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Sheet Metal Enclosure

Sheet Metal Enclosure

(OP)
I am dealing with a cabinet shaped sheet metal box with some large openings on the front and back of the cabinet.

I am wondering if anyone has any suggestions to reduce the final cost of fabricating the cabinet. I have already tried using thinner sheet metal, less expensive material, less number of bends and less number of parts. Are there other points that I am missing?

Please help!

RE: Sheet Metal Enclosure

Make it smaller.
Look for large pieces of scrap; optimize yield of every sheet. Sometimes you can save by using different sheet sizes.
Skeletonize it and cover it with e.g. fabric.

Mike Halloran
Pembroke Pines, FL, USA

RE: Sheet Metal Enclosure

Its not magic..Talk to the manufacturer to discuss where the cost is... You've got the cost of the raw material (easily known), you've got the cost "per hit" of the fabricator/punch press (known again)
Typically the sheet metal vendors just use a simple excel spread sheet for costing.

Then comes engineering/design optimization. Only you know the forces/strengths,etc.. do some engineering/run the math..see what can be removed/reduced,etc... Thinner sheets/stiffening ribs/braces/different materials/finishes,etc...

less is less...

RE: Sheet Metal Enclosure

(OP)
Thank you for all your responses! These are very good points...

This thread can become a great reference for everyone else...please add more if you have any other suggestions :)

RE: Sheet Metal Enclosure

Utilize a 'standard' box produced in high volumes and modify it for your special features. This avoids retooling the complete box.

Bill

RE: Sheet Metal Enclosure

(OP)
@Bill: Generally modifying a standard one will be a lot more cost efficient.

However, for my case the dimensions do not match any thing available. Is there any "standard" or "most efficient" way to design a sheet metal box? I can modify that design to my purpose.

RE: Sheet Metal Enclosure

There is no standard way to make a box.

Within any given shop, there is a customary way that fits the process in use, but it's very dependent on that particular shop's very particular abilities. ... which in turn were developed in response to the challenges presented and met over its entire history, and to the comings and goings of tradesmen and supervisors.

E.g., some shops prefer to weld boxes from simple rectangles, if they think they are good or efficient at corner welds.
... whereas some shops will bend as many corners as possible, to minimize the total weld length.
... and some shops will arrive at a compromise to maximize material usage.

Most shops also have their own preferred/customary way of making or adding hinges and latches.


As for using stock boxes, they are great for making one or a few identical boxes, but adding holes to a finished box is much more expensive than adding them to the flat blanks for a custom box. ... and many stock box vendors recognize that, and will make semi-custom boxes for more than the price of a stock box but much less than it really costs you to make them yourself, unless you're in the box business.

So one of the first questions to be resolved is how many boxes you need.

Mike Halloran
Pembroke Pines, FL, USA

RE: Sheet Metal Enclosure

When we design various enclosures we generally follow a few simple rules.

1. Balance the act of minimizing part count and adding complexity to the parts. The less parts you have the less expensive it will be, but the trade off is complexity of parts. Having only 3 parts to an enclosure is great, but if they are really complex, you may actually be adding cost especially in low volumes where set-ups aren't marginalized.

2. Properly size the sheet steel, I can't tell you how many 2ft x 3ft enclosures I have seen made out of 12ga. Unless you have some crazy strength requirment, generally speaking UL508A recommended guideline for enclosure thicknesses is a good starting point.

3. Eliminate secondary procedures. These are extra steps that may or may not provide any value. For instance you design a corner of the box that requires grinding after it is welded. That weld grind is a secondary procedure, could you have designed it differently where you don't need the grind? In some cases another secondary is tapped holes or pressed in hardware. Could you use different hardware that allows for a standard punched hole? As soon as you tap or press in hardware, now you have to mask or plug that in paint. You may have a better connection, but if you have 40 tapped holes and only 10 of them you use in each configuration, maybe you can engineer a lower cost mtg solution.

4. Consider assembly. You may have just followed 1-3 but when it comes to assembly of components into the box it is a royal pain. Consider how it is assembled. For instance putting thru holes on the box will be very cheap compared to blind pressed in hardware. However is you force assemblers to use nuts and bolts to put components in, they may not be very happy with you and ultimately your enclosure may be cheaper but your product is more expensive.

5. Cost down everything. The enclosure is just one piece of the puzzle, maybe adding cost to the enclosure saves on packaging for shipping, or adding cost to the enclosure could save on material handling. For instance you don't want to put a lifting eye on the enclosure because it costs you $2. Well it is going to cost a whole lot more if they have to lift it by hand or can't easily move it around in production. Remember a low cost enclosure is great, but the real goal is a low cost product.

StrykerTECH Engineering Staff
http://www.stryker-tech.com/

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