off topic - mold plating

any idea when how much cooling is lost when plating an aluminum
thermofrom mold with nickel?

 

How thick a plating?
For conduction only pretty easy to calculate I'd think.

 

I don't know anything about thermoform molds, but a quick look at a 15 year
old copy of a materials handbook says that pure Nickel has roughly 1/2 to
1/3 the conductivity of Aluminum, depending on which alloy is used. Since
the plating thickness is probably some hundreds of microinches and the
distance to your cooling lines is probably close to an inch, I would guess
that you can safely ignore it.

Here is a case where Cliff gave a perfectly reasonable and reasonably
helpful reply. Unfortunately, of the 89 posts when I logged on, 70 were from
Cliff or some of his pals ragging on JB. Since JB has started using
SolidWorks, I would guess that he has more than one useful post out of 70.
Give it a rest, Cliff et. al.

Jerry Steiger

 

Jerry,
All of that crap aside, hard coat aluminum.

 

I'm WAY behind. Just tried to catch up on jb in CCS .... much
more behind elsewhere & with other matters. Try to keep them brief

Might depend.
Plated Nickel can be rather hard ( ~ 400 Brinell or better, depending)
& wear resistant and there may be some specific chemical resistance
involved.

BTW, to calculate such conductances multiply the thermal conductances
of each material by their thickness, invert (1/product calculated), add the two
then invert again (1/sum) IIRC. But memory fades ... IIRC Harder material
states of a metal often have have slightly lesser conductances.

Matweb has Thermal Conductivity of 60.7 W/m-K = 421 BTU-in/hr-ft²-°F for
pure Ni and Thermal Conductivity of 167 W/m-K = 1160 BTU-in/hr-ft²-°F for
the Aluminum 6061 T6 alloy (& state).

 

BTW, I'm curious if the zinc substrate (used in the process) is also
calculated?
BTW2, if you do Ni, stress relieving is highly suggested! (cuz of the
therm diff, plating may lift)
Also, I agree with Carroll, do a hard coat and add PTFE (teflon)...
don't remember the spec,.. anyhow, it's worth doing imho.

...

 

If used, calculate the same way. 1/(1/a + 1/b + 1/c .....) IIRC.
Just adding up the resistances (in series) to conduction ... similar
to electrical stuff and then getting the resultant conduction.

Depends on specific plating & plating conditions I think. Ask the plater.
Don't know if the Ni stress relieving temps are above what the Aluminum
alloy in question ....

http://www.key-to-metals.com/Article32.htm
"Stress-relieving temperatures for nickel and nickel alloys from 425 to 870 C,
depending on alloy composition and degree of work hardening."

From Matweb:
6061 Aluminum alloy "Melting Point 582 - 652 °C " Bound to lose the T6
I selected too <g>.

Some things are electroformed .. very thick plating (for plating) ...
for some I don't think stress is a problem. IIRC The harder
(and faster) the plating the worse things get but don't quote me.

 

IIRC,.. the relieving temp was low,..~200F over a period of a few
hours?
It increases substrate bonding..such as, surface areas where expansion/
contraction or work surfaces which maybe suspect.
Doing some searches,.. it maybe a non issue... looks like it's common
practice or a minor added cost but I'd ask the plater about it
anyhow!?

...

 

I've used these guys a time or two as well.
http://www.dicronite.com/Applications.htm



--

John R. Carroll
Machining Solution Software, Inc.
Los Angeles San Francisco
www.machiningsolution.com

 

There are LOTS of different platings, plating processes & results.
If not quite happy with what the first plater says ask a few more
or ask them to suggest someone closer to the need & application.
They may specialize a bit and their chemistry matters a lot.

 

But what does he want the plating for? Unknown AFAiK.

I once wanted to use Gold on several bits of tooling .. once
to reduce energy losses from hot molds for rubber (reduced IR
emissivity) & once to coat precision surfaces on tooling
rarely used & usually long-stored in unheated warehousing
betwen uses. The former was a good idea I think <g>. Simple
Gold leaf would probably have done the job.

 

Sure, no doubt, there are many possibilities.. it's just advice and/or
speculation from the limited information we do have..

...

 

Hmm,... I know I've read about this before but honestly I've never
used it or know of anyone using it?

The Faq's look really nice!!

http://www.dicronitedrylubrication.com/faq.htm

My first guess is that's it's expensive? Is it!?

Is it worth using over something like PTFE? The thickness is really
nice!!

...

 

Not really "expensive" but it's not as cheap as hard anno.

Yes, it is. The thickness is less and it lasts orders of magnitude longer in
service.
It's also slipperier. Is that a word?
LOL

It is. I wouldn't normally have to go back and clearance a shutoff which
meant no masking and therefore no chance of chipping.
Parting lines also stayed cleaner during production runs - even when running
Nylons and Acetal's/PVC's wouldn't eat a mold.
This is a great coating if you want the high heat removal of aluminum
cavities while preventing corrosion for something like a PVC pipe nipple
mold.


--

John R. Carroll
Machining Solution Software, Inc.
Los Angeles San Francisco
www.machiningsolution.com

 

Thanks, John. Seems sweet!?
I sent a couple emails to molders and asked if they have used it..

... 8^)

 

Heat Transfer with a few thousandths of an inch thick coating won't
change heat transfer materially.

Coatings to alter friction, hardness, corrosion resistance, dent
resistance, chemical resistance, optical surface finish, etc. are many
and varied. I have used a half dozen and there are many more used in
molds depending on use and base metal, and there are a dozen commonly
used metal alloys.

look at: http://www.cdcralternatives.ctc.com/indexdisplay.cfm?i_t=c
lots more exists out there on the web no doubt, but I've not looked in
the last few years.

There have been articles in MoldMaking & Plastics magazines that I
recall seeing, and they can be of great help in getting overviews.

Bo

 

In addition to checking:

http://www.cdcralternatives.ctc.com/indexdisplay.cfm?i_t=c

Check out www.moldmakingtechnology.com

and search for plating = 59 hits.

Bo

 

Moldmaking Technology magazine had an August 2003 article on mold
coatings that you may find on their website with the search term "Mold
Coatings" which gives 12 hits.

Its worth reading the articles for just what you are looking for in
heat transfer.

Bo

 

Also check out the article & table in the following link for usedful
info on a number of aspects of platings and their issues.

http://www.ptonline.com/articles/200412fa2.html

Bo

 

The reason we use nickel is for wear, it extended the life from hard
coating by 4-5 x

a new custumer just wanted to make sure the cooling would be as good.
In real life we had not noticed a differnece in cooling and since we
coated the whole inserts it also keep them from getting corroded from
the cooling water so that is a added benifit