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Simpson Multi-Mull Continuous Mulling


The Most Advanced Sand Preparation Tool for Medium to Large Foundries

As molding lines get larger and faster, modern foundries require larger volumes of high quality molding sand produced at the lowest total cost. Foundries that use batch mixers experience downtime when they do not have an adequate supply of sand. In addition, these batch mixers produce non-uniformity in the molding sand which negatively impacts the quality of castings.

Imagine if …

  • Your total daily requirement of sand could be mulled in one big batch, stored in a sealed bin and fed to the system only as required
  • The sand properties of your last mold of the day could be as consistent as possible to the first mold that day
  • The above could happen primarily because all sand variables are cancelled out

Continuous mulling approaches the ideal situation.

The Simpson Multi-Mull® is a medium speed, high intensity continuous mixer that is like no other. The synchronized dual muller and overlapping dual plow design enables sand and additives to be circulated and recirculated in a figure 8 movement within the Multi-Mull where they receive maximum exposure to mulling action before final discharge through a modulating door.

Overall the Multi-Mull gives you an advantage over your competitors by:

  • Delivering a continuous supply of sand, on-demand
  • Consistently providing discharged sand of superior quality and uniformity
  • Producing high quality molding sand at a lower cost than any other solution
  • Protecting margins through lower energy consumption
  • Wasting no operating time on batching, charging, discharging, pre-mull dispersion or wetting of bond
  • Requiring far fewer system components Example: (1) Multi-Mull = 23 components vs. (2) Small Batch Mullers = 85 components
  • Lowering installation cost and reducing maintenance
  • Reducing profit-robbing downtime


The continuous Multi-Mull operates under the same proven principle as batch mulling, with one notable exception related to feedback.

Two sets of counter-rotating mixing tools serve to recirculate (back-blend) a large volume of retained sand between the mulling units while the sand traverses a “figure 8 pattern” toward discharge.  Because the sand is mulled on a continuous basis, corrective peaks and valleys are smoothed out.  The continued back-blending of material between the mullers gets rid of the “first-in/first-out” effect and eliminates variations in return sand properties.

Both the feed rate and the amount of sand recirculated can be varied.  Using sensors that monitor the motor load, the control system will adjust the discharge door opening to maintain a constant volume of sand inside the mixer and/or change the retention time required for different applications. Note that once in equilibrium, the discharge rate will equal the feed rate.

Recirculation was the vital but elusive principle which delayed the practical application of continuous mulling. With feedback, the Multi-Mull is capable of consistently developing sand properties equal or superior to those produced in a batch muller.

Efficiency Makes You More Competitive

For high-volume, high-quality, cost-effective casting production, the Simpson Multi-Mull is the best solution. This technology produces larger volumes of molding sand at a lower cost of installation and operation than any other mixer in the world.





“The muller does a great job…very little maintenance.”
– Kenneth Boatright, 1st Shift DISA Supervisor

Foundry: Grey Iron
Casting: Valves
Molding processes: DISA, HWS & Pipe
Mixer: Simpson Models 23G-200 and 26G-300 Multi-Mulls (Continuous Muller)
Controller: (3) Simpson Hartleys


“With our particular mold line system, we need all the effective bond we can get. We need high green strength characteristics to make it work. That’s where the Multi-Mull does its job, giving us twice the working bong strength of our old high speed batch system.”An Iron Foundry

“Multi-Mull is made to order for us…” – An Iron Foundry

“During the last forty years, I have built foundries across the country. Of the various mullers that I have seen, Simpson Multi-Mull not only looks the best, its performance is the best. [In one company alone]… I have installed five of them. And they’re all still going strong.” – An Iron Foundry

“Compared to a batch muller of the same size, the continuous muller is twice as good. We would need two 200 hp batch mullers to handle the same amount of sand.” – An Iron Foundry

“[Our Simpson Multi-Mull] keeps the sand down on the pan for less heat build-up and less energy loss, and its continuous mulling action gives us a more consistent mix. It’s doing such a superb job…” – An Iron Foundry

“Maintenance on the 22G is down 40% over our batch unit experience.” – An Iron Foundry

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