Micro Gear

Figure 1.7 Micro-gear system produced from a nickel iron alloy by means of LIGA technology [Source Micromotion, IMM) [108]. Reproduced by kind permission from the publisher.

Double flank roll testing as verification technique for micro gears... 

A broad range of verification techniques for gears are currently available in the market but not so many seem to be valid or extrapolated for a micro range (Figure 1). Thus a thorough analysis of these techniques and a definition of a double flank rolling test for micro gears were accomplished in this paper. 

Fig. 1. Micro gears image captured by Surface Seanning Microscope.

Here was generated the first design of the double flank roll tester machine for micro gears with pitch diameter from 1 to 10mm and radial composite deviation tolerances according to norm ISO 1328-2 [2] and DIN3963 [3]. Based on this first design, where the main functional blocks of the machine... 

Out of this measurement process, the radial composite deviation parameters Fi , fi and Fr which show the accuracy of the micro gear, could be obtained (Figure 3). 

On these grounds, the maximum tolerance values for radial composite deviations Fi , fi , Fr of the micro gear to be inspected considering accuracy grade 5 are shown in Table 2. Likewise the maximum tolerance values for the accuracy grades 12 and 4 could be calculated and will give a reference value for the measuring components selection to be included in the double flank roll tester. 

Due to the lack of existing commercial models for double flank roll testers applied to micro gears verification, a functional blocks design of the machine adapted to the selected micro gear dimensions (Table 1) is accomplished in this work. 

One problem faced in the model realization was the selection of the master gear to be used in the roll test. Both normal modules for micro gear and master gear should be equal, m=0.1 and given this value the pitch diameter d and number of teeth z for the master gear could be defined. 

Micro gear parameters Master gear parameters... 

According to DIN3970 [5], the master accuracy grade needed for the inspection of a micro gear with accuracy grade 5 according to ISO 1328-Part 2 [2] is accuracy grade A. 

In order to generate the first tester model, it is necessary to define the main tester dimensions which will be derived from the dimensional range of the micro gears to be inspected. In this case the pitch diameter d of the micro gear is 1.3mm and based on this dimension, it is fixed an admissible gear diameter range of the tester which will determine the final roll tester constructive dimensions. 

The tester model designed in this work is similar to a standard gear double flank tester but with the peculiarity of the need to adapt the tester to a micro measurement range (Table 4) and the high equipment resolution required. This fact will imply the selection of high precision components and the specific design of the mechanical fixations for the micro gear to be inspected. 

It is a steel carriage which holds the test gear. It will integrate several parts as the fixing system for the micro gear, the pressure system which will assure the tooth contact without backlash among both gears teeth once the nominal centres position is reached, and a capacitive sensor. 

Micro gear with the dimensions explained in Table 1. 

Gear which will be rolling against the micro gear to be inspected in the roll test. The master gear parameters are shown in Table 3. 

Double flank roll tester 2D model for micro gear inspection... 

Figure 8.2 SEM image of micro-gears after laser cutting of polyimide with short-pulsed frequency-tripled Nd YAC laser (pulse width 500 ps).

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