Custom aluminum chassis

[EBG]

I've used a few local fabricators to do some aluminum chassis for me in the
past but was wondering if there are any really big names that do business
like some of the big PCB houses.

For example, I have alot of boards done at PCB express and it's great the
way you can just email the files and get the boards in such a quick
turnaround.

I realize fabricated aluminum chassis are more complex, but if I email the
DXF drawing and complete info to them, it (should be) everything they need.

Are there any places like this that are high volume, do quotes online, have
quick turnaround and good prices?

Thanks.

 

[Joerg]

I don't have online fab addresses but one thing I found in the past is that
this task gets a lot easier when using steel. I try to convince my clients to
use steel whenever it is feasible. It can be welded, tapped, sheet metal
screwed and so on. That's not so easy with aluminum where there will be some
assembly work required. Steel is a lot sturdier as well even if the metal is
much thinner.

So if you look at steel you may even find a local shop that can take AutoCAD or
SolidWorks files and turn out chassis. Going local has the advantage that you
can drive over there to discuss an interference or tolerance issue face to
face, with the "corpus delicti" in hand.

To be fair I must mention one downside: After assembling a steel chassis (shops
often call that a "weldment") it usually needs to be plated. With ever tougher
environmental rules that may become an issue in some states. Aluminum usually
is treated but that can have its own caveats. Anodized material may lead to
some serious EMC headaches and alodine treatment is expensive.

Regards, Joerg

http://www.analogconsultants.com

 

[Activ8]

On Sun, 23 May 2004 13:48:22 -0700, Terry Given wrote:

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:40AFBEEF.1EF4ABD5@removethispacbell.net...
I don't have online fab addresses but one thing I found in the past is
that
this task gets a lot easier when using steel. I try to convince my clients
to
use steel whenever it is feasible. It can be welded, tapped, sheet metal
screwed and so on. That's not so easy with aluminum where there will be
some
assembly work required. Steel is a lot sturdier as well even if the metal
is
much thinner.

So if you look at steel you may even find a local shop that can take
AutoCAD or
SolidWorks files and turn out chassis. Going local has the advantage that
you
can drive over there to discuss an interference or tolerance issue face to
face, with the "corpus delicti" in hand.

To be fair I must mention one downside: After assembling a steel chassis
(shops
often call that a "weldment") it usually needs to be plated. With ever
tougher
environmental rules that may become an issue in some states. Aluminum
usually
is treated but that can have its own caveats. Anodized material may lead
to
some serious EMC headaches and alodine treatment is expensive.

Regards, Joerg

And the great thing about weldments is that welding changes physical
dimensions. If, like me, you design a 840h x 630v x 140mm frame, with 0.1mm
tolerance on h,v dimensions and critical hole positioning, you will quickly
discover this fact (if, that is, you bother to measure the stuff you
bought). We used Aluminium, because weight was a critical factor - these
units clip together (big clips), 15 high and as many wide as you want, and
its structural integrity is maintained in 100km/hr winds.....LED video
screens for football stadiums/concerts etc

Terry

Cheers
Terry

ISTM that a welder's job is to weld the material without changing
the dimensions. He'd clamp the workpieces in position and do the
weld. In fact, my stepdad had to do this for a test at work. He took
a tube, laid two wires on the end to allow space for the weld and
get his length dimension - no bevel allowed. Then he put the end cap
on the wires and tacked it to the tube in a few places then he just
filled in the rest without heating thing up so much that he'd loose
his dimension. Simple shit. 0.1mm tolerance? I'd have to ask him.
--
Best Regards,
Mike

 

[R.Legg]

"EBG" <maberger@comcast.net> wrote in message news:<J8GdndGWsuaH5TLdRVn-sA@comcast.com>...

I've used a few local fabricators to do some aluminum chassis for me in the
past but was wondering if there are any really big names that do business
like some of the big PCB houses.

For example, I have alot of boards done at PCB express and it's great the
way you can just email the files and get the boards in such a quick
turnaround.

I realize fabricated aluminum chassis are more complex, but if I email the
DXF drawing and complete info to them, it (should be) everything they need.

Are there any places like this that are high volume, do quotes online, have
quick turnaround and good prices?

High volume and low price mechanical detail generally involves earlier
design effort of hard tooling.

If you want good prices without this effort, then expect delays and
uncertainty while the vendor tools up, as best he can.

You should ask for early budgetary options, that include itemized
tooling options as a variable, from your vendors. Some consider this
proprietary and will only quote volume, with the tooling costs
absorbed, based on mechanical dwg. Finding a vendor that knows how to
do what you want, cheaply, can take time.

RL

 

[Terry Given]

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:40AFBEEF.1EF4ABD5@removethispacbell.net...

I don't have online fab addresses but one thing I found in the past is
that
this task gets a lot easier when using steel. I try to convince my clients
to
use steel whenever it is feasible. It can be welded, tapped, sheet metal
screwed and so on. That's not so easy with aluminum where there will be
some
assembly work required. Steel is a lot sturdier as well even if the metal
is
much thinner.

So if you look at steel you may even find a local shop that can take
AutoCAD or
SolidWorks files and turn out chassis. Going local has the advantage that
you
can drive over there to discuss an interference or tolerance issue face to
face, with the "corpus delicti" in hand.

To be fair I must mention one downside: After assembling a steel chassis
(shops
often call that a "weldment") it usually needs to be plated. With ever
tougher
environmental rules that may become an issue in some states. Aluminum
usually
is treated but that can have its own caveats. Anodized material may lead
to
some serious EMC headaches and alodine treatment is expensive.

Regards, Joerg

And the great thing about weldments is that welding changes physical
dimensions. If, like me, you design a 840h x 630v x 140mm frame, with 0.1mm
tolerance on h,v dimensions and critical hole positioning, you will quickly
discover this fact (if, that is, you bother to measure the stuff you
bought). We used Aluminium, because weight was a critical factor - these
units clip together (big clips), 15 high and as many wide as you want, and
its structural integrity is maintained in 100km/hr winds.....LED video
screens for football stadiums/concerts etc

Terry

Cheers
Terry

 

[Joerg]

Hi Terry,

That really depends on which shop does it. Tolerances need to be spec'd and the
vendor must agree to that spec. We never had problems. Mostly it was much larger
gear such as medical ultrasound systems. But there were some really critical
areas in them such as the card cages. The front of each circuit board panel was
screwed to the weldment for securing. The DIN connectors were almost a foot
behind that and had to really be within fractions of a millimeter. They always
were.

Regards, Joerg

http://www.analogconsultants.com

 

[Rich Grise]

"Terry Given" <the_domes@xtra.co.nz> wrote in message news:%lTrc.8714

And the great thing about weldments is that welding changes physical
dimensions. If, like me, you design a 840h x 630v x 140mm frame, with
0.1mm
tolerance on h,v dimensions and critical hole positioning, you will
quickly
discover this fact (if, that is, you bother to measure the stuff you
bought). We used Aluminium, because weight was a critical factor - these
units clip together (big clips), 15 high and as many wide as you want, and
its structural integrity is maintained in 100km/hr winds.....LED video
screens for football stadiums/concerts etc

I design weld fixtures for CRES & Alloy tubing. I draw to the
spec - the boss, who is also the chief weldor, specifically
told me not to do _anything_ about shrinkage - just put the final
dims on the print, and let the weldor take care of shrinkage.

IOW, if they deliver a part that's out of print, and blame
weld shrinkage, get a different vendor.

I also worked for a guy who got chassis bent & punched locally,
and they came in already powder coated, fwiw. You have to remember
to scrape the paint under the ground lug.

Good Luck!
Rich

 

[Jan Panteltje]

On a sunny day (Mon, 24 May 2004 04:51:37 GMT) it happened "Rich Grise"
<null@example.net> wrote in <tbfsc.7402$o97.5401@nwrddc01.gnilink.net>:

I also worked for a guy who got chassis bent & punched locally,
and they came in already powder coated, fwiw. You have to remember
to scrape the paint under the ground lug.
Hey, same problem here, and it was hundreds....

JP

 

[Joerg]

Hi Terry,

That is indeed a really tough spec to build to. I wonder if there is another way
to join the units together without relying on tolerance. But I bet you guys
looked into that and decided it just had to be done the way it is now. Anyways,
it looks like even a slightly rough landing of a freighter plane might give
these units enough deformation to run out of spec.

The Romans already had some bigshot mechanical engineers. I remember from a
story that they made huge caliper-like structures from marble (the expensive
Italian kind no less) for such purposes. Don't know if it worked but much of
their stuff is over 1500 years old and still holds up.

I wonder if aluminum lives up to these specs over time. There usually is some
creepage and sag. With steel you have more options, they can cook up an alloy
for you that is pretty stiff and temp stable.

Regards, Joerg

http://www.analogconsultants.com

 

[Terry Given]

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:40B112B0.B1AD6ABD@removethispacbell.net...

Hi Terry,

That really depends on which shop does it. Tolerances need to be spec'd
and the
vendor must agree to that spec. We never had problems. Mostly it was much
larger
gear such as medical ultrasound systems. But there were some really
critical
areas in them such as the card cages. The front of each circuit board
panel was
screwed to the weldment for securing. The DIN connectors were almost a
foot
behind that and had to really be within fractions of a millimeter. They
always
were.

Regards, Joerg

http://www.analogconsultants.com

Hi Joerg,

our biggest problem to date is measuring things accurately. We have a number
of safety-critical dimensions (these clip together to form a structure, that
is placed near large crowds of people). The solution is post-welding
machining of the critical holes/faces, which allows us to soak up the
inevitable manufacturing tolerances providing the NC machine is suitably
accurate (and calibrated regularly). Dont forget this thing is almost a
meter long, and we need guaranteed 0.1mm accuracy (ie around 0.01%).

Actually I lied - our biggest problem was that initially we didnt measure
anything at all, and just relied on the vendor to give us what we asked for,
which of course they didnt. So we bought a 1200mm vernier caliper (its a
2-man job using that thing!), straight-edges, engineers squares etc. and
promptly discovered how far off everything was. We hired a mechanical
black-belt (im just a lowly electron-pusher), and he has developed highly
accurate jigs that provide the manufacturer, and our inwards goods guy, with
a simple, easy-to-use go/no-go test.

Apparently, we independantly discovered "nasa theory" - closing your eyes
and crossing your fingers is a poor way to see if problems exist. Then
hurling them at mars makes it a costly approach too.

Terry

 

[Terry Given]

"Rich Grise" <null@example.net> wrote in message
news:tbfsc.7402$o97.5401@nwrddc01.gnilink.net...

"Terry Given" <the_domes@xtra.co.nz> wrote in message news:%lTrc.8714

And the great thing about weldments is that welding changes physical
dimensions. If, like me, you design a 840h x 630v x 140mm frame, with
0.1mm
tolerance on h,v dimensions and critical hole positioning, you will
quickly
discover this fact (if, that is, you bother to measure the stuff you
bought). We used Aluminium, because weight was a critical factor - these
units clip together (big clips), 15 high and as many wide as you want,
and
its structural integrity is maintained in 100km/hr winds.....LED video
screens for football stadiums/concerts etc

I design weld fixtures for CRES & Alloy tubing. I draw to the
spec - the boss, who is also the chief weldor, specifically
told me not to do _anything_ about shrinkage - just put the final
dims on the print, and let the weldor take care of shrinkage.

IOW, if they deliver a part that's out of print, and blame
weld shrinkage, get a different vendor.

I also worked for a guy who got chassis bent & punched locally,
and they came in already powder coated, fwiw. You have to remember
to scrape the paint under the ground lug.

Good Luck!
Rich

amen on the powder coat (I just had to explain to my dipshit boss that
polyester resin is about 1200x worse conductor of heat than Al, so dont
powder coat my heatsink!)

as far as who is to blame - moot point, it doesnt help me meet my deadlines
if I send everything back, even if they pay. which is why we are working
with the vendor to identify the root cause(s) and remove them. 0.1mm aint
much, especially over 840mm. A major improvement over our measuring nothing,
then wondering why they are hard to assemble in the feild.

Cheers
Terry