3D Scanning Services FAQs - Central Scanning

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FAQs

Frequently Asked Questions

Central Scanning

How can central scanning help my business?

At Central Scanning, our solutions enable companies to improve their processes. What we supply isn’t going to be the make or break of what they’re doing. But, we can really improve their workflow in their processes. We offer expert advice and technical assistance that can help businesses save time and money in the long run. By having the ability to scan during the manufacturing process or at different stages, manufacturers can see what is missing or what is needed before they waste time and money and have to start again.

For example, we work with a lot of foundries who would be making parts. When they would then go into other machines, they may not be usable because they haven’t got enough material. So, by providing the scanning equipment, they can scan the part and compare it to a nominal model to make sure there is enough ‘stock’ material to machine off to clean up the part. This saves them a lot of money further downstream. We try to see what customers need and offer them help to improve their workflow.

Can 3D scanners be rented?

There are a few companies that rent out 3D scanning equipment. It tends to be the larger, more established businesses due to having to hold extra inventory and the value of the items being rented. Mid-range performance scanners are generally rented as they perform reliably and provide good quality data thus avoiding issues when being rented by a person/company using scanners infrequently. It’s often a good way to evaluate the process benefits / ease of use before committing to capital investment. It also can help to understand the ‘supplier fit’ better before potentially investing in an in-house solution.

What about training?

Any reputable reseller of 3D scanning equipment will be able to provide comprehensive training and ongoing support for the equipment they sell. The level of training will often depend on the skills and experience of the reseller and hence it is a good idea to look at reviews and the accreditation that a particular company has. Has the company sold to similar industries and does it have references available and not covered by non-disclosure agreements? It is important that the company selling the equipment also has hands- on experience of using the equipment in the field as they can offer far more ‘tips and tricks’ that are not always covered in a manufacturers training course.

A reasonable understanding of 3D and general PC usage is very beneficial but often more importantly, the willingness to learn new technologies.

How much do 3d scanners cost?

3D scanners vary massively in price as well as performance. You can buy scanners from a few £100 to well over £100K. Entry level scanners can be bought as either hand-held or tripod mounted and some attach to tablets. As with a lot of things, generally you get what you pay for and the more you spend the better the performance.

However, a 3D scanner needs to be ‘fit for purpose’ and therefore if a few £100 scanner ‘does the job’, there is no reason to spend 10’s of £10,000’s of pounds. Conversely, there is no point in spending a few £100 and expecting high accuracy, resolution (detail capture) and repeatability. Generally speaking, if you are making a detailed or medium-high value product, you will need a scanner in the similar price bracket perhaps from £20,000 – £50,000 to match the requirement. If the frequency of use is very low for the medium-high value product and scanning requirement, scanner rental may be an option for you.

What industries or type of companies does central scanning work with?

We work with a wide range of industries, this includes aerospace, creative space and heritage preservation. We also provide technology and services for medical, tool making, animation, automotive mainstream, and also the historic and classic side of the market as well.

It is quite a diverse application in regards to what these scans can tackle. We can scan anything from coin sized objects all the way up to planes and buildings. Companies that want to remake products, inspect them, remake castings etc – we support all of those companies, basically called enablers, to manufacture their product.. At Central Scanning, we’ve got a very diverse portfolio of scanners and a range of client needs and requirements. We can do anything and everything within reason.

How does a technical application engineer and demonstration benefit companies?

When you send a technical application engineer, rather than a sales person only to a company, it is so that we can show all the engineering principles in action. In addition, it shows companies that we truly understand how the system works, rather than just giving out numbers or figures. We can physically show how the product works in the way that companies will use it. As a result companies can understand the product because they can see how it would truly be used for its own purpose.

Resolution

What is 'resolution'?

Resolution is the sharpness of the detail that you can capture. If you have a part with very fine detail, you need to use a higher resolution camera with a small measuring volume.

If you use say a 12 megapixel camera with a 1 metre measuring volume, the resolution will be considerably lower than using a 12 megapixel camera with a 100mm measuring volume. This is because the ‘point to point’ resolution is much lower and consequently, the data is sharper.

‘Point to point’ resolution is defined by a grid of points that is created by the camera when an image is taken – this is controlled by the optics within the scanner.

Is it best to scan everything at a high resolution?

If you scan at a resolution that is much higher than needed i.e the part is fairly smooth with not much detail, the result will be a very large dataset which, then needs more post processing and computing power further downstream.

What happens if I scan at too low a resolution?

Too low and you can miss key features that you are trying to capture. The trick is to use a resolution and measuring volume that allows for the detail to be captured with the largest volume to maximise the scanning efficiency.

What is post processing of scan data?

The 3D scanners simply create a vast cloud of points – point cloud. The 3D scanning software is then used to turn all those points into triangle meshes by using controlled algorithms to essentially filter the outliers and overlapping data and create a mesh. There are a number of ways this is done dependent on the software but what is essential, is to maintain the integrity/accuracy of the raw data during the process. The better software allows the user to have full control of the filtering and smoothing algorithms. As with most things, the higher value scanners tend to have the more user friendly and accurate software.

Note of caution: You do have to be careful as there are some software programmes on the market that will make a point cloud look very nice and smooth which is impressive visually but at the sacrifice generally of accuracy.

What is photogrammetry?

Using markers also enables the use of photogrammetry, which people use for measuring large parts and/or measuring parts where accuracy is paramount. Photogrammetry is a process that allows a series of images to be captured by the scanning device or a 3rd party camera with calibrated scaling information being introduced. This allows the images to be very accurately positioned.

The scaling information (scale bars) are normally factory calibrated to certify the accuracy. The can usually be re-certified on an annual basis or to fit in with your internal quality system requirements.

Photogrammetry: Do I need it?

Photogrammetry is a stand-alone measuring process. You position markers/dots onto the object and then locate scale bars (known length artefacts) into the scene. You then take high resolution images of the markers/dots with an SLR camera and the software creates a point cloud bundle of all the reference points. Photogrammetry is typically used for objects 2-3 times the size of the scanners measuring volume and/or for very high accuracy requirements such as turbine blades, engine components etc.

The other form of photogrammetry used a high resolution SLR type camera to take a series of images of an object. This data is then put through specialist software which uses clever algorithms to align the images. This process can be great for creative items where the look of the item and colour capture is more important than the accuracy.

What Can be Scanned?

Is 3D scanning industry specific?

Absolutely not. There used to be a perception that 3D scanning was only used in the aerospace and automotive industries. That has changed massively in the last 10-15 years. It is true that the automotive sector has a large influence on the development of 3D scanning, particularly when it comes to automation. In the last 16 years, we have seen a dramatic increase in 3D scanning requirements – toolmakers looking to reverse engineer and validate tools, turbine blades for inspection purpose, the toy industry for creating data from mock-ups often in clay or putty, plastics industry for reverse engineering and inspection, creative sectors for scaling / reproduction, classic cars for remanufacturing obsolete parts including car bodies, modern cars for root inspection and root cause analysis, medical sectors for maxi-facial, scoliosis, burns care to name a few of the industries using 3D scanning.

How small an item can a 3D scanner scan?

This comes down to the resolution of the scanner. The resolution is defined by ‘point-point’ spacing and is a figure that can be provided for all 3D scanning equipment. In simple terms, the smaller the detail on an item, the high the resolution needs to be. If scanning jewellery for example or a very small component, you need to use a scanner with a small point spacing so that features are described with the most detail.

If scanning an aeroplane for example, you can get away with much larger point spacing on the majority of the plane. If looking for detailed close up details, again high resolution would be needed. Generally speaking, the higher the resolution, the more expensive the scanner. If you have for example a 12 MegaPixel scanner and fit 500mm lenses, you will be measuring 12 points over a 500mm volume. If you then install a 50mm measuring volume, still on the 12 MegaPixel camera, you will have a much more dense and therefore detailed point cloud – much higher resolution. What you don’t want to be doing is scanning everything at a very high resolution if not required as file sizes would be very large, thus taking a long time to post process after scanning.

It is always worth asking a potential supplier to demonstrate some items and to recommend the scanner resolution combined with the lenses required to meet the requirement.

How large an item can a 3D scanner scan?

Drones can scan very large areas. Looking more at the smaller industrial type scanners, planes, trains and automobiles are very popular items to scan. Artic lorries, industrial machinery and factories/buildings are frequently scanned for re-fit and redevelopment purposes. A large volume laser scanner would be used for most of the above items as the smaller tripod and hand-held scanners would be too slow and the data files would be very large thus needing extensive computing power.

Can I scan in colour?

On some scanners, colour capture is possible and the output tends to be OBJ/VRML. The majority of the scanners that capture colour are hand-held light-based scanners but there are some laser scanners as well. They tend to be the mid-range scanners (£10K-£30K) and are typically used in the creative sectors. Higher value scanners can also be combined with colour capture but most of the time, they are used for high-accuracy work where colour capture is not normally needed. Although we are seeing more requirements for high resolution colour imagery mapped onto scan data in the medical and research sectors.

When it comes to 3d scanning, what is the worst kind of material to have?

The worst kind of material you could possibly get is something being completely transparent, black and shiny. The main reason for this is because if it’s black, it’s hard for the cameras to see. And then because it’s shiny, because it uses light to scan, all the light gets reflected in the wrong directions. This can confuse the scanner and generate high noise or maybe make it not even possible to see it. However, the T-Scan Hawk can easily scan dark parts, which are completely black. If you cannot scan, there are 3D Scanning sprays that evaporate after use now from companies such as AESUB.

What size and type of objects can you scan?

We can scan anything from a tooth to trains, lorries, planes, buildings and a lot of items in between.

For Instance:

  • Castings are often scanned for dimensional verification or reverse engineering (creating data from a physical object).
  • Vehicles are scanned for the design and manufacture of body styling kits where companies need to understand the shape of the car ‘as is’ to be able to create the new parts.
  • Electronic equipment is scanned to add new parts to the device or retrofit.
  • Body panels for re-manufacture.
  • Humans are scanned for medical reasons and to create maquettes.
  • Film props to bring into CGI.
  • Virtual and Augmented reality.
  • Clay models of items to bring them into a 3D world for tooling or scaling up and down perhaps for 3D printing.

Accuracy

How accurate are 3d scanners?

Depending on which type of scanner, they can be accurate to under 0.01.mm (a human hair is typically 0.070mm) and up to +/-2mm.

Why are some 3d scanners more accurate than others?

Typically, light-based fringe projection and fixed camera scanners are more accurate than laser-based scanners in the sub £100K range. By having the scanner and object in a fixed position, accuracy is enhanced by having stable equipment and also by a stable room temperature thus removing variables in the process.

Is a handheld scanner as accurate as a static camera system?

Generally speaking, fixed or tripod mounted scanners have the advantage when it comes to accuracy as everything is static in most cases. Static cameras generally provide higher levels of repeatability and measurement uncertainty.

That said, some of the more recent hand-held scanners on the market use markers and calibration artefacts to overcome some of these issues.

Which is more accurate - fixed or hand-held?

By fixing the position, there are less variables in the process introduced by movement of with the scanner or object. Hand-held scanners and getting more accurate with the higher end scanners, maintaining accuracy of 0.020-0.030mm reliable. A camera fixed to a robot and users markers (dots) applied to the fixture and/or the object is also very accurate, especially if the camera and part and static whilst capturing the image.

What is the difference between accuracy, repeatability and resolution?

Resolution is essentially the sharpness and level of detail the scanner can capture. low-resolution scanner miss the detail and look blurred like an out of tune tv! 0.010mm is how far apart points on point cloud from are each other, thus enable creation sharp/detailed imagery. Accuracy is generally speaking measured using 2 spheres of a known distance apart. The scanner measures them several times and the accuracy is then mathematically calculated and described using the centre point of the spheres. Accuracy is important for the majority of applications as scanners are often used for checking parts before added value processes and hence if incorrect, the added value would be wasted.

Repeatability is the measure of the systems/process ability to repeat the measurement several times. In a lot of industries, this would involve 30 parts being measured by 3 different people with the part being removed and re-positioned in a fixture/holding device 30 times. This is then input into a spreadsheet which calculates repeatability. Good levels of repeatability is important as you generally need to be confident that the scanner you are buying will measure the same dimension time and time again within the specified tolerances.

Reference Markets & Markers

Some scanners use markers and some don’t - why?

Most high-end metrology scanners use markers. The markers are recognised by the scanner algorithm. By accurately measuring the mid-point of each marker, the scanner patches can be located accurately.

A lot of scanner software uses very complex algorithms that analyse the scan data. It can very accurately position patches by free matching the data during scanning. This has the advantage of not requiring the time of adding/removing markers/cost of markers. But, the trade off can be accuracy if scanning for very high accuracy applications.

Do we need to always spray items white for scanning?

Absolutely not! If a part is highly reflective/gloss black for example, there is too much reflection and the cameras cannot see the surface being measured. This would be similar to taking a photo of a shiny surface in the sun – you get over exposed data. In these instances, a scanning spray is very beneficial.

Historically, these scanning sprays needed to be removed and it was very difficult to do so from certain surfaces. Such as, car interiors, stitching and textured surfaces. In the last couple of years, scanning sprays that disappear after scanning have been introduced.

These allow the scan data to be vastly improved. In addition, there is no need for cleaning as they completely evaporate after use. Consequently, this makes the scanning process much cleaner which has benefits for the equipment and the environment around the equipment. In some cases (AESUB), they do not contain Titanium Oxide which has health benefits for the technician as well.

If a surface is matt or a light colour, in most instances, scanning spray is not required.

What are the reference markers on the object being scanned & what are the benefits?

Known as reference markers, they are placed on the rotation table and the object being scanned. The 3D software looks at these markers on the part, and can triangulate where the markers are in 3D space and markers on the part. This means that as we move the part on the rotation table, the software knows it’s rotating, but thinks it stays still. This ensures accuracy and allows us to basically rotate the part without having to move the scanner. And then because we’ve got markers also on one side of the part, it allows us to flip the part once it’s been scanned. We can then scan the other side using those markers. We have points that we can then align the two scans to very high accuracies, taking micron inaccuracies aligning those two scans together.

Why do some scanners need markers/dots?

When marker dots are applied, the provide a ‘reference’ for the scanner to align itself to. The contrast between the black and white circles on the markers allow the scanner to accurately measure the centre point of the marker. This ‘reference’ is known to the scanners software and when an image is taken by the scanner that recognises the marker, it positions the scan accurately. Photogrammetry is the next stage on from ‘reference markers’ using scale information to accurately position the scan patches, especially on larger objects.

If a scanner does not use markers/dots, it normally uses surface/feature-based alignment to align the data. The features can be 3D or in some cases, graphics on the item or a combination of both. This can be very accurate but is dependent on the structure of the item.

Differences Between Scanners

Does the level of detail captured vary between a hand held scanner and a fixed scanner?

‘Detail’ is impacted by the ‘resolution’ of the scanner. Generally speaking, high-end static scanners have higher resolution cameras. Hence the ‘point-to-point’ spacing is smaller, giving a higher level of detail capture.

Why use hand held scanners rather than fixed scanners?

Hand held scanners are very portable. Therefore, if you need to work in confined areas or where access is limited, they are ideal. Additionally, the set up time is very quick and moving equipment from location to location very easy.

Can a handheld scanner be mounted onto a tripod to make it static?

Yes. Most scanners have a standard tripod mounting in them allowing them to be fixed to a tripod or robot etc. This is very useful when measuring repeat parts where having the scanner still can be beneficial depending on the geometry. You do have to be careful as one of the major advantages of a hand-held scanner are the ability to measure difficult areas. So, using a tripod can limit this benefit and therefore, is not a good approach for all parts.