Author Topic: Best way to cut holes in pipes?  (Read 10243 times)

samdavo

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Best way to cut holes in pipes?
« on: March 21, 2014, 04:27:25 PM »
So I've got two steel pipes in 3D, one (3m diam, red, layer 2), initially horizontal, which turns down a hill with two 30deg kinks; and another (2.25m diam, green, layer 4) which comes in horizontally at 45deg and meets the chamfer piece.  And you want to draw the pipes with the holes oxycut in them.

I find this pretty easy to do, but having said that, my way involves exploding solids, and I wonder if anyone has a better way.  (Call this chewing gum for the geometrically oriented mind gents :) )

I enclose a dcd with the axes of the pipes, and the cross sections.  I drew these as circles not planes, in order to get tubes not solids.  I used Ctrl+Shift+X in each case - dead simple - and Solid Defined each tube to make it a solid so that I could Bool around with them.

I then used Solid Segregate (clicking on the two tubes), and then deleted the bit of the smaller pipe that was inside the larger pipe.  (detail E in the final jpeg shows the bit that was deleted).

The problem is that the tube in each case has the hangover of the other intersecting tube.   To remove the green hangover from the red tube, I explode the tube, delete the green bits ( layer 4 ) and I am left with the pipe I wanted.

Likewise I remove the red bit from the end of the green tube. (2 cents).

To tidy it up, I redefine what is left of each pipe ( now a stack of planes)  as a new solid - although I suspect it would be just as easy to Group them.

Question then becomes - can anyone achieve the final jpeg outcomes without exploding ? 

After that I suppose there is the question, what is the easiest way to delevop the shape of the chamfer piece?  A macro maybe?

PS The dcd includes Detail E, which just shows the bit that was deleted after the Solid Segregate - not that it really is deleted lol -   Basically the Solid Segregate means that the red leaves its mark on green, and vice versa.
« Last Edit: March 21, 2014, 04:39:53 PM by samdavo »

samdavo

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Re: Best way to cut holes in pipes?
« Reply #1 on: March 21, 2014, 04:29:36 PM »
the dcd to do-cee-do with
« Last Edit: March 21, 2014, 04:31:17 PM by samdavo »

prl

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Re: Best way to cut holes in pipes?
« Reply #2 on: March 21, 2014, 04:54:53 PM »
After that I suppose there is the question, what is the easiest way to delevop the shape of the chamfer piece?  A macro maybe?

What do you mean by chamfer piece, piece E?  And why do you want it . . .  or is this meant to be a subtracting solid for each hollow pipe piece?

samdavo

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Re: Best way to cut holes in pipes?
« Reply #3 on: March 21, 2014, 06:13:29 PM »
prl - I was referring to the centre of the three pieces that make up the kinked red pipe.

I have (in the meantime) developed that shape - whilst listening to the radio Saty morning -  making use of Dempsey's pushapart macro, (with 100% expansion in Y and Z directions only = double the overall dimension in those directions) and laying those planes down side by side.    Again, I imagine there is a better way - although this is still pretty efficient.  ( 2 cents)

There are 36 planes to drag around and lay down (ignoring the occasional pairs at the hole) - flat in the XZ plane - , something akin to caterpillar track segments.  - cheers.
« Last Edit: March 21, 2014, 10:09:24 PM by samdavo »

prl

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Re: Best way to cut holes in pipes?
« Reply #4 on: March 21, 2014, 11:45:15 PM »
prl - I was referring to the centre of the three pieces that make up the kinked red pipe.

OK, thanks.  Interesting puzzle, both the hollow grid subtractions and your "unfolding laying down planes".
« Last Edit: March 22, 2014, 12:22:15 AM by prl »

samdavo

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Re: Best way to cut holes in pipes?
« Reply #5 on: March 22, 2014, 12:54:34 AM »
PRL, there is an error in that the developed perimeter should be (3.pi) = 9.42478,  whereas it measures 9.41257,  for an error of 0.1295% (probably due to the sum of 36 chords being less that the full circle) - So I should strictly extend the developed shape in the Z dirn by that ratio (9.42478/9.41257) - using Selection Scale obviously.  cheers
« Last Edit: March 22, 2014, 08:22:56 PM by samdavo »

prl

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Re: Best way to cut holes in pipes?
« Reply #6 on: March 22, 2014, 01:13:10 AM »
Sam, is your final objective the flat layout pattern?  Basically taking a  pipe, punching a hole in it with an intersecting pipe, and then taking the pipe with the hole in it and cutting along the length of it and flattening it out (running a steam roller over it)?

samdavo

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Re: Best way to cut holes in pipes?
« Reply #7 on: March 22, 2014, 01:23:45 AM »
Yep - develop the shape, so that it can be dimensioned, and/or a fitter can sketch the shape on a steel pipe and oxycut the hole(s) - common enough problem, (so I'm told), often up in the boondocks :) cheers.
« Last Edit: March 22, 2014, 01:33:00 AM by samdavo »

Bob P

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Re: Best way to cut holes in pipes?
« Reply #8 on: March 22, 2014, 03:14:29 AM »
I've had to do that several times by the "grunt" method.

Move a copy of the "holed" pipe into an orthogonal orientation for ease of manipulation.
Explode the pipe into its individual plane segments.
Flatten each each segment and move it to its adjacent segment.  If the hole is through the center of the pipe, I only do half the contour, then mirror it.

I've thought about a flatten macro, but I suspect that for the few times that I have to do a pipe-cut, the writing time wouldn't be worth it.  I wouldn't be surprised if there was a reasonable math solution, like a "2nd order" conic section for the hole.

prl

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Re: Best way to cut holes in pipes?
« Reply #9 on: March 22, 2014, 03:21:34 AM »
I've had to do that several times by the "grunt" method.

I've got more cold/crappy weather coming.  I'm chewing on it.

Dean

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Re: Best way to cut holes in pipes?
« Reply #10 on: March 22, 2014, 06:16:43 PM »
This is how I'd do it.
An un-wrapping of the pipe face would be great feature but can't you just do the math and draw it?
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samdavo

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Re: Best way to cut holes in pipes?
« Reply #11 on: March 22, 2014, 08:40:12 PM »
But Dean, I thought I'd simplified the problem - but you've reduced it to its simplest version (with radial pipes, lol).
I mean, the original red "chamfer piece" could be tapered, curved, (as you indicate), inclined to x, y and z axes -  and so too the green pipe intersecting with it.   (2 cents).

Here's a drawing of the Beijing Birdsnest I whipped up earlier (ok texture mapped if I did it at all, lol) - I tried to do the maths, but found it took longer than 30 mins, and went to the pub instead ;)

PS maybe by "do the math", you mean "do the hard yards of pasting the planes side by side" - in which case ignore my tongue in cheek cheekiness. 
cheers.   
« Last Edit: March 23, 2014, 12:03:35 AM by samdavo »

prl

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Re: Best way to cut holes in pipes?
« Reply #12 on: March 23, 2014, 03:19:19 AM »
Darn, I thought Dean's movie was going to be an animated unfolding movie.  I'm waiting for the sequel.

samdavo

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Re: Best way to cut holes in pipes?
« Reply #13 on: March 23, 2014, 03:48:18 AM »
I suppose Dempsey's pushapart.d3m at least handles all 36 segments (or whatever) - but it's probably a big job to rotate the nth one (10n) degrees and connect together to the rest.   Enough to know it can be done :)  To be honest I originally struck this problem talking to my son, who had use for it - I was trying to sell him DCAD at the time.

prl

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Re: Best way to cut holes in pipes?
« Reply #14 on: March 23, 2014, 04:01:56 AM »
For others that want to play along, here is the *.dcd study model file (from Sam's original file).  I've boiled it down to its geometric challenge essentials getting rid of all the other annotation distractions.

The posed challenge:   A green pipe intersects a larger red vertical pipe at a random angle in 3d space.  The green pipe has a diameter of 2.25 and the red pipe a diameter of 3.0.  Intersect the pipes with each other and determine the surface profiles for each pipe at the intersection locations and then unfold the profiles for each pipe onto a flat surface such as a sheet of roll-feed plotting paper.

If done correctly, the roll-feed plotting profiles can be given to a pipe-fitter who then wraps them around each of the real pipes, scribes the lines onto the steel and then makes the cuts.  The two pipes then come together perfectly at their intersections and are welded.
« Last Edit: March 23, 2014, 08:30:09 AM by prl »