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About Corbin DC-LEAD Program

The DC-LEAD program can be installed on your hard disk under the DC-LEAD folder, or it can be run from the CD-ROM directly.

The purpose of the program is to calculate the length, weight and volume of lead wire that can be extruded, in your choice of diameters, from a given diameter of lead billet, of a given hardness. It also estimates the required drive pressure, given a certain diameter of hydraulic drive cylinder to power the extruder.

A second window, accessed by clicking "Cores", calculates the length of a given diameter lead core to achieve a given weight using a selected material density. It also calculates the compressed length and effective density of powdered metal cores of a given weight and diameter, and calculates effective density of a mixture of given volumes of different core materials, up to three materials.

A third window, in current versions, calculates the weight and number of balls per pound for any diameter ball made with any density of material, within its range. This covers all standard small arms calibers and some cannon sizes.

The program provides feedback about illogical or extreme (impractical) values that may be entered, and self-corrects back to a reasonable number. The screens can be printed on any Windows-compatible printer. Density is given in pounds per cubic inch, and displayed in grams per cubic centimeter as well.

The extruder functions are based on certain assumptions about the amount of friction and resistance caused by moving the lead through a certain diameter extrusion die. In a practical system, there are variations in resistance due to die design, smoothness, lubrication, and temperature. Therefore, the program provides an adjusment factor called "lubricant efficiency" which adjusts the amount of resistance assumed, and changes the pressure for a given hardness and diameter of wire extruded with a given size of cylinder from a certain length and diameter of billet.

The normal setting for lube efficiency is "10", but it can be set from 1 to 100 to bring the results in line with experience from a given machine. To predict extruder size and pressure with reasonable margin of safety, always use the lower efficiency settings until you know for certain that your extruder does, in fact, allow lower pressures.

A larger cylinder has three negatives:

  1. it is slower to fill with oil using a given size of pump, so the cycle time is longer unless you use a larger pump, which requires more horsepower (larger electric motor and more current to operate).

  2. it costs more than smaller cylinders.

  3. it requires strength in the frame and supporting structures because of the additional weight and thrust, sometimes dramatically greater thickness of tie rods and head plates, increasing the size, cost, and weight of the machine.

But other than that, there is no drawback to using more cylinder diameter than you need. It is far better to over build the extruder, than to under build it.

Practical extruder systems operate at maximum oil drive pressures of 2000 to 3000 psi since that is the design limit of the most commonly available hydraulic parts. Therefore, it may be necessary to adjust drive cylinder diameters upward to get the pump system and oil pressures down to a practical level. Oil pressure times ram speed translates into horsepower. With a given power limit, you can make up for a higher oil pressure with lower ram speed.

Note that pressure goes up with increased billet diameter (a billet is the original lead cylinder that you are going to extrude into wire). It also goes up with decreased wire size. Obviously if the wire and billet diameter are the same, there is no significant oil pressure required to extrude, so that the only force needed is gravity to drop the billet through the die hole. The calculations assume zero pressure when the billet and wire diameters are equal.

As the lead wire diameter is decreased, the drive pressure is increased. The ratio of billet size to wire size determines the necessary extrusion force, with all else is equal. A factor not taken into consideration is the self-heating effect. When lead is pushed through the extruder die, it will generate frictional heat, which lowers the resistance to extrusion, and the lead will move more easily. But since the system must start with a cold billet, the starting pressure is what we need to know. The hydraulic cylinder will continue to move at the same rate as it fills with oil at a given pump volume (in gallons per minute or cubic inches per second) regardless of the lead hardness or resistance, unless the resistance approaches the stall force for the system.

By operating well away from the stall limit (which is just below the minimum pressure needed to move the lead), using as large a cylinder as is practical and as high a pump pressure as components safely permit, the rate of lead extrusion will be relatively constant, and the diameter of the wire produced will be held to closer tolerances after the first few inches of wire have been extruded and the die has reached a stable temperature.

Powdered metals are usually poured into a core swage die or jacketed bullet "cup" (the jacket itself) and then compressed. The volume and effective density of the core will change with compression. The basic metal density itself will always be higher than the effective density, since small amounts of space exist between particles of the powder which are not present in the solid form of the metal (or other powder).

The program asks for the basic material density of the solid, and then asks for the diameter of the core and the amount of compression as a percentage of original "as poured" volume. When you pour a powder into a die or jacket, it "stacks up" in a long column. Then, a punch is used to compress this column into the jacket or die, shortening the column. The ratio of the original column to the compressed core length is this percentage. A core cannot be compressed 100% because that would mean it went from some measurable length to zero (a black hole?) and the means to do that are beyond the normal realm of bullet manufacturing.

A typical compression might be between 20 and 50 percent. The core weight remains the same as the original volume of powder, but the density is increased as the length is decreased. The program gives you these figures.

The combination of materials, whether they be powders or solids melted together, or simply put one after another into a die or jacket as solid bits, results in a net effective density which would be the same as a single material of some type. The program lets you calculate two or three different materials in various ratios from 0 to 100 percent each, of different densities, in order to show this effective density. Zero percent means that there is none of that material, so it is taken out of the equation completely. One hundred percent means no other materials are present. Anything between these two numbers gives a valid calculation of effective density for two or three materials in one core.

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