Technical Tutorial - Low cost automation
Various Screw Application Issues in Automation Design
A screw (Stainless-steel Socket Head Cap Screw)
Screws (fasteners) are the most universal machine components absolutely needed for construction of any machinery. They are, therefore, classified into JIS, ISO, and other industrial standards according to shape, size, and strength (strength classifications). In actual automation design and build practices, however, shortcuts such as selecting fasteners by experience based intuition, as well as careless use of then-in-stock variety of fasteners are often seen. In this article, we'll discuss the key points of screws, bolts, and nuts as well as the basic theory that makes up the foundations of fasteners.
(1) Application issues related to screws during the design stage In automation design and construction, most of automated machinery and production jigs are fastened together by screws, nuts and bolts. The fastener design, therefore, will have the following influences.
Items affected by fastener design:
| Affected items |
Examples of design methods |
| Part machining cost |
Standardization, Easy to machine layout design |
| Part assembly cost |
Easy to assemble design, Standardization |
| Machine appearance |
Sophisticated design that shows no wastefulness |
| Operational reliability |
Strength, rigidity, fastening reliability, reliability over time |
| Functionality assurance |
Assuring and maintaining the machine precision |
| Maintainability |
Ease in disassembly and repair (layout / direction) |
The fastener design must not be overlooked for streamlined automation designs that are functional and cost effective.
(2) Screw issues during and after automation assembly
The screw issues during and after automation assembly can be categorized into the following two cases.
- Problems that occur when assembling / tightening --- Mistakes during design phase.
EXAMPLES
- Lack of proper bolts in stock for given counterbore dimensions and threaded hole depths.
- Threaded holes and bolts are not aligned.
- Thread damage during tightening.
- Distortion of parts due to tightening force.
- Problems occurring over time (post production) --- Part strength design mistakes during design.
EXAMPLES
- Screws becoming loose and the parts are no longer properly aligned — Equipment damage.
- Destruction of bolts.
- Both a) and b) above are typically caused by LCA designer's engineering mistakes.
