APS F4 gun problem

[sal]

Hi
We have got a problem with our APS system; running with F4 gun with WC insert in its anode during spraying Cr2O3 and other powders some of this WC insert gets removed and sit on coating surface like small dots which are detached during grinding leaving a small hole behind and on the other hand the inside of anode is kinda corroding/vaporizing/ melting and gets damaged.
we use 5X9 Ar and H gases; Ar as 38 lit/min, H as 13 lit/min and A as 600. has anybody got similar experience?
Regards,
Sal

[Lemster68]

What is your coolant temp, flow and pressure? Metco datasheet for F4MB-XL lists requirements for inlet temp. = 15-25 deg. C, inlet pressure 13.5 bar, flow = 10-14 l/min.

[sal]

What is your coolant temp, flow and pressure? Metco datasheet for F4MB-XL lists requirements for inlet temp. = 15-25 deg. C, inlet pressure 13.5 bar, flow = 10-14 l/min.

Hi
Our cooling setup is pretty much like what you have mentioned.
someone told me it could be due to the cooling water resistance.
is that true? if yes how much should it be?

[Lemster68]

Conductivity Max 5uS. Also, you mentioned you gas flows and amperage, but what volts are you getting? 55KW max power rating for F4. Finally, is there a lot of torch manipulation or just gentle up/down or side to side traverse? I have seen issues with rapid torch manipulation, causing gas lines to get pinched. Robotic manipulation, of course.

[Neufeld]

You may have already solved your problem by now...But I have also had these issues in the past.

I noticed your nozzle damage is localized to one side (at least it looks like it in the picture). In my experience, that can be caused by the electrode not being centered properly. During installation, it can easily be offset .010" .015" to one side causing it to wear out the nozzle on one side prematurely. Before installing the nozzle, i center the electrode as best as i can (within about .0005")

Another possibility that could cause "small dots" in your coating is the distance from your gun to shadow masking. I find that the closer my shadow masking is to my gun, the more "dots" that i get on my coating, because the closer my shadow masking is to my gun the more powder build-up i get on the masking, which eventually breaks off from the masking and gets pushed into the coating. I try to keep my shadow masking as close to my part as possible. It helps minimize this problem for me. Although i still do get a few random "dots" on my coatings but i just use a small diamond file to gently file them off as i see them appear between powder cycles. The coating adheres over top of the gently filed section nicely.

Hope this helps if your still struggling!