+x

 

S_Carbon_fibre - 7/16/2018 8:33:53 AM

Hello both,

many thanks for the very quick responses. I think what Hanaldo wrote describes better the problem, once I clamp off the bag between the bag and the catch pot the pressure gauge goes up and stabilizes at about -11.I will check again all the fittings and the catch pot. But it seems the bag is also leaking, after sometime it gets loose and loses the vacuum so this is also very helpful:  

"if you still have a leak then you might have a puncture in the bag itself. If this is the case then see if you can find it by listening carefully. This rarely works because the leak can be very hard to detect but it's worth a try. If you can't find it then it's probably time to cut your losses and re-bag the part (throw the bag and seal away and start again). The lesson to learn in this case is how the bag might have got punctured in the first place. Before bagging again, check your mould (particularly the reverse side and edges for anything sharp, especially stray fibres of glass etc.). You should cover the reverse of your mould with breather and cover the table you're working on with breather or a rubber mat or similar. Most bag-punctures come from the mould banging against the bagging table and putting a very hard-to-find pinprick or nick in the bag."

As far as I understand you have to be very careful and patient to get this right...

Best wishes,

SH
 

+x

 

Matt (Staff) - 7/16/2018 8:41:43 AM

+x

 

S_Carbon_fibre - 7/16/2018 8:33:53 AM

Hello both,

many thanks for the very quick responses. I think what Hanaldo wrote describes better the problem, once I clamp off the bag between the bag and the catch pot the pressure gauge goes up and stabilizes at about -11.I will check again all the fittings and the catch pot. But it seems the bag is also leaking, after sometime it gets loose and loses the vacuum so this is also very helpful:  

"if you still have a leak then you might have a puncture in the bag itself. If this is the case then see if you can find it by listening carefully. This rarely works because the leak can be very hard to detect but it's worth a try. If you can't find it then it's probably time to cut your losses and re-bag the part (throw the bag and seal away and start again). The lesson to learn in this case is how the bag might have got punctured in the first place. Before bagging again, check your mould (particularly the reverse side and edges for anything sharp, especially stray fibres of glass etc.). You should cover the reverse of your mould with breather and cover the table you're working on with breather or a rubber mat or similar. Most bag-punctures come from the mould banging against the bagging table and putting a very hard-to-find pinprick or nick in the bag."

As far as I understand you have to be very careful and patient to get this right...

Best wishes,

SH
 

Hi, yes, you do. We could write a book on vacuum bagging!

The best advice I can give anyone experiencing problems is to be logical and isolate individual areas to find exactly where the problem is. If you clamp off very tightly right at the point where the hose goes into the bag (and make absolutely sure that your other hose is properly clamped too) and you lose vac pressure in your bag (i.e. it goes slack after a few minutes) then there is work to do on he bag itself. Secondly; if you clamp off at the bag connection (again making sure this is done very tightly) and you see pressure go down in your catchpot then I'd suggest clamping off the other side of the hose (which goes to the pump) to isolate just down to the catchpot itself and see if the problem persists, if it does, check all those fittings again (especially the seal and gland). If clamping off the hose to the pump fixes the problem then you need to check the fitting into the pump itself (rare but possible, especially if it's been changed).

Let us know how you go. If you need direct support then you can email or call us too.

--Matt