Author Topic: pneumatic press questions  (Read 3333 times)

Offline Just Plain Fred

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pneumatic press questions
« on: September 04, 2013, 06:06:23 AM »
Hello all,
  I have recently found a source for farm milk, and have been making mozzarella .. I would like to now try some hard cheeses (cheddar) as well.The presses that i have looked at ...wooden contraptions, and some stainless steel types,are interesting but not what I'm looking for.  Being a "techie" and having a pretty good shop, thinking that i could do better... Question:(s)

 1. What would be a good diameter pneumatic cylinder to look for ? Don't know what ultimate pressure ( lbs) should end up at for hard cheese . My air compressor  will only put out about 125lbs psi.

 2. As far as the cylinders "stroke" I'm thinking about 12 inches would do...

 3. I have seen some "Home Builts" on this forum ..they seem to be all over the place varying in diameter and stroke length.

 4. So far I've  found some "Non repairable Stainless Steel " types and am looking at a 2" diameter Cylinder \ 12" stroke unit ( about $120USD's)

Any input would be appreciated   ...Thanks ... Regards Fred


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Offline Mike Richards

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Re: pneumatic press questions
« Reply #1 on: September 04, 2013, 09:59:10 AM »
I briefly looked into putting together a pneumatic press.  I stopped when our lab director said in his experience pneumatic cylinders (at least the lower price ones I was interested in) leak quite a bit (I don't know what experience he has, but I'm sure he's got more than me).  Because in pressing cheeses you need sustained pressure (6 hours is pretty common, 12, and even 24 are not uncommon), a leak in the cylinder, depending on the size, could lead to the compressor running frequently--not necessarily a problem, but possibly depending on your situation.

1. As for cylinder size, it depends on what you're looking to make.  I've seen pressure called for from 2 psi upto 40 psi, but it seems that around 6 psi works for most of the cheeses people make.  I think I'd figure out what size cheeses I was going to make, determine the maximum pressure for the cheeses I'm interested in and size accordingly.  If I were just winging it, I'd shoot for 10 psi on the biggest mold I plan on making.

2. A 12 inch stroke is pretty big for single cheese.  If you figure that from a hand pressed pile of curds to a solid cheese you lose about 1/2 the height (I'm not sure that's exactly right, but I think it's close to what I observe), a 12 inch stroke could be used to make a 12 inch tall cheese in a 24 inch tall mold.  If you plan on stacking and pressing multiple cheeses at once, a 12 inch stroke could let you, depending on your mold configuration, press a 4 or 5 cheeses that are each 1 1/2 - 2 inches thick.  Either way, that's a lot of cheese.

Hopefully, someone with experience with a pneumatic press will give you some insight...
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Offline jwalker

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Re: pneumatic press questions
« Reply #2 on: September 04, 2013, 10:43:45 AM »

 1. What would be a good diameter pneumatic cylinder to look for ? Don't know what ultimate pressure ( lbs) should end up at for hard cheese . My air compressor  will only put out about 125lbs psi.

 

Any input would be appreciated   ...Thanks ... Regards Fred

Just remember to calculate the area of the cylinder , 125 psi is way more than enough for most cheeses depending on cylinder size.

A 2 inch cylinder would have an area 3.14 inches , at 50 psi , that would be equivalent to pressing straight downward with a 157 lb weight.

A 4 inch cylinder would have an area of 12.56 in. , at 50 psi , that would be equivalent to pressing downward with a 628 lb weight.

When you double the diameter , you quadruple surface area and the total downward pressure.

So you would take the total down pressure , and divide it by the surface area of the cheese , 628 lbs , on a 6 in. cheese (28.27 sq. in.) would be 22.21 psi on the cheese . (628 divided by 28.27 = 22.21 psi.)

The bigger the cylinder , the less air pressure you would need to get a set pressure on the cheese , the larger cylinder would of course use more volume of air.

A stainless cylinder kept properly lubricated with a food grade oil  shouldn't have any leak problems , I would use a check valve in the delivery line as close to the cylinder as possible tho , and a regulator with as small a pressure differential as possible , they're usually about 5-10 lbs , at least the one I work with.

I would think 12 inch stroke would be plenty for the average guy.

All above values are approximate.
« Last Edit: September 04, 2013, 02:11:56 PM by jwalker »
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Offline FRANCOIS

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Re: pneumatic press questions
« Reply #3 on: September 04, 2013, 03:08:14 PM »
JWalker is right.  You need ot take into account the volume your compressor can produce. 

Offline Just Plain Fred

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Re: pneumatic press questions
« Reply #4 on: September 05, 2013, 06:27:06 PM »
Hello All,
 OK.... thanks for the input. I'm putting together the list of materials for this project, and have ordered the 2" pneumatic cylinder.. I have "firmed up" the design , and will start as soon as time permits . I will post a "pic" when finished ...Think that my design will take these "home presses" to a new level of adaptability.  Thanks again .... Regards Fred


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Offline Just Plain Fred

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Re: pneumatic press questions
« Reply #5 on: November 03, 2013, 01:00:19 PM »
Hello All,
  Well it's taken me awhile but i have finished my press ... I have reviewed what i consider the best features of the "presses" that have been posted, and incorporated them into my design... Here are of a few comments

 1. The tray ( food grade) is recessed and removable , with internal drain for hose attachment.

 2. This design lets the user choose and adjust for the height of any form ( hoop) combo.

 3. The machine threaded rods have been "Tapped " bottom and top ..so you could add any length rod to this ( for multiple form stacking)

 4. Can be easily disassembled for storage ... (Remove two lower threaded rod bolts)

 5. The setup does not leak ( much air... new parts)..( still testing as to the rate ) and am modifying an old fire extinguisher to run this rig . The ones i have can be filled to 140 PSI ( limit of regulator and valve) 

Can someone give a pressing schedule for Cheddar ( in PSI required...not dead weight ) so i can figure how much i need for my hoops\ forms square inches.

Thanks in advance ...Regards Fred

PS: trying to post pictures ...so far ..only one?...Help!.. Sorry about the "sideways pic" can someone please remove ..Ive tried with no results.
« Last Edit: November 03, 2013, 01:45:07 PM by Just Plain Fred »

Offline Mike Richards

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Re: pneumatic press questions
« Reply #6 on: November 03, 2013, 03:43:03 PM »
That's a nice looking press.  I'll be interested in hearing how it works out for you.  40 psi is what I have read for cheddar.  That's pretty high compared to other cheeses.
If only I could make cheese as well as I grow a mustache...

Offline Just Plain Fred

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Re: pneumatic press questions
« Reply #7 on: November 03, 2013, 04:17:37 PM »
Mike,
 Thanks ... Do you know if there is a specific schedule for cheddar? I have read that you start at some lower weight and after a time you progress to the final weight ... This is what i think is a problem ... Most recipes give some type of schedule for "dead weight" and don't say for what size mold to use ... Maybe this is because everyone knows what the size is for what type of cheese, and for how many gallons ...Me Ive no clue.. Thanks for the response... Regards Fred

PS: I'll post results as soon as i can "Firm up" (Cheddar joke) the recipe

Offline Mike Richards

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Re: pneumatic press questions
« Reply #8 on: November 03, 2013, 05:54:30 PM »
I don't know a schedule for PSI.  I'm not terribly good at following those schedules, any way.  I think you'd be fine, if you want to move up the pressure, to just press at some lower level for 15 minutes, flip and increase pressure for another 15, and keep it up until you get to the 40 psi.  Maybe someone else will give you something more concrete.
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Offline Digitalsmgital

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Re: pneumatic press questions
« Reply #9 on: November 03, 2013, 07:20:01 PM »
Those pictures = cheese porn

12 PSI 45 minutes

18 PSI  120 minutes

40 PSI 288 minutes
Regards, Dave


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Offline cowboycheese

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Re: pneumatic press questions
« Reply #10 on: November 03, 2013, 07:38:48 PM »
What material, if I might ask, did you use for the draining tray and followers? I haven't found the right stuff around here (yet) - it is all way to soft and pliable (standard HDPE cutting board stock).

Let us know how it test out and if you wouldn't mind sharing what your parts list was. The simplicity and expandability of your frame design is really cool and worth a cheese!

Offline Just Plain Fred

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Re: pneumatic press questions
« Reply #11 on: November 03, 2013, 07:58:48 PM »
"Cowboy"

 Hello... The Plastic (1" HDPE type cutting board type) was from TAP Plastics You can order and have whatever size you need ... I only at this point have my hand drawings and notes of the construction process .. If you want i will try to put together a parts list ( vendors) and clean up sketches that Ive made ... Maybe others would be interested ... Guess if you don't have access to machine tools ( Metal lathe, Welder, etc.) you could use my drawings and bring them to a local "fabricating metal shop " Have no idea what they would charge for such a project... took me several weeks ( hours that i could spare ) Thanks for your comments...Regards Fred

Offline Just Plain Fred

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Re: pneumatic press questions
« Reply #12 on: November 04, 2013, 08:36:38 AM »
Those pictures = cheese porn

12 PSI 45 minutes

18 PSI  120 minutes

40 PSI 288 minutes

"Digital"

  Hello.. Thanks for the reply and "Info" ... This is the confusion that i was trying to figure ...I'll try to explain my question ( Math not my strong point)

 1. In your example the PSI is for what size mold\follower? If i use a 4" diameter follower, this will translate into about 12.5 square inches ( follower area).. If i apply the first pressure 12PSI... Either you have to multiply this (12PSI) times 12.5 or an initial dead weight of 150#.. Or the other way ...divide the 12PSI by the square inches (12.5) of the 4" follower ..Or .96# So ...

 2. If you use the max PSI you give of 40# it's either 500#'s or 4#'s

 3. In my figuring you need to give the Dead weight for a given surface area ...and you would end up with a number for the actual PSI determined by the square inches of the follower... Hey what do i know?...can't even remember HS math class. To simplify... the pressure applied to a 4" mold ..can't be the same for a 8" mold

Any one have any thoughts about this?


Regards Fred
« Last Edit: November 04, 2013, 08:42:13 AM by Just Plain Fred »

Offline Sailor Con Queso

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Re: pneumatic press questions
« Reply #13 on: November 04, 2013, 09:14:47 AM »
Dead weight changes, but PSI is a standard that doesn't change from hoop to hoop. While you should use a different "weight" on a 4" or 8" hoop, the PSI remains constant.
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Offline jwalker

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Re: pneumatic press questions
« Reply #14 on: November 04, 2013, 09:21:30 AM »
First of all , let me say that's an impressive looking press.

Kudos and a cheese for that.

@120 PSI air pressure , a 2" diameter will exert just over 360 pound of force on your cheese.

A 4" cheese will have a surface area of about 12.5 inches.

So 360 pounds divided by 12.5 is just under 30 PSI exerted on a 4" cheese.

Remember , when you double the diameter , you quadruple the surface area , so an 8" cheese will only get 7.5 pound per square inch (PSI).

You're going to need some serious air pressure or a larger cylinder to get anywhere near 40 PSI on an 8" cheese.

You could use bottled nitrogen and quadruple the pressure to the cylinder , if it is rated for that kind of pressure.

It's always better to have a bigger cylinder than you think you will need though.
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