Steve,

We have a 6241B and are specifying hole sizes that are 0.014" over the lead diameter.
This hole size is a compromise between the 0.010" clearance required for wave soldering
and the Universal specification.  The Universal General Specification for this machine
,GS-341, states "Minimum printed circuit board hole diameter is typically 0.016 (0,41mm) +
lead diameter."  We specify PWBs at +/- 0.003 for hole size and hole location.

Does your equipment have the auto-correction feature?  On our machine we have the option
to program to find each hole, then insert the part.  This will probably run you 2 - 3
seconds per part.  You would definitely want to do as Richard suggests  with the depth
stop trick.  Insert every other part to the board level, then come back and fill in the
blanks at a higher depth stop.  Once the resistors settle in to place you will have long
lead lengths on the bottom side for all the parts that were inserted at the higher depth
stop.

Gary Camac


"Stephen R. Gregory" wrote:

> Hi All!
>
> Please forgive this basic question, but what would be the smallest
> lead-to-hole ratio in which you would attempt to auto-insert an axial part
> (with a Universal VCD 6287)?
>
> I'm fairly new in this arena, my focus has always been with SMT. But anyways,
> I've always heard that the holes should be .015"-.020" larger that the lead
> diameter. On Universal's web page they have a *.PDF through-hole design guide
> that says holes should be .019" +\- .003" larger than the lead.
>
> Well, we've got this board here that uses 1/2-watt resistors with .027"
> diameter leads, I got the pin gages out and measured the holes and they're
> .035"-.036". Only .008" clearance!!!
>
> Some here say I should go ahead and write the program and just try it, that's
> easy for them to say...this a very large board that has close to 400 axial
> parts on it, and practically all of the parts are these resistors of varying
> values.
>
> I'm saying that there isn't a snowballs chance in hell that the VCD is going
> to do even a half-way decent job, so I don't want to spend the time it takes
> to create this huge program. Oh another thing about the resistors, they'e
> been laid-out on .100" centers. The diameter of the bodies range from
> .103"-.107"...they're "Brick-walled" on the board with their bodies touching
> each other...fun stuff, huh?
>
> I'm telling them that our CS-400's are gonna be real busy for quite a while...
>
> So am I out to lunch or what? From you guys experience, is it wishfull
> thinking that our VCD will be able to insert these parts?
>
> -Steve Gregory-
>
> ##############################################################
> TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> ##############################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
> the body:
> To subscribe:   SUBSCRIBE TECHNET <your full name>
> To unsubscribe:   SIGNOFF TECHNET
> ##############################################################
> Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
> information.
> If you need assistance - contact Keach Sasamori at [log in to unmask] or
> 847-509-9700 ext.5315
> ##############################################################