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Die Casting News

NADCA, "Take a Detailed Dive into the Various Methods of Diecasting Process Control"

Posted by Dr. Morris Murphy on Apr 17, 2019 12:10:10 PM

It is important to know what type of control method is applicable to each of the die casting machine/die/process systems.

North American Diecasting Association (NADCA) has created a three level approach to addressing process control. This series is broken down by beginner, intermediate and advanced courses suitable for people with varying levels of knowledge in this area. Learn more at this NADCA page.

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Tags: Die Casting, Die Casting Lubricant, Die Casting Process, Die Casting Process Control Theory, NADCA Education

NADCA Video Highlight - Why Diecasting Plunger Shot Monitors are Important

Posted by Hill and Griffith Company on Apr 10, 2019 4:40:58 PM

The material presented in this video are some highlights from NADCA’s online webinar - Basic Diecasting Machine Operator Training: Why Shot Monitors are Important

Many die casting process variables affect the final porosity level in a casting. This course will discuss the effect of these different parameters on porosity. It will connect these processing parameters back to the underlying porosity formation mechanisms covered in the first porosity course. Start solving porosity by optimizing your process parameters for reduced porosity. For information on purchasing a downloadable copy of this webinar in its entirety, please visit: http://www.diecasting.org/store/detai...

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Tags: Die Casting, Die Casting Lubricant, Tim Cowell, Die Casting Porosity, Die Casting Gas Porosity, NADCA Video Highlight

NADCA Video Highlight - Control Diecasting Porosity with Processing Parameters

Posted by Hill and Griffith Company on Apr 3, 2019 5:07:54 PM

The material presented in this video are some highlights from NADCA’s online webinar - Porosity Basics: Control Porosity with Processing Parameters

Many die casting process variables affect the final porosity level in a casting. This course will discuss the effect of these different parameters on porosity. It will connect these processing parameters back to the underlying porosity formation mechanisms covered in the first porosity course. Start solving porosity by optimizing your process parameters for reduced porosity. For information on purchasing a downloadable copy of this webinar in its entirety, please visit: http://www.diecasting.org/store/detai...

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Tags: Die Casting, Die Casting Lubricant, Tim Cowell, Die Casting Porosity, Die Casting Gas Porosity, NADCA Video Highlight

NADCA Video Highlight - Basic Diecasting Operator Training

Posted by Hill and Griffith Company on Mar 27, 2019 9:52:04 PM

The material presented in this video are some highlights from NADCA’s online webinar - Basic Operator Training: Recognizing and Controlling Flow Defects.

The operator will learn how to recognize flow (surface) defects and what causes these types of defects. This course will address various operating parameters that impact flow defects, such as die temperature, die spray, cooling line flow rate, fill time and metal temperature. The operator will also learn corrective measures that can be taken to reduce and control flow defects, including preferred operating ranges for the various parameters.

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Tags: Die Casting, Die Casting Lubricant, Tim Cowell, Die Casting Porosity, Die Casting Gas Porosity, NADCA Video Highlight

Part 4/4 - Die Casting Porosity Causes and Solutions

Posted by Hill and Griffith Company on Mar 20, 2019 6:00:52 PM

By Tim Cowell, Hill and Griffith Company, Technical Director

Shrink Porosity (Temperature)

Note that the temperatures that effect the location of shrink die casting porosity are inside the casting itself. The die temperatures will influence the internal casting temperature, but they are not always effective in controlling it completely. Shrink porosity in a heavy section will be harder to move, shrink porosity in a thin section will be relatively easy to move. Complex shapes may respond different than you think.

Since the location of shrink porosity is also the hottest spot in that section of the casting, it is usually in the center of a heavy section. This hot spot location can be controlled to some extent by die temperature. The hot spot can often be moved by changing the die temperature - but this doesn’t reduce the porosity much - it just moves it.

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Tags: Die Casting, Die Casting Lubricant, Tim Cowell, Die Casting Porosity, Die Casting Gas Porosity

Part 3/4 - Die Casting Porosity Causes and Solutions

Posted by Hill and Griffith Company on Mar 13, 2019 4:40:27 PM

By Tim Cowell, Hill and Griffith Company, Technical Director

Gas Porosity (Lubricant)

The lubricant used on the dies or on the plunger can generate gas when heated by the incoming metal. This gas (like the steam) is only formed when the metal arrives, and so it is not possible to force most of the gas out the vents ahead of the metal flow - it will mostly be captured in the part as porosity. All lubricants give off some gas when heated to the temperature of the molten metal - the amount and type of gas will vary from lubricant to lubricant.

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Tags: Die Casting, Die Casting Lubricant, Tim Cowell, Die Casting Porosity

Part 2/4 - Die Casting Porosity Causes and Solutions

Posted by Hill and Griffith Company on Mar 7, 2019 2:13:25 PM

By Tim Cowell, Hill and Griffith Company, Technical Director

Gas Porosity (Runners)

The next location of trapped air is likely to be in the runners. Any sharp corners, high or low ejector pins, or small to large area changes in the metal flow path in the runner system will cause air entrapment. The main rule is that the runner has smooth, rounded corners, that it has ever decreasing area from the plunger to the gate, and that the ejector pins be flush. How much problem will a low ejector pin cause? It is very likely that it will not be noticeable on any given casting, but there is absolutely no question that it adds porosity to the casting somewhere, it is just a question of whether it is a quality issue for this particular casting.

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Tags: Die Casting, Die Casting Lubricant, Tim Cowell, Die Casting Porosity

Part 1/4 - Die Casting Porosity Causes and Solutions

Posted by Hill and Griffith Company on Feb 27, 2019 5:44:03 PM

By Tim Cowell, Hill and Griffith Company, Technical Director

Gas Porosity

Porosity is the biggest problem in die casting.

There are two basic types of porosity

  • Gas Porosity
  • Shrinkage

It is critical that the individuals who are responsible for solving defects determine the kind of porosity before trying to correct it. Each takes a completely different corrective action, however they can look similar. This presentation will show examples of the two primary types of porosity. Generally, a porosity defect should be examined under 5 to 10 power magnification as a minimum. Also, it is usually better to fracture a casting to look at porosity rather than cutting it. Pay particular attention to the geometry (shape) of the porosity.

The high gas content prevents heat treating or welding because it makes the strength unpredictable. Gas porosity is round and generally smooth, although it can be flattened to some extent by pressure. The actions taken to reduce gas porosity will be reviewed, but in general they are not the same as the actions for reducing shrink porosity.

There are three major sources of gas porosity for die castings:

  • Trapped air
  • Steam
  • Gas from lubricant

Any turbulence in the metal movement that allows some air bubbles to be trapped in the metal will mean that these bubbles will be there when the casting is solidified.

  • Air can be trapped in
  • Shot Sleeve
  • Gating System
  • Die Cavity

Gas Porosity (Shot Sleeve)

By the time the metal reaches the gate, the metal flow should be atomized, however, it is vital that efforts be made to reduce turbulence as much as possible during the time frame the metal is flowing to the gate. Starting with the shot sleeve, this presentation will review potential sources of trapped air and possible corrections. The first step is to maintain the same pour rate and shot delay time - this is especially important if the fill percentage is below about 50%. When the fill is less than 50%, a wave is generated by the pouring action, and this wave travels back and forth from the parting line to the shot tip.

If the wave is met by the tip as it moves forward, then extra splashing and sloshing is generated, and this captures some bubbles. However, if the tip is started forward just after the wave has been reflected from it, then the tip “chases” the wave, and this will give the best chance for minimizing air entrapment. The timer that sets the time delay between the end of pour and the start of shot will determine when the tip starts forward in relationship to this wave.

The next phase of the shot profile will be the critical slow shot speed (CSS) - this will be the speed that minimizes the trapped air during the slow shot phase. This speed is calculated from the formula:

Where k = 71 for mmps (inch system). This speed will minimize the air trapped in this portion of the shot.

The following settings should be considered important when trying to reduce air trapped in the shot sleeve. While one of these settings may not seem to be important by itself, there are interactions and it’s recommended they be repeated as close as possible once a good setting is found.

  • Pour rate
  • Delay time before shot
  • Slow shot acceleration
  • Pour hole speed
  • Change over point from pour hole speed to slow shot speed
  • Slow shot speed
  • Fast shot start point

We'll continue next week with die casting porosity caused by runners.


What are die casting release agents?

Die casting lubricants are designed to produce castings without defects such as soldering, staining or porosity. Too little application of lubricant can cause the part to stick to the die "Soldering." Too much can cause discoloration of the die casting "Staining." Too much lubricant in specific areas of the mold is only one of the many reasons for "Porosity." Proper use of die casting release agents combines an exact type, amount and time of application determined by careful observation and analysis.


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Tags: Die Casting, Die Casting Lubricant, Tim Cowell, Die Casting Porosity

ASTM Proposes New Standards for Zinc Diecasting

Posted by Hill and Griffith Company on Jun 20, 2018 2:44:58 PM

One proposal would improve high-temp Zn-Al-Cu alloy; another would define composition for high-fluidity alloy

ASTM International’s Committee on Nonferrous Metals and Alloys proposed two new standards: one for a zinc-aluminum-copper alloy with improved strength; another for determining requirements for thin-wall diecastings.

Zinc alloys are used to design diecastings because of their hardness, self-lubricating properties, dimensional stability, and high modulus make them suitable for working mechanical parts, like gears and pinions. Zinc also offers thermal and electrical conductivity and precise casting tolerances, which are useful for heat sinks, electrical components and applications requiring electromagnetic shielding.

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Tags: Die Casting, Die Casting Lubricant, Hydraulic Fluid System Troubleshooting, die casting lubricant management, Die Casting Lubricant Computer Simulation, zinc aluminum copper alloy

Die Casting Lubrication & Die Cooling Computer Modeling

Posted by Hill and Griffith Company on Jun 13, 2018 4:53:03 PM

NADCA will be hosting a Computer Modeling Workshop on July 24, 2018 in Grand Rapids MI.

Computer modeling and simulation has become common place for designing die casting dies. Flow simulation and solidification allow engineers to design gates, runners, overflows and vents to optimize the die casting process for a part. An important, but often overlooked, part of die casting modeling and simulation is thermal control.

Where should water and oil lines be placed?
How does the software account for cooling/heating lines?
How can simulation time be minimized for water/cooling lines?
Is die casting lubrication spray simulated and how does it affect the thermal controls?

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Tags: Die Casting, Die Casting Lubricant, Hydraulic Fluid System Troubleshooting, die casting lubricant management, Die Casting Lubricant Computer Simulation

 


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