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I purchased a hydraulic cold press

5/10/16       
Walter Member

Website: http://www.oodworking.com

I have always used a Wetzler screw frame press for veneer work, 25 screws over a 4' by 8', preferring it over a vacuum system for its superior developed pressure and flatness. But was intrigued when I saw an older hydraulic cold press at auction, picked it up, and sold my old screw press. Now I am having bad misgivings because of the following message sent by a helpful fellow at Italpresse, the mfg.:

"Based on 45 mm diameter rams, you have a total ram area of 9.855 square
inches. Given the range of the gauge, I will speculate that the relief is
set at 120 kg/cm2.

1 kg/cm2 = 14.2 psi hydraulic pressure
Ram area x hydraulic pressure = thrust
9.855 in2 x 120 kg/cm2 x 14.2 = 16,793 lbs of thrust = 7.6 metric tons

Thrust divided by the square inches of panel you are pressing = laminating
pressure

For instance: two panels 24" x 30" = 1440 in2

16,793 lbs / 1440 in2 = 11.66 psi laminating pressure (not much pressure,
but better than a stack of bricks)

This is an extremely light duty - low tonnage press by today's standards."

Can anyone verify those figures, or comment on this press? It is 39" by 87", four hydraulic rams 45 mm in diameter. Previous owner used it for veneering, but said the cutoff is 70kg/ square cm, not the 120 used in the example, making my pressure even less... If it is so light, why the heck does it exist? What could it have been used for? I fear I have learned a lesson the hard way, but have not powered it up yet or tried a sample press run.


View higher quality, full size image (2016 X 1512)


View higher quality, full size image (2016 X 1512)


View higher quality, full size image (2016 X 1512)

5/11/16       #2: I purchased a hydraulic cold press ...
Johann Huck  Member

Website: http://www.themachinewarehouse.com

Walter,

I can verify that the information for you is correct. Based upon the part sizes you gave at ~120 kg/cm2 hydraulic pressure and those rams. You would be looking at about 12 PSI specific pressure on your panels. If you were to fill up the entire press with one big panel, your specific pressure would be 5 PSI specific pressure on your panels.

This can do veneer and it really depends upon the glue you use. This is a older press and they now make them bigger to handle more pressure. But I am sure it was purchased mainly because of price when it was new.

Johann Huck
The Machine Warehouse, LLC.
704-839-6615
johann@themachinewarehouse.com

5/12/16       #3: I purchased a hydraulic cold press ...
Walter Member

Johann,
Thank you for the information! Regarding glue, what would be a suitable glue for a lower pressure setup? I am used to using urea resin glue for veneering, but was also recommended the Titebond Cold Press glue by the previous owner.
Thanks.

5/12/16       #4: I purchased a hydraulic cold press ...
Johann Huck  Member

Website: http://www.themachinewarehouse.com

Walter,

You can use that or almost any cold press glue for veneer. If you really want to make sure you have the right glue. Speak with a glue company to figure out your product and process.

Once company I have had good luck with is:
CP Adhesives

Cp Adhesives

5/12/16       #5: I purchased a hydraulic cold press ...
GRW

12psi works out to 1,728 pounds per square foot. My vac bag is about the same (I think) and I have crushed forms and bent parts that were not supported enough.

There is a point of diminishing returns.

5/12/16       #6: I purchased a hydraulic cold press ...
Walter Member

It turns out that the above calculation applies only to presses which close upwards. Mine being the type in which the cylinders are above the top platen, they are the double-acting type, which has a larger piston above the ram. If I could disassemble to find out its diameter, the larger piston is the value used to calculate thrust. So I have a higher but unknown value, and need to start doing test pressings.

My understanding is that hydraulic presses typically run at around 60 psi. Can anyone confirm? For flat panel work, I think the more the merrier to compensate for less than perfectly flat substrates and veneers. A vacuum system is great for form work, but I have always wanted a little more pressure, which I am pretty sure I got with the massive Wetzler screw frames.

5/12/16       #7: I purchased a hydraulic cold press ...
Johann Huck  Member

Website: http://www.themachinewarehouse.com

Walter,

You cannot go by the size of the ram up in the cylinder. You have to base all your calculations upon the diameter as it touches the platen. The pressure then goes at 45 Deg from the point of contact out on the platen. This usually determines the spacing of the cylinders. Granted you will get a little bit more pressure, but it is minimal the amount of the difference because your rams contacting the platen are only 45mm.

You also have to remember this is a press from the 60's, things were different back then. I would not worry about the pressure, but more on the flatness of the platen and making sure you have even contact on your panels. You will then have enough pressure to get a great bond.

Johann Huck
The Machine Warehouse, LLC.
704-839-6615
johann@themachinewarehouse.com

5/13/16       #8: I purchased a hydraulic cold press ...
John Costin

Walter, I think your mistrust of vacuum veneering is misplaced. We run a Joos hydraulic hot press (best in class), but its chief advantage over vacuum is throughput due to the heated platens. Pressure is maybe 150% of what you get in a vacuum system. For many years we ran our specialty veneer shop with two large vacuum tables. We pressed many thousands of square feet every year, and I don't think we ever had an issue around flatness or sufficient pressure. In fact, the pressure will be much more consistent in a vacuum system than in a screw press.

If you're seeking really flat panels, go with a fliptop system from Vacuum Pressing Systems. If you build a flat, rigid and sturdy table you can crank out flat panels, but they will only be as good as your table. If you were able to set your screw press up for flat work you're up to doing it with vacuum. I can send you some tips on building the table if you'd like.

Maybe the Italpresse you have would be good for holding things flat, like treated burls and crotches or pressed panels that are waiting for final cure.

Best of luck,

John Costin
Veneer Services Unlimited
vsu@gwi.net
(207)985-7221
Custom Veneered Products for the Woodworking Industry


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