Recently there are few inquiries about reverse engineering on bottle shape for oil, shampoo and etc. I am guest everyone think that is very easy job when look at it at the first time. But I goanna to tell you if you don’t know the tips & trick, I’m sure you ll regret because you are actually under estimate it.
Well. What so difficult about that?
Typically RE modeling started import the point cloud from scanner (May be if there is extra time I wish to share about digitizer within next topic). In CATIA V5, you can perform import the digitized data at digitizer shape editor workbench as shown image (a). Without processing the point clouds, it looks more points compare to image (b). it should do the filter to remove unnecessary points info, the filtering mode should be adaptive way, means to filter more point when there is face more planar. Like a plane it only needed at least 3 point above, the extra point will not affecting the result
Then, I mesh the points cloud (c) to help on better visualization for 3D presentation. Off course this is just started for the RE process. Before start the modeling, you need to align its position, means when you show side view it will rotate to side view. Why? Original point cloud position is based on the digitizer original position, it will not same when import into CAD system, it may position somewhere far away from CAD origin. You can use the compass help to align to origin position. It is helpful when there is prismatic feature to be used later. If you look at this data, it is half only captured. The reason is we identify this is symmetrical part. We aligned the meshing data in symmetry plane. At the end we can perform mirror function.
To start the CAD modeling, segmentation is help to separate the meshing data as few possible surfaces fit portion as image (d), another it is guidance for you to start to extract the CAD from meshing data, power fit like image (e). This will help you extract the nearest CAD surface from actual part. By the way
the extract surface should be achieving Class A quality, tangency control must be good and it can be resolve in freestyle workbench. In fact, this is the first challenging area.
But this method may not applicable for other area like corner fillet, corner fillet are depending whether desired design should be constant fillet or just any blend surface. This will affect the appearance product like. Let look at (f )Blend surface and (g) Constant fillet. These two functions are available in freestyle workbench. Both of them are different upon the requirement like whether you need the constant fillet or not. If not require, blend always is the fastest way to build the connection surface with tangency control.
Besides, there is also possible to create something differ from original data. Firstly the physical part you digitizer may deform already especially like this kind of plastic part. After fill in long time, the weight of liquid force out the body shape. So we have to double check the requirement before start the job. Based on the input from mould maker, we are able to understand more on the structure of bottle. Let look at the image (h) cross section at meshing data and (i) cross section at result CAD model. Try to compare the side vertical curve and most bottom curve. From the meshing data it look like a curve, for the CAD model it is straight along the axes. We should not feel hesitate to call client to verify the requirement. Else if they use your data without check it probably for mould fabrication. You will trap yourself in big trouble.
So some time we can use the generative shape design workbench help to fulfill requirement above. Anyway, there is much challenge area of the bottle where by the handle area, let look at image (j) oil bottle & (k) Shampoo
In order to handle this kind or design, power fit or generative way may not suitable tool to achieve it. To model this area, wireframe is the concept tool and try to trace out the characteristic curve then follow by using the multi section surface to loft, sweep surface, fill and etc. Let take a look on the wireframe image (l) wireframe Oil Bottle & (m) wireframe Shampoo Bottle
Last important tip is you cannot create undercut surface this kind of mistake. This will make you will lose the client forever. They will not longer confidence with your data and need to spend time to repair your data. You should understand the manufacturing process. This kind of product normally using blow mould, the mould direction is side view. You can use the draft analysis (n) to help you to figure out where is the undercut area. You can always use parting line creation method. Means to trace out the parting line and following create core surface. This step will help you save more steps.
As conclusion, bottle product it look simple to model CAD data. Remember the few important key points
- Aligning Scan data
- Segmentation as guidance
- Prismatic design
- Wireframe concept
- Class A surface Creation
- Symmetry Design
- Parting line
- Draft angle
For the Class A surface Creation it is require high level of understand on the curve continuity control. I may share this topic in other day. Lastly hope you enjoy this reading.
Written By: Wei Lun