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Is there a way to control small cracks in Plexiglass?


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#1 SLadd

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Posted 23 October 2014 - 09:28 PM

We have a lot of plexiglass machine guards, I mean a LOT. All of our fillers (cold fill beverage) use plexiglass as machine guards around the fill valves and other places where the person running the machine needs to see through the guards. We have a lot of issues with the plexi cracking, partly due to overzealous tightening of the bolts holding it in place and partly due to the heat from the Clean-In-Place process creating heat cracks, but mostly from handling of the pieces by maintenance and other personnel who need to get behind them to make adjustments, pull out containers that get hung up, etc. We obviously have a program in place to inspect these guards and replace them when needed which is expensive. Is there anything we can put on a small crack to stop it from spreading, much like the stuff you can put on a windshield of a car to prevent a crack from spreading? I'm a QA gal so to me it makes sense that something like this should exist but the maintenance technician I talked to looked at me like I was crazy. Anyone ever come across such a miracle substance?


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#2 Snookie

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Posted 23 October 2014 - 11:29 PM

Interesting question which I just had to google.  Have not tried this option but looks interesting.  

 

http://www.plasticge...plexiglass.html


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#3 it_rains_inside

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Posted 24 October 2014 - 01:51 AM

S LADD - I do believe we are in the same business, and I have exactly the same problem going on. For now we just document cracks like crazy, because replacing large custom cut pieces of plexiglass is not only financially a problem but is almost impossible with some of the machines we are using.

That answer hasn't stopped auditors from asking questions... lots of questions. Because even if a Crack is documented, how can we prove the plexiglass hasn't frayed off and is loose (in/near) the product. Our answer, aseptic filling. You might not be so lucky (?)

If you come up with a solution, please forward along!!


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#4 SLadd

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Posted 24 October 2014 - 01:38 PM

I talked to one of our maintenance technicians about the link provided by Snookie (thank you!). He agrees that drilling a small hole at the end of the crack will stop it from spreading which will help in the areas in which the product is already sealed up in it's package - we've agreed on a length limit for cracks in closed product areas so if we can stop them before they reach their limit we can at least combat those. However, we will have to think some more on how we feel about this solution for our filler guards. Hopefully someone out there has brilliant solution! anyone? anyone?


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#5 fgjuadi

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Posted 24 October 2014 - 01:57 PM

We have a similar problem with cracked plexiglass guards every where...but we hired a mechanic who is very, very good at making them, and he spent a couple months just going through the factory fabricating & replacing them.  I thought plexiglass was relatively inexpensive compared to what I wanted (stainless).  Is the costly part the fabrication?

 

If you want to prove that the piece is cracked in same place as when as when you documented, and the crack hasn't changed, you could always take pictures.  But documenting is more effort than correcting, and the amount of time a resources you spend documenting won't stop pieces of plexiglass from getting "all up in there".  So if you take a picture, and the crack is different, then you have to figure out where plastic went and you probably won't be able to. 

 

Maybe you can have the person holding the purse strings photograph the cracks once and then explain that you do this every day/week/month/quarter and that if anything is different, you have to go through all of the product since the last time you checked the crack.


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.--. .- -. - ... / --- .--. - .. --- -. .- .-..

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#6 Tomato

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Posted 24 October 2014 - 04:06 PM

I have placed metal collars in our plexiglass or plastic guard mounting holes. They are about 1/8" longer than the peice is thick. It allows the mechanic to tighten away with out compressing the plastic. An added benifit for the small guards that they become metal detectable. Before a bolt would fall off and be caught by the metal detector and then the guard would fall off later and not always be found.


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#7 Snookie

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Posted 24 October 2014 - 06:19 PM

While replacing may be expensive, personally think the repair wouldn't be cheap either when you consider man hours etc. 


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#8 Mike Green

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Posted 24 October 2014 - 06:59 PM

I talked to one of our maintenance technicians about the link provided by Snookie (thank you!). He agrees that drilling a small hole at the end of the crack will stop it from spreading which will help in the areas in which the product is already sealed up in it's package - we've agreed on a length limit for cracks in closed product areas so if we can stop them before they reach their limit we can at least combat those. However, we will have to think some more on how we feel about this solution for our filler guards. Hopefully someone out there has brilliant solution! anyone? anyone?

It may be possible to 'weld' cracks using a solvent (such as propanone or trichloromethane) which basically melts the plexiglass and then it resets (you would need to do this off the machine & in a well ventilated area!!!) -I know guys that have repaired plexiglass vivariums in this this way and they look pretty good (after a bit of polishing)-but I believe there is a bit of a 'knack' to it, in terms of determining how much solvent to apply!!!!

 

And as Snookie says- although the solvent is cheap, the time involved may push up the cost

 

Mike


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I may sound like a complete idiot...but actually there are a couple of bits missing

#9 Dood

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Posted 29 October 2014 - 05:37 AM

I luckily don't have to deal with perspex panelling on machinery (Hooray for not packing product anymore) but when I did, when a hole was seen. We drilled at the end point of the crack this stopped it from going any further.

We'd also us an indelible mark to line the crack and write a date next to the drill hole and photographed, (the machinery was mainly dry cleaned) this is good for getting it under control if you have legacy cracks/equipment. 

 

For prevention, drilling the holes larger then required and use a slot collar, this'll prevent crack appearing from over-tightening/vibration fatigue.

 

Both these things have been mention before, but they are also damn good ideas :)


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#10 SLadd

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Posted 29 October 2014 - 02:03 PM

You guys have been amazing and since you are so amazing, I have more questions! I have been told by two different people that Lexan does not need to monitored under the glass and brittle plastic program because it is not brittle plastic. What are your opinions on this? Some of the machine guards that I was told are Lexan are cracked, sooooo either Lexan is not as magical as they tell me or someone blew some smoke in an effort to get out of replacing guards. Being the suspicious type, I log and monitor everything that I can see through.


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#11 RMAV

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Posted 29 October 2014 - 04:21 PM

"Lexan is not as magical"

 

You're right.  We've got cracks in our lexan, it "fogs" due to cleaning chemicals, and it's annoying enough as it is to audit glass/brittle plastics without it breaking/cracking. 

 

Here's what we're doing: safety light curtains.  remove lexan guard, and installed light curtain that stops the machine when the beam is interrupted.  Test once per shift to ensure it is operating properly.  Cover up before using heavy-duty cleaning chemicals.  Not for everyone/everything but they sure are nice for us.

*edit: haven't had the light curtain very long, if it turns out I hate it in a few months, I'll report back


Edited by RMAV, 29 October 2014 - 04:26 PM.

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#12 Snookie

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Posted 29 October 2014 - 04:35 PM

"a rose by any other name..."  Lexan breaks and it needs to be monitored as any brittle plastic.  But a piece in the lunches of the people who said its not brittle and see if they like eating it.   Okay maybe you can't do that....but wouldn't it be great.  :roflmao:  :rofl2:


Edited by Snookie, 29 October 2014 - 06:58 PM.

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#13 RG3

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Posted 29 October 2014 - 05:56 PM

The glass register includes brittle plastic and other materials;

 

If it can break it needs to be monitored as any brittle plastic, hard plastic, glass, ceramic, etc.

 

A good idea is to have a column or row next to every machinery for length of crack (cm) of the plexiglass so it shows that you're monitoring it. If you have several on one machine guard, as mentioned by Magenta_Majors "take pictures", and write on the picture the length of the cracks. This will prove that you're monitoring the cracks and that they have not "gotten out of control".


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#14 OrganicCandyAng

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Posted 21 December 2015 - 05:27 PM

Lexan did solve my problem - it was also very affordable if not cheaper than plexi glass and I got it cut to size by a plastics supplier. No cracks yet


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#15 mgourley

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Posted 21 December 2015 - 10:49 PM

Lexan will crack. Give it time.

 

Great suggestions about drilling holes, inserting collars and monitoring with pictures and dates.

 

Marshall


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#16 SQFconsultant

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Posted 07 February 2016 - 04:59 AM

Several of our clients use Locktite 3030 adhesive. It is injected into the cracks and works rather nicely.

Glenn Oster


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#17 Vicki Gibson

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Posted 14 September 2016 - 04:14 PM

I don't know if this might help anyone, however, doing plexi boxes and covers, signs etc I find that using a rubber washer when applying a screw or bolt often stops cracking from happening in the first place. Sometimes I put one on both sides of the material.  I have also made thin washers with a craft material, which is disposable if need be.  I have taken the rubber washers off of roofing nails and used those, they work perfect!  And not over tighten the bolt! Back off 1/4 turn. This allows for movement and also can stop cracks from forming.  Even the cheaper plasitcs will be saved in this process. Also make a sign for all mechanics to READ...DO NOT OVER TIGHTEN BOLTS ON PLEXI COVERS!!!  LOL  OK, just a thought for the proecess! I have to make things kid proof in displays and this method has saved a lot of grief over the years.  Cheers! 


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#18 Scampi

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Posted 16 September 2016 - 03:25 PM

Just a thought.....if the plexi is not a food contact surface, would Gorilla Glue not contain the crack from spreading?


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#19 xylough

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Posted 16 September 2016 - 06:25 PM

Consider this: Plexiglass may not be the most suitable plastic for food equipment and exposed food areas because it is brittle and may contribute to the same hazard risks as glass. There are upgrades to plexiglass e.g., Lexan and other branded plastics that do not have the same propensity to crack.

 

Regards


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#20 mgourley

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Posted 17 September 2016 - 04:14 AM

We only use Lexan. But it will still crack if you torque down the fastener too much. At that point, we do not put a band aid on it, we just replace it.

 

Marshall


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#21 M33

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Posted 20 May 2017 - 05:36 PM

Hi, not in your line of work but happen to come across this when looking for different Perspex question. I don't know if this will work, but the issue of where the spell pieces of Perspex from the cracks is the main health and safety issue. Can't you just wrap the plexiglass with some what we call in UK as cling film, I think in America you have a different name for it, flexi wrap or something. The really thin sheets of plastic you may cover a sandwich with or cover a food item one opened to prevent it from contamination. It doesn't have glue on it but it sticks to everything, especially itself and any thing you don't want it to stick to. Comes on a roll in a box, the box has a serrated edge as though it's really thin if you try to just rip it you end in a mess as it will stretch stick to itself, anything but rip unless you use the serrated edge on the box, hence why it's there. It's see through, doesn't tear without a fight, come in different lengths and thickness, you can even leave it on the food it's covering, unless you by the cheep stuff then in melts into your food, so read instructions on box first. If boiling potatoes in the microwave, you can make a couple of holes to let the steam out and the holes don't get bigger.
My point, if you put it against the food side of the plexiglass, when the plexiglass cracks it will just stick to the cling film. It's see through so you'll still be able to see when it's in place. If you see a crack in the Perspex you can remove the cling film which will contain any particles. So you know your product is not contaminated. Follow other processes and attach knew cling film.

Solution 2. I don't know if this will work, if it does it solves all your problems.
Before you fix your plexiglass in place, can't you cover all sides with a thin layer, or thick layer, intact as thick as you can and I still see through, of dry clear appoxy glue. Once dry it won't break, it will even keep the plexiglass it's touching from breaking, more the plexiglass tries to break the harder the glue fights to prevent any break. Just contact a manufacturer, tell him your plans for their product, they may be able to make you a special batch for your needs. It may cost quite a bit upfront, but once done you should never need to replace them, wasting money each time on all the costs involved and a persons time checking and photographing all the time. The outlay could be covered in a year as you can apply the appoxy to the plexiglass already damaged, so you shouldn't even have to replace the plexiglass you have. Interested if this works, make sure you get back to me if it does. Also connect the appoxy firm to me as if you think of the number of companies in your situation!!!! I'm Disabled and largely bed bound, an extension with a small hydrotherapy pool would change my life, giving my time with my wife and nine year old son. My wife had to give up her work to care for me. This isn't a begging letter, but if it works and saves your companies thousands in the long run & between you, the amount to give me a life and my family time with their dad would only cost a fraction of what it could save you, and I'm sure both the appoxy and disability aid or payment to technical advisor (Me) could be written off against tax. I would even provide evidence that I am bed bound & not conning you. Even if none of you helped me if the idea works, I still hope it solves your problem.


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