depostion rate dercrease

[cheshires science engineer]

Evening all I am fairly new to all this and it isnt strictly speaking my job but.......
we have a thermal spray system at work which uses the triplex pro 210 gun(oerlikon metco) to spray chromium oxide onto steel and aluminium printing roller. Two silvents on the gun with two air jets as well to "control the spot size" is what im being told. Im the maintenace engineer so its my job to keep the machine running so two weeks ago i changed one of the silvent nozzles. it has been brough to mine and the shop foremans attention today that is taking a lot longer to spray a standard roller. basically it was only putting 9microns down in a 9 second pass(372mm face length) we have managed to get that up to 13microns by changing the exhauster and spreaders in ouy two powder hoppers and the powder injectors and elbows but it is still down we expect 18microns a pass. So my question is could one silvent be slightly block and therfore the new silvent is pushing the spray away from where it should be spraying.Im going to change it tommorow so i have a new pair. yhe machine is set so the spray doesnt hit the center of the roller but it has always been like that

[Vadim Verlotski]

(11-27-2019 06:14 PM)cheshires science engineer Wrote:  Evening all I am fairly new to all this and it isnt strictly speaking my job but.......
we have a thermal spray system at work which uses the triplex pro 210 gun(oerlikon metco) to spray chromium oxide onto steel and aluminium printing roller. Two silvents on the gun with two air jets as well to "control the spot size" is what im being told. Im the maintenace engineer so its my job to keep the machine running so two weeks ago i changed one of the silvent nozzles. it has been brough to mine and the shop foremans attention today that is taking a lot longer to spray a standard roller. basically it was only putting 9microns down in a 9 second pass(372mm face length) we have managed to get that up to 13microns by changing the exhauster and spreaders in ouy two powder hoppers and the powder injectors and elbows but it is still down we expect 18microns a pass. So my question is could one silvent be slightly block and therfore the new silvent is pushing the spray away from where it should be spraying.Im going to change it tommorow so i have a new pair. yhe machine is set so the spray doesnt hit the center of the roller but it has always been like that

Hi,
Cooling nozzles have great influence on the coating including deposition efficiency (DE) and also on the coating quality (porosity, roughness and so on). However, this is not about a displacement of the spray spot, but about the cooling of molten spray particles: the smallest molten particles of chromium oxide become solid through the air cooling and are blown away instead of forming a layer.

Your new nozzle has a larger (unclogged) cross-section, delivers more compressed air and cools down the spray particles more. This leads to a deterioration of the DE, but also to improves the coating quality (roughness is becoming less).

If you install a second unclogged silvent tomorrow, DE will be even smaller. In order to restore the old deposition rate, you have to reduce the air pressure with new silvents.

Regards
Vadim