# Grinding Fluid Jet Characteristics and Their Effect on a Gear Profile Grinding Process

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## Abstract

**:**

## 1. Introduction and the State of the Art

## 2. Research Approach and Objective

## 3. Materials and Methods

#### 3.1. Nozzle Designs

_{jet}= 35 m/s) at the outlet for the same flow rates (Q

_{f}= 100 l/min) (Figure 2). For comparison, the reference nozzle {r} was also investigated. This nozzle represents the current state of technology in the industrial environment. This nozzle differs from the nozzles {1–5} in the grinding fluid flowrate (Q

_{f}= 330 l/min) and in the jet velocity (v

_{jet}= 12 m/s). Due to the low jet velocity, the jet does not break up before it reaches the grinding contact zone.

_{c}.

#### 3.2. Characterization of Fluid Dynamic Aspects of Grinding Fluid Jets

#### 3.3. Grinding Process

_{n}= 4.5 mm, a bevel angle of β = −16.55°, a pressure angle of α = 24°, and a width of b = 65 mm. The material is AISI 5120 and the gears are case-hardened and blast-cleaned. The gears have a hardness of 718 HV and a case hardness depth Chd of 1.13 mm.

## 4. Results and Discussion

#### 4.1. Characterization of Fluid Jets and Their Breakup

_{coherent}before atomization makes it possible to compare the fluid jets. The results for these lengths, which are the average lengths of nine measurements of each nozzle, are shown in Figure 7.

_{nozzle}= 13.8 bar is measured, whereby for 3D printed nozzle B {5} a pressure of p

_{nozzle}= 5.7 bar is measured. The nozzle {2}–{4} are between these values. These pressure values correlate in inverse manner with the coherent lengths. These different power drops in the nozzles generate a corresponding turbulence flow, which correlates with the jet break up.

#### 4.2. Grinding Technology

_{e}of 50 µm in each case. The dressing conditions were precisely adjusted to the requirements, so that an increased thermo-mechanical load of the surface layer could be achieved after grinding only a few gear gaps. The results for this reference process are shown in Figure 9.

_{W}of 345 ± 15 mm

^{3}/mm was removed before this limit had been reached.

_{W}, before thermo-mechanical damage occurs, for each nozzle are shown in Figure 10.

_{W}= 345 ± 15 mm

^{3}/mm was reached. This result can be attributed to the much higher grinding fluid flowrate (Q

_{f}= 330 l/min) and the coherent jet. For the nozzles of the category “atomization” and “wave & droplet”, a significant lower grinding fluid flowrate of Q

_{f}= 100 l/min and a higher jet velocity of v

_{jet}= 35 m/s was adjusted which corresponds to the cutting speed v

_{c}. With the needle nozzle {1}, the flat nozzle {2}, and the 3D printed nozzle A {3} (category “atomization”), a specific removed material volume of V’

_{W}= 311–349 mm

^{3}/mm was achieved. The highest specific removed material volume of V’

_{W}= 415–436 mm

^{3}/mm was reached with the nozzles of the category “wave and droplet”. The results of the grinding tests correlate with the coherent lengths of the jets and the calculated positions in the Ohnesorge vs. Reynolds number diagram. A longer coherent jet leads to a higher specific removed material volume. This might be due to a better wetting of the grinding wheel for a “wave and droplet” jet breakup. In conclusion, for the optimized grinding fluid supply versus the reference fluid supply, the specific removed material volume can significantly be increased (up to 26%//436 mm

^{3}/mm {5} to 345 mm

^{3}/mm {r}) with a simultaneous decrease of the grinding fluid flow rate (reduction of 70%//100 l/min {5} to 330 l/min {r}). For a reduced grinding fluid flow rate (100 l/min), an appropriate inner design of the nozzle alone can lead to an increase in the process performance by up to 40% (436 mm

^{3}/mm {5} to 311 mm

^{3}/mm {1}).

## 5. Conclusions and Outlook

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

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**Figure 1.**Ohnesorge vs. Reynolds number diagram and jet breakup characteristics (after [10]).

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**MDPI and ACS Style**

Geilert, P.; Heinzel, C.; Wagner, A. Grinding Fluid Jet Characteristics and Their Effect on a Gear Profile Grinding Process. *Inventions* **2017**, *2*, 27.
https://doi.org/10.3390/inventions2040027

**AMA Style**

Geilert P, Heinzel C, Wagner A. Grinding Fluid Jet Characteristics and Their Effect on a Gear Profile Grinding Process. *Inventions*. 2017; 2(4):27.
https://doi.org/10.3390/inventions2040027

**Chicago/Turabian Style**

Geilert, Philip, Carsten Heinzel, and André Wagner. 2017. "Grinding Fluid Jet Characteristics and Their Effect on a Gear Profile Grinding Process" *Inventions* 2, no. 4: 27.
https://doi.org/10.3390/inventions2040027