powder flow not coaxial (HELP!)

[CHI3]

I am hoping someone out there can help me with an issue I am having.
I am spraying Metco 58NS with a 9MB gun, 7MC console & 9MP powder feeder using Metco suggested parameters. When the powder is injected into the plum it is not coaxial. The spray stream is passing through the plum approx. 30 degrees off from center.

What can i do to get the powder flow coaxial to plum?

Is this normal?

Is there another gun I could use that would be better? (maybe an internal feed gun?)

Thank you in advance for your suggestions.

[kschewe]

sounds like the carrier gas is to high from the powder feeder. adjust it so the powder is being injected in the flame. make sure you are using the recommended powder port feeder on the gun. #2 or #3

[Gordon]

Hi Chico

I am spraying Metco 58NS with a 9MB gun, 7MC console & 9MP powder feeder using Metco suggested parameters. When the powder is injected into the plum it is not coaxial. The spray stream is passing through the plum approx. 30 degrees off from center.

Not total clear on what you mean

Powder port #2

This should perpendicular with respect to nozzle axis (spray stream) and aimed at the centre point or nozzle axis. If it is not then you should think about replacing the powder port clamp ring.

If you are referring to the spray stream deviating away from the plasma flame axis, then this is normal. The term 'target point deviation' comes about because of this and sometimes needs to be taken into consideration particularly when setting up robotic spraying.

kschewe's point about carrier gas flow is correct in as far as the higher the flow, the higher the spray stream deviation. BUT if you are using the correct carrier gas flow (assuming your recommended parameters are correct) then don't change this setting. I have seen people adjust carrier gas flow to correct the deviation only to find a marked adverse effect on coating quality and deposit efficiency. There is always some deviation, its down to physics and is quite normal for the 9MB gun.

[CHI3]

Thank you for the quick responses.

The #2 powder port is perpendicular and centered of nozzle axis. My carrier flow is 8 SCFH @60 psi on the 9MP powder feeder anything lower does effect coating quality.
My biggest issue is the angles I have to program my robot to spray the work piece. It is almost impossible to determine the true angle and spray stream that will hit the repair area. Any suggestions?
I currently use a wood dowel as a pointer when teaching my robot program points. But it is not the true angle or spray stream to the repair area. How can I estimate the target point deviation?
Would an internal feed plasma gun like a SG100 have a more coaxial spray stream?

[Gordon]

Hi Chico

Spray onto a flat surface using your desired powder and parameters. Gun and substrate need to be in fixed position. Compare position of coating build-up with that of gun axis. Use this off-set in your robot programming

You will also see that not only do you get deviation opposite the powder port but also deviation (rotation) from the plasma swirl. So take note of the off-set and angle relative to the powder port position. Becomes more complex if the gun undergoes rotation on its axis.

[CHI3]

Good morning Gordon. Thank you again for your input. This will help me.

[loriolo]

The problem for your application is the 9MP, which is a fluidized bed system, and you cannot change carrier gas parameter without change powder rate, in some cases for example to spray turbine components with SM68 NS with a robot very complicate movement setting, I updated a twin powder feeder instead of 9MP, in which you can center the powder stream doing change in carrier gas settings, without have any change in parameters setting before.
So the solution will be like Gordon recomanded you or the more expensive one, changing the powder feeder, not the gun, becouse 9MB is a very good gun, SG100 do not has all the coating result of 9MB.