When we launched M1 & M2 Native ROs, nobody 'designed' our first assembly station. We just... assembled. The parts would arrive and people assembled them. It worked, mostly.
Except there was this one step where the operator had to hold a module elevated with both hands while someone else slotted a component in from below. It was slightly awkward but everyone managed. We didn't think much about it because it was all so new to us.
Few months in, someone finally said out loud what everyone had been doing quietly. These folks were rotating their shoulder at the end of every shift. That small move people make when something is wrong but they haven't decided to complain yet. It was some more months later when we started fixing things on the line to optimise production speed and the specific issue, along with many others, gradually got solved. That specific issue must have taken one short afternoon to think about and solve.
I've been making hardware in India for a very short time period. Roughly short of 3.5 years. It's long enough to have made most of the expensive mistakes. Some once. Some more than once. Through this period we built a team of Design Engineers & Industrial Designers along with a great support ecosystem of tooling experts and manufacturing experts. I've written some of these learnings down so they can function as a working checklist of things to catch in CAD, things to ask the vendor, things to check before the design is locked, and most importantly as things to avoid or be cautious of. These 100 odd things below come from those mistakes, from conversations with foremen and machinists and tooling vendors, and from taking apart a lot of products to understand what the people who made them were thinking.
Design schools don't teach you this (or, don't teach you exhaustively). The knowledge exists in factories, in the head of the foreman who has watched fifty designers make the same mistake. It doesn't make it into product requirement documents.
Part of why is structural: design studios and shop floors are kept at arm's length in most Indian hardware development. The designer finishes drawings and hands off. The manufacturing problems become the vendor's problems and the designer usually isn't there when they show up. Part of it is work culture grooming as asking a vendor "what would you change about this?" feels like admitting the design isn't finished.
I've tried to put these together by starting with what a user notices first, working back to the first decision you made. Bookmark this post or get a printed copy as a reference to keep by your side.
1. Surface finish
Imagine two different products which have the same function, and are similarly priced. If one of them looks finished but the other one looks like a part that came out of the machine and looks 'raw.' The difference is almost always surface finish which is almost always under-specified. Many Indian toolmakers work with a separate vendor for surface finishing and under-specified finishes will mostly mean a random job done optimised for the vendor's default one optimised for their speed. Write down details like texture card sample, gloss levels, directionality, treated and non-treated surfaces, Ra (roughness average) values along with a physical reference sample.
Every product has faces nobody will ever see. For instance, the underside of a bracket or the back of a panel against a wall. There's no reason to finish these, and Indian vendors rarely push back on over-specification. They'll finish a surface they know will never be seen and charge for it. Mark hidden faces explicitly as "as-cut" in your drawings. Doing this simple thing will drop cost and even potential post-processing steps. Don't pay for finishes nobody will see or interact with.
Run your finger along the main face of a poorly made product and you'll often find a faint raised line (which will also have mismatched colour) that's impossible to miss once you notice it. Usually it means the parting line is in the wrong place. Where you put the parting line is a design decision. When we didn't understand the details, mould makers would place it wherever it's the easiest for tooling unless you specify otherwise. Avoid putting it on a cosmetic face and you'll avoid this mismatch.
Vertical walls in a mould look fine in CAD. On the actual sample, they come out with drag marks and ejection scuff marks. Basically, the plastic grips the mould wall on the way out. The fix is usually a 1.5 degrees of draft on walls that would otherwise be exactly vertical (I wish). Assume it to be the normal, especially with textured surface, and start Industrial design with this expectation.
There's a specific kind of sink mark that shows up in plastic parts. This is a shallow dimple on the outer surface, usually sitting above a thick boss or rib profile. Sinks happen because the outer surface cools and solidifies while the thick inner section is still shrinking. If you core out the boss & connect it with ribs, the problem gets significantly reduced and in many cases, solved. Do it today and you'll save weeks in trials. This is an important one because a common response from mould makers is, "we will adjust in the process." Which loosely translates to longer cooling time, higher injection pressure, etc. which can bring up other issues. Just fix it from the start.
Texture patterns on injection moulded parts need to align with the direction the part exits the mould. A texture running perpendicular to draw gets dragged across the mould surface on every ejection with severe scoring marks. We faced such issues and eventually had to remove texture from the part completely. Btw, EDM and hand-polished textures are both common. These don't reliably align to draw direction. Put the draw direction on the drawing.
Tap the large flat panel of a product. If it makes a low hollow drum sound, it sounds cheap and poorly built. It could have a few shallow ribs or none at all if you see severe warpage on the part. Indian consumers tap products at retail spaces. This tap test is an actual pre-purchase behaviour. Simply put some reinforcements like ribs or slight curves wherever design allows. Adds negligible material cost and your product will sound 'solid.'
Any feature where the part can't slide straight out is an undercut. This requires a slider, lifter, or well… side cavity lifter. These add both cost and new failure points. Designing with undercuts is quite common and doesn't require much problem solving. Benchmarks you'll find around you will have these as well. I don't have solutions here but designers should ideate on how to heavily reduce undercuts. Could be revolutionary.
Use stickers as a last resort. In Indian conditions of humidity, cooking heat, and daily cleaning cycles, a sticker won't last long. Put essential information in moulding of the part itself that doesn't any real cost and removes long term field failures.
Choose surfaces, colour, and texture carefully for Indian kitchens. Indian kitchens are one of the harshest environments a consumer product can live in. There's oil mist, turmeric, hard water deposits, even abrasive cleaning cloths all around that's used every day for years.
2. Ergonomics & feel
Ergonomics references like handle diameters, grip depths, serrated surfaces, actuation force guidelines are mostly built on Western anthropometric data. Indian hand dimensions differ, particularly for women, who make the majority of kitchen appliance purchasing decisions in India. A grip geometry calibrated to a Western reference may require more force or reach than is comfortable for your actual user. The Indian anthropometric data exists (Indian Anthropometric Dimensions by Debkumar Chakrabarty). Use this to establish your ergonomic design system.
Weight matters a lot. With many purchases still happening at physical stores, the weight is evaluated on the spot. For certain category of products heavier ones feel better and communicates better quality. Weight becomes a design variable which when customers pick up should articulate as 'heavy' or 'sturdy.' But be careful because a heavy product may still feel wrong. If the balance is off and the hand-held product becomes top-heavy, like it'd tip, it'd feel wrong. For hand-held products the centre of mass sits relative to the grip point (think pens) and this becomes more important than the total mass.
This is a simple one but important when you're trying to do heavy design differentiation. People who buy kitchen appliances are used to picking the product in a specific orientation. If you do massive changes where the form of the product isn't communicating a lifting guide, the form is still incomplete. It'll make the user think which is the right orientation. Under-the-sink water purifiers is a classical example here. Since the product category is fairly new, there's no learned muscle memory. Design form so the grip points guide the hand.
Speaking of grips… Indian kitchens operate with wet hands. We usually design grip surfaces keeping dry contact in mind. They'll fail the moment it's in contact with water or oil. Test your products with wet hands during development, fix the surface texture, use depth in surfaces intentionally, work with your service partners to observe how they operate the machine with wet hands.
Document all actuation forces and their respective changes in design. How much force does it take to press a button, actuate a lever, open a lid, or to disengage two parts? This has a number. These decisions too are linked with the profile design of the part and the force target that translates into a tolerance value of the material. In rapid prototypes, a snap could feel right with the right spring force effect but could change completely with ABS or HIPS during manufacturing.
If your product has a mix of materials like metal, plastic, rubber, remember that metals feel cold, plastics feel warm, and rubber feels neutral. Essentially, this is thermal conductivity pulling heat away from your hand at different rates. Keep two things in mind. One that in India, there's historical significance of metals (steel tiffins, aluminium cookware, or even the rising popularity of cast iron cookware) where it gives a good purchase confidence. Second, try to bake in context of the product and usage while deciding where would you want metal, rubber caps to cover screws, and plastics in a single product.
3. Fasteners & serviceability
Reduce the number of screw types & sizes in a product. Ideally, keep it to two. This simplifies assembly line tooling and minimises mix-up errors. This also becomes a good constraining factor at the time of designing sub-assembly parts which increases your part standardisation changes and putting snap fits to do most of the job.
If hand tools must be used for tightening, allow at least 60 degrees of lever swing. Tight swing arc means under-tightened fasteners, which means field failures that look like product quality problems. Design the clearance geometry before the fixture is made.
A separate washer almost always gets dropped at the time of assembly. If it's put upside down, the part drops, gets collected from the floor and put back in the wrong assembly too. Instead of using standard screws, use flange screws with an integrated washer face built into the head. It gives you the same clamping surface with one fewer part.
Thread-forming screws for plastic don't require pre-tapped inserts in non-service areas. Brass inserts need heat staking or ultrasonic insertion. It adds cost. Identify areas in your product that don't need servicing and simply switch to self-taping screws.
This is an important one and very easy to keep missing. Products that look easy to service in CAD often aren't. The front-housing slides off cleanly in the animation but catches on a harness connector in real life when the service partner tries to open it in rush. Walk through the full open-and-close sequence physically by yourself, with your team, and most importantly with service partners before the design is locked.
4. Assembly
Every part that needs to be placed accurately should have features that put it in position. Avoid assemblies that require slow careful placement; they will either be done incorrectly at speed or will slow the whole line. Use locators generously to solve for misalignments issues and assembly speed.
If a part can go in backwards, it will go in backwards. Poka-yoke is a Japanese term that means "mistake-proofing." Error-proof your parts geometry as it's a very reliable quality mechanism in assembly context without over-relying on training. Put asymmetric connectors, keyed inserts, asymmetric internal part geometry, and even features that prevent the housing from closing if something's wrong.
Think about the direction of parts and how they move during assembly. Assembly fatigue in Indian contract manufacturing is real and under-reported . They'll not appear in any defect log. They appear as random rejects with no clear pattern. If a part has to be held mid-air while another is added from below, that's an overhead step.
Some parts need to stay in position before the housing closes over them. Use retention profiles like legs, minor extrusions, or nubs to keep things put. For instance, in humid Indian conditions, silicone gaskets absorb moisture and swell slightly. If you put a few small retention nubs that held the gasket in place without clamping it would not create interference.
When a hole receives a screw, add a lead-in or chamfer to it. Since most screws used in appliances are self-tapping, they cut new threads into plastic every time they're driven. Each time the screw misses the entry and has to be repositioned, it cuts a partial thread in the wrong place, weakening the hole. Indian appliances get disassembled by technicians who vary widely in technique. A chamfered hole survives 5-10 service cycles.
Tiny parts get dropped. It's that simple. Handling them with slightly damp grip is difficult. Be conscious of making parts slightly bigger, maybe with a small tab for fingers to grip.
Before the design is locked, write out the full assembly sequence with actual photos. It's typically done in CAD. But do with physically with a prototype. Every step that requires two people, or a third hand, or holding something against gravity is a design problem that's cheap to fix in CAD and expensive to fix in tooling.
5. Part count
Before adding a part, ask what it's doing that an adjacent part couldn't do. The cost of part is what BOM will document; the cost of part complexity is higher if not reviewed properly. Put each and every part under the microscope as if it were a candidate for elimination. This question, applied consistently in design reviews, removes more unnecessary parts than any other practice.
When you merge two parts into one, you almost always reduce total cost even if the merged part is more complex individually. Just ensure that the parts you're merging don't qualify to become standardised parts for another SKU.
When you have two small daughter boards connected by cables, you have assembly variation, vibration failure risk, and connectors that can work loose. Wire harness assembly and quality upkeep is complex. If your design permits, go for a single PCB which can eliminate all three failure modes simultaneously.
PP or Polypropylene can flex repeatedly without fatiguing which makes it possible to mould a hinge directly into a part (living hinge). Living hinges are underused in Indian product design despite PP being cheap and widely available. Find opportunities to do this in your products.
You don't need screws for battery doors and access covers that users or service technicians open repeatedly. A well-designed snap fit opens cleanly and requires no tools.
7. Other things that matter too
When you're specifying tolerances, use the loosest one that still works. Tighter tolerances cost more, take longer, and require better process control. A ±0.5mm tolerance on a non-critical bracket dimension is correct. Reserve tight tolerances for surfaces that actually mate, seal, or carry load.
If a design has a spring in it, ask whether the spring can be built into the part itself. In theory, a flexure moulded into the PP housing could replace it. One less failure mode.
If something in your product has to be waterproof or moisture-resistant, design the seal path first and the rest of the product around it. It's typically approached the other way where the product is designed, then someone tries to find a place to put a seal. The sealing geometry ends up compromised by everything that was already decided.
If a product has a filter, membrane, or any consumable that needs periodic replacement, design the replacement path before you design the product. The Native RO taught us this directly. The filter replacement sequence determined the housing geometry. If we had locked the housing first, the replacement path would have been an afterthought and ,for sure, a bad one.
Design for disassembly. Think about the order in which things need to come apart. The part that needs to be replaced most often should come out first, with the fewest steps.
When a product has multiple user-facing openings, standardise the opening mechanism across all of them. Service technicians or users shouldn't have to remember multiple different sequences. Standardising to one mechanism across all three reduced services errors.
When you're choosing between two materials that are otherwise equivalent, pick the one your vendor already runs. This sounds obvious but in practice, designers almost never ask vendors what materials they stock before they specify.
Use curves whenever possible inside part body. When a product has sharp internal edges that a service technician's hand will pass near, break those edges. A deburring operation costs almost nothing. You wouldn't want a cut finger on a service call.
Cable routing is almost always the last thing considered and almost always causes problems (we covered it earlier as well). Cables need a minimum bend radius, enough play to move parts around, and need to be captured somewhere so they don't interfere with moving parts. They need enough slack to allow for the assembly sequence. Route them before you finalise the housing dimensions.
Test your product installation process with someone who has never seen the product before but installs things for a living. Even better if you can get one who installs other appliances.
Think about gate marks at the time of specifying injection moulded parts. The gate is where the plastic enters the mould, and it leaves a small witness mark on the part surface. Your mould maker will put the gate wherever is convenient for tooling unless you specify. On a cosmetic face, that mark is visible for the life of the product. Specify the gate location on the drawing. This is critically important.
When you're designing a product that has two variants (with and without a particular feature) try to make the mechanical housing identical for both. The pre-requisite is of course get clear variant description before designing. The cost of maintaining two mould tools for a feature difference that could be achieved with a blanking panel or a functional change is rarely worth it.
The PCB mounting decision is important from the beginning. Think about the consequence of a PCB (a control PCB or display PCB) failing in the field. If the PCB is glued down, the whole product comes back. If it's on standoffs with accessible screws, a technician might be able to replace it.
Products have a visible seam where two housing halves meet. A uniform 0.4mm gap around the perimeter looks intentional. A gap that varies between 0.2mm and 1.2mm looks like a poorly built product. This is quite common in Indian automobile OEMs. Parting line mismatch and gap consistency are two of the most visible quality indicators on a finished product and are both controlled by mould tooling precision. Specify both in your inspection criteria.
When you're designing a door, lid, or access panel that has to feel solid when it closes, add a hard stop. A cover that closes against a foam gasket feels soft and uncertain. The same cover with a hard stop just before the gasket engages feels solid and precise.
Kitchen products get cleaned regularly. Think about where cleaning fluid goes when it runs off the surface. In Indian kitchens this is almost always water, soap, or a dilute surface cleaner. These fluids will find every gap, every unsealed joint, every cable entry, and every vent hole. Design the drainage path deliberately if there are usual ingress points.
Almost all of our products have multiple injection moulded parts that have to fit together. A ±0.3mm tolerance on each of four mating parts can produce a total variation of up to ±1.2mm at the last feature in the stack. Calculate the stack-up before the moulds are cut.
With products that have a plastic housing over a metal chassis (like in door locks), think about where the plastic is constrained and where it can move. Plastic and metal expand at different rates. If the plastic is constrained at multiple points along a long run, it will develop stress over temperature cycles and eventually crack.
When you're designing a product for a price-sensitive market, resist the temptation to reduce cost by thinning walls or reducing material in structural areas that carry load. Instead, focus on removing parts, simplifying assembly, or anything that can reduce process steps.
In India specifically, remember that installation is often done once, badly, and never revisited. The mounting that goes up on day one is usually the mounting the product lives with for its entire life. Design the installation to be forgiving of a single imperfect attempt.
This should be your takeaway
This list, by any stretch, is not as exhaustive as I'd like it to be. The idea of this post was not to be exhaustive but to push us into an operating mindset. At Native, one of our goals is to make each bucket a standardised checklist internally available at most relevant development stages from design inception through moulding. When we do, we'll publish it so others can benefit as well.
Every product has three cost buckets when it comes to manufacturing.
The first is design cost. This is your time, the team's time, the analysis and the prototyping and the rework. This one gets better with experience. You get faster, make fewer mistakes, and stop redesigning things that didn't work earlier. But this happens with every consecutive product development.
The second is manufacturing cost. This is where DFM comes in. This is knowing enough about how things are made to design them so they're not expensive or difficult to make. It's a huge amount of learning and it happens on the floor, with experience.
The third is assembly cost. This is DFA. DFA is designing so that putting the product together takes less time, fewer mistakes, and less skill than the alternative. Every step in an assembly sequence is a cost.
The frustrating part is that DFM and DFA don't always pull in the same direction. A part that's cheap to machine might be awkward to assemble. A part that drops in perfectly might require a complex mould.
We improve the first bucket automatically, with time. The second and third require you to go looking and understanding the commonly occurring issues or methods of DFM and DFA will improve your value as a designer. Remember, the best design engineers produce parts which achieve the desired function at the lowest cost.