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Simple Fabrication
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* December 11, 2019, 05:39:36 PM
Got a request to create a simple object, then it morphed into a more complex design, so how can I simulate the requirements. Starting with the specs.jpg I created the required object, then received a request to design by the fab lines.jpg. Seems that the customer wants a complete build by incrementally bending the object, unless theres another way forward?


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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.


* December 11, 2019, 05:50:59 PM
#1
Yeah, I agree that's what he seems to want. But I don't think he's gonna get it, because I don't think it's feasible for several bend lines to meet at one point. Wouldn't bet much money on that opinion, though.

Henry H

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* December 11, 2019, 05:59:46 PM
#2
I used to have a technical fabrication manual from my navy days that was published in the 70s that covered this  type of design ( in general ) oh how I wish I had it now.

Im thinking that its possible but its gunna take a lot of trial and error to get it right. Im also tipping that its not gunna be cost efficient for the customer.


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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.


* December 11, 2019, 06:15:26 PM
#3
I'm starting to change my mind; I think mebbe it can be done. I can't do it in TCad with more than 3 lines meeting at a point, but in real life it might work.

Henry H

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* December 12, 2019, 06:34:06 PM
#4
Punch out or allow clearance around the coincidence point (ie so that the lines don't meet) and bend material and it'll work.   

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* December 12, 2019, 06:56:18 PM
#5
Punch out or allow clearance around the coincidence point (ie so that the lines don't meet) and bend material and it'll work.

Bend relief. Yup. Except that it is usually made large enough to keep bends from encroaching on their neighbors. With seven bends converging to one point, wouldn't the bend relief become enormous?

Henry H

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* December 12, 2019, 07:02:23 PM
#6
It would be a practical necessity though, not only a theoretical CAD issue.

If it were done in material say .4mm or thinner, it wouldn't be difficult, the drawing doesn't specify a radius either. 
« Last Edit: December 12, 2019, 07:05:14 PM by murray dickinson »

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* December 12, 2019, 07:14:57 PM
#7
I just realized that the smaller the bend angle the less it encroaches upon its neighbor, so maybe the relief needn't be so humongous after all.

Henry H

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* December 12, 2019, 07:42:14 PM
#8
Looked like an interesting TCad exercise, so here it is...

The bends don't quite meet at a point, BTW.

Henry H

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* December 12, 2019, 09:42:38 PM
#9
I did find a pdf on sheetmetal design called steelworker2.pdf from the US Navy archives, it covers the same designs.

Was that bend radius @15°?

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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.


* December 12, 2019, 10:52:40 PM
#10
I havent tried the sheetworker pdf design yet, but how did you derive lengths of the lines and angles of 3D profile from a 2D perspective?

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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.


* December 13, 2019, 09:00:23 AM
#11
Your "Specs.jpg" shows the overall dimensions; "Fab lines.jpg" indicates that the "round" opening should be a 24-sided polygon. I drew 2 lofting profiles--a 24-sided polygon for the small end and a 24-segment Polyline for the large end. The Pline looks like a rectangle from afar, but each corner is really 5 line segments, a little less than 1 mm long, parallel to the sides of the polygon. (See he attached screenshot.)

Actually, I cut each profile into quarters and lofted a quarter of the 3D object. The loft was a sheet object since the profiles are open. I filleted the edges where the bends will be, then shelled to a 1mm thickness. Unbent the result without a hiccup.

Henry H

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December 13, 2019, 09:28:56 AM
#12
Your "Specs.jpg" shows the overall dimensions; "Fab lines.jpg" indicates that the "round" opening should be a 24-sided polygon. I drew 2 lofting profiles--a 24-sided polygon for the small end and a 24-segment Polyline for the large end. The Pline looks like a rectangle from afar, but each corner is really 5 line segments, a little less than 1 mm long, parallel to the sides of the polygon. (See he attached screenshot.)

Actually, I cut each profile into quarters and lofted a quarter of the 3D object. The loft was a sheet object since the profiles are open. I filleted the edges where the bends will be, then shelled to a 1mm thickness. Unbent the result without a hiccup.

Henry H

RE ""Fab lines.jpg" indicates that the "round" opening should be a 24-sided polygon":

     I was working under the assumption that "round" bottom of the hopper (which I've decided to call this thing, until corrected) was actually supposed to end up round.  So the UnFold Face sheet result would be similar to the result of the base when UnFolding a Cone-- a Spline.

Also, RE "I filleted the edges where the bends will be":
     I would imagine that would be quite difficult for a person to achieve in the sheet-metal shop-- the fillets.  I would think-- and I assumed, based on the image the "Fab lines" image the customer sent-- the desired method was to have those flat; just like what modeling does requiring actual-curved objects to be faceted, for ease and less computations, I assumed the customer was going the same route.
« Last Edit: December 13, 2019, 09:33:38 AM by Alvin Gregorio »

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Alvin Gregorio
Intermittent TurboCAD user since yr. 2000 (ver6.5).  No formal CAD Training.
---TurboCAD: V21PP; V20.2PP; V19DL; V11.2Pro; Windows-7-Pro/64-bit; Intel-Core-i3 CPU; 2.27ghz; 4GB RAM; Intel HD Graphics (CPU based)


* December 13, 2019, 12:39:51 PM
#13
Your "Specs.jpg" shows the overall dimensions; "Fab lines.jpg" indicates that the "round" opening should be a 24-sided polygon. I drew 2 lofting profiles--a 24-sided polygon for the small end and a 24-segment Polyline for the large end. The Pline looks like a rectangle from afar, but each corner is really 5 line segments, a little less than 1 mm long, parallel to the sides of the polygon. (See he attached screenshot.)

Actually, I cut each profile into quarters and lofted a quarter of the 3D object. The loft was a sheet object since the profiles are open. I filleted the edges where the bends will be, then shelled to a 1mm thickness. Unbent the result without a hiccup.

Henry H

RE ""Fab lines.jpg" indicates that the "round" opening should be a 24-sided polygon":

     I was working under the assumption that "round" bottom of the hopper (which I've decided to call this thing, until corrected) was actually supposed to end up round.  So the UnFold Face sheet result would be similar to the result of the base when UnFolding a Cone-- a Spline.

Also, RE "I filleted the edges where the bends will be":
     I would imagine that would be quite difficult for a person to achieve in the sheet-metal shop-- the fillets.  I would think-- and I assumed, based on the image the "Fab lines" image the customer sent-- the desired method was to have those flat; just like what modeling does requiring actual-curved objects to be faceted, for ease and less computations, I assumed the customer was going the same route.

Alvin, I was just trying to explain how I made the TCad drawing.

Henry H

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* December 13, 2019, 12:50:43 PM
#14
 How did you get the bending to work from non straight edges?

Ive only ever used genie to bend of edges and they are always right angled, whereas your are like slightly offset from one end to the other.

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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.


* December 13, 2019, 03:05:09 PM
#15
How did you get the bending to work from non straight edges?

Ive only ever used genie to bend of edges and they are always right angled, whereas your are like slightly offset from one end to the other.

I did not bend anything. I created the 3D object with the Prism tool (essentially a simplified Loft tool) as a zero-thickness "sheet" object; filleted edges to 1 mm radius; Shelled to 1 mm thick. Then I UNbent this object to create the flat pattern.

(Actually, I created one quarter of the object, Unbent it, then mirror-copied to make the complete 3D object and the complete flat pattern.)

Mebbe the attached screenshots will help...

Henry H
« Last Edit: December 13, 2019, 03:09:12 PM by Henry Hubich »

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* December 14, 2019, 11:25:35 PM
#16
Henry would you enlighten me on the following:
So Im trying to reconcile your method of creating the shape with my starting point of this simple fabrication. So I created a 2D profile and extruded it to 5mm.

So the 1st aspect on not clear on is how you created the node points on the green hilited corner from the 2D profile. what was your process here?

Then how did you bend the object and what method did you use to place the bend lines on the extruded shape, what was your process here?

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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.


* December 15, 2019, 12:42:20 AM
#17
The ah ha moment came 10 minutes after posting, so Im gunna draw an arc at the green circled area from the 2D profile of around 6mm in length approx, then draw 1mm coincident lines ( as a rounded corner ) every 15 degrees and then extrude then bend on those vertexes. Easier now Im thinking about it. 😀

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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.


December 15, 2019, 05:39:33 AM
#18
The ah ha moment came 10 minutes after posting, so Im gunna draw an arc at the green circled area from the 2D profile of around 6mm in length approx, then draw 1mm coincident lines ( as a rounded corner ) every 15 degrees and then extrude then bend on those vertexes. Easier now Im thinking about it.

I've been working on this  A LOT the past couple of days Darryl.  I need to take a break from it actually.

I know I can do it with a 24-sided polygon for the bottom hole.  The challenge I am creating for myself is I want the hole to actually be 115 diameter round.
I'm curious Darryl, are you going to settle, for lack of a better word, for a polygonal hole?-- is that the method you're going with?

Being as obsessive as I am, I'll probably have another go at it today.  Something came to me last night that might be a way to go.
I can model the "skin" of it easily enough now; but getting it to fillet or unfold is very much my challenge; I might not ever be able to achieve the unfold, other than to do it "manually" in TurboCAD, such as a sheet metal fabricator would have to do.

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Alvin Gregorio
Intermittent TurboCAD user since yr. 2000 (ver6.5).  No formal CAD Training.
---TurboCAD: V21PP; V20.2PP; V19DL; V11.2Pro; Windows-7-Pro/64-bit; Intel-Core-i3 CPU; 2.27ghz; 4GB RAM; Intel HD Graphics (CPU based)


December 15, 2019, 11:26:35 AM
#19
Attached is a compromised facsimile of a half a hopper with 115mm round hole and ~5mm sheet metal thickness.
The two quarters didn't want to 3D Add.
I created a quarter-hopper, with only a "sheet" thickness (surface thickness... 0 thickness), then copied it in the X & Y directions 5mm.  Then Face2Face Lofted those.  Then Mirror-copied that.

I keep feeling/thinking that if I can make the sheet, incorporating the round hole, I can somehow give it the 5mm thickness.  How to use that to create a sheet metal fabrication drawing, I have no idea-- other than to do it with math and geometry, such as an experienced sheet-metal worker would do, I'd guess.

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Alvin Gregorio
Intermittent TurboCAD user since yr. 2000 (ver6.5).  No formal CAD Training.
---TurboCAD: V21PP; V20.2PP; V19DL; V11.2Pro; Windows-7-Pro/64-bit; Intel-Core-i3 CPU; 2.27ghz; 4GB RAM; Intel HD Graphics (CPU based)


* December 15, 2019, 02:14:07 PM
#20
Hi Alvin its early morning here and Im gunna revisit this today. What if you could extract a face from the object and give it 5mm ?

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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.


December 15, 2019, 02:31:35 PM
#21
Hi Alvin its early morning here and Im gunna revisit this today. What if you could extract a face from the object and give it 5mm ?

"extract a face"?

In my file, Block "Hopper_2" has the cleanest/simplest hopper object.  It's a sheet.
« Last Edit: December 15, 2019, 02:33:58 PM by Alvin Gregorio »

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Alvin Gregorio
Intermittent TurboCAD user since yr. 2000 (ver6.5).  No formal CAD Training.
---TurboCAD: V21PP; V20.2PP; V19DL; V11.2Pro; Windows-7-Pro/64-bit; Intel-Core-i3 CPU; 2.27ghz; 4GB RAM; Intel HD Graphics (CPU based)


* December 15, 2019, 02:46:12 PM
#22
A 24-sided polygon deviates from a 115 mm diameter circle by less than half a millimeter. I'd say that's plenty good enough.

Henry H

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* December 15, 2019, 03:33:45 PM
#23
Here are the profiles I used. Loft them (or use the Prism tool), Fillet the 6 inner edges to a 1 mm radius, Shell to a 1 mm thickness. Unbend to create one-quarter of the flat pattern. Mirror copy the flat as required to make a full pattern. Mirror copy the 3D object as required to model the full transition/hopper/whatever.

Henry H

P.S. And here's a version saved in v18 [really!] format...
« Last Edit: December 15, 2019, 06:05:38 PM by Henry Hubich »

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* December 15, 2019, 04:13:53 PM
#24
Re reply #20. Im not an experienced sheet metal worker, more mechanical and general in experience only. I did manage to partly create the object with the exception of 1 bend out of the 6 required. I suspect that the arc of flat edges at the corner would need to be much larger for actual bending to take into account for a bend radius of say 2.5mm being half the plate thickness and that enough material distance is required to give clearance for the bending tools shape. In practice where Ive done hand drawings in a workshop I normally give a wider distance from each section that needs bending, the last time I bent something similar to this was 15 years ago well before I got into cad stuff.     

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Daz
TCW V21, 2015-2019 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly.


* December 15, 2019, 09:40:42 PM
#25
I have a suspicion that, if you create the funnel/hopper feed/whatever with Henry's method, the angular increment of each bend will be different.  My reasoning is that an arc coned to a point that isn't normal to the arc's centre creates an elliptical cone, equal chords of an ellipse span different angular displacements.   It's a hunch, I haven't tested. 

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December 16, 2019, 06:07:53 AM
#26
I have a suspicion that, if you create the funnel/hopper feed/whatever with Henry's method, the angular increment of each bend will be different.  My reasoning is that an arc coned to a point that isn't normal to the arc's centre creates an elliptical cone, equal chords of an ellipse span different angular displacements.   It's a hunch, I haven't tested.

One version I created of trying to model the thing with a round hole was:  I inserted an offset Cone, specifying the 115 circle as the base, and a corner of the upper rectangle as the height/point.  To me, that provided the truest illustration of what it would actually geometrically be.
I just couldn't get TurboCAD to unfold that offset cone.
I feel like if I were in my garage with building paper, I could create a model of this hopper-- in its optimal theoretical form-- easier than I could with a computer.

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Alvin Gregorio
Intermittent TurboCAD user since yr. 2000 (ver6.5).  No formal CAD Training.
---TurboCAD: V21PP; V20.2PP; V19DL; V11.2Pro; Windows-7-Pro/64-bit; Intel-Core-i3 CPU; 2.27ghz; 4GB RAM; Intel HD Graphics (CPU based)


* December 16, 2019, 07:05:47 AM
#27
Hi,

Quote Alvin: I just couldn't get TurboCAD to unfold that offset cone.

Lay a workplane from the corner point of the rectangle to the quadrants of the cone. Make a slice with a workplane.
Then unfold face.


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