The art
of grinding


Welcome to Swiss Tower Mills Minerals AG. We are an innovative company in the regrind, fine and ultra-fine grinding industry.

Swiss Tower Mills Minerals AG (STM) was founded in 2011 to introduce the well proven fine grinding technology of industrial minerals to the mining industry. Today more than 200 grinding mills are operating today to grind industrial minerals with truly minimized energy requirements; over 30 units are currently operating in the hard rock mineral processing industry. STM’s technology enables the mining industry to profit from more than 40 years of development and operational experience in fine and ultra-fine grinding.

In the meantime, the HIGmill™ has been accepted by the hard rock mineral processing market. Numerous tests have been successfully performed, both laboratory or on site. STM has received several orders from very small test and pilot mills, up to several large 6.5 MW HIGmills. A 700 kW HIGmill for a copper concentrate regrind application at the Kevitsa mine in Finland has been commissioned in February 2015 and is operating successfully; both the copper recovery and the copper grade in the final copper concentrate have been increased significantly, where at the same time the nickel grade in the final copper concentrate has been reduced. Other HIGmillsTM are in Operation now in a copper and in a platinum concentrator.

Experienced Team
with proven track record
in minerals processing

About Us


Ralf Hesemann
Managing Director

Tel: +41 58 590 3519
Cell: +41 79 369 0085
Maarten van de Vijfeijken

Tel: +41 58 590 3512
Cell: +41 79 593 0804
Per Thorn

Tel: +41 58 590 3501
Cell: +41 79 251 3012
Evgeny Zhmarin

Cell: +41 79 899 8378
Patricio Huencho
Sales Promoter South America

Tel: +56 2 2946 4383
Cell: +56 9 6678 4707


Fritz Moser
Bernhard Schupp
Robert Lang
Markku Teräsvasara

Partners & suppliers

In 2012 Swiss Tower Mills Minerals AG and Outotec entered in to an exclusive technology agreement to market STM’s VRM (Vertical Regrind Mill) type mills. The Outotec brand name is HIGmillTM (High Intensity Grinding mill).

Outotec HIGmills »

Swiss Tower Mills Minerals AG has an agreement with KMF (Kärntner Maschinen Fabriken) GmbH to manufacture the HIGmills. During the last 40 years KMF has produced more than 200 of these mills for the industrial minerals market. KMF has over 40 years’ experience in manufacturing fine grinding mills for the industrial minerals industry. KMF is ISO 9001 and ISO 14001 certified and holds numerous special certificates for welding and safety. »
out of ore



Declining ore grades and more complex ore bodies lead to a clear trend for fine grinding. Fine grinding technology has already been used for more than half a century in the ceramics, pigment, paint, paper and pharmaceutical industries. The unique grinding technology, which Swiss Tower Mills Minerals AG offers for the mineral processing industries, has been well proven over more than 40 years in the industrial mineral segment: over 200 fine and ultra-fine grinding mills are in operation, with a total installed power of over 300 MW. The largest units in operation have each an installed motor power of 5 MW. Swiss Tower Mills Minerals AG has made this exceptional grinding technology available to the mineral processing industry.

The ceramic grinding beads in the mill shell are put in motion by the grinding rotors which are mounted on the mill shaft. The mill shaft is powered by a motor and gearbox arrangement. The high packing density of the grinding media produces strong friction, which causes efficient grinding of the product. The variable speed of the milling shaft allows for an energy efficient grinding process to reach the required product particle size.
The feed material is supplied as a slurry from below by a feed pump. The mineral particles, which become smaller during the grinding process, rise up in the mill cylinder and leave the mill via a natural overflow on top. Gravity supports to retain the grinding beads, which have a higher density than the slurry, in the milling chamber.

The fineness of the final product (slurry) is adjustable through the following factors:
  • Feed rate
  • Slurry concentration
  • Amount of grinding beads
  • Speed of the mill shaft

Key Benefits

The HIGmill™ provides the following key benefits:
  • High energy intensity
  • Efficient transfer of energy from the mill shaft into the grinding bed
  • Low required specific grinding efficiency (SGE)
  • Steep particle distribution curve (PSD) without external classification
  • Single pass grinding (no re-circulating loads)
  • High flexibility to handle fluctuating process conditions:
    • Fluctuation in slurry feed rate
    • Fluctuation in slurry particle feed size
    • slurry consistency / ore characteristics
    • required product size
  • Simple flow sheet leads to cost reduction
  • Minimized footprint due to vertical milling arrangement
  • Easy maintenance
  • High availability due to long maintenance intervals
Both CAPEX and OPEX are significantly minimized with this regrind mill technology.

HIGmill™ Portfolio

Swiss Tower Mills Minerals AG has established an extensive portfolio of vertical regrind mills, in order to ensure a perfect match between project specific demands and the selected mill type.

Pilot Mill Production Mill
Standard designation for mill HIG 75 HIG 125 HIG 250 HIG 500 HIG 700 HIG 1100 HIG 1600 HIG 2300 HIG 3500 HIG 5000 HIG 6500
Nominal power [kW] 75 125 250 500 700 1100 1600 2300 3500 5000 6500


Installed base

Installed base of HIGmills in industrial minerals (up to 5 MW).

HIGmill™ reference list in hard rock mineral processing

Simple flow sheet
efficient, flexible & single pass


Flow sheet

Typical overall flow sheet

The typical HIGmill™ flow sheet for regrind circuits is simple and straight forward. Regrind feed from the flotation goes to a scalping cyclone. The cyclone overflow (typically 10 – 50%) bypasses the HIGmill™. The cyclone underflow is pumped into the mill, where the target product size, with a steep particle distribution curve, is produced in one pass. Having no re-circulating loads, pumps, piping and mill cylinder volume can be significantly reduced, while achieving a product with a steep particle size distribution curve.
Typical regrind circuit flow sheet



The HIGmill™ provided the following process related advantages:
  • Steep particle distribution curve (PSD) without external classification
  • Single pass grinding (no re-circulating loads)
  • Flexibility to handle conveniently process variables as:
    • Fluctuation of slurry feed rate
    • Fluctuation of particle feed sizes
    • Feed slurry consistency / ore characteristics
    • Required product size
  • Simple flow sheet leads to cost reduction
  • Relative small pumps (no re-circulating loads)
Both CAPEX and OPEX are significantly minimized with this regrind mill technology.


The HIGmill™ cover a wide range of applications for fine and ultra-fine grinding, such as:
  • Concentrate regrinding (gold, copper, moly, platinum, lead, zinc, ...)
  • Iron ore fine grinding
  • Tailings regrinding
  • Slag & fly ash grinding for recovery of recyclable metals
We are here
to serve the customer



The HIGmills are designed by Swiss Tower Mills. The main mill components are manufactured by KMF in Villach, Austria. KMF is a leading company specialized in tilting rotary furnaces, mills and grinders, special machinery, plant construction, process engineering and contract manufacturing. KMF has over 40 years’ experience in manufacturing fine grinding mills for the industrial minerals industry. Naturally KMF is ISO 9001 and ISO 14001 certified and holds numerous special certificates for welding and safety.


Swiss Tower Mills Minerals AG has the required know how to provide the necessary engineering services, such as:
  • Finite element modelling and analysis of the separate mill components as well as the complete mill
  • Identification and mitigation of resonance frequency issues
  • Design and build in accordance with project specific seismic requirements
  • Design of all main structural components to withstand the applied dynamic forces as well as calculation of expected lifetime
  • Spare part management support
  • Creation and implementation of the control and protection philosophy for the regrind mill
  • Drive system engineering


The partnership with Outotec ensures that end users have access to an established worldwide and state of the art service network.

Outotec: Operations Services »


Swiss Tower Mills Minerals AG and Outotec operate several mobile and stationary test HIGmills units with three different mill sizes and offer these test services to customers globally. The stationary test units are located in Villach, Austria and at Outotec Research Center (ORC) in Pori, Finland. Additionally the portfolio includes the larger HIG75 pilot mill. Base line test work with the HIG5 test mill requires a minimum of 4 kg of dry test material.
On-site testing is possible with the HIG25 containerized mobile test unit or with the HIG75 pilot mill. Additional testing can be performed at ORC. ORC develops metal processing technologies, processes and equipment and its expertise covers the entire processing chain from ore to metal, starting from mineralogical analysis.

HIG25 test container

SGA Liebenburg in Germany

HIG5 test mill in Austria

HIG5 test mill in South Korea
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