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Machine and Alloy Data

Overview

This worksheet contains the common data on Machines and Alloys which is used throughout the modules.

DC-CALC comes with a small selection of Die Casting Machine data sets already entered in this worksheet. The main reason is to give you a starting point.

However, before you will be able to use DC-CALC effectively, you will need to collect and enter the data about the specific Die casting machines in your plant.

Index and Quick Links to Help Topics on this page

Data Collection Machine Lock-Up Data Alloy Data
Machine Data Maximum Lock-Up Alloy Code
Symbol
Machine Code No. of Tiebars Alloy Description
Description Diam. of Tiebars Liquid Density
Hot or Cold Chamber Tiebar Length (ave) Solid Density
Plunger Diameter Horizontal Tiebar Distance Minimum Flow Temperature
Shot Cylinder Diameter Vertical Tiebar Distance Solids Factor
Protruding Shaft Diameter Pressure Peak Coefficient J Factor
Accumulator Pressure Die Venting Data Specific Heat
Max. Plunger Speed Shot Channel Volume, Hot Ch. Latent Heat
Intensification Ratio Shot Sleeve Length, Cold Ch.  
  Machine Costing Data Alloy Cost Data
  Cost Rate Cost

Data Collection

You will need to refer to the machine manufacturer's manuals to collect some of this data and some will need to be measured on the machines directly. Instrumentation to measure plunger speed and hydraulic pressure during a shot at a high sampling frequency is the most accurate, but even if you do not have access to such equipment, reasonable estimates can be made.


Machine Data

Feasibility

The following data is required for you to be able to use the 'Feasibility' worksheet of DC-CALC

Machine Code

Enter any coding system you like to identify each machine in your plant. It may be a simple sequence of numbers, 1,2,3.. and so on, or you may want to use the factory asset number, workcell number or abbreviated name.

Description

Enter a description of this machine that will be meaningful to people in your plant.

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Hot or Cold Chamber

Enter the full word 'Hot' or 'Cold', so that DC-CALC knows how to treat data cells which refer to each process.

Plunger Diameter

The diameter of the metal injection plunger.

If you use different plunger sizes on the same Die Casting machine, you need to create a separate Machine Code for each. For example, if you have an 80 ton machine with plunger diameters of 50, 55, and 60 millimeters, you could create machine codes such as :-

Shot Cylinder Diameter

The hydraulic shot cylinder on a Die Casting machine is usually one of two types :-

Single Shaft

In this case a single shaft connects the hydraulic piston to the plunger.

The full diameter of the hydraulic cylinder is exposed to hydraulic pressure.

Cylinder with single shaft.

Protruding Shaft

In this case, a second shaft is attached to the hydraulic piston and it protrudes through the top of the cylinder cap.

The area of the piston for pressure calculations must be reduced by the area of the protruding shaft.

Cylinder with protruding shaft

In both cases, the 'Shot Cylinder Diameter' (D) is the diameter of the hydraulic piston.

Protruding Shaft Diameter

If applicable, this is the diameter of the protruding shaft, as described above.

If it does not have a protruding shaft, the value should be 0.

Note:To enter this information into the Data worksheet of DC-CALC you will need to refer to the machine manufacturer's manual to get these two diameters Dand d. This data is needed for DC-CALC to arrive at the pressure on the metal, knowing the hydraulic line pressure. If D and d are not provided, an equivalent can be calculated using the technique described below.

Accumulator Pressure

This refers to the hydraulic line pressure (Ph) in the shot end accumulator.

Note: The three variables above, (D, d and Ph), are used by DC-CALC to calculate the maximum and transient metal metal pressures in the process. If D and d are not known, an equivalent value can be calculated if the machine manufacturer provides you with the values of static metal pressure, as related to plunger diameter and hydraulic line pressure.

Use the equation :

Dh=SQRT((Pm x Dp x Dp)/Ph)

Where:

In this case, d can be set to zero, even if a protruding shaft actually exists, because Dh is only a calculated equivalent diameter.

Max. Plunger Speed

This is the maximum achievable plunger speed.

Machine manufacturers often provide this data, but it can be measured in two alternative ways and it is important to be aware of the difference.

One way is the 'dry shot speed', achieved when there is no plunger in the machine.

The other way, is with a plunger installed, and it is measured as the metal is being pumped through a given nozzle bore. The speed achieved in this instance will be less than the 'dry shot speed', because of the friction of the plunger rings and the resistance of the metal flow through the gooseneck and nozzle.

It is preferable that all the machines in your plant are measured using the same method. If so, the Discharge Coefficient in the Feasibility worksheet can all be set to the same initial value. Where 'dry shot speed' is used, the Discharge Coefficient will probably be about 0.55, and where the plunger speed is measured through a nozzle, the Discharge Coefficient may be about 0.70. The point to be aware of is that the Discharge Coefficient is the measure of the total metal feed system including the path through the die, so it is not strictly correct to relate it only to the machine.

Measurement :

The best way to establish both the Maximum plunger speed and the Discharge Coefficient is to measure them accurately with high speed instruments.

If this is not possible, you can make an estimate, and even that will enable DC-CALC to establish reasonable results. This is because most dies fitted into real life Die Casting machines are actually operating at shot-end speeds and powers far less than they are able to achieve.

Making an estimate:

Even very low specification machines can usually achieve a plunger speed of 2 meters per second.

Some over-powered machines will achieve a 'dry shot speed' of 5 meters per second.

Air powered machines would probably be at the higher end of the speed range.

P-Q Squared Diagrams :

Some Die Casting machine manufacturers provide a P-Q2 Diagram, and some even provide the data for both methods of measuring plunger speed. You can use this data to calculate the maximum plunger speed as follows : -

Read off the maximum metal flow rate of the machine in litres per second (Q) with the given plunger diameter (Dp). Then use the equation below to derrive plunger speed : -

Sp=(4 x Q) / (PI x Dp x Dp)

Where: -

Intensification Ratio

If the machine has a third 'Intensification' phase which puts a higher pressure on the plunger after cavity fill, it is specified in DC-CALC as the ratio of the intensification pressure to the normal maximum pressure.

An example : - If the maximum hydraulic pressure during intensification is 15 MPa and the normal accumulator pressure is 10MPa, the the ratio would be 1.5 to 1.

This ends the data entry required to use the Feasibility worksheet.


Machine Lock-Up Data

If you wish to use DC-CALC to calculate Tiebar loadings for off-centre dies, you need to collect and enter the following data.

Maximum Lock-Up

Enter into this cell the maximum clamping force of the machine , in tonnes.

A 'tonne' is a metric ton, equal to 1000 Kilograms, however, within the accuracy required here, it can be considered to be the same as a non-metric 'ton' (2240 pounds).

No. of Tiebars

Most machines have 4 Tiebars, but this field is to allow DC-CALC to be used for those machines that have only 2.

Diam. of Tiebars

Enter here the diameter of the Tiebars.

Tiebar Length (ave)

This data is used to calculate the amount of Tiebar stretch required to achieve the Lock-Up force. It may be available from the manufacturer's drawings.

If not you will have to measure it. Run a tape measure along the Tiebar and measure from the back of thr front fixed die platen to the back of the rear machine platen. Of course die height adjustment will cause this length to vary so make an estimate of the average length.

Horizontal Tiebar Distance

This is the distance between the centers of the left and right Tiebars.

This is not the same as the 'Distance Between Tiebars' which appears in most Die Casting machine manuals. This specifies the largest dieblock which can be fitted to the machine. However, if you add the 'Tiebar Diameter' to the 'Distance Between Tiebars', you will come up with the required data. The sketch below shows the relationships.

Tiebar dimensions

Vertical Tiebar Distance

Same as above, except applied to the upper and lower Tiebars.

Pressure Peak Coefficient

This data is not mandatory, but will lead to a more accurate determination of die Lock-Up requirements.

As the plunger comes quickly to a halt at the point of cavity fill, a pressure peak (spike) will be generated in the molten metal. This is due to the rapid deceleration of the total mass of :-

This pressure peak is responsible for the flashing of dies. The machine Lock-Up must be great enough to overcome the die-opening force due to the static metal pressure plus this pressure peak.

The 'Pressure Peak Coefficient' is used by DC-CALC to predict if the Lock-Up force is sufficient to prevent die flashing.

Using accurate machine instrumentation, look at the output traces for metal pressure, and carefully examine the pressure peak at the point of cavity fill.

The pressure peak is created by the conversion of kinetic energy into pressure energy. The equation for kinetic energy is

KE = 1/2 x M x V2, where M is the Mass and V2 is the square of the velocity.

Therefore, you would expect that the pressure peak would be proportional to the square of the plunger velocity. This was the generally accepted view of the die casting fraternity up until 2001. In that year a paper presented at the Congress of the North American Die Casting Association showed that it was not quite that simple. (See Reference 9, in this Manual). Due to tie bar stretch and the movement of flash between the die faces, there was an off-setting cushioning effect, and it turns out that the pressure peak is more closely proportional to the velocity of the plunger, not the square of the velocity.

This new finding has been incorporated into DC-CALC commencing in Version 2.9, Issued 3rd of February 2003. Therefore, this version of the Manual, describes how to enter the data for both new and older versions.

Version 2.9 and later

The equation for the pressure peak is :

Pp=K x Sc

Where:

Take a number of shots on the machine at different plunger speeds and record the pressure peak. Measure the pressure peak as the increase in pressure over and above the static pressure at the end of cavity fill.

Now plot a graph of this pressure peak increase versus the plunger speed. The gradient of the graph will be the 'Pressure Peak Coefficient'.

In the metric system its units of measure will be MPa.Sec. per metre. So if we multiply the Coefficient by the plunger Speed, we end up with a value in MegaPascals, which is the increase in pressure over and above the static pressure.

In the Non-metric system, its units of measure will be psi.sec. per inch. So if we multiply the Coefficient by the plunger Speed, we end up with a value in inches per second, which is the increase in pressure over and above the static pressure.

If you do not have the ability, or time, to measure this coefficient, just set it to zero. That way DC-CALC will use just the static metal pressure to calculate die opening force.


Version 2.8 and earlier

The equation for the pressure peak is :

Pp=K x Sc x Sc

Where:

The pressure peak rises with the square of the plunger speed.

Now take a number of shots on the machine at different plunger speeds and record the pressure peak. Measure the pressure peak as the increase in pressure over and above the static pressure at the end of cavity fill.

Now plot a graph of this pressure peak increase versus the square of the plunger speed. The gradient of the graph will be the 'Pressure Peak Coefficient'.

In the metric system its units of measure will be MPa.Sec2. per metre2. So if we multiply the Coefficient by the Square of the plunger Speed, we end up with a value in MegaPascals, which is the increase in pressure over and above the static pressure.

In the Non-metric system, its units of measure will be psi.sec2. per square inch. So if we multiply the Coefficient by the Square of the plunger Speed, we end up with a value in inches per second, which is the increase in pressure over and above the static pressure.

If you do not have the ability, or time, to measure this coefficient, just set it to zero. That way DC-CALC will use just the static metal pressure to calculate die opening force.


Die Venting Data

If you intend to use the die venting module in DC-CALC then you need to collect this data.

Shot Channel Volume (Hot Ch.)

This is only required for Hot Chamber Machines.

It is the total volume of air in the shot end system that must ultimately be expelled through the air vents in the die.

It consists of two main components.

1. The air in the gooseneck riser, above the metal level.

This can be calculated using:-

Vg=(PI x Dg x Dg x Lg)/4

Where:

You will need a drawing of the gooseneck to obtain the diameter of the riser channel, and its length. You will have to estimate where the average metal level reaches to obtain a value for the length above it.

Some gooseneck risers have a series of stepped diameters, decreasing towards the nozzle. Use the same techniques and equation for each diameter, and add together to get the total volume.

2. The air volume in the nozzle.

The same equation and technique as above using the drawing of the nozzle (and adaptor if applicable).

Shot Sleeve length (Cold Ch.)

This is only required for cold chamber machines.

It is the total length of the shot sleeve, from the die to the plunger in its fully retracted position.


Machine Costing Data

Cost Rate

If you intend to use the Product Costing module in DC-CALC then enter the total cost rate for this machine, as a rate per hour.

The cell is non-currency specific, and you have two decimal places available.


Alloy Data

This data is mandatory because it is used in the feasibility module of DC-CALC. However, values for the three common Die Cast Alloy groups, aluminum, zinc and magnesium, are already created in the table.

If you wish, you can add specific Alloy Codes of your own, one for each actual alloy used in your plant. This will enable the Alloy Description to appear in the Feasibility worksheet and form part of the quality documentation for the die design. You can simply copy the existing data into the corresponding new alloy codes.

If you have detailed informationon each alloy, with differences in any of the specifications, enter it in the appropriate cell. The definitions are provided below.

Alloy Code

Choose any appropriate coding system for the alloys used in your plant.

Symbol

Here you add the chemical symbol for the predominant metal element in the alloy being either:

Zn - for Zinc

Al - for Aluminium

Mg - for magnesium

DC-CALC uses this to calculate or allocate certain parameters in the worksheets. ( An example is the High and Low Die Temperatures in the Feasibility worksheet.)

Alloy Description

Enter a description that will be meaningful to people in your plant.

Liquid Density

The density of the alloy in its liquid form.

In the metric system, to convert from grams per cubic centimeter (g/cc) to kilograms per cubic meter (Kg/m3) multiply by 1000.

In the Non-metric system, use pounds per cubic inch.

Solid Density

The density of the alloy in its normal solid form, as you would expect to find it in a casting, in kilograms per cubic meter. Conversion factor is as described above.

Minimum Flow Temperature

Solids Factor

J Factor

The three parameters above, are used in the gating equation to determine the percentage of solids in the casting during cavity fill. It will be sufficiently accurate if you just copy the standard values for each main alloy type to the specific alloy code you want to create.

For detailed information as to their definition, refer to the following publications:

"Gating Die Casting Dies", by E.A. Herman, published by NADCA, No. E514

"Die Casting Process Engineering and Control", by E.A. Herman, published by NADCA

Specific Heat

The heat content of the alloy due to changing temperature.

Latent Heat

The heat content of the alloy due to changing state from liquid to solid.

Cost

If you wish to use the product costing module in DC-CALC, enter the cost of the alloy, including any purchasing oncosts, delivery charges and other related costs.

The cell is non-currency specific, and you have two decimal places available.

The units are Kilograms for the metric version and pounds in the Non-metric version.

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