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pilotspike

Senior Aircraftman
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Posts: 7
Reply with quote  #1 

Hey All,

I had to pause my return to modeling for a year or two as we moved, but now am back at it.  Having started to paint the latest creation I have been getting very inconsistent results with my airbrush (Iwata HP-CS), which is starting to jog some memories of frustrations before I moved.

Basically, what I am finding is that the brush appears to behave inconsistently in the type of spray that its putting out.  One very specific example is that with a fairly thin paint mix, when I start pulling back on the valve, paint will flow, for 2 - 3 seconds and then stop.  This really seems to apply when trying to do detailed lines. So for instance, I get very close to the surface, pull back enough to start a fine line, move the brush 2 or 3 inches, and then it stops, all without changing needle position.  Sometimes it will start again on its own, sometimes I have to move the needle a fraction of an inch for it to start again, which it will do without splatter or a mess.

The brush also seems to be really inconsistent with how it handles paint of any given thickness. Sometimes it will splatter with fairly thinned paints, sometimes it wont, etc.

With that said I have deep cleaned this thing very thoroughly. The paint cup is clean, the needle is perfectly clean, the nozzle is spotless, and so is the nozzle cap.  To the naked eye the needle is quite straight and seats well in the nozzle. The nozzle itslef appears to be very well formed in that when assembled the nozzle is concentric to the opening in the nozzle cap.

One thing that I did notice, however, is that the needle does not retract in a concentric manner to the nozzle. When its being pulled back the needle always slides to one side and rides the edge of the nozzle back into the brush.  Is this an issue? I know that ideally this would not be the case, but at a .35mm opening, I find it hard to believe that all of these brushes are machined with tolerances that are good enough to prevent that.

At this point I am thinking of just ordering a couple of new needles and nozzles for the brush because I can't come up with any other solution. I feel like I have tried every combination of pressure and viscosity that I can think of.


 Id love to get any feedback or ideas that you have.

 

Thanx

John

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Laurie

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Corporal
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Posts: 187
Reply with quote  #2 
My first port of call john would be the nozzle. If the needle is being pushed to one side then something could possibly be interrupting it's course.

Just wonder if you have looked down the nozzle under magnification. I put a torch at the pointed end shining into the nozzle to see if the
orifice is nice and round not damaged. Then a light down the other end all under magnification. problem with Iwata the nozzles are so minature
to clean easily. H & S are so simple.

I always keep a spare needle/nozzle. Worth getting one and trying.

Another couple of thoughts. While getting the needle/nozzle get a set of seals and change them. After sitting dormant for a couple of years
it does no harm for the cost to give the brush a clean bill of health.

Also put a drop of oil on the plunger under the trigger. Probably very dry after all that time.

Laurie


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pilotspike

Senior Aircraftman
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Posts: 7
Reply with quote  #3 
Laurie,

I did look into the nozzle with my Optivisor and strong lights and its clean as a whistle. I believe this non-concentricity is a needle issue as I can rotate the needle within the brush and the needle rub will rotate to a different portion of the nozzle edge.

i just didn't know if this was acceptable or not.

John
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Brundledonk

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Posts: 6,244
Reply with quote  #4 
It definitley sounds like a nozzle or needle issue (needle might have a slight bend ) but it's worth changing both to ensure you eliminate the problem

I am having the spattering you are experiencing with mine and need to replace the nozzle and needle too. I can see the end of the nozzle has corroded when I examine it under magnification but it has been a long time since I changed it and it has had a lot of use since then. I use a lot of cellulose and I think it does take its toll on the nozzles after a time.

Pete
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Laurie

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Posts: 187
Reply with quote  #5 
Quote:
Originally Posted by pilotspike
Laurie,

I did look into the nozzle with my Optivisor and strong lights and its clean as a whistle. I believe this non-concentricity is a needle issue as I can rotate the needle within the brush and the needle rub will rotate to a different portion of the nozzle edge.

i just didn't know if this was acceptable or not.

John


I would say not acceptable John. You will get a build up of paint on the point where the needle nozzle
touch or get close to each other. Plus an excess of paint sprayed to one side on the other side. Plus blobs now and then where the paint builds up where the needle hits the nozzle.

Think John it is a big overhaul. Yucks. But bright at the other end when all is complete.

Laurie

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