Simple Bulls eye

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graham
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Simple Bulls eye

Post by graham »

Ok here is todays question.

Im a newbie here but seem to be making great bullseyes (just a bullseye, not a combo). Some I have filled fine, but a few seem to have a very thin sliver apparent at the base of the cone after curing, which I am guessing is air. (my practice screen is inside and never been wet yet).

After reading in the forum about NOT applying too much injector and/or bridge pressure, I make sure to do it just as in the training dvd.

Just popped a neat bullseye, filled it with first pressure cycle, but a small dark patch appeared at the bottom, about a 2mm crescent shape. No worries, it will go when I pull a vacuum. It didnt, still there! Next pressure cycle...it was gone. Great I thought. Did another vacuum...it came back. It seemed like I was sucking the resin OUT as when I re-pressured it it disappeared again.

So removed the bridge, seemed as if it was gone, pit filled and tabbed it but it slowly re-appeared. It couldnt be sucking air thru the drill hole as it was full of pit filler? An as I said it was a perfect bullseye, no minute cracks etc within it or outside the perimeter. I pressed real hard with my finger tip onto the tab and it vanished again! Let go and its back.


What is happening here and is it me?
screenman
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Re: Simple Bulls eye

Post by screenman »

I would bet a bit more time or a few more cycles would have got rid of the air, that is assuming you really are using as little injector seal pressure as possible.
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Brent Deines
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Re: Simple Bulls eye

Post by Brent Deines »

How long did you leave in each pressure cycle? Don't rush this step.

If a small amount of air is compressed to the edge of the damage but not completely removed it may appear to be gone but will slowly reappear when the injector is removed, just as you said happened to you. If the vacuum is not pulling the trapped air it is typically caused by one of two reasons. Either there was not enough resin in the end seal or there was not enough plunger pressure. If you don't use enough plunger pressure or you don't have the end seal completely full of resin you won't get enough vacuum. It is very common for new and experienced technicians to use too little plunger pressure. That is not to be confused with pressure against the glass, which should be minimal.

Air cannot be pulled in from the pit area and migrate to the outer edge of the damage so assuming there are no surface cracks you are not pulling new air into the damage.

Pressure from the outside will cause the air space to constrict so it will appear filled but as you mentioned when you release the pressure the air will still be there. If you did not have too much pressure against the glass the damage was not filled properly before the bridge was removed. That much is clear.

Be sure you are ending in the pressure cycle.

I agree with Graham that an extra pressure/vacuum cycle may be necessary after you feel the damage has been filled. When properly filled you should not see any air movement in the vacuum cycle.

Feel free to call if you want us to walk you through a repair. I'm confident this is a simple problem to remedy if you are using a Delta Kits injector.
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graham
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Re: Simple Bulls eye

Post by graham »

Thanks Screenman and Brent, much appreciated.

Definitely just had the injector lightly touching the glass plus a quarter turn, followed by just 2-3 HALF turns of the ends screws was just enough to seal it well.

Just releasing the plunger made the air disappear, but did follow it up with some thumb pressure too. Left for the 5 minutes, 30 secs vacuum and then the two 2 minute press/vac cycles etc.

I am using the Delta B250 bridge. I use a syringe to fill and used 0.03- 0.04 ml. I removed the seal and checked its volume which seemed to be 0.01ml so I thought 0.03ml would be more than enough.

Will retry again today but use some extra time on each cycle and a coupla extra cycles.

Thanks guys. :)
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Brent Deines
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Re: Simple Bulls eye

Post by Brent Deines »

Sounds like you are doing everything right but I still feel the most likely issue is the amount of resin or the amount of pressure on the plunger simply because I have watched many hundreds of technicians over the years who were not using "enough" pressure on the plunger. You have to have, not only enough resin to fill the end seal, but enough to fill the cavity just above the end seal. That way when you pull a vacuum and air comes out, resin completely fills the seal again prior to the next pressure cycle. This is critical for top quality repairs and even many experienced technicians fail to get it right.

I could be completely wrong of course, as I did not witness the repair, but I suggest using more resin for a few times to see if that takes care of the problem. If it does you can start scaling back until you get it dialed in, keeping in mind that the more vertical the glass the more resin you will need. Not a lot more, but a drop or two depending on the angle of the glass.

I'm basing my theory almost entirely on your comment about the air not moving during the vacuum cycle. In a tight start break it is sometimes difficult to see the air traveling through the damage but in a simple bullseye you should see the air trapped around the edge being pulled up through the injector during every vacuum cycle until the damage is completely filled with resin and no air remains. If that is not happening there has to be a simple explanation and above are the two most likely reasons.

I have made a couple of assumptions however. I assumed you are 100% sure there was no moisture in the damage since you created it and you did not mention introducing moisture. Sorry screenman, I know that is a foolish assumption. I also assume it is not a pressure ring since a pressure ring will not disappear and reappear by flexing the glass.
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screenman
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Re: Simple Bulls eye

Post by screenman »

Have a look in your mirror when everything is set up and under pressure, use a torch if need be, look up inside your injector and you do not want to see an air bubble at all.
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Re: Simple Bulls eye

Post by GlassStarz »

Sounds like you needed to take a little mo re time cycle more
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Re: Simple Bulls eye

Post by Nomad »

If you take a probe and put it down the center of the injector after removing the plunger, then pushing down on the center of the bull with the probe to push the loose center piece of glass that was broken a few times, just watch the resin flow around wile you are doing this. This doesn't always help but it does enough times to give it a try.
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benswindshieldrepair
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Re: Simple Bulls eye

Post by benswindshieldrepair »

To follow up on Brent's advice, I have had this happen to me and have added just a couple drops of resin to solve the problem. Sometimes these breaks are pretty cavernous and require more resin that the dropper line indicates. Add a few more drops and I bet you'll be golden.
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Re: Simple Bulls eye

Post by screenman »

The few more drops is to make the injector work correctly. The breaks are tiny in terms of volume, if you think about it there is only the pit missing, which in most cases extremely small in area.
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