@ herman: You don’t have to close the vacuum line, you use the MTI hose so that nothing can be evacuated if the resin reached the MTI hose.
@GAB981: thats correct, by that high diggerence you can controll your VF. Our test showed that by 1 m difference you will have a VF of 52-55%
I closed it, as if the resin would be wet for too long, I might have air running back. I don’t think it WILL happen, but I did not want to take any risk. Besides that, closing the vacuum line closely to the part was easy using special clamps.
Gab: you are totally right.
Keep in mind that this part was optimised for visual appearance, not for weight reduction. For a very lightweight part, apply more vacuum. (perhaps even connect the resin inlet to the catchpot.)
ok, understand. With a full vacuum what is the VF? To get an idea of comparison.
VF is volume fiber, right? I’m never interested to VF and WF, it’s time to deepen my knowledge.
I would like to get a compromise between appearance and weight…
0,1 bar seem too little as vacuum force…
I think to do a test with infusion at full vacuum and then reduce to 0,4/0,5 bar…the problem is that if I close resin inlet and decrease vacuum, my fear is that the thickness of laminate increase, then it needs more resin. If the inlet si closed, laminate recalls air from vacuum line. I don’t know if it can be true or are just paranoid.
Otherwise keep inlet resin open, and apply a vacuum to inlet resin pot and controll so vacuum level (so without vacuum I will have 0,1 bar of vacuum for the resin column, with vacuum I can controll).
The question now is…what is the vacuum level to have a compromise between appearance and weight? 0,3/ 0,5 bar?
If working with the MTI hose you should not close the vac line! And there is no compromise between optic and technic.
For a optic/visual part don’t close the resin feed and place the pot on the same high than the deepest point if the part, than your fabrics will swim so that they don’t flattn. Thats what I think you understand by a optic part.
For a technic part do not apply more than 200mbar pressure difference to your resin feed or you may create a too dry laminate or may be voids. The 200mbar are the forces the fabrics create when compacted.
And never applay vacuum to the resin feed before the part is complete impregnated or in a to early stage in the infusion process.
I like the optic of flattend fabrics wich is a indicator for a light and strong part.
I must to say big thanks to Dominik for a MTI hose sample, the parts came out perfect
every time i use it. I already ordered more MTI, and plan to use it all the time.
I want first to thank DD for the sample of MTI I got threw your distributor in USA
I didn’t have the time yet to use it but it will be soon
I would like to understand
The parts that I intend to make should be technical light weight and very good cosmetic apparences
So he is my issue we need to vacuum as much as possible 29.9HG
And now I’m reading a lot about. BAR pressure so can you explain how This work and how to calculate the Bar And also how to apply this to our vacuum
Maybe do we need a vac regulator ? To be able to adjust
My gauge only give me inHg and all of you are starting to speak about mbar (thousands) etc
Thank to anyone who can be helpful
BTW Beautiful part nice work look more than professional
Maybe you want to tell us how this part was made and which products did you used
The part look more than professional and if it’s a 2 pces where are the seams?
I just use regular infusion materials and MTI hose The mold is 2 pieces mold, and the seam (I marked it red) is pretty visible.
[QUOTE=phsledge;43351]I want first to thank DD for the sample of MTI I got threw your distributor in USA
I didn’t have the time yet to use it but it will be soon
I would like to understand
The parts that I intend to make should be technical light weight and very good cosmetic apparences
So he is my issue we need to vacuum as much as possible 29.9HG
And now I’m reading a lot about. BAR pressure so can you explain how This work and how to calculate the Bar And also how to apply this to our vacuum
Maybe do we need a vac regulator ? To be able to adjust
My gauge only give me inHg and all of you are starting to speak about mbar (thousands) etc
Thank to anyone who can be helpful[/QUOT
You can easily find the different values in some conversion calculators in the internet. The reason for that confusion is that some people talk about relative pressure or differential pressure and some about absolute pressure. The middle hydrostatic pressure of the earth atmosphere at sea level is 1013mbar or 29,9inHG. When you talk about a vacuum of 29,9inHG you are talking about relative pressure. The absolute pressure of that number is 0 inHG or 0 mbar. To produce perfect parts you should reach a vacuum level below 20mbar or 0,59inHG absolute or 29,9inHG - 0,59inHG = 29,31inHG relative pressure.
Then what is the 200mbar for a technic part?
Does it mean to do less vacuum power?
Meaning we need to have a Vacuum Regulator to be able to control the intensity of the suction?
Is it the way ?
Thanks
The 200 mbar should be applied on the resin pot. The vacuum for the infusion should always be as high as possible.
The low vacuum on the resin pot prevents a resin overfeed in the part anf makes sure that you have a high VF.
But it should be applied at the end of the infusion, not in the beginning.
Ok but how do you apply the low vacuum to the resin pot?
I believe you need a vacuum regulator to do that?
And if yes then where do you connect this regulator?
Thanks
I place the resin pot for example in an exsikkator. And you need a vacuum controller. Another method is placing the resin pot deeper than the mould. 3ft ~ 100mbar
I think I understand
It mean if I have the resin pot 3feet under the mold then the infusion will go slower and with less power
To adjust the height of the resin pot it give us the control over the infusion
Correct me if I’m wrong
And depend of the height I get a different mbar?
Just for the calculation minus 3 feet =100mbar
Minus 1 foot = ?
I will study also your exsikkitor look interesting its like a vacuum chamber with an opening for the infusion and must permit degassing the resin before infusion . Nice
Thank you
Also Herman said that you don’t need to take in consideration the mbar if you use the MTI hoses what would you say about it??
You are right. There is no need to reduce the vacuum after infusion. You can work the whole time with the full vacuum.
During infusion I would place the resin pot at the same hight, in the end I would place it deeper.
So now if I understand even better when you slow down the infusion of the resin is to give more time to wet the fabric and to fill up all possible gaps that are created by air.
And then when the infusion is finished you close the resin injection tube but keep full vacuum on the bag until full cure. Is that right?
Thanks
You have to know that there is no vacuum left in the system when the set up is fully saturated. When the resin hits the MTI hose it closes the micropores of the hoses membrane so that the pressure get reduced automatically during the process. Exactly that is the self-regulating mechanism that leads to a minimization of voids (collapse of possibly entrapped air bubbles). Unless the standard vacuum infusion process with spiral hose in which the permanent vacuum forces embedded air bubbles to expand to its maximum size. The only way to put a differential pressure on the MTI set-up is to set a height difference between mould and resin pot or to put the resin pot into an exsikkator. When you once know that mechanism you also know that its crucial to have a 100% tight vacuum bag.
Thanks
But then do we need to keep the vacuum running until the end of the cure or because of the MTI hoses we don’t need it?
Most of the people leave the vacuum on until the cure end but I don’t see so much the reason if the membrane is locked with the resin ?