Casting : Cycle Time Reduction and Process Optimisation.

I would like to blog about the opportunity most of us have in the casthouse to increase throughput in our operational areas and briefly give an example. The purpose of such a project is to maximise the output from any casting facility and identify any snags, bottlenecks, maintenance, production or process constraints.

The project should be run with focus, individually (i.e. 1 x VDC process route at a time) don't try and boil the sea and run several process streams in the casthouse in one go, you will get lost, swamped and possibly cross contaminate the data. Communicate, as always, communication is the key to making such a project a success. Take the time to discuss the project, the goals and expectations and outcome with the teams. If you have the option to discuss with the larger group during a town hall meeting, for example, then this would be the place to raise the focus on the project and get everyone's buy in from senior management to shop floor employee.

Things to consider:

Personnel

Identify the skill set for the team, this would include production planning, maintenance and process technicians, production operatives. Use SME (Subject Matter Experts) during the project to ensure stability and buy in from the team. Training may be an issue but dont jump the gun, let the project find that out and address.

Cycle Time

Measure each process step and record the results. A realistic sample rate should be used to give an overall representation of the process. Note : This process will be alloy specific as casting speed will vary. A rule of thumb should be say 10 drops, but the more the better. Remember processing the OES results should also be taken into consideration as delays in laboratory releasing the data directly impacts the casting performance. Operations management will always want to limit your exposure and disruption on the floor, keep that in mind, stick to your guns and respect the sample rate, after all the benefit is for operations after all.

Metal Delivery

Please consider feeding the furnaces with an unconstrained supply of metal from the smelter or remelt furnace. This should not mislead the project with slow deliveries effecting cycle times. Ask the planning team to feed your furnace(s) as priority.

Take off

As with metal flow, ensure that the pit can be stripped and the slabs stored without holdup or disruption through a full offloading area or down end table.

Maintenance

Run the project ensuing there are no major or minor outages planned. This would also include site service work such as launder repairs or replacements, filter box replacements (such as ABF etc) or process trials on materials or consumables that may effect cycle times.

Process Ready

Ensure the casting area is fully ready for the trials, perform a 5S on the area, prepare the casting materials and consumables and make them available. This would include filters, combo bags, spouts and metering pins, launder coating materials, ceramic ropes, mastics, oils and lubricants, fluxes, alloying elements, vehicles etc.

The best way to do this is to have a list of process materials and vehicle equipment that is needed and tick them off as you validate.

Launders, inline treatment and filtration should be preheated and up to temperature.

Starting heads should be clean, dry and coated (if necessary).

The operations team needs to be briefed upon this project and fully available. Its a stress test so they should be ready to be stressed!

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Below is a typical example of a cycle time study conducted on a slab VDC line. The sample was for 8 drops, however as I said earlier the bigger the sample rate the better for data statistics. Don't be tempted to run the project over a period too long as this may impact the operations team and negatively effect the process.

Typical record : 8 drops (Slab Casting)

From the fictional (but representative) data presented during the 36 hours period of the test, a total of 8 drops were cast. The average cycle time reached was 4:40 hours. This leads to a pace of 5.1 drops/day.

Now for the stress testing :

By excluding the downtimes for equipment and process issues, the cycle time decreases to 3:42 hours for a potential pace of 6.5 drops/day.

We can see that the main bottlenecks in the turnaround time are the pit stripping (partially based on operator skill (variation between shifts)) and the cooling of the slabs. During the test, the 25 minutes cooling time was used as per the recipe and safety instruction..

An interesting observation was found that except for one case due to furnace temperature, the preparation time did not impacted the overall casting cycle time.

With such 'hard' data you can clearly see that improvements are possible, with even just one additional cast per day (metal input permitting) the casthouse can make significant improvements, reducing the CIP (Cost of Ingot Produced) conversion cost and giving the sales and marketing teams more metal to sell, and in the current climate with the LME so strong that's not a bad thing!

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Many thanks for taking the time to read this blog, please feel free to share with your friends and colleagues.

Should you still require further help on this particular subject reach out and please contact : albergtech@gmail.com

George