Electronics Components

We used the 400 V version of our Universal Cutting Mill PULVERISETTE 19 with a housing made of stainless steel for our trial. This equipment is not required to comminute such a type of sample. Also, a standard version with lower voltages could be used for grinding as well.

Provided samples mainly contains electronic components on top of PC-boards. We divided the sample into two fractions (see photo). Softer parts which could be ground easily with a side cutter were fed first. Those fragments can be ground in higher amounts without damaging the mill. The relays with steel housing where separated because our side cutter test was tough for those fragments. When metal fragments with a thickness of wire > 1 mm are fed (ferrous alloys), damages can happen to the knives. Therefore, we strongly recommend using a disk milling rotor with indexable inserts and knives made of hardmetal tungsten carbide. The knife inserts can be rotated up to three times before a replacement is required. Replacing of those indexes can be performed on the customer side; there is no need to send such a rotor to Fritsch for sharpening.

The 32 grams of softer parts were comminuted in our first trial. We used a 0,75 mm sieve cassette for our trial to make sure all output will pass a 1 mm mesh test sieve.

The feeding was performed slowly and grinding sound was observed. The fed fragments produced a typical grinding sound without too harsh sounds as expected. Feeding was performed in smaller batches to avoid too much of sample inside the grinding chamber. All sample was fed after 30 seconds. The grinding sound was vanishing constantly. The main output was achieved after 60 seconds of total grinding time (24,5 g). After two minutes, only 3 grams of additional output was found inside the used 3 liters collecting vessel. We stopped the mill after 5 minutes of total grinding time. Only 0,5 g of additional output was transferred into the collecting vessel in the last three minutes. We would recommend interrupting and cleaning after 2 minutes of total grinding time.

The perforations are not clogged significantly; surely even higher amounts of sample can be ground this way. When higher amounts should be ground, we recommend using a sample exhauster system with cyclone separator (or high-performance cyclone separator) to reduce dust exploration which could escape by the standard funnel. The optional protected funnel with sample pusher is also capable to reduce dust exploration with its two separated chambers. See result two for the harder relay fragments.

The housing of the pre-cut relays were possible to cut with our side cutter test. Those two fragments were fed first and produced a softer, typical grinding sound.

The intact relay was too large to use a side cutter for our pre-cutting test. Metal pieces which got bended and become too thick; or explicitly hardened ferrous metal fragments (e.g. screws) can damage the tungsten carbide inserts. Such thicker fragments might be separated and not be fed into the mill.

We also tested the intact relay. Also such an intact relay produced a typical grinding sound and was ground without problems. The complete sample was fed within 20 seconds. The main sound of grinding vanished within the first minute of comminution. We found an output of 10,6 grams after this first minute and the output rose by 1,6 grams after the second minute of grinding.

This trial was aborted after two minutes of total grinding time. Residues inside the grinding chamber were cleaned rapidly by vacuuming with a soft brush. The 0,75 mm trapezoidal perforated sieve cassette was not clogged significantly, higher amounts can be ground this way, too.