Hydraulic Press Questions

Tad Lynch

Tad Lynch

Joined
Nov 14, 2006
Messages
1,109
Guys, I am currently building my first press and have a couple of questions. I thought some of you might be kind enough to give me some advice.

1. I am planning on using a 4" x 8" cylinder with an 11 gpm pump. Is that a sufficient pump rate for a decent speed operation, or would you change either of those?

2. In setting the distance b/t the plates that the dies mount to, I thought I might leave enough of a gap so that at full stroke using ladder dies, for instance, the billet thickness is uniform. My question is: to maintain consistent thickness do you use a block/stop or do you have an adjustable stop on your valve, or something along those lines? How much gap b/t the plates at full stroke w/o dies?

I would really appreciate any input that you could give.

Thanks,
Tad Lynch
 
tdl said:
Guys, I am currently building my first press and have a couple of questions. I thought some of you might be kind enough to give me some advice.

1. I am planning on using a 4" x 8" cylinder with an 11 gpm pump. Is that a sufficient pump rate for a decent speed operation, or would you change either of those?

2. In setting the distance b/t the plates that the dies mount to, I thought I might leave enough of a gap so that at full stroke using ladder dies, for instance, the billet thickness is uniform. My question is: to maintain consistent thickness do you use a block/stop or do you have an adjustable stop on your valve, or something along those lines? How much gap b/t the plates at full stroke w/o dies?

I would really appreciate any input that you could give.

Thanks,
Tad Lynch
Click to expand...

With a 1750rpm motor, you should be moving a little over an inch per second. 1-3 inch/second is what many run presses at. Some say over 2"/second is too fast. Some would use a 5" x 8" with the same motor and pump (a two stage gear pump). The speed would be about 1"/second or a little less... certainly useable. A double acting cylinder, not single acting.

I'd have as much room as possible between the dies/die bases... a little less than 8" on an 8" throw cylinder... enough less so the rod doesn't bottom on the internal stop.

Here's a link to Don Fogg's hyd. press page: http://www.dfoggknives.com/hydralic.htm

Lots of links to lots of press pictures at the bottom. Jim Batson's book is good... can do all the calculations from it fairly easily. One of the neatest presses in the picture file is a little "C" frame with added yard-arm and threaded rods that makes the "C" an "H", and all of it sits on a steel table. Kirk Rexroat (MS, Wright, Wyoming) has a little "C" like this but without the rods. He kept the flex out by adding two more webs, one each side of the 6" to 7" H-beam... sits on a metal table... two people can load and unload it into/out of a pickup. Great quick change die system, too.

Mike

Edit: Should have added... some don't use two stage gear pumps. They use 5hp motors and 16 gpm pumps. It works and there are valid reasons for running this way... I just can't remember what they are.
 
I built my press and if I had to do it again I would go with a minimum of a 5" cylinder and a H frame configuration. I have a parts listing from when I built mine. Let me know if you want it???:D I also have some pic's on my website in the building of Bertha.
 
Mike Krall said:
Edit: Should have added... some don't use two stage gear pumps. They use 5hp motors and 16 gpm pumps. It works and there are valid reasons for running this way... I just can't remember what they are.
Click to expand...

The biggest reason I see for using a single stage pump is for timing. If you want to set up an electronic switch to cycle the ram every one second or so, you will end up with the ability to draw out billets quite efficiently. With a two stage pump you cannot get the timing right to do this since the ram speed changes once it switches from one stage to another.

Here is what I am leaning towards in my press design.

Cylinder - 5"
PSI - 2500
Tons - 24.54
Single Stage GPM - 4.8
Ram Speed - .94 inches per second
Horsepower - ~7.5

With this configuration, I will be able to use an electronic foot pedal setup. If the timing switch is turned on I will be able to adjust the amount of time it takes to cycle the ram up and down automatically. If the timing switch is turned off I will be able to manually control upwards or downwards movement of the ram with the foot pedal as well.

All my calculations are from Jim Batson's book. Get this book if you are building a press. You will be able to calculate exactly what you need to meet your expectations.

Eric
 
Eric,

Is that with a 1750rpm motor? Like 4.8gpm x 2 = 9.6gpm... being an 11gpm pump at "efficiency loss"?

What single stage pumps are good ones? Do you know good places to get them?

There was something other than the switching reason some are using higher hp and gpm with single stage pumps... with the same cylinder they are faster but there was another reason or two and I'm just not remembering.

Mike
 
Mike Krall said:
Eric,

Is that with a 1750rpm motor? Like 4.8gpm x 2 = 9.6gpm... being an 11gpm pump at "efficiency loss"?

What single stage pumps are good ones? Do you know good places to get them?
Click to expand...

Hello Mike,

The pump I am looking at is a .40 cu in PARKER HYD PUMP

3.19 GPM @ 1725 RRM
6.38 GPM @ 3450 RPM

RPMs control GPM. I plan on using variable speed to achieve a variable GPM depending on what I want to do. You can find these at surpluscenter.com

Eric
 
Surplus Center is a good source for this stuff. They can help you engineer the particulars too. Tell them what you want to accomplish and they can give you specific advice. That's one way to go.
I'd recommend a 5.5 inch cylinder moving about 1-inch/second. Single-stage pump, for sure.
I use a simple electric circuit with one limit switch and a time-delay relay with a double-acting solenoid valve (instead of the log-splitter valve many use) to control the range in which the ram reciprocates. Works like a champ.

Here are some pics from my OLD, OLD site, if your interested.

http://www.caswellstudios.com/SwordPages/BodyPages/tools/Hydpress1.html
 
JCaswell said:
Surplus Center is a good source for this stuff. They can help you engineer the particulars too. Tell them what you want to accomplish and they can give you specific advice. That's one way to go.
I'd recommend a 5.5 inch cylinder moving about 1-inch/second. Single-stage pump, for sure.
I use a simple electric circuit with one limit switch and a time-delay relay with a double-acting solenoid valve (instead of the log-splitter valve many use) to control the range in which the ram reciprocates. Works like a champ.

Here are some pics from my OLD, OLD site, if your interested.

http://www.caswellstudios.com/SwordPages/BodyPages/tools/Hydpress1.html
Click to expand...

That is a great idea that I have not seen before. Thanks, everyone, for the info.

Tad Lynch
 
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