Grinding belts are manufactured as displayed in Fig. 4.5. The manufacturing route starts with the backing material, which can be paper, cloth of natural or synthetic fiber, or metal (in the case of diamond coated abrasive tools) [BORK92, p. 47]. In addition, the backing can be wet-proofed or reinforced with wire. Strength and flexibility are main characteristics of the backing material.
The bond material to hold the abrasive grits can be applied in one or more layers, with the make coat as base bond and size coatings as upper bonds [BORK92, p. 47, KONI86]. Additional coatings can have dust-repellent effects [KLOC09, p. 66]. First, the make coating is applied and will form a gel after cooling or drying [KONI86]. This gel fixes the abrasive grits, which are applied in the so called mineral coating step either by gravitational force (gravity scattering) or by electrostatic scattering. [KLOC09, p. 69 f.]. In the gravity scattering method, a distribution device applies the grits on the coated backing material. In the electrostatic scattering method, the coated backing material is moved upside down over a transport belt, on which the abrasive grits are oriented by an electrostatic field [KLOC09, p. 69]. The advantages of the electrostatic scattering method are an even grit distribution, a higher reproducibility, and higher grit protrusion (Fig. 4.6).
After positioning the grits, the size coating is applied. It supports the retention of the grits amongst each other. After drying and hardening, the belt is rolled, cut, and possibly joined. The type of belt splice is crucial for the process stability and can be reinforced with foil [BORK92, p. 45]. Overlapping splices can be used for all
Fig. 4.5 Manufacturing of grinding belts after [KONI86]
Gravity scattered grits
Fig. 4.6 Scattering methods for grinding belts
applications. However, the area close to the lap splice might differ in thickness, which can lead to marks on the finished surface. Therefore, lap splices with removed grits are recommended if the ground surface needs an unmarked surface finish [KONI86]. Straight or sine wave butt splices can withstand extremely high stresses, e. g. for high performance applications [KONI86]. However, every splice can set up vibrations in the machine/tool/part system, resulting in chatter and surface marks on the parts [KONI86]. New endless, spliceless belts overcome these troubles [CHRI96].