4.8       Internal Combustion Engine Piston - Industrial

4.8.1   Background

 

It was required to capture the internal geometry of the piston. This data would then be used to create the multiple split core during a low-pressure casting process.

The plan was to capture the piston’s inner geometry, produce the five multiple split core sections, build them on the SLA500 stereo lithography machine in Quick Cast format, cast the core sections by using the investment casting process, final machining.

The CMM was also used to capture some of the piston’s geometry. Another identical piston was cut in sections to display some of the hidden areas that could not be reached. The piston was not symmetrical and it was therefore necessary to capture all the geometry of the complete piston.

At that stage, the CSIR’s CAT scanner could not be used as it was still being repaired. The only other option would be to scan it at one of our local hospitals. Most medical CAT scanners are not capable of scanning metal materials. Only some materials can be CAT scanned, such as Stainless Steel, Molybdenum, Titanium, Copper alloys and pure Aluminum. Other materials normally cause a scatter of X-rays and may result in artifacts or noise. The amount of x-ray power also plays a large role. It was decided that the only option at the time was to manufacture a print of the inside of the piston. Room Temperature Vulcanizing (RTV) rubber was poured into the piston after the section was sealed at the gadget pinion. The rubber print was removed after it stabilized and hardened. The rubber print was hollowed out to allow the print to collapse then it was removed from the piston.

The rubber print was then taken to Krugersdorp Hospital to be CAT scanned. The 2D CAT scanned data was once again stored on microfloppies as part of a routine backup procedure. A lot of time was spend touching up the 2D CAT scanned images, as the rubber print was hollowed out and displayed some casting flaws. More detail than required was also present on the rubber print, which was later removed. The 2D editing were required to obtain a usable 3D representation.

 

 

4.8.2   Conclusion

 

Proper project planning was required. Proper planning would make a difference between a possibility of capturing data and actually making the data work for you. Proper planning would allow one to capture the correct data that is required for the suitable down stream process.

Once the rubber print was scanned, it has some limited end applications for various reasons. The correct tools to manipulate STL format files were not at that stage in place at the CSIR. It may be better to scan the tool, if it is available, if it is the final required product. If the tool itself is not available then proper planning is required to get to the final product. The rubber print, a complete rubber replica of the inner geometry was scanned. The final product is that this geometry is required to be split in five different sections to form a multiple split core arrangement. The data was captured and the 3D representation was acceptable. A tolerance of 0.4mm was achieved. This was however far from the product, multiple core sections. The data was however not applicable to what was required due to poor planning and inadequate tools to manipulate the data.

A great deal of various reverse engineering methods exist. It is very important to determine what product is required to select the correct RE method. Another important factor is what sort and form of input and output are required. The old cliché can be here applied, "Different Horses for Different Courses".

If data manipulation is required of a certain part, a different route and method may be followed, compared to the normal data capturing method. The two main applications of reverse engineering are direct copy related work or a modified copy of the original. Various results of RE can be a finite element modeling (FEM) analysis, a casting or manufacturing process simulation, an identical scaled prototype, tooling or a modified copy of the original.

 

 

4.8.3   I.C.E. Piston Data Sheet:

 

 

Description

Options (Default)

Data

 

1

CT Image Names

 

Piston.001

2

Patient/Project Name

 

kolben.pat

3

Number of First Input Image

 

000

4

Number of Last Input Image

 

030

5

Number of First Output Image

 

000

6

CT or MRI

CT, MRI

CT

7

Horisontal Nr. Of Image Pixels

0 to 65535 (265,512,1024)

512

8

Vertical Nr. Of Image Pixels

0 to 65535 (265,512,1024)

512

9

Number of Images per File

(1)

1

10

File Swap Format (0,3)

0,3

CCELSC

11

Pixel Type

B,UB,S,US,L,UL,F

-

12

Header Size

*see formula below

-

13

Inter Image Header Size

0

-

14

Add Value

0 to 4095

-

15

Scale Value

0 to 4095

-

16

Table Position

(mm)

0

17

Distance Between Slices

(mm)

1

18

Slice thickness

(mm)

1.2

19

Pixel Size SQ.

F.O.R./Nr. Hor. Pixels (mm)

 

20

Gantry Tilt Angle

Degrees

0

21

Field of Reconstruction/View

(mm)

0.6

22

Number of Images

 

30

23

File Size of CAT Image

kb

75

24

File Size of Converted Image

kb

60

25

.3dd file size

Mb

4

26

.STL file size

Mb

4.006

27

RP Method

(SLA,FDM,OTHER)

-

28

.IGS file size

Mb

-

29

RP Slice file size

Mb

-

30

RP Download File size

Mb

-

31

Grow Time

Hour

-

32

Tip size

(T12, T25)

-

33

Slice Thickness

(0.01", 0.014")

-

34

Finishing Time

Hour

-

35

Processing Time

Hour

10

36

Data Retrieval Time

Hour

3

37

Total Cost

Rand

1950+500=2450

 

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