Pneumatic or Servo gun?

[Robotter]

A fellow forum mate and I had a difference of opinion on the servo guns and the pneumatic guns, while I respect his/her thoughts I wouild like to know how the other users think of these two widely used technologies..


Edit by Martin H: Title changed from "Pneumatic or Air gun?" to "Pneumatic or Servo gun?" 

[tony gast]

Most of the systems I have worked on had pneumatic....thus I guess i am more comfortable with them.....
You have better control of the weld, I believe, with a servo gun......

[Robotter]

Thanks Martin for correcting my oversight 

[Robotter]

4798 members and only 4 votes...  What a Pity...

[cunaf]

Pros of Servo Gun:
-Re-programable easily for new parts or re-sequencing welds
-Better cycle time due to infinite opening control
-No real need for steppers if used with tip dressers and tip wear compensation
-Longer tip life due to above
-More consistent pressure control so less expulsion due to pnematic lines leaking pressure etc

[SkyeFire]

I pretty much agree with Cunaf on all his points.  A few years ago, air guns were faster than servo guns, but that gap's been pretty much closed these days.

Servo guns are also quieter, which means a lot when you have 500 robots all operating them at the same time under a single roof.

Servo guns also have more future improvement potential.  Air guns had more or less reached their maximum level of refinement

One odd duck is the "pneumatic servo" guns used by Volkswagen.  It combines a pressure transducer and linear encoder in the air cylinder to duplicate the effectiveness of a servo gun using pneumatics.  It tends to be bouncier and slightly less controllable than a servo gun, due to the compressibility of air, but might serve well in situations where a normal servo gun isn't usable for some reason (say, a robot and/or weld timer that don't support servo guns for whatever reason).

[Robotter]

Another benefit of servo gun is that you dont have to worry when you are running the program backwards.. the gun opening at each point is automatically taken care of where as with the pneumatic ones one needs to remember to manually operate the valve to open/glose the guns...

I had an experience with the "odd duck" pnematic servo combo guns 
we used FTS guns and these guns had pneumatic equalising... given a choice I would either opt completely pneumatic or completely servo

[Robert Kenny]

Servo guns are definitely better, for all these reasons listed above, except for the steppers comment.  I thought steppers were to account for growth in the cap face due to mushrooming, which is present in both types.

I say cycle time payoff is the main driver, especially when compared with air gun applications where air gun backup open/close times are significant.

[Servo]

Cost being the only downside that I can come up with worthy of mention, I'd pick ServoGun every time.
Most of these are redundant, but here are my reasons:

*In most situations cycle time can be decreased due to programmable stroke.
*Cycle time can also be reduced because of the reliable reaction time.
*There is a definite benefit in regard to force control.
*Some users even vary the force during the weld.
*Less apt to crash the machine due to timing issues, or failed sensor.
*Air is inefficient at delivering power, might not seem important until your company tries to go green.
*Air is loud.
*Air systems are generally more problematic once in production.
*Servo can be made to measure tip wear automatically.

Of course there are reasons to go air, number one being up front cost and as SkyeFire pointed out some older systems may not support servogun.