Drop Forging Questions

[44-henry]

Hello, I am new to this forum and figured that this might be the place to ask this question. I teach several manufacturing process classes at the University of North Dakota and am interested in adding a forging activity in one of my classes. We have a fully equipped machine shop and foundry, but our program has not done any blacksmithing in many years and I would like to bring this back in the form of a drop forging activity. I would like to make the process as safe as possible and space is also an issue, so would a 20 ton H-Frame hydraulic press and a suitable forming die be appropriate to demonstrate this method? We wouldn't be working with anything very large or complex, but It would be nice to demonstrate the process using some small parts. Any ideas would be greatly appreciated.

Regards,

Alex Johnson
Department of Technology
University of North Dakota

[ptree]

Alex Johnson, Perhaps you are a little confused. In Drop Forging a drop forge hammer is used. These are varied in construction, but function by raising a ram with a die on it and then either allowing free fall drop to meet the bottom die or a powered drop. The powered drop hammers can be steam, air, or hydraulic. All use the kinetic energy of the mass moving to impart the forging energy. This is a short impluse energy transfer.
What you are describing is a press forging operation. This is a long impluse energy transfer, that maintains almost even forge thru the stroke travel.

In the early days, the only way to get the high energy to make big forgings was the drop forge. Mechanical means could be used to raise a quite large weight, whereas then there was little means to seal a hydraulic means.
John Nysmyth(SP) is credited with inventing the large steam drop hammer, and it was originally used to make propellor shafts for British naval war ships.

In america, the steam drop hammer, the rope drop hammer, Board drop and the air drop hammers were the dominat forge processes in industry until about the 1920 or 30s with mechanical forge presses then becoming more practical. Mechanical Upsetters were similar in timing.

For some photo's, search Erie drop forge hammers, National Machinery forge presses and upsetters, and lastly Erie hydraulic forge presses.

Now to demonstrating safely. A 20 ton press, especially if hand pumped will not be effective. If powered, one must consider the possibility of leaks. A pinhole hose leak that gets to the forging will make a flame thrower.

To demonstrate drop forging, a simple weight of a 50 pounds, supported from a pully, running in a simple guide sytem would make a nice demonstration rig. Remember that the bottom die must be on an anvil that is at least 10 times the weight. Again a fairly simple and safe demo. One could even throw some variables like changing height and weight to really make mass times velocity a visual process.
Often in drop forging, a multi-impression die was used to progressively form the work piece. I think though for this process, I would be tempted to make one die flat, and the other a disc impression that might have a simple logo, say of the school. Put a nice 2250F slug of steel on the lower die, and drop. Bingo, keepsake paper weight. The bottom die could have a simple, very shallow relief to locate the vertical round billet. To get maximum work, a lubricant will be needed. Industrial water based forge lube would be best, as less smoke. I may have a commercial source that would donate a sample.
Send me a private message if you need more.

Ptree, who has worked in large commercial drop, press, and upsetter forge shops.

[ptree]

Alex, I forgot to mention that the impressions need to have draft to allow the forged part to be removed. In drop forge dies the industry standard is 7 degrees. Use a tapered cutter if milling. You could roll EDM process into the training, as this is the prime method to sink dies now.

[Mills]

Here is drop forging and hydraulic forging as well as open die.

Most of us here do open die.

to lend a visual to what ptree said.

Drop forging YouTube - Drop Forging with Beche KGH 8.0 B

Hydraulic forging YouTube - Forging

Open die forging YouTube - open die forging at AMP FORGING

Edited June 21, 2009 by Mills

[44-henry]

Thanks for the info, I knew the process used a weighted hammer but I was hoping that similar results could be obtained by using a hydraulic press. It is an interesting idea making a drop hammer and one that I might try in the future. Are there any links showing construction of one of these in a home shop setting, it would be interesting to see the results that could be obtained with one. Thanks for all the info and the videos are really good.

Regards,

Alex Johnson

[ptree]

Alex, Simple drop hammers using a rope pulled by hand were usually shop made. There are indeed "rope drop" hammers made by factories, but are usually much larger than you intend. I have even seen the remains of a rope drop hammer that used a mule for lifting the weight, pulling the hammer up till it latched, then the mule walked backwards to the strat point. Took a well trained mule:)

Don't know of any construction plans, but a tech school should be able to knock out a design I should think. I personally would make the thing stone simple. Use a greased V guide on each side, say nice heavy angle iron, and a mating angle on the ram. Fair clearance. Have a cross head to join the top of the angles to hang the rope pulley from.

For a 50# ram, I should think a decent drop would be 5 foot.

The Erie hammers I knew, have multi V guides, lots of grease and a little sloppy.
The smallest drop hammer I have been around was a 1500# Erie steam drop.
I have built a mechanical open die hammer of 45#. It has a 9" stroke, but then it is powered in the down stroke by a loaded leaf spring.

[ptree]

Alex, another thought, that would demo forging, but small sacle would be a flypress. A small flypress is inexpensive probably less than a $1000 delivered and mounted, and a simple coin type die could be made, and the flow of the plastic steel would be shown.
Search "Flypress" or look at Blacksmith suppliers.
These are nifty little presses, using multistart (often 3 lead) screws to translate a rotational energy to a linear force.

[ThomasPowers]

coining was what came to my mind too. The flypress also has the fast pressure spike as the ram bottoms out and reverses that helps "squiret" the metal into the hollows of the die.

Most hydraulics have a slow steady pressure ramp that doesn't act the same.

[Charlotte]

As an observer may I say the for instructional purposes i would lean toward a fly press although I don't own one. There are any number of operations that can be done with flypress of even modest size. In terms of absolute versility I believe that flypress are unnmatched. Coupled with a milling machine and a lathe they can fab repeatedly a wide variety of small items. They are capable of working with hot or cold materials and, lacking electric or pneumatic power, they are inherently easier to provide safety instruction for. This is of course just my sideline observation.