Ahead of a very difficult and important job I do some test laminates, to practise and test my equipment etc.
Yesterday and today something strange happened (one test per day), I made good bags and had full vacuum,
the pump pulled the bag hard on the mold and carbon and it was the same after a 15minute drop test,
but as soon as I open up the resin inlet the bag goes slack, not all over the bag at ones, only as far as the resin has reached,
so first at the inlet and at then all over the part, but it is worse and the resin inlet, quite ok at the vacuum hose.
There is not leak that I can see or hear, no typical pumping in the vacuum hose or small stream of air bubbles that occurs if there is a leak.
The part gets fully infused but there is extra resin on top is the dist mesh.
If I close the inlet and let the pump work some resin is drawn out, but the bag never goes really tight again.
The vacuum gauge on the pump indicates full vacuum and today I clamped off the hoses and put a 10cm hose with a
brand new vacuum gauge on the inlet to the pump, that also showed full vacuum.
I also tried to have the vacuum hose directly to the pump for a minute, to exclude the catch put, no difference.
The day before yesterday I made a small test without a catch pot, stupid yes I know, I had a 2 meter hose to collect the resin,
but the bag had a leak I did not find before and one mistake led to another and the resin reached the inlet of the pump.
But that was only for a second and the pump has some large diameter plumbing pipes between the inlet and actual pump,
today I took those pipes apart and there was a little hard epoxy there, but now close to the pump, I cleaned that and a mesh-filter
that had some dust and dirt on it, on the underside of that mesh there is a membrane and a spring, that was clean.
But yes this problem occurred after the epoxy reached the pump inlet.
The pump is a German Busch R5 RA0016 single stage pump, all the other parts are from easy comp, the mold is a flat ureol piece
that is sealed with a two comp sanding primer.
I have never experienced this before, usually the bag and vacuum is good and the bag stays firmly sucked down through the whole process,
so what could be the cause of this?
Some problem with the pump even though I cant find dirt of epoxy after the first pipes?
Pulling vacuum on dry carbon stack is ofcourse an easier job for the pump than pulling resin,
but the bag is very tight on the stack before I infuse, then the epoxy fills the slack in the bag and it goes loose.
That tells me the vacuum just isnt good enough, but how can two separate gauges show full vacuum then?
Because they are on the pump side?
I will try again and put a hose and gauge on the inlet side and see what the vacuum is there.
This might play a part in the problem, yesterdays bag was made with the wb160 bag and I didn't have large enough
plets to allow the bag to go down around the silicone connectors, and today's test was made with the
stretch bag, which wants to un-stretch, but would that let the resin to overflow the bag? no..
I also noted that the shut off valve on the pump lets some vacuum through when it is closed,
that shouldn't be a problem since I experience this problem when it is open, but maybe that indicates a malfunction in that valve,
maybe it sucks air through its axle, impossible to hear with the pump running.
Any advice or speculation is welcome.
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