jim,
Thanx for getting back to me.
If you can show me a work-flow that’s simple and reliable, and that does what you claim, then please show me. I’m no expert in anything (except getting old!).
Thanx …
Parametric and non-parametric CADs both have their advantages and flaws. As far as I know, “History” has become a bit more potent in Rhino 6, which is certainly a step in the right direction.
Whether you should prefer one over the other depends on so many variables, that a forum won’t help you in any way. Ask the same question in a Solidworks or Inventor-board and you will get a completely different opinion than in this thread.
I said I would show you if you supply the 2d geometry.
Why do you think I should draw the 2d geometry if you can’t be bothered to do it?
I am totally convinced you are not really interested in a solution, but just in case that’s not true…
The model I posted was based on the assumption that the flights were perpendicular to the drum. The drawing shows that the flights are actually defined as at a fixed angle to the centerline
That makes it fairly simple and easy to generate the flights independent of the drum and then trim the flight surface where they intersect the drum surface. The way to do that is map the variable pitch helix to a cylinder by extending the lines of the 2d flight geometry to locate the points where they intersect the cylinder.
You can then use the points to draw a series of curves that can be mapped to the cylinder using the command ApplyCrv. At that point you have a variable helix that looks something like this.
You then can use the helix to create the flight surface
The inner flight surface can be created the same way. Extend the lines to find the points on the cylinder to create that helix and generate the surface. After that the main flight surface can be trimmed with the inner flight on one side and the drum on the other.
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jim,
Thanx for the input.
I don’t understand what you mean about projecting.
The drum is a cone not a cylinder.
How do you project the flight onto the cylinder based on where it hits the cone?
Back during the project, I tried doing that various ways (amongst other things), and it never came out clean.
Please clarify …
The drum is a bunch of different cones that are joined. That obviously means that there will be discontinuities in the intersection of the flight and drum. But that only means the flight surface, to be made smooth, has to modeled extending past the drum surface and be trimmed back.
By extending the flights to locate where they intersect the cylinder. the cylinder has the same centerline as the drum
Its simply a matter of extending the 2d lines.
The angle which the extended flights intersect the cylinder is the same everywhere. That makes it easy and simple to create the flight surfaces after you develop the helical curve where the extended flight surfaces intersect the cylinder.
I already explained it. Post the 2d geometry and I will show you.
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Hi Jim,
Thanx for your explanation.
Please pay attention, b/c I’m only going to say this once more:
it’s not as simple as you say.
Take a look at the drawing I posted and you’ll see.
Besides that, the key here is getting the flights to smoothly transition at the cone joints, which is something you failed to do as seen at the transition between the cone and dished end. I believe that’s what I said was the big problem from the beginning of this discussion.
Thanx for your input …
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DISCLAIMER I just randomly ran into this thread, and have only casually browsed it, so I am 99+% convinced I am walking into a full-speed buzz-saw, but…
Just as a completely different perspective, instead of working from the outside in on the drum where all the discontinuities are (between cones), and all the problems that poses… Could you create a INNER construction geometry/surface (without discontinuities) model the flights (as they are apparently known in your industry) from the INNER geometry (say, individual drums with the "I.D."s on the PDF, wrap the flights onto those ID drums, and trim(?) ), then TRIM them by the outer drum(?). Abstractly speaking, model a screw with long threads, and use the drum to trim the excess. That way, the cone seams show up perfectly in the smooth flights as they should to fit properly in the drum.
Best Regards!
Hi Km,
Thanx for weighing-in.
Great idea.
I had tried that too (it’s what I get paid for, haha!).
Not that do everything right all the time, but I couldn’t figure out how to do it that way either (in Rhino).
Can’t recall how I ended up doing it in Inventor, but I DO remember it was a PITA, b/c I had to use multiple methods to get the job done, and rely on the shop guys to make the adjustments when connecting the various flights.
Cheers …
I seem to be late for this discussion but still would like to contribute. The assessment for which software you use as main CAD tool has to be done very thoroughly because you’re risking hundreds or thousands of hours of less productive work. I have tried out many CAD packages before proposing Rhino as main CAD tool to my co-workers.
Although you can argue that parametric tools are generally better for product design/part design, it really depends on the type of modelling that you are more likely to be doing.
I’ve used Solidworks and NX extensively, but I looked into Solidedge, Creo, ProE, CATIA, Evolve, Inventor and probably some others that I can’t recall at the moment.
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Modelling in Rhino is for the most part a lot faster than in constraints based system. And when I say a lot, depending on your knowledge of the software and modelling habits, it could mean 3 to 4 times faster.
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For modelling simple parts, Rhino is much more efficient. No advantage being parametric there.
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For modelling extremely complex parts run away from parametric. The last thing you want is that a complex parametric model, with lots of dependencies and constraints breaks on you. Normally the break will be from the middle to the beginning of the chain and you will have to find and fix every feature and operation one by one. It’s faster to build the entire model from scratch again, 3 to 4 times slower than in Rhino.
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If Rhino didn’t have Grasshopper I would argue that it could be difficult to replace a fully parametric tool for certain applications. The beauty of the Rhino-Grasshopper system is that you can optimize between the two modelling paradigms to better suit your specific needs and meet your productivity goals.
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That being said, I still think that there’s many room for improvement in Rhino. B-)
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As explained above, that entirely depends on the type of industry and the client structure. Low quality clients that don’t pay see smaller design studios having to adopt low-cost approaches. Nothing wrong with that. In FMCG packaging design, product design and industrial design, the constant flow of weekly or even daily design changes - as well as the many supplier’s components one has to integrate and design around - make any non-parametric software painful if not impossible to use.
Besides, now that SolidWorks offers great tools to work with G2 continuity while still maintaining the complete project tree intact, it is not surprising that ever more design studios are going that route.
I agree with you for the most part, but I meant modelling speed from scratch - pick some object in your vicinity and model it in Rhino and some other software. My bet is that, for the same proficiency, the more complex the object, the bigger the difference in execution time. The only thing slowing Rhino down could be some problems with filleting or chamfering edges.
I am not so sure. If you consider a football cleat, an aircraft seat, a portable oxygen breathing apparatus, an articulated task light or a golf cart, the number of auxiliary components from internal and/or external suppliers already from the outset makes “in the air” designing with NURBS surface modeling software a very cumbersome affair.
It’s ok for some early concepts, before the proper design process starts in the aforementioned sectors like FMCG packaging design, product design and industrial design.
In the end the truth is (client structure, budgetary considerations, etc.) that there luckily is no “one size fits all” solution.
So wait, you had to rely on your shop guys? Did you go to the inventor forum and ask the same questions?
Can we see what the final product looked like? With the final inventor drawing? Now I’m curious
Hi,
Just saw this.
Sorry for the delay.
Find attached a pdf of the GA drg.
All the fab drgs are confidential.
Cheers…
CementMixerDrum_Page_1 - Clipped.pdf (2.3 MB)
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