Mounting bolts are used in assembly systems and production equipment for the reception and positioning of work pieces for the assembly process. Due to this function they are in direct contact with component surfaces. A fact which is particularly important when used in cleanliness-sensitive mounting areas, since particle entrainment towards the work piece is largely effected by means of contact surfaces. What tips should designers have to take into account when designing mounting bolts in order to meet the requirements of technical cleanliness?
The present practical example shows two different design approaches for receiving bolts which are used in the cleanliness-sensitive area of a mounting process. While the right-hand bolt mirrors a “conventional” design, the right-hand bolt has been designed to ensure clean design principles.
Reduce contact surfaces
In order to maximize particle transfer from the receiving bolt to the work piece, product-contacting surfaces are to be kept as small as possible. A line contact is thus preferable to a surface contact. In addition to the vertical support of the work piece, the contact surfaces for horizontal positioning must also be taken into account.
Vertical support as surface contact, “particle collecting bag”
In the left-hand-side implementation example, the work piece support was implemented by a linear contact, while a surface support is present in the calculation problem on the right.
The contact surfaces for horizontal positioning have been reduced in both cases, in that only circular sectors have the contact diameter.
Particle-repellent radii and bevels
A central principle in the cleanliness of the construction is the avoidance of horizontal surfaces or of dirt sinks and “dirty pockets”.
In their place, particle-repelling radii and slopes are to occur. On the one hand, particles are prevented from accumulating in a larger number; on the other hand, zones which are easier to clean are generally also formed.
In the present practice, this principle was implemented in two ways in a clean-clean design (on the left-hand side). On the one hand, the horizontal image was taken as a radius on the other hand, a particle-deflecting slope was applied in the connection area of the receiving bolt.
In the conventional right-hand side approach, “dirt sinks” are found in both places, which are difficult to clean and prolong particle entrainment.