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raygreenwood
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Joined: November 24, 2008
Posts: 21519
Location: Oklahoma City
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 Posted: Wed Jul 28, 2021 8:47 pm Post subject: Re: EGR valve diaphragms finally getting off the ground |
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| Clatter wrote: |
Damn…
You GO Brother…!  |
Hoping to get a first mold on this one on Sunday. I baked the mold and durometer increased slightly (pictures in a day or so). The buck came out perfect so it can be used to make more molds to do multiple pours at one time.
Just been a busy week....Friday is a webinar I am doing on new material for functional printed components...it snuck up on me. Saturday....the new ignition housing has to go into the Golf....its been down for a week. Sunday will be molding....and other things!
Ray |
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raygreenwood
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| Posted: Sun Aug 08, 2021 4:09 pm Post subject: Re: EGR valve diaphragms finally getting off the ground |
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So....much better mold and molding
But...still a few minor issues I will be correcting. This part is fully functional. I just have to punch the oval hole in the dome.
Ok...here is the mold block in a new Lego Holder. It is clamping all around the edge to keep the pressurized rubber from squirting out the edges as it chases the air out. Its not 100% successful at this...more in a minute.
Ok...here is the top of the mold after curing.....and after I CUT off the blobs of rubber forced out of the vents. The fact that I had to "cut" them off is important....more on that in a minute.
Here is the dome side and its surrounding air bleed sheet. It demolding perfectly. Notice the slight funky texture? Those are brush marks in the mold release.
Here is the o-ring side....and then the dome side .Everything is just fine...but more brush marks captured in the mold detail....which will not hurt anything. But....
Here is the gasket after trimming sprues....and cutting perimeter and punching holes...all except for the dome center. Notice the thickness difference from side to side. Its functional...but I am fixing that. ...more on this below
The gist of all of these little pointers is this:
1. The beige mold material was used because its VERY low viscosity which helps let bubbles slip out of the mold when making it
2. But...it also means that the durometer of this beige molding material is VERY low.....like 30 duro. Its very flexible.
This is why the thickness of the base gasket portion is thicker from side to side. The viscosity of the high temp red silicone...is over 2X that of teh beige rubber....and its hardness when cured is double as well.
Pumping the thicker red rubber in...is literally stretching the soft beige mold. It bulged on one side
3. Notice at the beginning...I noted that the red rubber blobs on the outside had to be "CUT" off?.....in general its widely held that silicone casting rubber will not stick to silicone molds....and "generally"....you should not need a mold release (but it helps they say).
But I already KNOW thats not true. If you are using VERY high viscosity silicones or RTV's....the surface tension can defeat the natural release properties of soft silicone.
The little knobs of vented silicone stuck to the outside of the mold because there was no mold release on the outside. It demolded perfectly on the inside.
4. Knowing the risks ...this is why I use mold release inside.
However.....the mold release I am using...while it works very well....is a micro powdered "wax" spray. You spritz it on...and then brush it with a fine brush...dry....to disperse it evenly.
AND...the low viscosity, fine detail molding rubber I using....captures those brush marks.
5. So...two things will change shortly.
A. I am moving to make the next pair of molds (production molds) out of the same red, 60 durometer, high temperature silicone that I am making the part from.
It will be twice as hard and will therefore not flex...and bulge. So the part will be more uniform. It will be a little more sensitive to bubbles but it should not be a big deal in the form its in now...as compared to the very first mold.
B. I am switching to a micro-powdered urethane spray mold release that needs no brushing. It should be smoother.
More to come.
I have other projects that have to be worked on including work. But...the EGR valve I have can get back to its owner this week....with this new working diaphragm and his old one. I have all the forms I need.
The object is to have 2-4 molds...so I can make a single 60 ml batch once a day on my way out the door...pump all four molds full. When I get home i demold the parts and throw into the toaster oven...and set the molds out for the am.
When i start molding maybe next weekend.....I hope to do four parts a day for about 10 days so I have a production batch to get out the door.
Ray |
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airschooled
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| Posted: Sun Aug 08, 2021 6:45 pm Post subject: Re: EGR valve diaphragms finally getting off the ground |
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Sign me the heck up for a bulk buy!
Seriously Ray, thank you for continuing your progress here.
Robbie
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ivwshane
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Location: Sacramento ca
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| Posted: Sun Aug 08, 2021 8:11 pm Post subject: Re: EGR valve diaphragms finally getting off the ground |
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It's kind of nice knowing that when I "rebuilt" my EGR that I had a similar idea as what ray is doing. Of course my attention to detail isn't anywhere near what ray's is.
I'm curious to see how this material handles flexing and stretching.
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raygreenwood
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Joined: November 24, 2008
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Location: Oklahoma City
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| Posted: Sun Aug 08, 2021 8:23 pm Post subject: Re: EGR valve diaphragms finally getting off the ground |
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| ivwshane wrote: |
It's kind of nice knowing that when I "rebuilt" my EGR that I had a similar idea as what ray is doing. Of course my attention to detail isn't anywhere near what ray's is.
I'm curious to see how this material handles flexing and stretching. |
Yes.....the very first molded part.....was VERY easy to tear.
This was partly because the cross section at the critical flex joint for the dome....was wrong. I fixed that.
The other problem.....is that it had MANY tiny voids....air bubble in it. It was more like a foam.
This batch I vacuumed down to 25" and held it for 10 minutes. It almost doubled in volume but it took a while to expand because the viscosity is so high.
This easily doubled the density and tear strength. It went up 5 durometers in hardness.
After a four hour bake...it went up another 3 durometer. Its very stretchy and tear resistant but is also slightly stiff....though I do not think it will be an issue.
I will post not far off...a minor mod for the shaft it goes on. The square shank area on that cam shape .....I will recommend to take a fine file and knock teh corners off of. I am going to make the punch out in the dome....an oval "capsule" shape. Its more tear resistant than having corners.
The nice thing about this re-design of the dome...is that it will never HAVE to stretch. Unlike the original which was at half height of the entire stroke.....this one is at full length of the stroke.....inside the dome....so as it returns to closed....it only has to compress...not stretch.
Ray |
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ivwshane
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| Posted: Mon Aug 09, 2021 7:24 am Post subject: Re: EGR valve diaphragms finally getting off the ground |
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I didn’t know that baking it could increase its elasticity. Good to know.
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raygreenwood
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| Posted: Mon Aug 09, 2021 8:55 am Post subject: Re: EGR valve diaphragms finally getting off the ground |
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| ivwshane wrote: |
| I didn’t know that baking it could increase its elasticity. Good to know. |
The post cure bake gets rid of any alcohols and plasticizers that were not consumed in catalyzed curing. Since the excess plasticizers are between molecules.....it can affect tensile strength in the short term. Eventually they will all migrate out of it. But leaving the plasticizers in the rubber will keep it softer and extend the natural cure time over days or weeks.....so its just faster to get to total cure by doing a low temp, post cure bake. About 150°F to 225°F.
The "elasticity" of this material is not a problem with or without post bake. Its rated at 331 psi at 100% of its rated elongation.
Its rated elongation....is 132% of a tested parts length. This type of catalyzed rubber.....if its mixed accurately and cured at normal temps.....will gendrally reach its rated elongation either way.
What tends to mess a part up...or appear to screw up its elasticity.....is variation in part cross section.
Example.....when they do this type of testing (ASTM 412).....they can use various set shapes....either a dumbell shaped part.....where the shaft between the knob at each end is uniform in diameter. Or....a rectangular or square section bar shaped coupon....or a punched out disc.
But lets say you are using the rectangular bar shaped coupon. Lets say its 1/4" X 1/4" X 3" long.....and gripped at each end. Lets say the grippers take up 1/2" each.....so the part length between grippers is a total of 2" long.
Now lets say somewhere in the middle of this 3" piece....you have cast a notch into it.....a notch with dimensions of.....3/16" X 3/16" X 1/4" long.
So.......when you start the adding tension and stretching/elongating the sample coupon/part.....the cross section will narrow as the part stretches longer right? Until it reaches its rated limit .....say 132% in this case.
So.....in a perfect test part without the notch cast into it.....the 2" part will stretch to 132% of its length. This does not mean that it just stretches its own length + 32%. It means it stretches 2.64" to be a total of 4.64" long.....where it breaks. If you observe while its stretching.....its cross section reduces by quite a bit. The material for it to grow longer has to be displaced from somewhere right?
BUT.....if you have a notch cast into the center of the bar....while the smaller cross section area will still elongate/stretch the same 132%.....it has less cross section to give toward "elongation". It will snap earlier at the notch you created.
This can give a false sense that elongation is lower in a certain area. Now....if you have voids or air bubbles inside.....these not only displace material.....so its kind of the same as having a thinner cross section.....they can create tear starting points.
So processing is important....and also design. The original part....had a very thin cross section at the flex joint between the base of the dome and the flat gasket part.
While this design is not a problem when it was made of Viton....because basic commercial grade viton has a 200% elongation factor ....at a pretty hard 75-80 durometer....and the original seals were from what I can tell about 55-60 durometer.....it means they probably had an elongation factor of about 250%+.
So that thin flex joint was really the only flex in the original part and the dome contributed very little to its range of flex.
My first molded part was simply a dead on copy of the original part and all of its design features....but with a material that does not have enough elongation to USE that original design feature.
So I designed around it. I made the lower flex joint area thicker.....and made the dome roughly 2X the height.....so it does not HAVE to stretch to reach where it needs to go.
The rest of it was just getting the voids out of the rubber. That was probably as much of a factor as the cross section change. I have been carrying this part around in my pocket fiddling with it....trying to tear it. No issues so far.
Ray |
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ivwshane
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| Posted: Mon Aug 09, 2021 9:14 am Post subject: Re: EGR valve diaphragms finally getting off the ground |
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Interesting and it’s exactly what I observed in my amateur attempt at making the part. Bubbles and thickness differences really played a negative part in how “durable” it seemed. I’m glad you know about this stuff and how to mitigate it.
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aeromech
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Joined: January 24, 2006
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Location: San Diego, California
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| Posted: Mon Aug 09, 2021 9:53 pm Post subject: Re: EGR valve diaphragms finally getting off the ground |
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Link
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Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
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alman72
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Joined: October 09, 2014
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Location: MICHIGAN
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| Posted: Tue Aug 10, 2021 6:06 am Post subject: Re: EGR valve diaphragms finally getting off the ground |
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| ^ that guy is exhausting. |
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Abscate
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| Posted: Tue Aug 10, 2021 7:26 am Post subject: Re: EGR valve diaphragms finally getting off the ground |
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| alman72 wrote: |
| ^ that guy is exhausting. |
u
He is great in the body shop, his voice removes paint
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aeromech
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| Posted: Tue Aug 10, 2021 7:49 am Post subject: Re: EGR valve diaphragms finally getting off the ground |
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I guess you need to get used to him but he has a masters in anthropology but went into the family garage business more than 50 years ago. He tells it like he sees it.
Scotty Kilmer was born on October 2, 1953 in Niagara Falls, New York. At age 14, he learned to be a mechanic from his grandfather, Elmer Kilmer, who was the chief mechanic at the Texaco gas station Scotty's father owned. He studied at York University for his undergraduate degree and then attended the University of Illinois at Urbana–Champaign, receiving a master's degree in anthropology. He was in the process of working towards his Ph.D., but eventually quit to become a mechanic in defiance of the tenure system. Kilmer wrote a book, Everyone's Guide to Buying a Used Car and Car Maintenance, originally published in 1994, upon the suggestion of his wife. Upon release, it led Kilmer to be on the front page of the Houston Chronicle, which attracted the attention of the local CBS affiliate KHOU.[5]
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
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raygreenwood
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Location: Oklahoma City
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| Posted: Tue Aug 10, 2021 8:10 am Post subject: Re: EGR valve diaphragms finally getting off the ground |
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| aeromech wrote: |
I guess you need to get used to him but he has a masters in anthropology but went into the family garage business more than 50 years ago. He tells it like he sees it.
Scotty Kilmer was born on October 2, 1953 in Niagara Falls, New York. At age 14, he learned to be a mechanic from his grandfather, Elmer Kilmer, who was the chief mechanic at the Texaco gas station Scotty's father owned. He studied at York University for his undergraduate degree and then attended the University of Illinois at Urbana–Champaign, receiving a master's degree in anthropology. He was in the process of working towards his Ph.D., but eventually quit to become a mechanic in defiance of the tenure system. Kilmer wrote a book, Everyone's Guide to Buying a Used Car and Car Maintenance, originally published in 1994, upon the suggestion of his wife. Upon release, it led Kilmer to be on the front page of the Houston Chronicle, which attracted the attention of the local CBS affiliate KHOU.[5] |
He does tell it like he sees it.....and he is entertaining.....but a significant portion of what he actually says.....is absolute BS. Yes....there is a good portion of good/useful information......but....I quit watching his garage videos quite a while back when some of what he was expounding on in specific videos was instantly recognizable as poorly researched.....shade tree mechanic driven..... wives tails.
Ray |
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Hoody
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| Posted: Fri May 05, 2023 2:14 am Post subject: Re: EGR valve diaphragms finally getting off the ground |
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| Any progress on the finished product? Are you still perfecting the design? I have couple of valves that I may lap the plunger and have them ceramic coated to fill any pin voids. I think I am going to put classic plates on it but I would like to have a couple of functioning valves if god forbid the smog nazis adopt the Cali protocols over in this neck of the woods. Bob |
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alman72
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| Posted: Fri May 05, 2023 4:45 am Post subject: Re: EGR valve diaphragms finally getting off the ground |
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| Hoody wrote: |
| Any progress on the finished product? Are you still perfecting the design? I have couple of valves that I may lap the plunger and have them ceramic coated to fill any pin voids. I think I am going to put classic plates on it but I would like to have a couple of functioning valves if god forbid the smog nazis adopt the Cali protocols over in this neck of the woods. Bob |
yes. did you send out test parts? did they come back? show us the pics! this R&D of the gasket/part is downright fascinating! no joke. guess thats just the way i roll. nerd cred. |
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SGKent 
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| Posted: Fri May 05, 2023 7:47 am Post subject: Re: EGR valve diaphragms finally getting off the ground |
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Ask Robbie. He stepped in to take over the project. The prototype valve was complete at the point he stepped in. That was about 2019. Ray's diaphragm is too thick but it is a start towards making them. It would not be hard for someone with CAD skills to make a drawing to have a injection mold made for a thinner diaphragm.
And yes - California Nazi like regs are coming to a lot of states. I hear that some states like NY have even outlawed natural gas for heating on new HVAC systems, stoves, garage and warehouse infrared heaters because they want all sources of NOX gone. EGR valves lower NOX on ICE.
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raygreenwood
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| Posted: Fri May 05, 2023 2:21 pm Post subject: Re: EGR valve diaphragms finally getting off the ground |
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| SGKent wrote: |
Ask Robbie. He stepped in to take over the project. The prototype valve was complete at the point he stepped in. That was about 2019. Ray's diaphragm is too thick but it is a start towards making them. It would not be hard for someone with CAD skills to make a drawing to have a injection mold made for a thinner diaphragm.
And yes - California Nazi like regs are coming to a lot of states. I hear that some states like NY have even outlawed natural gas for heating on new HVAC systems, stoves, garage and warehouse infrared heaters because they want all sources of NOX gone. EGR valves lower NOX on ICE. |
Yes...it is too thick. Worse yet....its the wrong material. Not because its silicone but because its the WRONG silicone.
The flat section that clamps between the shafts has to be thick in this type of silicone in order to have the flexibility it needs (I am coming to realize it does not really need that much flexibility).
However....this particular high temperature silicone I am using....is just too soft. So when the shaft section and ferule that clamps the dome of the diaphragm is clamped together....it crushes the silicone like cheese and shears it.
After long last I was getting around to shipping the EGR I have back to its owner last week. Installed the nifty new diaphragm.....and it crapped out after a few cycles from the crush  .
But, I reassembled it with its original diaphragm and sent it back so the owner can at least pass smog.
My reply to him today:
| Quote: |
My apologies this has taken years. I am a week late in getting it out the door. But it did go out today. USPS tracking #
9505 5161 7098 3125 4496 02
It should be there by maybe Tuesday.
Good news and bad news.
Good news: its assembled and should function. I installed a new flanged nut. You will also find a couple of 6mm screws and nuts that are just on there to hold the assembly together until you can install it.
The pushrod/piston stack up is not super tightened down. I think that is a bad move to make them as tight as they were. But they are assembled with a small amount of removeable blue Loctite.
Bad News:
The new silicone diaphragm....crushed and ripped when tightening down the shaft and ferrule. I was really worried it would do this.
On one hand , looking at it , anyone would say its just too thick. However, this particular silicone has to be that thick to have enough stretchability. But its also too soft...durometer wise....so it crushed down like cheese and just shears. While it is high temperature enough...its just the wrong material.
The original stock diaphragm is installed back in it and it will get you through smog check just fine.
The original gaskets are held in place loosely with the spare nuts and bolts. If it somehow leaks on the outside side of the diaphragm ...take a small screwdriver, lever it apart and apply a thin smear of Permatex 81160 red high temp sealant, bolt it back together and let it dry.
I still have the molds. I will still be making some of these. The material I really wanted that WILL work for this....has been hard to get and very expensive since Covid (about $200 a quart when available).
I have other ideas that my be simpler.
Sorry for the long delay. Ray |
So....onward and upward. If I can get the fluoro-elastomer silicone I need in a reasonable sample I will try that. I have used it on other things...at other peoples expense.... 
It would be awesome to cast PR tube seals from....its a pourable 600*F, oil and fuel proof silicone made in Japan. Bad-ass....expensive....but I digress.
Things I have speculated in the past but I have come to a near certain conclusion on:
As I have played with this EGR valve laying on its project tray on my desk ...for a couple of years...  ....I learned a couple of things.
1. This "diaphragm" may not actually need a molded in "dome". Its total throw or stretch...is only 0.167".
A thin sheet of a fluorelastomer rubber like Viton....may work just fine.
If one could get say...two years out of it before you had to spend 20 minutes and strip this thing down and throw another one in....would that be good enough?
2. The molded in half o-ring on the outer side....is unnecessary. It gets squashed flat. The pressure is just not that high. A thin smear of something like Permatex 81160 (good to 650*F) on the outer side of the Viton gasket sheet....let dry and then contact to a crush tight seal.....should seal it just fine.
Something I will look into. Ray |
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SGKent
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| Posted: Fri May 05, 2023 4:50 pm Post subject: Re: EGR valve diaphragms finally getting off the ground |
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Ray - you get an A+ for trying.
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Hoody
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| Posted: Fri May 05, 2023 9:52 pm Post subject: Re: EGR valve diaphragms finally getting off the ground |
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| I think you are on the right path with your thinking. As thoughtful as these German engineers were on so many levels I would contend that they never went to such great lengths to develop this small seal that really only does so much. The change out intervals for them were not terribly long if I am not mistaken. They needed something cheap and easy to make this valve function for a very limited market and time duration. A high temp piece of whatever that was slightly flexible….enough that it filled the void without breaking with a small hole punched into it and sandwiched into place. The heat from the gases over time actually formed it into what looks to be a molded part. The stainless cup on these is the shape of the seal. Just a thought. You went above and beyond Ray. Perhaps we have all overthought this. I am always over thinking some things at times. You know the old saying….Keep it simple stupid….well I could have saved myself countless hours by abiding by this more often. Being the guru that you are of such materials. What is heat resistant enough and flexible enough to just stick in that space? Some one at one point was pointing towards a product used in the dental industry if I recall. |
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raygreenwood
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| Posted: Fri May 05, 2023 10:49 pm Post subject: Re: EGR valve diaphragms finally getting off the ground |
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| Hoody wrote: |
| I think you are on the right path with your thinking. As thoughtful as these German engineers were on so many levels I would contend that they never went to such great lengths to develop this small seal that really only does so much. The change out intervals for them were not terribly long if I am not mistaken. They needed something cheap and easy to make this valve function for a very limited market and time duration. A high temp piece of whatever that was slightly flexible….enough that it filled the void without breaking with a small hole punched into it and sandwiched into place. The heat from the gases over time actually formed it into what looks to be a molded part. The stainless cup on these is the shape of the seal. Just a thought. You went above and beyond Ray. Perhaps we have all overthought this. I am always over thinking some things at times. You know the old saying….Keep it simple stupid….well I could have saved myself countless hours by abiding by this more often. Being the guru that you are of such materials. What is heat resistant enough and flexible enough to just stick in that space? Some one at one point was pointing towards a product used in the dental industry if I recall. |
I think we have over thought this. Perfectly said.
I think....visualize this now....and if you have never had one apart some of you may not be able to visualize this.
if I can find a thin sheet of viton (and it has to e the right kind)....like maybe 1/32" thick. Think 3" square.
Right in the center, cut or punch the "tombstone" shaped hole. Stick the main shaft through, install the flat ferrule washer and thread on the inner shaft and tighten.
You now have a big sheet diaphragm attached to the shaft. Install the shaft and the far end valve assembly.
Take an exacto knife and poke two holes for the roll pins. Apply the metal operating block and lever. Tap with mallet to seat the block on the roll pins.
At this point the spring on the operating shaft will push the valve full forward stretch ing this sheet inside the metal dome the full 0.165"....and you now have a flexible gasket inside.....and you have this sheet protruding all around the outside. Trim that off with a sharp knife.
Clamp the assembly together tight with a simple squeeze clamp.
Where the two long bolts go through....either trim out those holes with a thin exacto blade....or I would bet that with a piece of copper tubing and a file I could make a pair of tubular punches in about 10 minutes.
I was thinking about this method all day right after I mailed part out .
Once you bolt it together...I bet that would work.
6" x 6" X 1/32" viton sheets at McMaster are $14.16 each. Temp range about 400F constant. In reality if I cut these sheets about 1.5" x 3"....I could get maybe four attempts out of this.
We all got hung up on that dome in the diaphragm.
Ray |
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