Resin infusion - How long do you keep the vac pump on for?

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#1

Hi everyone,

Im having a bit of trouble working out how long to keep the vac pump on for during the resin infusion curing process.

Watching the following video on carbon mods and speaking to somone at their company, im told to turn the vac pump off as soon as the infusion is complete.
http://carbonmods.co.uk/products/resin-infusion-complete-starter-kit.aspx

However when i read their guide it says that the vac pump must be kept on until the part has fully cured.
http://carbonmods.co.uk/Downloads/carbon-mods-guide-to-resin-infusion.pdf

When do you guys turn off the vac pump?

Thanks

UPDATE:
Just a quick update as to why im asking if people are wondering. Their guide and video says that the resin takes 24 hours to cure at room temperature. I dont really want to keep the vac pump on for 24 hours 5 days a week. Their guide also shows the faster curing times at elevated temperatures so i thought about putting together a home made curing oven. The person at carbon mods then told me that what they have supplied me to make my moulds will start to deform at around 50 degrees C, but it doesn’t matter because i can turn the vac pump off after the infusion is complete.

#2

I’ve done both ways and it depends on a few factors. First off if there is a leak in my bag I’ll leave the vacuum on to keep compaction on the laminate. That being said in an ideal infusion there shouldn’t be any leaks so you can turn off the vacuum at the conclusion of the resin flow.

If the part is critical and structural though I’ll leave the vacuum on. If it’s a body panel or some other non load bearing component I’ll turn it off.
Lastly if you didn’t degas your resin properly you’ll need to keep the vacuum on to keep removing the evaporating vapors.

It boils down to how good are you with sealing a bag and how paranoid you are. Keep in mind that I do very basic infusions, I can imagine that some infusions require the vacuum to be running for the duration of the cure.

#3

I sometimes run a venturi vac genny that runs off my air compressor. I dont want a 2.5kw compressor motor running constantly so a built in a vacuum switch in to the vac lines. A one way valve prevents vacuum loss. When vacuum drops below a set limit the vac switch triggers an air solenoid feeding the venturi genny.

#4

I keep running regardless evan if a leak test dosnt show a leak

#5

We leave it running until the resin has gelled. For the resins we use this is around 8hrs or quicker on a hot day, so 24 hours will be for the resin they are using. As we don’t bother degassing our resin it pulls the air out too.

#6

Keep the vacuum on.

In an ideal world, there are no leaks, so you can clamp the vacuum line, but infusion of 62 meter long boats is not an ideal world.

How long? Depends on the resin totally. Our epoxy resin with 5 hours gel time, takes at least 48 hours.

The pumps we build are all equiped with pressure switches, so they shut down once the desired vacuum is reached:

-exact control of the vacuum level
-pump not running 24/7 (power consumption, noise)
-if the pump starts running more often, it is time to check, else not. (audible alarm, sort off…)
-the pump shuts up when doing leak checks, so easier to hear leaks (with or without leakdetector)

#7

Thanks for the help, i think ill keep it on for the whole cure time as this seems the safest option. Ill just have to make some high temp moulds :slight_smile:

#8

Keep it on until it has cured!! Even if you shut it off when it gels, or is still soft, if you loose vacuum, the part can misshape.

#9

on this topic, does anyone know any good sources for vacuum switches that aren’t $80+. I’d love to have one, but as a hobbyist, i don’t really want to spend that much…i’m a cheap bastard.

#10

Check veneersupply.com, but it is a bit of a dodgy thing. Works, but hysterese is large.

#11

Same here, we don’t de-gas the resin either, we have a time set-up on our vac system set for 10 hours. It automatically turns off then, we generally leave the part overnight and pull it in the morning unless we post cure the part in the oven.

#12

Ditto. We run the pump on a timer and usually keep vacuum on until after the resin has gone to a solid state. Usually setup molds during the day, infuse and then pull parts in the morning.

#13

I bought a PIAB EVS100 on eBay for $25 new, I was the only bidder. From memory the buy it now price was about $60.

#14

I got a programmable vacuum controller for about € 30.- on ebay. Lets me ramp up my vacuum so I can get my bag pleated right before pulling a complete vacuum. It the holds that level for a predetermined time. It’s in the upper left corner on this picture:

#15

Brilliant! I normally just control the flow via the ballvalve, but sometimes if the part is complicated, it’s a pain to adjust the bag and valve at the same time!

#16

About the running of the pump, I always leave the pump on till I see the resin getting high temperature. I am not going to spend money for just 1 hour work. Of course this dependings from the pump and the time of cure.

#17

Perfect. That’s exactly what I’m looking for

#18

I bought one off of ebay as well, although I think I paid about $50 shipped for mine.
I these switches are on ebay all the time.

I used the pressure switch that I got from Veneer supplies.com for a couple years but I was never happy with it. Although it is adjustable the dead zone is pretty big (upwards of 5mm hg) Although the switch does only cost $25, you will also need to buy a relay to wire up your pump so it ends up costing about the same as buying a used PIAB.

#19

There are these nice switches from for instance SMC:


If the pic went missing, do a picture search for “smc vacuum switch” and it will return a couple of square blocked small switches.

Keep in mind however that these need a power source (12 or 24v), a relay, and some auxillaries to make it look nice.

I took one, put it in a small electronics box, and added the neccesaries. Now I can plug in the pump, I even have a spare “always on” power socket, so I do not lose a socket by using a pump, and I have to hook up a 4mm hose to the vacuum, so the switch can read the vacuum. This gives me a completely controllable vacuum pump. (switch on, switch off, hysteresis).

However, I am working on a mechanical cheaper (not ghetto-style) solution as well.

#20

Herman: I’ve been looking for those smc vacuum switches. But I faced interesting problem. Even smc Finland customer service didn’t know if those 12v 30’s serie vacuum switch could operate 5v relay. What model do You have? Every shop that I have called have said that they don’t know anything about those switches and they have adviced me to call to smc Finland. But it seems like they neither know anything about those switches. After a long phonecall they promised me to send email and answer to my questions, but they never did.