Graco Inc.

Combining Merkur™ & ProMix™ 2KS works wonders for a large wheel manufacturer


In early 2010, the Graco distributor Mewes Oberflächentechnik, near Hannover, Germany, was contacted by a large wheel manufacturer to help them optimize and improve their paint line for large wheel hubs with the objective to become VOC-compliant.

The manufacturer produce up to 25,000 wheels every year and are the largest supplier of specialist wheels in Europe. The wheels are manufactured for agricultural and construction vehicles and attain speeds of up to 80km/h. Customers of the manufacturer can choose any RAL colour to paint the large wheels, however, standard colours are red, yellow and silver.

The first step to being VOC-compliant involved switching to a 2K PUR high solid topcoat paint. The primer, still 1K, but in future should also be 2K, and will then be treated wet-on-wet with the topcoat. Every year, around 14 tonnes of 1K, and 24 tonnes of 2K high solids are processed.


Paint Specifications:

  • Paint type: 2K High Solid PUR
  • Viscosity: 40 sec. DIN/4 ( mixed )
  • MV: 5.3:1 n. Vol.
  • Pot life: 2 hours

In the paint-shop, old Böllhoff technology was replaced with new 2K Graco technology. In the topcoat area, a ProMix 2KS with a four-colour high pressure integrator was installed. In order to reduce the flushing time and flushing flow rate, the mixing unit was mounted as closely as possible to the booths. In addition, the mixing units were installed in a cabinet to protect them from any overspray. This saved several metres of hose in the mixing area.

The three main colours are now transported with Merkur pumps from 200 litre barrels to the ProMix 2KS. Agitators on the 200 litre barrels ensure that the high solid paint is always homogeneously stirred. The hardener, which is pressurised with nitrogen in the 800 litre container, is transported using a Bellow pump to the ProMix 2KS. Separate fluid pressure regulators ensure that the correct pressure can be set for each fluid.

The maintenance of the ProMix 2K takes place every six months (dosing valves, mixers, check valves). Maintenance of the pumps takes place quarterly (filters and change of the purge compound). No issues have been reported since June 2010.


The data settings on the spray gun:

  • Tip: 413
  • Fluid pressure: 80-100 bar
  • Atomising pressure: 2.5 bar
  • Bundled hoses: 5m long NW 4
  • Permanent colour change: 20 seconds

By using the installation, the large wheel manufacturer has saved a great deal of time and solvent. Flexibility has also increased, as a special colour can be prepared in the system while a standard colour is still being painted. In addition, data concerning the usage of the ProMix 2KS can be downloaded to update the balance of solvent, thereby resulting in an consistent high quality finish.