News from our Sanding Technology Centre

The design of our drums, perfected over many years, and the optimized manufacturing process support a reliable, low-vibration and precise sanding processes, which our customers have relied on for years.

To evaluate the effect of an unbalanced drum on the sanding process at our Technology Centre, we investigated the quantitative relationship between the vibration of a calibration drum and the resulting chatter marks on the workpiece. The extent of the chatter marks was measured as a function of the strength of the vibrations. For this purpose, a calibration drum was equipped with weights of between 10 g and 40 g. Figure 1 shows the experimental setup: The weights were mounted in the position marked «A» on the drum and, on account of the unbalance, caused vibration in the contact drum. The object marked «B» in the figure shows the sensor for measuring vibration.

The reverse procedure is familiar to all of us as drivers: When the wheels of our cars are balanced, the unbalance is reduced and vibration minimized by attaching weights.


(Figure 1)

 
After setting up the system, several panels were sanded using the calibration drum equipped with the different weights.
The resulting surfaces of the sanded MDF panels were analysed with a digital surface scanner (Alicona) suitable for contactless surface analysis. The data were then imaged in a 3D model. Figure 2 shows a chatter mark, its shape and height/depth.


(Figure 2)

 
The following table shows the numerical results.

Weight on calibration drum [g] Vibration of the calibration drum [mm/s] Height / depth of the chatter marks [µm]
0 0.11 5.70
10 0.52 6.82
20 1.14 6.19
30 1.79 9.96
40 2.74 19.44

 
The analysis results plotted on a diagram (Figure 3) show the relationships between the unbalance (and therefore drum vibration) and the resulting chatter marks.


(Figure 3)

 
For someone skilled in the art, these results certainly do not represent new findings. Nevertheless, they are significant because they are based on repeatable measurements and show the real, i.e. quantitative, correlation between vibration and the height/depth of the chatter marks. While further trials will improve the quality of the data and the informative value of the diagrams, one thing is already clear: The curve is definitely not proportional, i.e. the depth of the chatter marks increases disproportionately with increasing unbalance. Put another way: The better the drums are balanced, the lower the risk of chatter marks. Perfectly balanced drums from Steinemann guarantee low-vibration operation and therefore are a prerequisite for a precision sanding process.
Using them pays!