Plastic Products and Mold Design

Calipers and micrometers are usually where I start.

You can also take a picture, import it into your CAD design, size the envelope from a known length, trace the features and measure them from there. Sometimes image manipulation is needed to get the image in black and white. I use inkscape, a free software. This is useful for hard to reach features or complicated surfaces with a hard edge.

Hand held 3D scanners can be useful for complicated lofted surfaces, but may need a stand or gantry to function properly. For products with organic surfaces that don't have overhang, some people with put it in a bucket with a camera above and fill little bit by little bit with milk to generate a series of cross-sectional pictures. Those then get imported and placed on a series of planes, sketches traced out, and then connected in 3D.

Calipers and micrometers are usually where I start.

You can also take a picture, import it into your CAD design, size the envelope from a known length, trace the features and measure them from there. Sometimes image manipulation is needed to get the image in black and white. I use inkscape, a free software. This is useful for hard to reach features or complicated surfaces with a hard edge.

Hand held 3D scanners can be useful for complicated lofted surfaces, but may need a stand or gantry to function properly. For products with organic surfaces that don't have overhang, some people with put it in a bucket with a camera above and fill little bit by little bit with milk to generate a series of cross-sectional pictures. Those then get imported and placed on a series of planes, sketches traced out, and then connected in 3D.

Calipers and micrometers are our best bet as mentioned above.

In the past I also used a digital microscope to variable optical zoom and good software to measure cross sections and small detail areas. Found this to be a bit time consuming but very accurate.

I never heard of the milk idea. Can you post any additional information on it?

I guess the setup is pretty easy with just an object, a bucket, a camera, and some milk... I'd just like to see some photos of the setup, and maybe what the milk/object interface look like.

I searched a bit, but I have no idea what to call this milk based reverse engineering process.

At my last job I often needed to reverse engineer injection molded plastic parts because a client would want something just like it, but with some changes. Or, I'd need to design something that fit closely to an existing product which I had no CAD data for.

I fully agree with all of the methods mentioned above, and I've used them all (with the exception of the milk photos, that I have to try).

Other tools and methods I've made use of:

• A bandsaw, mill, or other tool to cut a model in half, or to remove slices. Consider how a 3D printer builds layer by layer. Now reverse that process by removing a layer of material, photographing the part, then removing another layer.... repeat as needed.
• A flat bed scanner is great for flat objects like ones which are having layers removed from them. The scanner gets a much closer image, and it most eliminates a lot of the distortion present in cameras when the view has any perspective.
• Angle gauges. These are little pieces of cut metal used to measure angles. They are great for things like chamfers, or draft angles.
• Radius gauges. A lot like angle gauges, but these are used to measure the radius of a fillet, or other round feature.
• Thickness gauges. Multiple thin slivers of metal which can be used to measure otherwise difficult spaces and gaps.
• Depth gauge. Different sizes are needed to measure the depth of various items. Blind holes, rib height, small lips. I converted a .09mm mechanical pencil into a depth gauge by replacing the lead with a steel wire. It was great for very small holes.
• Pin gauges. If you need to accurately measure the diameter of a hole, dial calipers won't work. Pin gauges work very well. You could also use telescoping gauges.
• Ultrasonics can be used to measure the wall thickness in a non-destructive manner.
• A camera is great.
• Sometime simple works well, and I'd simply trace an object on a piece of paper before scanning the paper with the flatbed scanner.
• A microscope does wonders when your eyesight is shot, or you are dealing with tiny features. I hooked a camera to my microscope, and was able to measure to a half thousandth (.0005") in Photoshop.
• Several times I made use of an old optical comparator for profile views of objects. Maybe new ones even save the display digitally?
• Laser, and visible light scanners are great in some cases, but they sometimes require so much extra work in processing of the data that their time savings is far less than imagined.
• Lately I've been experimenting with photogrametry software. It is not as good as a commercial 3D scanner, but the results are surprisingly good.

https://youtu.be/XSrW-wAWZe4

Really great advice here. Gunna print or CNC out some radius and angle gauges.

thank you ALL friends..

Great, that really helped to visualize the process. It works a little like the slice data obtained from a CT scanner in the medical field.

Also be sure to checkout photogrametry options. I mentioned it above, but here is a video comparing it to 3D scanning. I skimmed through the video without sound, but there are a lot of comments about the narration: https://www.youtube.com/watch?v=20jvnEtgRIU

Just be sure the printer/cutter is really accurate. If the gauge is off, then using it to measure and evaluate models will be less helpful.

I measured some parts off of our lab's 3D printer today. Overall things were pretty good, but hole diameters are about .01" undersized (for a 1" hole), and most other dimensions were about .005" larger than designed.

I've printed custom angles, or complex profiles on card stock, then trimming away the excess material. It is not very durable (like a set of stainless steel gauges), but custom profiles are most likely only going to be used on a single project anyway.

If you have money you can ask for a tomography (X-Ray), you will have :

• a stl file with a point cloud,
• the accuracy is depend on the size of your parts (like digital photo),
• you can also see the glass fiber orientation ans porosities size/location

but it is expensive 500 to 1500 $

https://youtu.be/SW2WRO6OQjU

We are using Rapid I vision measuring system for plastic as well as sheet metal parts