Figure 1: Phillips Norelco Shaver (courtesy of Tristan Rose)
When reverse-engineering a product (and I recommend doing this often! – it’s a great way to learn), you should consider two things:
Firstly, consider what your objectives are. There’s lots to learn by taking something apart, but what are you specifically after? Try to refer this to Design for Manufacture and Assembly (DFMA) principles by Boothroyd et al (2010) where possible. Below are a list of things SOME that you might want to consider.
Secondly, consider what you’ll need to disassemble the product. Will you need specialist tools? will you require personal protective equipment (PPE) in the form of gloves, goggles, labcoat? will you need a cutting mat? will it be messy? will you need lots of space? how will you lay out the object to the best effect? will you need to re-assemble the object, in which case how will you layout and/or label the objects? when you record the process, how will you do this? pen/paper? photographs? if so, how will you stage this to get the best effect using a tripod? or how will you keep your camera/phone still? and with good lighting? with a suitable clean backdrop? will you be able to capture it all in one go or will you need to piece images together in photoshop? (for the big products – like the tractor – Todd McLellan (2013) did just this).
A sample list of things to take to a reverse engineering party:
- pen and paper
- a decent camera (or camera phone) and something to mount it on (ideally tripod) – also consider how you’ll take pics to maximise the visual effect (a nice matt white background is always good!)
- white sheets of paper taped together to lay things out on
- steel and plastic rulers
- screwdrivers (normal size and small terminal size), both phillips and flat head
- other flat tools for prizing open troublesome products
- allen keys (and other specialist tools for unfastening?)
- sharp stanley knives and cutting mats
- blue tak or superglue (to hold small parts on the table)
- sticky tape and masking tape
- digital callipers
- possibly board (painted white) and pins/screws/wire/fishingline to mount things permanently!
For the super keen, mount all the parts neatly onto a piece of painted board (possibly with a small label) and we’ll put it up in the studio!
General assembly/disassembly considerations (related to Design for Assembly – DFA guidelines):
- how many parts does the product have? often products have individual part numbers actually shaped into an internal surface.
- how many of the parts are standard? how many are “designed”?
- how many different materials are actually used?
- what is the assembly process?
- to what extent is the product able to be disassembled at end of life?
- what type of fit is there for the product? is it possible to measure the tolerances for any mating components to understand how much clearance or overlap is there?
Plastic specific considerations:
- how was the part made? is there any evidence on the part to give you a hint? this could be a parting line (showing where the mould cavities meet), or an ejector pin mark.
- what material is it? often it’s labelled.
- what draft angles are used? you’ll need to measure this!
- has the product been glued, ultrasonically welded, rivetted, screwed, snap fit, other? look for clues before you take it apart.
- what features are included internally and why? consider tabs, ribs to stiffen, bosses to screw into, slots to guide, other mounting features, strain relief etc.
- what are the material wall thicknesses? these vary from main walls to ribs, bosses, other features. There are recommended wall thickness for different plastics. It’s always good to check that the material you’re looking at fits with these guidelines!
- what are the thick to thin wall transitions like? are they suitable? are there voids or sink marks present on the part?
- what are the surface finishes like on the surfaces of the part? these should give you a hint about the quality of the mould, or the requirements of the part itself. They can also help to show or hide any manufacturing problems (e.g. masking sink marks).
- is there a mix of flat or curved surfaces? does the quality of their surface finish differ?
- for any living hinges what’s the material thickness? and how have they designed this into the part bearing in mind moulding processes? this is clever indeed!
- for any snap fits, what is the shape of the cantilver that “bends”? does it taper or is it straight? how does this fit with the design guidelines for snap fit? (or not!) are there signs of strain at the join?
- if it’s a moulded part, is it a straight pull mould (ie where the mould can be pulled straight from one side to leave the part – with no undercuts), or would inserts be required to allow for undercuts to be produced? often there is evidence in the sign of parting lines to indicate various inserts for the mould.
Electronic specific considerations:
- try to identify what electronic components are present?
- try to identify which are sensors and which are actuators?
- how are things mounted to a) each other, b) the case?
- for any circuitboards, are the components surface mounted or through hole mounted?
- are the technical specifications of the components obvious? what are they?
- what does the main circuit look like? can you draw this? for battery driven products, are the batteries in series or parallel? and if so what’s the voltage?
Figure 2: Nikko radio controlled ford fiesta RS (courtesy of Chloe Fong).
Electrical specific considerations:
- how has strain relief used for mains cables?
- is there an earth? what colours are used for the wires? do they conform to relevant BS safety standards?
- how is the wiring connected to terminals/pins?
- is the casing suitably insulative?
- is it waterproof? it’s worth looking into IP (ingress protection) requirements for electrical products.
Sheet metal considerations:
- what processes were required to make the part? these could be cutting, bending, punching, rolling, stamping, etc…
- in what order were these processes done? is there a way to tell?
- what kind of fastening was used? welding, rivets, screws, glues, etc.
- what kind of tools or punches were used to make certain features?
- what are the bend radii for any bends?
- are there any notable design features, e.g. reliefs in the corners?
- are there any surface treatments used to finish, coat or debur the part?
Machining specific considerations:
- what processes were required to make the part? drilling, milling, turning?
- in what order were these processes done? is there a way to tell?
- were any tertiary processes required to finish the part to give a particular surface finish or detail?
- how was the object held while it was made?
- are there any key datums, e.g. surfaces on the part?
Others? there are plenty more things to consider and to learn from these exercises!
Boothroyd, G., Dewhurst, P., and Knight, W. 2010, Product Design for Manufacture and Assembly, Third Edition, CRC press.
McLellan, T. 2013, Things Come Apart: A Teardown Manual for Modern Living. Thames & Hudson.