Sheetmetal Best Practices.

Forum|Forum|15 years ago
September 8, 2010
4 replies
2646 views

Associates,

I'm sure this topic has been discussed in the past, and I
apologize for my lack of foresight for not paying attention to them
thinking they weren't relevant to me, but I am looking for information on
best practices for the use of the sheetmetal function. We are in the
process of creating a general best practices manual for ProE and, although
we have been able to obtain a considerable amount of information regarding
basic functions, we have found little published literature on best
practices for sheetmetal. If anyone has access to, or knows the
whereabouts of, such a document and is willing and able to share it with
us, that would be greatly appreciated. In addition, if you have any
personal recommendations, experiences, guidelines or "rules of thumb" that
you're willing to share that would be relevant to a best practices
document for sheetmetal, they too would be warmly received. Once we have
compiled the data, and if the contributors agree, we would be happy to
share our findings en masse with the user community. Thanks.

Dave
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General

frederick.burke

1-Visitor

Hi David,

I have 5 main sheetmetal rules that I stick to...

1) The best advice I can give for sheetmetal is... Put it off as
long as possible.

The most difficult part of sheetmetal is trying to control your overall
dimensions.

If you start with a plate and add walls, you are going to be wrestling
with your overall dimensions.

Did it add a wall thickness? Did it not add a wall thickness? Did I
remember to add room for the bend radius?

Instead of wrestling with these time-consuming issues, start with a
block that is your final shape.

Add rounds where ever the bends will create them. Then shell your block
and cut some bend relief where you need it.

Then import into sheetmetal. The result is an extremely easy to
manipulate sheetmetal part.

2) Flat patterns are for friends only!

You can add an undimensioned flat pattern for reference only. However
flat patterns are NOT your friend.

Every sheetmetal shop has a table for their k-values. (tension and
compression effects on size change of bending areas)

Pro/E's k-values are typically different from most sheetmetal shops.
This means that your flat pattern will NOT look like theirs.

Also, if your sheetmetal shop makes a mistake, they can blame it on your
flat pattern! Sheetmetal shops are flat pattern

experts... It is far better to leave the flattening up to them and only
dimension the final product. Then there is never a

question as to who is responsible for errors in the end product.
Honestly, you can't inspect the flat pattern anyways.

3) 3 place dimensions are for holes only ... 2 places everywhere
else

This sounds really simple to experienced sheetmetal designers, but it is
a big deal that beginners miss all the time. The tightest

Wall to wall dimension that can be held is about +/- .03". Otherwise the
sheetmetal shop is going to throw away many parts

that miss the tolerances and this will be reflected in the price quote.
Usually, 3-place dimensions are Pro/E's default. Letting that

default through check will push your sheetmetal parts way out of the
affordable range with no value added.

4) Rounds all around

Another simple one that designers miss until they assemble their own
stuff and carve themselves up with their own parts.

Sheetmetal is freakin sharp and an excellent way to draw blood. Adding
rounds wherever possible takes very little effort and

Makes your technicians love you instead of hate you...

5) Standardize parts whenever possible

It is great to have an arsenal of sheetmetal "L brackets" for every
occasion. Cables frequently need disconnects. A family table

Full of the full gamut of D-hole-with-a-lockwire-hole-L-brackets save a
huge amount of time, energy and grief. Also, "L brackets"

And "S brackets" with 2 rivet holes on one side and a nutplate on the
other makes mounting new "P-clamps" for cable routing easy.

If you have a cabling reference guide with your company's family tables
for all of these parts, it doubles as a cabling training guide.

Let me know if they make the best practices.

Best regards,

Frederick Burke

merrill.rosenow

1-Visitor

My first piece of advice is to always model the formed part, then flatten it as well. This makes the part much more resilient.

Use the flat pattern feature as it was intended. You can use unbend and bend all, however as the model goes through different revisions and different hands I have seen people not realize what certain bends/unbends do and just create more so that they can easily make their flat pattern. This leads to an unnecessarily large and complex looking family table.

If there is any obscure feature that "fails all of the sudden," change your accuracy to the smallest allowable absolute accuracy. To be honest, the accuracy is the only real issue I've had with sheetmetal.

This is more for drawings than Pro/Sheetmetal itself however, always indicate which side of the metal you are dimensioning in the drawing. Either specify OS. for outside dimensions, INS. for inside dimensions, or indicate in a note that all are one or the other unless stated.

General best practices still apply, like when making a portion of the part out of multiple features make them by each other in the model tree and give those logical self-descriptive names always helps. Good luck!

DeanLong

1-Visitor

Well stated Fred....Agree with it all.

In Reply to Frederick Burke:

Hi David,

I have 5 main sheetmetal rules that I stick to...

1) The best advice I can give for sheetmetal is... Put it off as
long as possible.

The most difficult part of sheetmetal is trying to control your overall
dimensions.

If you start with a plate and add walls, you are going to be wrestling
with your overall dimensions.

Did it add a wall thickness? Did it not add a wall thickness? Did I
remember to add room for the bend radius?

Instead of wrestling with these time-consuming issues, start with a
block that is your final shape.

Add rounds where ever the bends will create them. Then shell your block
and cut some bend relief where you need it.

Then import into sheetmetal. The result is an extremely easy to
manipulate sheetmetal part.

2) Flat patterns are for friends only!

You can add an undimensioned flat pattern for reference only. However
flat patterns are NOT your friend.

Every sheetmetal shop has a table for their k-values. (tension and
compression effects on size change of bending areas)

Pro/E's k-values are typically different from most sheetmetal shops.
This means that your flat pattern will NOT look like theirs.

Also, if your sheetmetal shop makes a mistake, they can blame it on your
flat pattern! Sheetmetal shops are flat pattern

experts... It is far better to leave the flattening up to them and only
dimension the final product. Then there is never a

question as to who is responsible for errors in the end product.
Honestly, you can't inspect the flat pattern anyways.

3) 3 place dimensions are for holes only ... 2 places everywhere
else

This sounds really simple to experienced sheetmetal designers, but it is
a big deal that beginners miss all the time. The tightest

Wall to wall dimension that can be held is about +/- .03". Otherwise the
sheetmetal shop is going to throw away many parts

that miss the tolerances and this will be reflected in the price quote.
Usually, 3-place dimensions are Pro/E's default. Letting that

default through check will push your sheetmetal parts way out of the
affordable range with no value added.

4) Rounds all around

Another simple one that designers miss until they assemble their own
stuff and carve themselves up with their own parts.

Sheetmetal is freakin sharp and an excellent way to draw blood. Adding
rounds wherever possible takes very little effort and

Makes your technicians love you instead of hate you...

5) Standardize parts whenever possible

It is great to have an arsenal of sheetmetal "L brackets" for every
occasion. Cables frequently need disconnects. A family table

Full of the full gamut of D-hole-with-a-lockwire-hole-L-brackets save a
huge amount of time, energy and grief. Also, "L brackets"

And "S brackets" with 2 rivet holes on one side and a nutplate on the
other makes mounting new "P-clamps" for cable routing easy.

If you have a cabling reference guide with your company's family tables
for all of these parts, it doubles as a cabling training guide.

Let me know if they make the best practices.

Best regards,

Frederick Burke

ColinFuller

1-Visitor

Here's a tip that can prevent a few headaches. If you are going to have a flat pattern instance of the sheetmetal part, it's good practice to create the final unbend as a 'flat pattern' feature, NOT an 'unbend all'. Unlike the unbend all feature, the flat pattern feature always remains the last feature in your model tree. This prevents other features being created after the flat pattern.

Features such as cuts, created after the unbend all feature, referencing the geometry of the fully formed part, can fail when the flat panel instance is regenerated. This is because in the flat state, the cut's references to parent features can be lost.

This can be a problem if you use Intralink because the family table has to be verified before you can check the part in.

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