In a former position, we had a machine for trimming leads. It had a
horizontal blade, high speed saw.
We had to use it on one type board for a customer that wanted very short
lead protrusion.(RF stuff)
The blade had to be very sharp. Setup errors could easily destroy a board.
Bow and Twist issues could easily destroy a board. Our system was manual, X
and Y plane. Move too fast or too slow and you got flags, and metal chips.
The vacuum (ESD?!) could not clean up every thing. So, the station quickly
became a mess of little tiny metal pieces. It was a nightmare to control the
process. DON'T GO THERE IF YOU DON'T HAVE TO. Do not even think of it if you
have a no-clean process.
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Stephen R. Gregory
> Sent: Tuesday, December 18, 2001 12:12 AM
> To: [log in to unmask]
> Subject: [TN] Mass lead trimming systems...
>
>
> Hi All!
>
> The subject has come up here about mass lead trimming systems.
> From what I've
> learned, they have their place. But in our situation, I have the
> opinion that
> they aren't warranted here. We do a lot of class-3 electronics,
> have hardware
> (screws and whatnot from connectors) that hang below the lead length
> requirements.
>
> Many of the requirements on the asssembly drawings of products we build,
> still call out MIL standards, even though they are obsolete, we are still
> obligated to build to these standards...those that build product
> according to
> these standards, and have tried to deviate, or change, from what is
> documented on these standards know what a task that is...it isn't going to
> change.
>
> So, in my opinion, mass lead trimming systems have no place here.
> There are
> too many things that call out extra work that will need to be
> done because of
> these systems.
>
> The J-STD's call out that if lead trimming is performed after wave solder,
> then the joints should be either re-reflowed, or inspected under 10X to
> ensure that there has been no fractures...
>
> I've also heard that these systems need METICULOUS maintenance. If they
> aren't maintained perfectly, they will cause major problems.
>
> Just want to hear from any of you that have direct experience with these
> systems..
>
> My position is that you either prep PTH components so that lead length
> requirements are met after soldering, and/or you make the adjustments that
> are available on your auto-insertion machines so that you meet lead length
> requirements...if you have to trim after wave solder, then either
> you haven't
> specified the proper component prep, or you need to adjust the
> cut and clinch
> on your auto-insertion equipment...I come the school that you can
> do things
> before wave solder that keeps lead length requirements within
> specifications,
> and not require mass lead trimming afterwards.
>
> So with that being said, what opinions are out there about mass
> lead trimming
> systems?
>
> As always, all ya'll are the best...
>
> -Steve Gregory-
>
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