out on the shop floor.

Allow clearance on the notches for the manufacturing tolerance. "

 

 

Sure they can. As long as the designer/draftsman understands the process that will be used to create the parts.

I get so many parts where they want to machine a 1/8" fillet into a part 8 " deep and cant understand that it just cant be done.

[JD Mather]

Sure they can.

 

Nonsense. Every manufacturing process has tolerances.

[neophoible]

Nonsense. Every manufacturing process has tolerances.

Designs don't show perfectly on my screen either, nor in plots. Everything has practical limits. Go figure.

[Jimmy111]

Tolerance is just acceptable error. Mostmachines built in the last 20 years or so will hold whatever tolerance theywere built for. For example. My mills will hold a 0.0001 tolerance and thegrinders 0.00001.

 

Acceptable tolerance has changed along withthe increasing accuracy of the machines. Parts that 30 years ago had acceptabletolerance of+- .005 today are calling for +-.001 or .0005. Same part. there isno need for such tight tolerances. It is just that designers have gotten use tosteering at a computer screen that has a tolerance of lots and lots of zeros.

 

The tolerance issue in machining comes fromolder manual machines. Not todays CNC equipment. If you want to cut a part to1.0001, You can do it. Repeatable, over and over and over again.

 

30 years agoa finish of 250 micro inch was usually acceptable. Today it is creeping slowlytowards 32 with many customers expecting mirror like machined finishes.

 

Here is a modelfor a part I first made 35 years ago. At that time the pattern was made of woodand pretty much there was no tolerance. They really didn't care as long as theygot their castings. Today they want it machined from 7075 with a tolerance of.0005.

 

First photois of the model in AutoCAD. Second is of a STL and the rough finish cut done on a cadcam program. I usually do the rough by hand. Much faster. The last is of thesemi finished part. After this it gets the final finish which will be a mirror like finish.

 

Many parts Iget today have no tolerance assigned to them. They say they want 1.7495 andthat is what they accept. Nothing else.

 

 

 

 

 

[JD Mather]

Snicker.

I know when to leave it alone.

[JD Mather]

fastfox,

Even if you could purchase (or make yourself) this 2x tubing off-the-shelf as perfect (we'll call .0001 perfect) along the entire length and even if you could machine that notch to our definition of perfect 2" the parts would not assemble together.

 

You would have to press fit or cool down the frame tube to fit in the plate slot (hmmm, that throws a wrench into our definition of perfect - looks like at .0001 we need to specify temperature as well).

 

If I gave you the "perfect" AutoCAD file the 2" red occupies the same space as the 2" white lines.