The angle of the spray gun
08-18-2010, 07:34 PM,
#1
The angle of the spray gun
Hi all,
I am new to this forum also new to ASP,I work for a company which
uses the suzler metco spray system to repair the coating of the gas turbine engine.

There is a problem for me.we use the F4 gun for plasma.Owing to there are about 100 different engine's parts to repair and the shape of the parts are definitely not same.Some parts,e.g.small one .may could not use the gun to spray on it at 90 degree.(may at the range of 30-90 degree.)

I wonder if it is do have a bad effects to the coating? Or some suggestion to solve the angle problem.(buy other type of gun?Sad)
With thanks and regards.
Sam xu
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08-19-2010, 11:05 AM,
#2
RE: The angle of the spray gun
Hi Sam,

Yes, as you realised some parts size and geometries won't allow the ideal of a 90 degree 'attack'. As the angle becomes more severe the coating quality and deposit efficiency (DE) deteriorates. Investing in an F1 (or other system compatible small inner diameter gun) will allow you to apply better quality and less waste coatings. The ID guns do have slower feed rates but this is the compromise.

I don't know which mark/model of F4 (MB?) you have but the earlier guns have wide diameter plastic exterior gun shells. With these you can consider machining them down a little to allow you to lessen the angle on some parts. OK you may have to fabricate a new smaller "secure ring" or clamp collar. I have found that a jubilee type clamp or plasma tape works just fine. Ironically the hand based F4-HB & F4-HBS offer more versatility and processing of a greater diversity of work pieces than the F4-MB!
Len Wood
METAL MONSTER LTD
BIGGER BETTER FASTER MORE!
Ph: +64 9 4730705
Fax: +64 9 4730706
Email:: len@metal-monster.com
www.metal-monster.com
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08-19-2010, 08:35 PM,
#3
RE: The angle of the spray gun
(08-19-2010, 11:05 AM)LEN WOOD Wrote: Hi Sam,

Yes, as you realised some parts size and geometries won't allow the ideal of a 90 degree 'attack'. As the angle becomes more severe the coating quality and deposit efficiency (DE) deteriorates. Investing in an F1 (or other system compatible small inner diameter gun) will allow you to apply better quality and less waste coatings. The ID guns do have slower feed rates but this is the compromise.

I don't know which mark/model of F4 (MB?) you have but the earlier guns have wide diameter plastic exterior gun shells. With these you can consider machining them down a little to allow you to lessen the angle on some parts. OK you may have to fabricate a new smaller 'secure ring' or clamp collar. I have found that a jubilee type clamp or plasma tape works just fine. Ironically the hand based F4-HB & F4-HBS offer more versatility and processing of a greater diversity of work pieces than the F4-MB!

Hi len,

First of all ,thank you very much for your honest reply.
Sorry for I didn't describe the gun type clearly. We use only F4-MB gun. As you know ,there is a big plastic exterior shell for the gun. I don't know exactly the function of it.(protect the gun from dusty and tough condition? )But a friend of mine from suzler told me that some company even don't use the shells at all.
Fabricate a new small shall is not practical for me at present. May be I can try the plasma tape. (just enlace the gun with the tape for several cycles?)
There is a fixed distance form the nozzle to the part surface for every powder. In our production, the distance is between 120mm to 140mm. some parts(diameter less than 120mm e.g.)can not avoid to spray at a severe angle. In such circumstances , I could not ensure the quality of the coating.
I wanna know how does people check the quality of the coating in plasma process normally.
Thank you.Smile

Sam
p.s. we supervise the coating's quality by checking samples which has the same powder coating with the part.
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08-23-2010, 02:13 PM,
#4
RE: The angle of the spray gun
Hi Sam,

Quote:As you know ,there is a big plastic exterior shell for the gun. I don’t know exactly the function of it.(protect the gun from dusty and tough condition? )But a friend of mine from suzler told me that some company even don’t use the shells at all.
The F4-MB exterior shells are as you said to protect from dust and impact and to prevent shorting of positive and negative sectors. Depending on the workpiece and application I often do not run them but you must take care that nothing can allow a short to occur. Even a build up of metallic dust can cause the insulator to be 'bypassed'. I also once saw a coated piece of tape jump the rear water pipes and burn a hole.

Quote:Fabricate a new small shall is not practical for me at present. May be I can try the plasma tape. (just enlace the gun with the tape for several cycles?)
Turning down these exterior shells is quite easy and quality tape wrapped around the shells a few times works just fine.Cool

Quote:There is a fixed distance form the nozzle to the part surface for every powder. In our production, the distance is between 120mm to 140mm. some parts(diameter less than 120mm e.g.)can not avoid to spray at a severe angle. In such circumstances , I could not ensure the quality of the coating.
With very small and deep IDs you need to have the gun angle as minimal as possible abut also clear the lower coating limit. Here at the bottom of the coated surface you will have a tapered/bevelled edge which can be a problem. Sometimes (if it's possible) you can turn the part over. Then spray so many cycles on the other side then turn and so on. This will minimise the bad lower edge.

However with extreme angles the coating hardness and integrity will be unacceptable. If you cannot overcome negative coating effects then the only option is a small ID gun.

Quote: I wanna know how does people check the quality of the coating in plasma process normally.
The only conclusive test of a plasma coating is metallurgical examination. The test-piece should be as close to the conditions of the actual part/application as possible. This will provide an as accurate assessment. However the only true verification is to run a scrap part and 'section' - NOT always an option!
Len Wood
METAL MONSTER LTD
BIGGER BETTER FASTER MORE!
Ph: +64 9 4730705
Fax: +64 9 4730706
Email:: len@metal-monster.com
www.metal-monster.com
Reply
08-25-2010, 12:09 AM,
#5
RE: The angle of the spray gun
Hi Sam,

Sign0016 to the Surface Engineering Forum.

Glad to see Len helping out on this one Smile
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