MTI hose

General Composites Discussions Products Talk
#421

I do indeed have a break zone that’s actually longer than an inch :/.

A reason that I thought the length might have some play into the problem is because those void/cavities were actually on the resin feed side of the part, where the resin is flowing much much faster during initial wet out, rather than on the vacuum draw side, by which time the flow front will have slowed down considerably.

I was especially stumped because I was getting pinholes/ mini voids only at the very extreme edges at the vacuum draw side when I wasn’t using MTI hose.

I’ve never really understood what ‘slowing down’ the infusion meant, since it’s so damn hard to meter how quickly resin is flowing through the feed piping. I’ll try and keep my clamp plugged up on it though if the part I pull today isn’t good.

#422

When you place the feedline in the resin pot, let the resin climb slow to where you clamp the feedline, wait a few minutes so that the air you just sucked in the part can be evacuated.
If you place the feedline in the resin pot and open it direct you will suck in air and mix it with the resin. That can cause voids at the inlet area.

#423

Ok so I have my mold ready to make a part. How should I prep my mold?

#424

Looks like the length of MTI hose being too short might have played into it. I pulled the old part out of the trash and measured it again today and the total length was only 4 inches (11cm). The fresh part that I demolded today that had a 10 inch (25cm) length of tube did not have any of the voids on the resin feed side…although it still has them on the vacuum draw side. I think I know the cause of this though, so I’ll work on sorting that out over the next week - I don’ think it’s related to the MTI hose.

Thanks for all the help!

#425

Make sure you check the pressure level at the part with a digital absolute pressure gauge, and not just at your vacuum pump. There can be big differences between actual pressure levels at these two points. You should be sure to be at least under 20mbar of pressure at the part before infusing.

#426

Definitely, I have an analog gauge set up that reads right into the vacuum draw side of the part (I debulk the bag from the resin feed line when I use MTI hose, just to make the process faster)

I’m not ready to drop 300 bucks on a digital gauge, but I will eventually. I’m guessing I’ll just end up going with the gauge that German Advanced Composites sell on their page, as it’s really the only gauge that I’ve heard about on the forums so far.

#427

Best place would be your resin inlet to read pressure level at part. If on vacuum side it still may not be accurate. GDH200-14 is a great absolute pressure gauge, Vacmobiles sells this as well

#428

Another two points; First, I noticed you said you use Green flow 75 mesh, I have found that this mesh tends create surface problems (either pinholes, or “dry looking” surface). I personally prefer the red mesh better, though the resin content tends to be a bit higher, but surface quality is better. Second; what type of leak check are you doing? It is very difficult to do a good check with analog as you cannot “see” a leak unless you do a long leak check, at least 30 min. Thats why I like digital absolute pressure gauges as you can almost instantly see a leak in 1 mbar increments. Typically you can do 5 to 10 minute leak checks and have a very high confidence and understanding about the real vacuum situation.

#429

One other thing: when the oil goes bad, the pump might not reach its vacuum level. But again, it can only be checked with a digital gauge. (most analogue ones are pretty dodgy, although I have seen a logarithmic one which I would love to have, but the price is overwhelming. (buys you 6 digital ones…)

#430

My pump is outside and it’s already hot down here in Texas, so it generally burns off/evaporates oil at such a rate that the oil has to be refilled every couple of weeks. I know that a vacuum pump ‘burning’ (misting) oil is a bad sign, as it means there is an air leak that is actually misting the oil, and this is true: there is some pin hole leak somewhere deep in my plumbing that means I can’t get below 28.5" on my analog gauge, but I can’t find it and can’t do anything about it ATM.

The GDH electronic gauge is what GAC composites sells, so I will indeed be picking that thing up once I get some free cash to do so. I do my vacuum integrity check through a prolonged drop test, which also serves as an evaporation period for residual moisture. I usually give it around 30 minutes. My bagging line is fairly simple (a rectangle with just 2 pleats per side) so it’s quite easy to tell when it’s bagged properly and if there is a leak or not.

Hojo: Thanks for the tip concerning the greenflow. I’ll look into getting some redflow, which I know is a thicker product that allows more resin movement. Interesting to hear that it could be introducing surface imperfections. Although I think my void problems are unrelated - in my case, there is a very hard corner, perpendicular to the flow front, that resin appears to be racetracking to somehow and then filling. This occurs before the area immediately before this corner is fully wetted out, or at least I think that’s what’s happening. Luckily, I think I can get away with just cutting the IM extra short, it’ll only result in an extra inch of carbon that the resin has to flow through without assistance.

Of course, I’m out of my required fabric now so I won’t be able to make another test until the end of the week :cool:

#431

If your pump is smoking there is a leak! Thats will be the reason why you have the problems.
Make sure everything is tight! And the Greisinger is a good investment if you want to infuse seriously.

#432

Here’s a simple test to see if your pump is up to the task. Put a cup of water in your degassing chamber and see if it will boil. No boil, no good

#433

Hi.

I’ve been thinking about testing some infusion and I just placed an order for some MTi Hose, but when I looked at my vacuum pump (Thomas VTE 3) I saw it can only make 25,1 inHg. Since I just do this for the fun of it Im not looking for a “mega professional pump”, but I wonder if someone has any suggestions?

Since I live in sweden it should be able to handle 220V.

#434

Would this pump do it?
http://www.ebay.co.uk/itm/1-5-CFM-48-lpm-2-Stage-Rotary-Vane-Vacuum-Pump-/261303583022?pt=UK_BOI_Medical_Lab_Equipment_Lab_Equipment_ET&hash=item3cd6e8412e

#435

Hello, buy a cheap oil lubricated vacuum pump from ebay.
Fir example this one ebay vacuum pump

#436

Ok so far I have made 2 pieces with infusion and the Mti hose and my. Results have been better than vac bagging but still some issues. 1st my pieces appear dry and have holes in between the weaves, I did place my resin 2.5 feet below the mold. I also didn’t clamp my line until the part was fully saturated. The weave also looks pressed or pushed into the mold. My second issue is that I feel like I’m wasting a lot of resin, I ended up using a envelope to bag my mold as I could not get a good seal by bagging just the top. When I finished my last part there seemed to be an abundance of resin soaked in the free flow, Mti hose, and all round the mold top and bottom. Also my pump pulls 29 inhg, maybe I should turn it down? Any ideas?

#437

Did you do a vacuum leak check? How did you check? Whats the viscosity of your resin? What flow media you use?

#438

The resin is adtech 820, the flow media I am using is green mesh and I did a leak check, it held at 29 inHG for 20 min, it was still at 29 inHG the next day.

#439

Which hardener did you use? Did you end the flow mesh short of the laminate? Whats your laminate stack of materials? Any photos of your set up?

#440

If you let the feedline open, had such a stable vacuum, degased you resin and used MTI this failure should not have happened.
Did you seal the MTI hose so that no resin can enter it? Is the Resin for infusion? As hojo said pictures will help.