Aluminum Headaches

[nornrich]

All,

We have an application where we are inserting an aluminum part into a plastic part. We are feeding the aluminum parts down a vibratory rail and using the part insertion plunger to gate the queued up aluminum parts. We are struggling with the build up of aluminum on the plunger. We have tried various things: carbide with a Titanium Nitrided coating, Tool steel with a Teflon impregnated coating, bare tool steel with a miror polish. None of these are getting us to the operational life we would like. Any other suggestions from my eng-tips.com compatriots would be appreciated.

Rich.......

Richard Nornhold, PE

http://www.personna.com

 

[IRstuff]

Aren't you sort of asking the wrong question?

Why is the aluminum building up at all? In order to get aluminum, you have to abrading it from the parts as they go by. And while aluminum is a relatively soft material compared to others, it's by no means that soft, particularly with Teflon coatings and mirror finishes.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[MiketheEngineer]

I am guessing your parts are arriving with AL crap (dust, chips, etc) on them. Try an air curtain or blast to "clean" them before they arrive.

 

[nornrich]

IRstuff,

We are using air to position them under the plunger and we have stack of them queued up behind the plunger. So you are getting stack pressure on the aluminum part and high cycles per minute on the equipment.

MiketheEngineer,

We are having the parts cleaned after they are stamped out. We get minor amounts of debris, but this isnt' what is causing the buildup of aluminum. The build up is from the part to plunger interaction as the plunger moves past and gates the next part to be put into position.

Rich......

Richard Nornhold, PE

http://www.personna.com

 

[hydtools]

So the side of the plunger is getting the aluminum buildup as it rubs past the next part in the queue?

Ted

 

[nornrich]

hydtools,

Bingo!

Rich.......

Richard Nornhold, PE

http://www.personna.com

 

[IRstuff]

How many parts before the build is noticeable?

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[nornrich]

IRStuff,

About 500k or 2 weeks worth of runtime. Our goal would be 5-10 million cycles before we would have to tear down to clean.

Rich.....

Richard Nornhold, PE

http://www.personna.com

 

[IRstuff]

What exactly is the residual aluminum doing? Is it embedded in the plunger surface? Or is it more like a dust problem?

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[nornrich]

IRstuff,

It causes the gated part to misfeed and then causes a jam in the plunger. This in turn causes downtime on the equipment.

Rich.....

Richard Nornhold, PE

http://www.personna.com

 

[MikeHalloran]

Then use a separate gate, or come up with a misfeed detector.



Mike Halloran
Pembroke Pines, FL, USA

 

[IRstuff]

So:
> There ought to be a secondary gate, as Mike suggests
> Reduce the number of parts in the queue to reduce the pressure that's forcing the next part against the plunger
> Drill a set of holes in the plunger and push air out to keep the part from contacting the plunger


Is your vibratory rail possibly causing adjacent parts to rub against each other in the portion adjacent to the plunger, and then that residue gets transfered to the plunger?

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[Tmoose]

Can you give the plunger a teflon overcoat?

 

[dgallup]

Can you use a harder grade of aluminum or anodize it?

 

[hydtools]

Is a lubricant permitted? Perhaps a light spray or powder.

Stack with wax paper/oil paper/plastic sheet, use a vacuum to strip the top piece of paper as the plunger passes back to engage the next aluminum piece. Removes the one-contact-only surface, plunger side never contacts the aluminum.

Ted

 

[FACS]

Rich,
Have you looked at using an escapement to separate the queued part from the plunger?

Perhaps a small indexing wheel to pull a gap

Maybe a picture would help me, we do this stuff all the time.


Charlie

http://www.facsco.com

 

[FreddyZ]

Plastic sleeve over the plunger, so only plastic contacts the parts awaiting insertion?

 

[dvd]

I think that a drawing note stating "aluminum buildup on plunger is not permitted" should help.

 

[nuche1973]

I'm gonna take a swing at this, so be gentle: how about putting grooves on the side of the plunger that is making the contact and adding a chamfer to the end? It would give the particulate a place to go.

Again, it was a swing.

There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.

 

[racookpe1978]

Your problem appears to be an excessive downwards "pressure" on the part going into the machine (the part being fed by the plunger) as that plunger, part and the next-to-be-fed part are rubbing together as the four items (two parts and the plunger and the feeding trough bottom and walls) experience relative motion under load.

So, you need to reduce the force pushing the stack of parts being fed from pushing down on the final two parts: the part being fed, and the one immediately above it. (You may actually need a "stack" of five or six parts to keep everything aligned, but you probably have 50 to 60 i the stack.)

So, reduce the height of the stack. Reduce or eliminate any spring pressure on the top of the stack. Increase the friction on the 2nd from bottom, 3rd from bottom, and 4th from bottom parts so they carry the weight of the parts above, not the last part and the part being pushed in by the plunger.