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I am looking for a cap. sensor that can read the water level of a semi clear 5 gallon water jug. I need to stop the fill at a specific level on a consistant basis. Other challenge is the sensor needs to be able to overlook splash without turning off as the machine fills at a high rate. Does anyone have any ides? Also open to other than a cap. probe. Also the probe has to be food a beverage grade, so stainless steel is a must. THought I would add a description of the machine. The empty bottles are unloaded by a Fanuc robot onto a conveyor line...run through a washer...and then sent into the rotary filler the works the way it sounds. it rotates at a set speed, recieves bottle, fills them, then sends them out on a conveyor all the while never stopping. This machine washes, fills, and caps 2500 5 gallon water jugs an hour! Once filled and capped another Fanuc robot loads them into racks to be put on big rig trucks. |
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You could split the process into 2 sequential steps. Step 1 fills 95% of the bottle really fast, and step 2 fills the last 5% at 1/20th speed to prevent splashing and either use weight or a level sensor. Or you could weight the almost full bottle, calculate how much mass you have to add, and use a slow regulated flow and a timer again. The way you describe the fill cycle is how we are doing it but weighing the bottles is a problem because the bottles are cleaned in a water and cleanser solution before being filled and though it seems small the water on the outside of the bottles after cleaning changes the weight.
(Dec 07 '09 at 23:19)
Jordan D
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Sometimes controlling the process is more accurate than a direct measurement. If you were able to regulate the flow into the water jug really accurately, then a precise on/off valve with a timer might do the trick. You could also monitor the flow with a sensor to adjust the timer during the fill. Thats actually what they are doing now. The process has a "fast" fill and a "slow" fill but due to different shape bottles and distance of nozzles from the bottles the timing is not consistent and the measurements are not to customer standards.
(Dec 04 '09 at 21:25)
Jordan D
Scott is Bang-on! Though CAP sensors are cheap, flow meters can easily be accurate to 0.5%. I don't doubt that it could be done with a CAP sensor, but you can probably expect to be in there tuning it every few weeks!
(Dec 04 '09 at 22:21)
Marc G.
@Jordan D: Have they already explored a more accurate flow meter, etc.?
(Dec 04 '09 at 22:24)
Scott Whitlock ♦♦
I actually like the idea of a flow meter but the customer insists upon it's inaccuracy. The nozzles never enter the bottles and that leaves alot of room for over spray that never makes it into the bottles. So the even if the flow meter says it is full the bottle may actually only be 75% full.
(Dec 07 '09 at 23:31)
Jordan D
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Alternatively... Keyence has some fiber-optic liquid detection probes. Because diferent mediums refract light at different angles, they can be "tought" to turn on when submerged in water or oil etc. I believe they have food grade options. You'd just have to strap it onto the side of your fill nozzle and make sure the depth of penetration of the nozzle is constant. If I'm not mistaken, the sensors go for about 1500$. The big trick with this will be tolerance to splashing: Big De-bounce! The light refraction would be a problem. This machine fills for multiple companies and each company have different shape necks on their bottles so there would be no consistency. And though a cap sensor works for a while if during the fast fill cycle you get any amount of big splash the sensor reads that and turns off the fill cycle. Big Headache!
(Dec 07 '09 at 23:22)
Jordan D
The sensor head isn't "aimed" into the bottle, it's a plastic coated "Dip-stick". It detects submersion. Perhaps the solution is to use nozzles that insert into the bottles... As I had mentionned above, this is what I've seen at a local bottling facility. By doing this, you only waste water once the bottle is already full...
(Dec 08 '09 at 15:36)
Marc G.
Keyence is definitely a good suggestion. They have a tremendous range of high quality products - that come with a corresponding high price. I would suggest you contact your Keyence representative and have them look at the application - they have giant demo kits and can test the application for you.
(Dec 10 '09 at 15:29)
Jason K
I've had a fair amount of luck with some Omron "low cost" capacitive sensors as well. I'm sure that Keyence will be able to find a solution, but Omron might be in the right price range. Once again, contact your local distributor and have them bring a demo kit to look at your application (this might be a bit more of a challenge than with Keyence though).
(Dec 10 '09 at 15:30)
Jason K
Finally, I would seriously look at Balluff as well. Balluff is well known for their proximity sensors and they also have tremendous service! This would probably be the best fit between: - Best product at a very high price (Keyence) - Lowest price and less then perfect service (Omron) I would call your Balluff rep immediately...
(Dec 10 '09 at 15:33)
Jason K
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