rookie needs some help. system design

timbo4255

Member
Join Date
Sep 2003
Posts
16
Hello all. What a cool site! First some info about myself and my project. I am a farmer with enough knowledge to be slightly dangerous. I have this problem with coming up with good ideas and for some reason I can't just let them rest. My banker hates this. Have you guys ever seen a small square bale of hay? 16"x18"x38" and weighing about 80 pounds. Take a pair of hay hooks and manually handle about 50,000 a year. After a while you think of every possible way to avoid manual labor. Well, I think I have it figured out. I am in the process of building a system to organize the bales and strap 18 into a package with plastic poly straps that can be handled with loaders, thus producing lever bales.(Levers on a loader instead of hay hooks)
 
Oops, I pushed tab.
Anyway, my system is fairly simple in the sense of control. I have 5 hydraulic cylinders, 2 automatic strapping machines, and a handful(8-10) of proximity sensors and microswitches. My problem is that I have only dealt with basic ladder logic in the past and it was only on/off, yes/no programming. There were no variable inputs. Now I must figure a way to stop my cylinders in many different locations, not just in or out. I have found cable pull transducers that I believe would work great for positioning cylinders, but I have no clue about how a plc understands a variable 4-20ma signal. I have not purchased any sensors, hydraulic valves, or a plc yet. Could anyone please help me choose the appropriate plc, transducers, and sensors for this project. Any suggestions or ideas would be greatly appreciated Remember, you are dealing with a college educated, yet dumb farmer.
 
I'm an old farm boy that spent a lot of my youth throwing bales around on hot midwest summer days. (Note to the un-initiated: do not do this with a hangover - I once proved this with one of the most miserable morinings of my degenerate adolescence!)

Essentially you read the signal into an analog input card. It shows up as data, for example 0 to 4095, that can be converted to 0 to 100% of stroke or inches of cylinder travel. Look at this post: http://www.plctalk.net/qanda/showthread.php?s=&threadid=3914&highlight=engineering+units

Then you can use comparisons (>, <, =, and so on) to determine if you are at the desired position.

You may have some problems with hay wrapping around cable pull transducers. Since you have a finite number of steps in the cylinder travel, and can live with less than exact positioning, you might consider a cylinder with proximity switches that pick up hte piston in the cylinder. You can use the proximity switch as discrete inputs to the PLC for indicating 18", 36" etc.

Just out of curiosity, why not go with the round bales that seem to have taken over?
 
I think I can answer that, ever tried to physically handle a round bale? It jes aint no fun. At least the square bales can be moved individually if needed.

Its quite amazing to see so many country folks on things like this.

Taking words from a Hank Williams Jr song COUNTRY FOLKS CAN SURVIVE.
 
To tell you guys the truth, it's all about the $$$$$$$$$. The high dollar hay market is in the small square bales because of the ease of handling. All of my product is for sale and along the front range of Colorado everyone thinks they are a cowgirl/cowboy. You cant be a cowboy on your 14 acres without a couple of horses. We do also have a large square baler (4'x4'x8') for the lesser quality product and the cow market.
 
If you have the $$ then I would suggest going with Temposonic probes for cylinder positioning. The Temposonic probe fits inside the cylinder and gives you a 4-20mA signal.
First class product.

Roger
 
Aren't you reinventing the wheel here? Here in the dairy capital of California they move alot of hay around all ready with equipment like this:
rrpic4.gif

This is called a Hay Squeeze and it picks up the units of bales by compressing the unit from the sides.
And the units of bales are put up in the fields using:
1309-14656.jpg

The only thing you're doing different is strapping the units together.
 
plc doctor, I already own a 1089 new holland stacker. My question for you is this: How do you suppose those bales get unloaded from that truck after they have been loaded with a squeeze? Do you have any clue what a squeeze costs? I do. Dont meen to be rude, but my family has been in the hay business for over 50 years and my grandfather was the first person to build a self-propelled bale stacker. I know about 99 percent of the equipment in the industry, and no I am not reinventing the wheel, I am building a tire for a sports car.
 
timbo4255 said:
Now I must figure a way to stop my cylinders in many different locations, not just in or out.
Don't know nuthin' bout no hay balers so I gotta ask - Why? What exactly is the reason for stopping at different positions?
 
Back to your original question. For the cyclinder positioning I would use something similar to what Roger suggested, which is a Temposonic (which has become kind generic to refer to a sensor technoloy called magneto-resrictive). The temposonic is manufactured by MTS. I personally prefer Balluff brand (have received better support from local distributor).

Check out this catalog link which will show you how the sensor is embeded in the hydraulic cylinder.

http://www.balluff.com/MicropulseCatalog2002/New_pdfs/Btl_z.pdf

Now to order that it is a multipart process. First choose the cylinder you want (Parker is a common one used on custom mobile hydraulics), let the distributor know that you want to install a Temposonic (or other brand) linear displacement sensor, most likely the distributor handles one of the better known brands and he can price you a complete assembly (cyclinder and position feedback). This is what I would do until you have a chance to see all the part numbers that are involved, it will cost a little more this way, but any mistake made in ordering will be your resposibility, so let the distributor handle the first few.

As for the PLC, what ever brand you are comfortable with and know your way around. In general you will find more people that are familiar with Allen-Bradley in the US, but I would not consider it hardened enough for mobile equipment duty. I have seen some nich manufacturers of PLC for mobile equipment and that may be a better choice.


Darren
 
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Just some thoughts....

timbo4255, If you only neen two or three stopping points for each cylinder, why not use ganged cylinders..ie, two cylinders joined at the ends opposite the rods...each pair will give you three different stopping points, using two 4-way valves...we use them for pattern forming on our palletizers...very repeatable and dummy resistant. As for a mobile PLC, A-D has a nice brick that runs on 12VDC...I haven't had a chance to use one, yet, but I want to soon. Fiesto and SMC make some sweet little 12VDC hyd manifolds...also some intergrated cylinder/valve/position feed-back units. You might also concider using a char-lynn hyd motor with an encoder/prox sw driving a chain with dogs on it...you can get some really fast speeds w/ a hyd motor, and if done right they can be very accurate .
Please keep us posted on your progress...as old hay farmer from NJ, I know what it is like putting 4,000 bales up in a hot hay mow!! I think that I would do almost anything to avoid doing that again...Hey, I guess I have...now I make concrete blocks and stack them!!!????????? :rolleyes:

David beerchug
 
If there is any way to configure your square bailer to give you a bail that is twice as long as it is wide it will stack in a nice square cube for strapping.

Just thinking out loud...

John
 
Thanks for the great info from everyone. I have already built almost the entire machine and I have purchased my cylinders, so it is a little late to make many design modification, or package configuration changes. The reason why I must stop my cylinders in many different spots is because I will have multiple straps spaced evenly accrossed my package. i.e.(move 18" then strap, move 18" then strap) I could only find one reasonable source for 8 foot long cylinders, and I have build a compound extension to get 16 feet of travel from my 8 foot cylinder. One must have 5 stopping positions plus full retract and full extend. The other must have 6 stopping positions plus full retract and full extend. My new question is this; how reliable would it be to have a couple of proximity switchs on each and use counters in my program? Thanks for the info.
 

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