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Rolling Mill - Metal getting wavy


#1

Greetings all.

I have a problem with the metal getting wavy/ rippled coming out of
my rolling mill. A search of the archives did not turn up a
definitive answer to the problem or how to correct it. Back about
2000 there was a discussion about the relationship of the teeth in
the gear drive and the ripples. Can’t say I completely understood
it. Is the issue “slip” between the gear teeth? I am curious if the
problem is related to the pitch circles of the gears being different
due to the length of the teeth that are necessary for the roller
vertical movement. Seems to be the “nature of the beast”. How do
the refiners/manufacturers deal with this problem? Does the diameter
of the roller figure in here? I remember recently reading about
roller diameter and stress. There was a link to an article about
rolling mills using small diameter rollers with multiple backup
rollers for support.

I use my mill ( Pepe 90mm) primarily for roller printing at my
studio/school. I have put a dial indicator on the rollers and they
run almost true with or without a piece of metal passing through.
That is, I can read a fluctuation of .001" in one revolution of the
upper roll. The lower one runs true. The alignment is correct and
the rollers themselves measure round. I do not see what could cause
the number of ripples which are generated. I do not get the ripples
when a sheet is backed. I am also paying attention to the annealing
and rate of reduction. The results are the same no matter the
configurations in the experiments. I love my hammers and anvil.
Those I understand. We have a saying at the school, “Don’t just
annoy the metal, HIT it!”

Suggestions? Comments?

Bill Churlik
@Bill_Churlik
www.earthspeakarts.com


#2

Bill,

Rippling in the metal as you roll it is generally a result of one of
several reasons.

1 - Not annealing it evenly

2 - using scrap gold

3 - using the wrong alloy for the metal

4 - rolling in different directions with out annealing in between
changing the direction.

5 - Not rolling with a smooth continuous roll ( starting and
stopping as you roll the metal )

I hope this helps
Good Luck
Greg DeMark
email: greg@demarkjewelry.com
Website: www.demarkjewelry.com
Custom Jewelry - Handmade Jewelry - Antique Jewelry


#3

Gregg,

I am working primarily with copper and silver. Gold responds the
same way also.

There is no scrap involved. The metals involved are sheets that are
being reduced for specific projects. I teach everyone to anneal the
sheets before rolling. I also anneal before changing directions and
teach that as a necessity to avoid cracks. I am strong enough to
maintain an even roll, unless there is a heavy reduction on a wide
sheet. The problem still is there either way.

The one thing that does seem to help is to have the assistant
support the metal as it comes out of the rollers.

Maybe I need to sacrifice someone from the sales and use tax
division or the local zoning board before starting a project. The
bench gods do request strange things from time to time.

Bill Churlik
@Bill_Churlik
www.earthspeakarts.com


#4

Probable cause of rippling is not annealing often enough and trying
to reduce too much in each pass. Sheet should be annealed each time
it reduced by half. Have them ease up on the pressure as well and
see if that doesn’t correct the problem. If that doesn’t work, I’m
out of ideas.

Jerry in Kodiak


#5
If that doesn't work, I'm out of ideas.

One other possible problem is if one or both of your rolls are not
completely flat-- where the metal is squeezed more, it will thin
more and buckle. Try closing the roller completely then turn it
while shining a bright light on the meet point (I like those teensy
lights you can carry on a keychain-- very bright, very local). If
you see light anywhere at any time, there’s your problem. HTH!

–Noel


#6

You need to anneal it more often.


#7

Hi, My mill usually makes the metal wavy. When it gets to the right
thickness, or very close, I just keep putting the metal through, at
the same setting, until the metal is flat. Maybe 3 or 4 passes. I
don’t anneal it.

Fredricka Kulicke
www.FredrickaKulicke.com
www.KulickeJewelrySchool.com