Best way to fabricate this large steel motor enclosure?

[nanobot29]

Hello,

I'm working on a motor enclosure design for a large electric motor. Originally it was designed as a one-piece solid cast part. I've been instructed to make a machined design instead. my plan is to take the original cast design and break it up into sections which would be welded together. after some initial sketches, I'm not happy with how the design looks structurally. based on the attached sketches, am i taking the right approach or is there a better way of doing this? i'm mostly concerned with the tubular section of the housing. i figured that my two options would be to (1) weld tubes together, or (2) machine from one larger/thicker tube (i would probably to start with a 6" thick tube and machine down.

I would greatly appreciate any tips or advice. some section views are attached for reference. The pdf contains 3 images. The first is a 3-D view, second is a cross-section of the one-piece design, and the third image is a sketch of were i'm planing to break up into section.

Wall Thickness = 2.0 in
Max Outer Diam = 46 in
Min Inner Diam = 34 in

I plan on doing a full FEA, modal analysis, and dynamic analysis once i feel that i have a cost effective solution.

 

[BillPSU]

I don't believe you will find any tubing close to the size you need for this enclosure. I did a quick look and found some 24" OD but nothing larger. The casting will probably the only way to make this part.

Heavy walled tubing is a seamless tubing product. Thin walled tubing 5/8" or smaller is an ERW product.

Bill

 

[mfgenggear]

nanobot29

as Bill suggested, & as follows",
you need to take your drawings to sheet metal fabricated of heavy wall pipe & welding.
The flanges can be made from plate, the pipe can be Brake formed, rolled & welded, the various diameters can be fabricated & welded.
then it can be machined & all welded up.
But it is very well expensive., a casting might be the method instead.
what is the material required & how many?
get a quote as a casting vs fabrication. then decide.

Mfgenggear

 

[mfgenggear]

see the attached modified sketch

Mfgenggear

 

[dvd]

You may find some insights in "Design of Weldments" by Omer Blodgett: section 4.9 Motors and Generators

http://ssldev.lincolnelectric.com/foundation/item.asp?prodnum=DW&PID=16

 

[arunmrao]

If you have the pattern,casting will be fast and economical. Welding and machining,though technically possible, may prove a challenge in finding 2inch plate,forming it,on a plate bending machine,fixturing etc .

Any reason for changing the process?

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[ornerynorsk]

Having worked on some large, heavy fabricated tubular sections for shell handling and loading machinery for a naval gun project, I would definitely concur with those who are advocating a casting. You could have up to triple the amount of labor in a fabrication, depending on how good the welding shop is, how accurate the plate can be rolled, and how much oversize things need to be for machining allowance based on the confidence of all involved. Not to mention harmonic and damping qualities that may be to your advantage in a casting. Just my 2 cents.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[BrianGar]

Casting all the way.
Keep in mind even with the best strategy, you may lose the first weldment due to warping.
Its is sometimes easy to underestimate how hard it is to weld something up in the correct order first time without something pulling.

Just yesterday I saw some 30mm plate in pretty small sizes turn into S hooks due to poor jig/tack up design.

Brian,