Robotic Welds are Moving!
you've spent any time around robotic welding, then you've heard the
number one complaint: "The welds are moving!"
it’s that they are missing, off, wandering, drifting, or they’ve
relocated to a different zip code. Either way, those statements are
misleading at best, and I think we need to dispel the myth of moving
are several reasons a weld will appear to be moving; I take a
systematic approach to resolving this issue with the help of a simple
is an acronym I use
for troubleshooting; another way to remember it is with this phrase:
Try And Find Our Problem. It stands for Tips, Alignment,
Operator, Parts. Use this process when the reason is not as
obvious as something like the welds being out of joint after a robot
One of the very first things you should do when troubleshooting is
replace the contact tip. You should know that these wear
the course of the day, and a robot cannot make the subtle adjustments
required that a manual welder can. So, regardless of when you
last replaced the tip, go ahead and replace it again.
Since you’ve already taken the cell down to replace the contact tip,
check the alignment while you’re at it. Hopefully your
(or the person responsible for setting the cell up) has created a
quick, operator-friendly alignment program that checks all axes of the
robot. This can be done by using an alignment sleeve or
similar. I don’t recommend using the alignment or witness
on the robot axes as they are typically a rough, visual method of
checking the alignment, but can be difficult to determine just how many
pulse counts an axis may actually be off. Additionally, you
to check the alignment of the torch neck with a checking
A checking fixture is a must-have because I’ve had torch necks come
from the factory out of alignment.
I know this is a sore-spot for some, but the fixture must be free of
dirt, debris, oil, grease, and spatter. If and when the
is clean, check the clamps and locators to make sure they are tight,
and the parts are securely located in place. Check for any
movement in the fixture; are the bolts or clamps holding it in place
secure? It is a good idea to regularly PM your fixtures to
these issues in check.
Is the operator loading the parts correctly? I know,
fixture locate the parts in the same place every time regardless of
operator?” Ideally, yes; but sometimes fixtures have
can be unintentional or by design. Either way, make sure
operators are loading the parts in the exact same manner.
seen one operator push a certain part to the right before clamping, and
another push that same part to the left before clamping. If
fixture does allow for a little slop, correct the problem, or at the
very least you should have a work instruction in place that specifies
how all parts are to be loaded.
This is by far the most critical component of the process, and nearly
always the last one that anyone wants to address. Robots are
extremely repeatable; they are going to go the same place every
time. Your parts must also match that same level of
repeatability. It’s crucial to measure parts from different
batches; I’ve seen parts repeatable only to their respective run, but
not from batch to batch. Remember: garbage in, garbage out.
walking through these steps, be critical on every one.
like “it’s always been like that” are not quantifiable and will only
hamper your attempts at identifying the issue(s).