I just got the following parts quoted (I asked for a ballpark quote, got
a detailed one -- hmph). Here's a rough sketch, with unnecessary detail
_and_ things left out:

http://www.wescottdesign.com/Seminar...iner_Frame.pdf

Over the phone we modified things such that I'd be responsible for the
indicated holes, and the finish would be brushed & clear anodized. The
quote came back at around $36 each in lots of 50.

Is this just what I can expect to pay for these things? Did I go to the
wrong shop? What are the cost drivers here?

I'm trying to put together a training device that I can include in the
cost of a seminar, $36 is more than 1/3 of the worst-case BOM cost that I
was contemplating. I need to know if I can beat this down by being
creative, if I need to bite the bullet and accept a higher BOM cost, or
if I should yank my eldest out of school and put him to work in the
garage bending metal!

The principal of this thing is that there's a counterweighted arm that
swings on a shaft that's pivoted on bearings in the large holes in the
frame. A microprocessor monitors the position of the shaft through a
potentiometer and controls the voltage to a motor/propeller, with the
goal of holding the arm at a commanded position. The hole locations are
assumed to need tight tolerancing because of the apparent tolerance needs
of the pot I'm planning to use, but I'll be re-thinking that decision
here soon.

Thanks in advance.

Sorry this is off topic - would it help if I mention that I'm putting my
vote behind Hillary McBama, with Ralph Paul as her running mate?

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

On Sat, 08 Mar 2008 00:15:56 -0600, Tim Wescott
wrote:
snip
Is this just what I can expect to pay for these things? Did I go to the
wrong shop? What are the cost drivers here?
snip
===========
Looks like an interesting project.

The first cost driver is the low volume.

I would take a walk through WalMart, a kitchen/restaurant supply
with lots of pans, etc. and see what was close enough to modify.
Possibly something plastic, unless you need metal. A plastic box
with a snap on lid is good as you can pack everything inside.

These sites also looked interesting (stand on end?)
http://www.radiodaze.com/catalog-306-page62-63.pdf
http://www.hammondmfg.com/dwg20.htm
http://www.hammondmfg.com/dwg11.htm
(many other types on hammond site)


The brush/anodize finish looks nice but is extra handling and an
avoidable cost. If possible get a prefinished container or
chassis

It may be cheaper to drill oversize holes for the bearings and
then use separate bearing pieces with sheet metal screws to allow
adjustment/alignment rather than trying to hold close tolerances
on position and size on a single fabricated/folded part.

I would consider plastic for the bearings also. You should be
able to make quite serviceable bearings yourself from plastic
strip, possibly reaming the bearing hole for a good finish if
required.

You can also make a long reamer/alignment tool from a piece of
drill-rod to insure that the holes are inline from side to side.
Indeed, you might be able to use pop rivets here also eliminating
the sheet metal screws and speeding assembly.

If you need it, as a box or pan with closed ends will be
considerably more rigid, you may also be able to use
off-the-shelf L brackets and pop-rivet to the sides.

A little value analysis and you should be able to knock these out
at home with a drill press. For sheet metal a special drill is
helpful. For examples click on
http://www.castlewholesalers.com/GEN...-Capacity.html
http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3


Another possibility is a wood base with the "sides" made from
commercial L brackets attached to the base with screws.

Good luck and let the group know how you make out.

Feel free to email if you think I help.


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).

Tim Wescott wrote:

I just got the following parts quoted (I asked for a ballpark quote, got
a detailed one -- hmph). Here's a rough sketch, with unnecessary detail
_and_ things left out:

http://www.wescottdesign.com/Seminar...iner_Frame.pdf

Over the phone we modified things such that I'd be responsible for the
indicated holes, and the finish would be brushed & clear anodized. The
quote came back at around $36 each in lots of 50.

Is this just what I can expect to pay for these things? Did I go to the
wrong shop? What are the cost drivers here?

I'm trying to put together a training device that I can include in the
cost of a seminar, $36 is more than 1/3 of the worst-case BOM cost that I
was contemplating. I need to know if I can beat this down by being
creative, if I need to bite the bullet and accept a higher BOM cost, or
if I should yank my eldest out of school and put him to work in the
garage bending metal!

The principal of this thing is that there's a counterweighted arm that
swings on a shaft that's pivoted on bearings in the large holes in the
frame. A microprocessor monitors the position of the shaft through a
potentiometer and controls the voltage to a motor/propeller, with the
goal of holding the arm at a commanded position. The hole locations are
assumed to need tight tolerancing because of the apparent tolerance needs
of the pot I'm planning to use, but I'll be re-thinking that decision
here soon.

Thanks in advance.

Sorry this is off topic - would it help if I mention that I'm putting my
vote behind Hillary McBama, with Ralph Paul as her running mate?


I'm going to jump up and guess that you do not yet have a working
prototype.

That might be a better place to start.


Richard

Tim Wescott wrote:

On Sat, 08 Mar 2008 01:40:02 -0600, cavelamb himself wrote:


Tim Wescott wrote:


I just got the following parts quoted (I asked for a ballpark quote,
got a detailed one -- hmph). Here's a rough sketch, with unnecessary
detail _and_ things left out:

http://www.wescottdesign.com/Seminar...iner_Frame.pdf

Over the phone we modified things such that I'd be responsible for the
indicated holes, and the finish would be brushed & clear anodized. The
quote came back at around $36 each in lots of 50.

Is this just what I can expect to pay for these things? Did I go to
the wrong shop? What are the cost drivers here?

I'm trying to put together a training device that I can include in the
cost of a seminar, $36 is more than 1/3 of the worst-case BOM cost that
I was contemplating. I need to know if I can beat this down by being
creative, if I need to bite the bullet and accept a higher BOM cost, or
if I should yank my eldest out of school and put him to work in the
garage bending metal!

The principal of this thing is that there's a counterweighted arm that
swings on a shaft that's pivoted on bearings in the large holes in the
frame. A microprocessor monitors the position of the shaft through a
potentiometer and controls the voltage to a motor/propeller, with the
goal of holding the arm at a commanded position. The hole locations
are assumed to need tight tolerancing because of the apparent tolerance
needs of the pot I'm planning to use, but I'll be re-thinking that
decision here soon.

Thanks in advance.

Sorry this is off topic - would it help if I mention that I'm putting
my vote behind Hillary McBama, with Ralph Paul as her running mate?



I'm going to jump up and guess that you do not yet have a working
prototype.

That might be a better place to start.


Richard


A student of mine built the prototype, which worked admirably well. Cost-
wise, it made oodles of sense as a one-off, but not in any volume over
onesie-twosie.

I'm trying to figure out how to achieve the desired behavior, but at a
reasonably low cost.


Shoot!

Welcome to engineering 101...

On Sat, 08 Mar 2008 01:40:02 -0600, cavelamb himself wrote:

Tim Wescott wrote:

I just got the following parts quoted (I asked for a ballpark quote,
got a detailed one -- hmph). Here's a rough sketch, with unnecessary
detail _and_ things left out:

http://www.wescottdesign.com/Seminar...iner_Frame.pdf

Over the phone we modified things such that I'd be responsible for the
indicated holes, and the finish would be brushed & clear anodized. The
quote came back at around $36 each in lots of 50.

Is this just what I can expect to pay for these things? Did I go to
the wrong shop? What are the cost drivers here?

I'm trying to put together a training device that I can include in the
cost of a seminar, $36 is more than 1/3 of the worst-case BOM cost that
I was contemplating. I need to know if I can beat this down by being
creative, if I need to bite the bullet and accept a higher BOM cost, or
if I should yank my eldest out of school and put him to work in the
garage bending metal!

The principal of this thing is that there's a counterweighted arm that
swings on a shaft that's pivoted on bearings in the large holes in the
frame. A microprocessor monitors the position of the shaft through a
potentiometer and controls the voltage to a motor/propeller, with the
goal of holding the arm at a commanded position. The hole locations
are assumed to need tight tolerancing because of the apparent tolerance
needs of the pot I'm planning to use, but I'll be re-thinking that
decision here soon.

Thanks in advance.

Sorry this is off topic - would it help if I mention that I'm putting
my vote behind Hillary McBama, with Ralph Paul as her running mate?


I'm going to jump up and guess that you do not yet have a working
prototype.

That might be a better place to start.


Richard

A student of mine built the prototype, which worked admirably well. Cost-
wise, it made oodles of sense as a one-off, but not in any volume over
onesie-twosie.

I'm trying to figure out how to achieve the desired behavior, but at a
reasonably low cost.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

On Sat, 08 Mar 2008 01:33:04 -0600, F. George McDuffee wrote:

On Sat, 08 Mar 2008 00:15:56 -0600, Tim Wescott
wrote:
snip
Is this just what I can expect to pay for these things? Did I go to the
wrong shop? What are the cost drivers here?
snip
===========
Looks like an interesting project.

The first cost driver is the low volume.

I would take a walk through WalMart, a kitchen/restaurant supply with
lots of pans, etc. and see what was close enough to modify. Possibly
something plastic, unless you need metal. A plastic box with a snap on
lid is good as you can pack everything inside.

These sites also looked interesting (stand on end?)
http://www.radiodaze.com/catalog-306-page62-63.pdf
http://www.hammondmfg.com/dwg20.htm
http://www.hammondmfg.com/dwg11.htm
(many other types on hammond site)


The brush/anodize finish looks nice but is extra handling and an
avoidable cost. If possible get a prefinished container or chassis

It may be cheaper to drill oversize holes for the bearings and then use
separate bearing pieces with sheet metal screws to allow
adjustment/alignment rather than trying to hold close tolerances on
position and size on a single fabricated/folded part.

I would consider plastic for the bearings also. You should be able to
make quite serviceable bearings yourself from plastic strip, possibly
reaming the bearing hole for a good finish if required.

You can also make a long reamer/alignment tool from a piece of drill-rod
to insure that the holes are inline from side to side. Indeed, you
might be able to use pop rivets here also eliminating the sheet metal
screws and speeding assembly.

If you need it, as a box or pan with closed ends will be considerably
more rigid, you may also be able to use off-the-shelf L brackets and
pop-rivet to the sides.

A little value analysis and you should be able to knock these out at
home with a drill press. For sheet metal a special drill is helpful.
For examples click on
http://www.castlewholesalers.com/GEN...tal-Drill-1-8-
to-7-8-Capacity.html
http://www.use-enco.com/CGI/INSRIT?
PMAKA=302-1109&PMPXNO=947556&PARTPG=INLMK3


Another possibility is a wood base with the "sides" made from commercial
L brackets attached to the base with screws.

Good luck and let the group know how you make out.

Feel free to email if you think I help.


I'm planning on either using Rulon bearing inserts from McMaster, or just
running the shaft against the aluminum.

Dunno about the adjustable bearing idea -- I've considered it, but if I'm
paying to have it assembled it may be worth a bit of time on a milling
machine to avoid having to find someone who's capable of doing the
bearing adjustment right. The whole bearing adjustment issue is being
driven by the sensor, so I'm going to look into that part independently.

It's important that it look reasonably professional, but bare aluminum
may be good enough -- I may ask for another quote without the anodizing.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

Tim Wescott wrote in
:

You would be cheaper to make it 3 pcs and use the bracket for afixing the
3. The reason is that the parts can then be cut on a waterjet or laser, at
very low cost, including tight location holes. When you get into bending,
you cannot put the tight tolerance holes in prior to bending, because of
tolerance stack-up. This makes fixturing for the holes to be put in later a
difficult task. The savings would more than pay for a snap-in plastic
corner strip to cover the sharp edges.
I would re-think it along these lines Tim.



--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

Tim Wescott wrote:
I just got the following parts quoted Did I go to the
wrong shop?

I will venture another opinion. It's your drawing. You are asking a guy
to quote on a print with words like "about" and "3-4" with tolerances of
..001". From where? Center to center? You didn't say that. The sheet
metal guy sees trouble, and he will quote a premium price to compensate
for the potential trouble. He or she is not in the engineering prototype
business.

You might want to look at extruded C channel, in aluminum or plastic. In
plastic you wouldn't have to worry about a bearing material. McMaster
has some.

Kevin Gallimore


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On Sat, 08 Mar 2008 02:08:24 -0600, Tim Wescott
wrote:

I'm planning on either using Rulon bearing inserts from McMaster, or just
running the shaft against the aluminum.


Dunno about the adjustable bearing idea -- I've considered it, but if I'm
paying to have it assembled it may be worth a bit of time on a milling
machine to avoid having to find someone who's capable of doing the
bearing adjustment right. The whole bearing adjustment issue is being
driven by the sensor, so I'm going to look into that part independently.

It's important that it look reasonably professional, but bare aluminum
may be good enough -- I may ask for another quote without the anodizing.

$36 doesn't sound out of line based on my understanding of the sketch.
What's the piece marked "bracket"? A welded-in gusset? Depending on
the configuration and requirements, welding may be expensive.

Assuming the shop has a Timesaver belt sander, the brushed finish and
anodize shouldn't add more than a couple dollars to the price.

You may be able pay for the finish by buying your bushings from Igus.
http://www.igus.com/

--
Ned Simmons

On Sat, 08 Mar 2008 10:47:45 -0500, axolotl wrote:

Tim Wescott wrote:
I just got the following parts quoted Did I go to the wrong shop?

I will venture another opinion. It's your drawing. You are asking a guy
to quote on a print with words like "about" and "3-4" with tolerances of
.001". From where? Center to center? You didn't say that. The sheet
metal guy sees trouble, and he will quote a premium price to compensate
for the potential trouble. He or she is not in the engineering prototype
business.

You might want to look at extruded C channel, in aluminum or plastic. In
plastic you wouldn't have to worry about a bearing material. McMaster
has some.

Kevin Gallimore

My plan was to get budgetary pricing so I knew if I should even start the
business, or use that approach, then to pay a mechanical engineer to
finish the design with a nicely detailed and toleranced drawing.

Clearly this shop doesn't understand the notion of budgetary pricing -- I
was getting back an honest-to-god quote with four significant digits; a
"budgetary price" with more than 1-1/2 significant digits is either a lie
of a wildly premature quote.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

I'm planning on either using Rulon bearing inserts from McMaster, or just
running the shaft against the aluminum.

Dunno about the adjustable bearing idea -- I've considered it, but if I'm
paying to have it assembled it may be worth a bit of time on a milling
machine to avoid having to find someone who's capable of doing the
bearing adjustment right. The whole bearing adjustment issue is being
driven by the sensor, so I'm going to look into that part independently.

It's important that it look reasonably professional, but bare aluminum
may be good enough -- I may ask for another quote without the anodizing.

--
Tim Wescott


Tim,
I believe there are several expensive areas in your design.
First off, expecting .001" tolerance means it must be milled or wire
EDM.
Can you tell me why the tight tolerance?
Does the mating part have the same tolerance?
What size holes in the mating part?

Next, I don't understand the bracket. Is this a purchased item, or is
it formed into the sheetmetal?
Or, is it to be fab'd separately and attached, if so how?

Material thickness?

Anodize is not a big cost. Here, it's about $50 run charge, plus $1/
part. IIRC.
Dave

On Sat, 08 Mar 2008 02:01:42 -0600, cavelamb himself wrote:

Tim Wescott wrote:

On Sat, 08 Mar 2008 01:40:02 -0600, cavelamb himself wrote:


Tim Wescott wrote:


I just got the following parts quoted (I asked for a ballpark quote,
got a detailed one -- hmph). Here's a rough sketch, with unnecessary
detail _and_ things left out:

http://www.wescottdesign.com/Seminar...iner_Frame.pdf

Over the phone we modified things such that I'd be responsible for the
indicated holes, and the finish would be brushed & clear anodized.
The quote came back at around $36 each in lots of 50.

Is this just what I can expect to pay for these things? Did I go to
the wrong shop? What are the cost drivers here?

I'm trying to put together a training device that I can include in the
cost of a seminar, $36 is more than 1/3 of the worst-case BOM cost
that I was contemplating. I need to know if I can beat this down by
being creative, if I need to bite the bullet and accept a higher BOM
cost, or if I should yank my eldest out of school and put him to work
in the garage bending metal!

The principal of this thing is that there's a counterweighted arm that
swings on a shaft that's pivoted on bearings in the large holes in the
frame. A microprocessor monitors the position of the shaft through a
potentiometer and controls the voltage to a motor/propeller, with the
goal of holding the arm at a commanded position. The hole locations
are assumed to need tight tolerancing because of the apparent
tolerance needs of the pot I'm planning to use, but I'll be
re-thinking that decision here soon.

Thanks in advance.

Sorry this is off topic - would it help if I mention that I'm putting
my vote behind Hillary McBama, with Ralph Paul as her running mate?



I'm going to jump up and guess that you do not yet have a working
prototype.

That might be a better place to start.


Richard


A student of mine built the prototype, which worked admirably well.
Cost- wise, it made oodles of sense as a one-off, but not in any volume
over onesie-twosie.

I'm trying to figure out how to achieve the desired behavior, but at a
reasonably low cost.


Shoot!

Welcome to engineering 101...

Well, yes. My frustration is compounded by the fact that I'm
accomplished at other aspects of engineering. Ask me how to make a low-
cost circuit, or how to write software to allow for a processor that
costs 1/2 as much, or to design a control system that maintains
performance with a cheaper sensor or actuator -- I can do any of those.

But a feel for how much it costs to put a bend in a sheet of metal, or a
hole, or what features of a mechanical design may drive the cost up or
down? Not there.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

On Sat, 08 Mar 2008 08:12:03 -0800, Mechanical Magic wrote:

I'm planning on either using Rulon bearing inserts from McMaster, or
just running the shaft against the aluminum.

Dunno about the adjustable bearing idea -- I've considered it, but if
I'm paying to have it assembled it may be worth a bit of time on a
milling machine to avoid having to find someone who's capable of doing
the bearing adjustment right. The whole bearing adjustment issue is
being driven by the sensor, so I'm going to look into that part
independently.

It's important that it look reasonably professional, but bare aluminum
may be good enough -- I may ask for another quote without the
anodizing.

--
Tim Wescott


Tim,
I believe there are several expensive areas in your design. First off,
expecting .001" tolerance means it must be milled or wire EDM.
Can you tell me why the tight tolerance? Does the mating part have the
same tolerance? What size holes in the mating part?

I knew I should have erased parts of that damn drawing and re-scanned it.

At this point I'm just trying to understand the cost drivers for the part
without the holes -- I'll either have the cost to have the holes put in
at a machine shop as a second operation, or I'll see if I can eliminate
the need for such accuracy altogether.

Next, I don't understand the bracket. Is this a purchased item, or is
it formed into the sheetmetal?
Or, is it to be fab'd separately and attached, if so how?

Fabbed separately, screwed on.

Material thickness?

The bearings I'm contemplating require moderately thick material -- it
works out to 14 gauge, but I'm damned if I can remember exactly what the
bearing spec is at the moment.

Anodize is not a big cost. Here, it's about $50 run charge, plus $1/
part. IIRC.
Dave

That's good to know, and a reasonable price.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

Tim Wescott wrote:

My plan was to get budgetary pricing

That changes things a bit. You may find "budgetary pricing" is a foreign
concept to most working fab shops (the fellows here that run shops could
tell us).

You apparently are in contact with engineering students- You might want
to slide one of them a few bucks and get dimensioned/toleranced drawings
to send out - or - have it given out as a mechanical engineering problem.

If you can give us more detail about what you need to do (having mounted
a fair number of servo pots I don't understand the .001" tolerance) the
folks here can give you some ideas about how to do it in budget within
the design parameters. We can't help it.

Kevin Gallimore


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---= - Total Privacy via Encryption =---

On Sat, 08 Mar 2008 12:09:28 -0500, axolotl wrote:

Tim Wescott wrote:

My plan was to get budgetary pricing

That changes things a bit. You may find "budgetary pricing" is a foreign
concept to most working fab shops (the fellows here that run shops could
tell us).

You apparently are in contact with engineering students- You might want
to slide one of them a few bucks and get dimensioned/toleranced drawings
to send out - or - have it given out as a mechanical engineering
problem.

I'm a consulting systems engineer, so I'm in contact with any number of
working mechanical engineers. Some of them are willing to help out for
beer, in little bits at a time. Some of them are willing to expend
chunks of time -- but they're the consulting mechanical engineers, who
have this strange notion that they should be paid for that sort of thing
(it's a fine notion, but only when I'm getting the money :-).

All of this is complicated by the fact that most of the places where I
rub shoulders with such people are either instrumentation houses or
aerospace houses. For those sorts of places "cost effective" means that
you hog it out of 6061-T6 with 1/2 inch sections for rigidity and a nice
web of pockets for lightness, and then you don't expend any more
engineering time later messing with things falling out of spec. I would
get a design that could be used for aligning lasers, but not, perhaps,
for selling to individuals.

If you can give us more detail about what you need to do (having mounted
a fair number of servo pots I don't understand the .001" tolerance) the
folks here can give you some ideas about how to do it in budget within
the design parameters. We can't help it.

I could be totally wrong with that, which is why I'm working on opening
it up. The tolerance comes from what appears to be a 0.005" off-center
requirement from an under-specified but really cheap pot, then the
necessary stack up to get from the bearing center to the pot center with
the pot mounted on a circuit board.

See my post titled "Anyone with experience with this sensor?" for the
part I want to use. It's way cost-effective, so I can't imagine that it
would demand tens of dollars in the mechanical assembly to mate up to it,
yet I can't figure out how to make it work without holding tolerances
that tight.

I'd love to see an assembly where it's used -- that would probably clear
up a lot of confusion.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

On Sat, 08 Mar 2008 12:43:26 GMT, with neither quill nor qualm,
Anthony quickly quoth:

Tim Wescott wrote in
:

You would be cheaper to make it 3 pcs and use the bracket for afixing the
3. The reason is that the parts can then be cut on a waterjet or laser, at
very low cost, including tight location holes. When you get into bending,
you cannot put the tight tolerance holes in prior to bending, because of
tolerance stack-up. This makes fixturing for the holes to be put in later a
difficult task. The savings would more than pay for a snap-in plastic
corner strip to cover the sharp edges.
I would re-think it along these lines Tim.

I picked up a 20' stick of 3/4" x 3/4" angle iron a few days ago and
it cost a bleeding $14.90! He told me it had gone up 30% two weeks
ago and was going up another 10% today. Steel plate is being rationed!

Hayseuss Crisco, it's getting expensive out there...

--
The best and safest thing is to keep a balance in your life,
acknowledge the great powers around us and in us. If you can
do that, and live that way, you are really a wise man.
-- Euripides

At this point I'm just trying to understand the cost drivers for the part
without the holes -- I'll either have the cost to have the holes put in
at a machine shop as a second operation, or I'll see if I can eliminate
the need for such accuracy altogether.


Tim,
I'm a very poor estimater, but::

Initial shearing of the parts is cheap, IF you don't have tight
tolerances. If you are OK with +- 1/8" then things are cheaper than
+- .010". 1/8" can be done on a cheap shear, .010" has to be done on
a laser machine costing $300,000+

Bending tolerance, same issue, looser is cheaper.

A sheetmetal shop cannot hold .001" tolerance on hole position, unless
they have CNC controlled equipment. You are asking for the equivalent
of .05% resistors. Yes, they exist but is it required?
A qualified machine shop will be required if you insist on that
tolerance.
BTW, how are you going to inspect the part to verify the tolerances
have been met?

Dave

"Larry Jaques" wrote in message
...
On Sat, 08 Mar 2008 12:43:26 GMT, with neither quill nor qualm,
Anthony quickly quoth:

Tim Wescott wrote in
:

You would be cheaper to make it 3 pcs and use the bracket for afixing the
3. The reason is that the parts can then be cut on a waterjet or laser, at
very low cost, including tight location holes. When you get into bending,
you cannot put the tight tolerance holes in prior to bending, because of
tolerance stack-up. This makes fixturing for the holes to be put in later
a
difficult task. The savings would more than pay for a snap-in plastic
corner strip to cover the sharp edges.
I would re-think it along these lines Tim.

I picked up a 20' stick of 3/4" x 3/4" angle iron a few days ago and
it cost a bleeding $14.90! He told me it had gone up 30% two weeks
ago and was going up another 10% today. Steel plate is being rationed!

Hayseuss Crisco, it's getting expensive out there...

China is sucking up a lot of steel. As much as they make, they've been in
deficit for a few years. Hold onto those used nails, we may need them.

That is, if there's anything left to eat. They're sucking up a lot of grain,
too. They've developed a taste for finished beef, and beer. If they increase
production by three beers per year per Chinese adult, they will consume more
grain that all that grown in Norway. And we're using a lot of ours to make
ethanol, which consumes almost a gallon of oil to make a gallon equivalent
of ethanol.

And once those Chinese get loaded on their three beers per year, they'll
need something to drive. d8-)

--
Ed Huntress

Seems cheap to me.

First, look at material costs- aluminum is not cheap these days- I
figure you get 20 parts from a 4x8 sheet- and bare material alone, in .
080 6061, has gotta be around 10 bucks per part.

Me, I lose money on anything that goes thru my shop that doesnt bill
out at at least 5 times materials.

Assume that a decent sheet metal shop, even without any cnc machines,
is going to be a minimum of $50/hr- and most are more. With CNC, they
are going to be wanting closer to $100/hr shop time, and you would
too, if you had a million dollars or so worth of equipment to feed.

An hour per part on these, in small quantities, is not unreasonable-
without cnc, you would need to shear 18" strips from the sheet, then
cut each one down into 12" wide pieces, then shear 4 more times for
the angles- thats six cuts per part.
Then, bending, then punching the holes and reaming to size (at least,
thats how I would do it for precision)

Fabbing up the angle- thats more money in material, more time in
measuring, setup, shearing, bending, and punching.

deburring- every part is gonna need hand deburring.

Then, somebody has to drive it to the anodizer, and pick it up when
its done. More time, more overhead on truck expenses, diesel, and so
on.

And I have never found anodizers to be cheap- $50 setup and a dollar
per part- thats at the extreme low end of anodizing prices- and pretty
much out of the picture in LA, with its high cost of pollution
controls, or up here in the Seattle area where I live.

In short, I think you got a screaming deal on a quote, and, unless you
were buying em by the container load from China, its unlikely to go
down by more than 10% or so.

I really doubt you could find a bid that low, up here in Boeing land-
when the average house (and nobody I know can find an average house)
in Seattle is $500,000.

Any good shop will have a standardized quote system. Just plug in the
material, the setup times and run rates for each op, click 'store',
click 'print'. You read the print as it is presented, tolerances and
all. Any part like this will have a sequence of ops, you need to think
about how you would make the part and which machines you would use
regardless of the precision of the quote.

In a previous life I had all of the sales and presales for a high volume
job shop. I had not the slightest interest in quoting to a low volume
entrepreneur type. My large customer could get an on site visit from
one of my sales engineers to work with the design engineer and CAD tech
to wring every penny out of it. The small guy got ignored.

A quick look at your drawing shows .001" tolerances. On a formed part,
that is just not going to happen without tooling, exotic equipment, or
some very labor intensive processes.

A couple of comments to cut the costs:
1) Make sure the shop you are talking to does sheet metal and likes
small, one off projects.
2) you need to figure out which features need the tolerances, which don't


Tim Wescott wrote:
On Sat, 08 Mar 2008 10:47:45 -0500, axolotl wrote:

Tim Wescott wrote:
I just got the following parts quoted Did I go to the wrong shop?
I will venture another opinion. It's your drawing. You are asking a guy
to quote on a print with words like "about" and "3-4" with tolerances of
.001". From where? Center to center? You didn't say that. The sheet
metal guy sees trouble, and he will quote a premium price to compensate
for the potential trouble. He or she is not in the engineering prototype
business.

You might want to look at extruded C channel, in aluminum or plastic. In
plastic you wouldn't have to worry about a bearing material. McMaster
has some.

Kevin Gallimore

My plan was to get budgetary pricing so I knew if I should even start the
business, or use that approach, then to pay a mechanical engineer to
finish the design with a nicely detailed and toleranced drawing.

Clearly this shop doesn't understand the notion of budgetary pricing -- I
was getting back an honest-to-god quote with four significant digits; a
"budgetary price" with more than 1-1/2 significant digits is either a lie
of a wildly premature quote.

On Sat, 08 Mar 2008 10:47:45 -0500, axolotl wrote:
Tim Wescott wrote:
I just got the following parts quoted Did I go to the wrong shop?
....
http://www.wescottdesign.com/Seminar...iner_Frame.pdf
....
You might want to look at extruded C channel, in aluminum or plastic. In
plastic you wouldn't have to worry about a bearing material. McMaster
has some.

Or, if you can have a top on it, consider 6" square tube, as at
http://www.discountsteel.com/index.c.../itemID/92.htm
or http://www.metalsalesusa.com/sq6063.htm which show 6"x6"x0.125 6063 Al.
With a 4" top and 12" bottom, you would get two pieces per 16" of tube,
ie a materials cost of about $7 each.

On Sat, 8 Mar 2008 14:06:26 -0500, with neither quill nor qualm, "Ed
Huntress" quickly quoth:


"Larry Jaques" wrote in message
.. .

I picked up a 20' stick of 3/4" x 3/4" angle iron a few days ago and
it cost a bleeding $14.90! He told me it had gone up 30% two weeks
ago and was going up another 10% today. Steel plate is being rationed!

Hayseuss Crisco, it's getting expensive out there...

China is sucking up a lot of steel. As much as they make, they've been in
deficit for a few years. Hold onto those used nails, we may need them.

I asked the steelmonger about that. He said that they were buying
mostly scrap, but some fresh arn, too.


That is, if there's anything left to eat. They're sucking up a lot of grain,
too. They've developed a taste for finished beef, and beer. If they increase
production by three beers per year per Chinese adult, they will consume more
grain that all that grown in Norway. And we're using a lot of ours to make
ethanol, which consumes almost a gallon of oil to make a gallon equivalent
of ethanol.

Ethanol is a losing proposition. I hope we don't waste any more money
on it. I get 10-15% lower mileage with our newly mandated oxygenated
fuels now. That's 10% ethanol here.


And once those Chinese get loaded on their three beers per year, they'll
need something to drive. d8-)

1000:1 that ain't gonna be DEEtroit stock, either.

--
The best and safest thing is to keep a balance in your life,
acknowledge the great powers around us and in us. If you can
do that, and live that way, you are really a wise man.
-- Euripides

On Sat, 08 Mar 2008 10:03:36 -0800, Larry Jaques
wrote:
snip
I picked up a 20' stick of 3/4" x 3/4" angle iron a few days ago and
it cost a bleeding $14.90! He told me it had gone up 30% two weeks
ago and was going up another 10% today. Steel plate is being rationed!

Hayseuss Crisco, it's getting expensive out there...
snip
==========
When you no longer domestically produce "stuff" and your currency
tanks compared to that of your supplier, and you gotta' have
"stuff," you are *SCREWED,* be it oil or angle iron.


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).

On Sat, 8 Mar 2008 14:06:26 -0500, "Ed Huntress"
wrote:


"Larry Jaques" wrote in message
.. .
On Sat, 08 Mar 2008 12:43:26 GMT, with neither quill nor qualm,
Anthony quickly quoth:

Tim Wescott wrote in
:

You would be cheaper to make it 3 pcs and use the bracket for afixing the
3. The reason is that the parts can then be cut on a waterjet or laser, at
very low cost, including tight location holes. When you get into bending,
you cannot put the tight tolerance holes in prior to bending, because of
tolerance stack-up. This makes fixturing for the holes to be put in later
a
difficult task. The savings would more than pay for a snap-in plastic
corner strip to cover the sharp edges.
I would re-think it along these lines Tim.

I picked up a 20' stick of 3/4" x 3/4" angle iron a few days ago and
it cost a bleeding $14.90! He told me it had gone up 30% two weeks
ago and was going up another 10% today. Steel plate is being rationed!

Hayseuss Crisco, it's getting expensive out there...

China is sucking up a lot of steel. As much as they make, they've been in
deficit for a few years. Hold onto those used nails, we may need them.

That is, if there's anything left to eat. They're sucking up a lot of grain,
too. They've developed a taste for finished beef, and beer. If they increase
production by three beers per year per Chinese adult, they will consume more
grain that all that grown in Norway. And we're using a lot of ours to make
ethanol, which consumes almost a gallon of oil to make a gallon equivalent
of ethanol.

And once those Chinese get loaded on their three beers per year, they'll
need something to drive. d8-)
==========
check the price of hops.


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).

"F. George McDuffee" wrote in message
...
On Sat, 8 Mar 2008 14:06:26 -0500, "Ed Huntress"
wrote:


"Larry Jaques" wrote in message
. ..
On Sat, 08 Mar 2008 12:43:26 GMT, with neither quill nor qualm,
Anthony quickly quoth:

Tim Wescott wrote in
:

You would be cheaper to make it 3 pcs and use the bracket for afixing
the
3. The reason is that the parts can then be cut on a waterjet or laser,
at
very low cost, including tight location holes. When you get into
bending,
you cannot put the tight tolerance holes in prior to bending, because of
tolerance stack-up. This makes fixturing for the holes to be put in
later
a
difficult task. The savings would more than pay for a snap-in plastic
corner strip to cover the sharp edges.
I would re-think it along these lines Tim.

I picked up a 20' stick of 3/4" x 3/4" angle iron a few days ago and
it cost a bleeding $14.90! He told me it had gone up 30% two weeks
ago and was going up another 10% today. Steel plate is being rationed!

Hayseuss Crisco, it's getting expensive out there...

China is sucking up a lot of steel. As much as they make, they've been in
deficit for a few years. Hold onto those used nails, we may need them.

That is, if there's anything left to eat. They're sucking up a lot of
grain,
too. They've developed a taste for finished beef, and beer. If they
increase
production by three beers per year per Chinese adult, they will consume
more
grain that all that grown in Norway. And we're using a lot of ours to make
ethanol, which consumes almost a gallon of oil to make a gallon equivalent
of ethanol.

And once those Chinese get loaded on their three beers per year, they'll
need something to drive. d8-)
==========
check the price of hops.


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).

This is an era of technical break throughs. They have finally discovered
how to turn lead into gold. I bought a 12"X12"X1/8" sheet of lead from
Aircraft Spruce. $63.!! Invest in precious metals now includes lead.

Stu

"Stuart & Kathryn Fields" wrote in message
.. .

"F. George McDuffee" wrote in message
...
On Sat, 8 Mar 2008 14:06:26 -0500, "Ed Huntress"
wrote:


"Larry Jaques" wrote in message
...
On Sat, 08 Mar 2008 12:43:26 GMT, with neither quill nor qualm,
Anthony quickly quoth:

Tim Wescott wrote in
:

You would be cheaper to make it 3 pcs and use the bracket for afixing
the
3. The reason is that the parts can then be cut on a waterjet or laser,
at
very low cost, including tight location holes. When you get into
bending,
you cannot put the tight tolerance holes in prior to bending, because
of
tolerance stack-up. This makes fixturing for the holes to be put in
later
a
difficult task. The savings would more than pay for a snap-in plastic
corner strip to cover the sharp edges.
I would re-think it along these lines Tim.

I picked up a 20' stick of 3/4" x 3/4" angle iron a few days ago and
it cost a bleeding $14.90! He told me it had gone up 30% two weeks
ago and was going up another 10% today. Steel plate is being rationed!

Hayseuss Crisco, it's getting expensive out there...

China is sucking up a lot of steel. As much as they make, they've been in
deficit for a few years. Hold onto those used nails, we may need them.

That is, if there's anything left to eat. They're sucking up a lot of
grain,
too. They've developed a taste for finished beef, and beer. If they
increase
production by three beers per year per Chinese adult, they will consume
more
grain that all that grown in Norway. And we're using a lot of ours to
make
ethanol, which consumes almost a gallon of oil to make a gallon
equivalent
of ethanol.

And once those Chinese get loaded on their three beers per year, they'll
need something to drive. d8-)
==========
check the price of hops.


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).

This is an era of technical break throughs. They have finally discovered
how to turn lead into gold. I bought a 12"X12"X1/8" sheet of lead from
Aircraft Spruce. $63.!! Invest in precious metals now includes lead.

Stu

Maybe aircraft lead is lighter. d8-)

--
Ed Huntress

I'm trying to put together a training device that I can include in the
cost of a seminar, $36 is more than 1/3 of the worst-case BOM cost that I
was contemplating. I need to know if I can beat this down by being
creative, if I need to bite the bullet and accept a higher BOM cost, or
if I should yank my eldest out of school and put him to work in the
garage bending metal!

The principal of this thing is that there's a counterweighted arm that
swings on a shaft that's pivoted on bearings in the large holes in the
frame. A microprocessor monitors the position of the shaft through a
potentiometer and controls the voltage to a motor/propeller, with the
goal of holding the arm at a commanded position. The hole locations are
assumed to need tight tolerancing because of the apparent tolerance needs
of the pot I'm planning to use, but I'll be re-thinking that decision
here soon.


Hi, Tim.
You have investigated fabricating your device from scratch. Have you
considered going the other way? Take a square or rectangular tube of
the size you need and cut it to the shape you need. Add two spacers
screwed to the walls so when you machine away the top, the sides
remain parallel. Simple to make and the wall thickness is whatever you
need. Perhaps you can find an aluminum extrusion that will be the
basis of the structure.

And don't ask us to place that sensor on a circuit board for you. The
specs look like pure smoke and mirrors. If you let it out of the box,
it will die!

Paul
Redmond, Oregon

Thanks in advance.

On Sat, 08 Mar 2008 10:47:45 -0500, axolotl
wrote:
snip
You might want to look at extruded C channel, in aluminum or plastic. In
plastic you wouldn't have to worry about a bearing material. McMaster
has some.

Kevin Gallimore
snip
=============
Good idea!

A little web surfing and I located a supplier of rectangular
extruded aluminum tubing. 4 X 6 w/ 1/8 wall runs 18$ /ft, but if
you cut the end at a slant for accessibility you should be able
to get 2 housing per 18 inches.
https://walden.saf.com/safcustomerwe...ExtrusionQuote

This was one of the first sites I came to so some additional
searching may get better prices. Also they offer cut to length
and finish also.

these urls may also be helpful
http://www.zycon.com/Products/Aluminum-Beams.html


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).

Tim Wescott wrote:

I just got the following parts quoted (I asked for a ballpark quote, got
a detailed one -- hmph). Here's a rough sketch, with unnecessary detail
_and_ things left out:

Maybe you should have your kid make them.

http://www.harborfreight.com/cpi/cta...emnumber=45877

24" bench box break, should handle aluminum.

Cut out blanks using router and router guide

Or try this.

http://www.harborfreight.com/cpi/cta...temnumber=5907

It will shear and bend.

A plywood drill fixture with a few drill bushings inserted could handle your
holes.

Wes

Tip: Put the holes in last using a drill jig, and eliminate costs associated
with close tolerances

"Tim Wescott" wrote in message
...
I just got the following parts quoted (I asked for a ballpark quote, got
a detailed one -- hmph). Here's a rough sketch, with unnecessary detail
_and_ things left out:

http://www.wescottdesign.com/Seminar...iner_Frame.pdf

Over the phone we modified things such that I'd be responsible for the
indicated holes, and the finish would be brushed & clear anodized. The
quote came back at around $36 each in lots of 50.

Is this just what I can expect to pay for these things? Did I go to the
wrong shop? What are the cost drivers here?

I'm trying to put together a training device that I can include in the
cost of a seminar, $36 is more than 1/3 of the worst-case BOM cost that I
was contemplating. I need to know if I can beat this down by being
creative, if I need to bite the bullet and accept a higher BOM cost, or
if I should yank my eldest out of school and put him to work in the
garage bending metal!

The principal of this thing is that there's a counterweighted arm that
swings on a shaft that's pivoted on bearings in the large holes in the
frame. A microprocessor monitors the position of the shaft through a
potentiometer and controls the voltage to a motor/propeller, with the
goal of holding the arm at a commanded position. The hole locations are
assumed to need tight tolerancing because of the apparent tolerance needs
of the pot I'm planning to use, but I'll be re-thinking that decision
here soon.

Thanks in advance.

Sorry this is off topic - would it help if I mention that I'm putting my
vote behind Hillary McBama, with Ralph Paul as her running mate?

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

Tim Wescott wrote:
I just got the following parts quoted (I asked for a ballpark quote, got
a detailed one -- hmph). Here's a rough sketch, with unnecessary detail
_and_ things left out:

http://www.wescottdesign.com/Seminar...iner_Frame.pdf

Hey Tim,

I saw this in a hobby shop for U$20 this afternoon and
thought of you for some reason:

http://www.centralhobbies.com/props/balancer.htm

--Winston

On Mar 13, 1:10*am, Winston wrote:
Hey Tim,

I saw this in a hobby shop for U$20 this afternoon and
thought of you for some reason:

http://www.centralhobbies.com/props/balancer.htm

--Winston

And this could replace the troublesome angular position sensor:

http://www.acroname.com/robotics/parts/R48-IR12.html

Jim Wilkins