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SMT electronics assembly manufacturing forum.


Universal GDM users?

JB

#24529

Universal GDM users? | 19 May, 2003

We currently use a Universal GDM for our glue dispensing applications, piston pumps.

My question is: Have you had any problems with air getting in the dispense system that will cause missing dots? If so, how have you approached to this problem?

Interested to hear from GDM users.

Thanks

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Gav

#24534

Universal GDM users? | 20 May, 2003

Hi, I have had this problem in the past and the best method I found was...

Before removing the old syringe and fitting a new one, ensure the viton tubing is doubled over and pinched. This will help to eliminate any airlocks in the viton tubing which would adversely affect the glue deposition later. The tube must now remain until the new syringe is fitted.

Before attaching the new syringe push the plunger down inside the syringe until a small amount of glue is visible.

Attach new syringe and purge the glue (10-15 seconds).

I hope this helps you with your problem.

Regards,

Gav.

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JB

#24536

Universal GDM users? | 20 May, 2003

Hello Gav,

We have tried the procedure that you described, and it didn't work well for us. Even though the viton tubing is doubled up and pinched, no amount of glue is visible at the tip of the tubing. So getting the glue to protrude from the syringe is not a problem, getting glue to protrude from the tubing is.

What we do now is, when the cartridge needs to be replaced, we perform the procedure that you describe. And with the new syringe attached, we purge the glue for 4000 cycles, which is the amount of cycles needed to get the new glue to come out. Once the new glue starts coming out, we are then positive that any airlocks between the old and new glue have been purged.

We are considering the option of alternating the color of the glue between red and yellow, same properties, to make it easier to "see" the new glue coming out. Meaning that all airlocks are out of the system.

Thanks for the info Gav!

JB

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#24537

Universal GDM users? | 20 May, 2003

JB

#24538

Universal GDM users? | 20 May, 2003

So far we haven't had any problems with air in the syringe, but in the process of replacing the old syringe is were we had the problem. I'll keep your tip in mind if we ever have the need to get air out of a syringe though.

Thanks for the info.

JB

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