Iteration in Design: Why Research, Testing and Evaluation Continue Throughout

A change can solve one problem and create another. You improve the shape, but make the product harder to use. You increase the clearance, but lose the grip. How do you know whether your design is actually getting better?

You investigate, test and evaluate again. This returning to an earlier question—or asking a new one because of what you have discovered—is iteration. It gives each change a reason.

My speaker-holder development: continuing the pattern improved its visual continuity, but removing the access opening introduced another consideration.

Research does not end when sketching begins

Needs Analysis, Idea Conceptualisation, Development and Prototyping describe different purposes within the design process. They do not divide research, testing and evaluation into separate boxes.

Research helps you find out what you need to know. Testing produces evidence by trying something under relevant conditions. Evaluation means judging what that evidence tells you against the intended need and requirements.

You might observe a difficulty during Needs Analysis, study an existing product while exploring ideas, or measure an object while developing its holder. A prototype test might reveal a problem that sends you back to investigate the user's activity. The question determines the work.

Returning does not mean restarting the whole project. It means revisiting the decision that the new evidence calls into question.

One change affects other decisions

In my portable speaker-holder project, I developed a curved body with a perforated pattern. An earlier version included rectangular openings that gave access to the inside.

I removed those openings so that the pattern continued around the body. The CAD comparison shows the visual change clearly. However, the same change restricted access for removing printing supports and handling the speaker.

Was the revised version better? It was more visually continuous. That alone did not establish that it was better overall.

This is where evaluation matters. The next checks would include whether the internal supports can be removed adequately, whether the speaker can be inserted and removed conveniently, and whether charging access remains practical. These are checks to carry out, not results established by the CAD image.

A photograph of the completed holder with the speaker fitted shows an assembled outcome. It does not, by itself, prove stability or convenient repeated use. Different claims need different evidence.

Choose a test that answers your question

You do not need to make the entire product every time you are uncertain. Choose the simplest useful representation that can answer the question.

A sketch can help compare access-opening positions. A cardboard mock-up can reveal whether a hand can reach an opening. A small printed section can investigate a fit before committing to a full print. A complete prototype becomes useful when you need to examine how the parts and the user work together.

Each method has limits. A cardboard mock-up cannot establish the durability of the final material. A CAD view cannot tell you how comfortable an edge feels. Use the evidence for the judgement it can support.

If a test reveals a problem, identify the likely cause before changing the design. After a revision, check the original problem again—and any other requirement the revision could affect. A wider opening may improve access while changing the appearance or the way an object is retained.

Make each return worthwhile

Iteration is not repeatedly changing things until you like the result. Be able to explain the connection: What was uncertain? What did you find out? What changed because of it? What still needs checking?

Record these connections in your design journal as they happen. Keep the useful sketch, test observation or photograph and explain the decision it informed. Do not invent earlier alternatives afterwards to make the process appear orderly.

Nor must iteration continue indefinitely. Judge the design against its intended use and agreed requirements. Resolve the important uncertainties within the available time and resources, and acknowledge limitations where evidence is still incomplete.

Before proceeding, know what your latest change has improved, what evidence supports that judgement, and what else the change may have affected.

This independent explanation uses the design-process terminology in the Singapore–Cambridge Secondary Education Certificate D&T syllabus. It is not an officially endorsed resource.

#DesignProcess #Iteration #DesignResearch #Testing #Evaluation #DesignJournal #DesignAndTechnology #DesignJournalSOS

Previous: The Design Process: Needs Analysis, Idea Conceptualisation, Development and Prototyping
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The Design Process: Needs Analysis, Idea Conceptualisation, Development and Prototyping

If I ask where you are in your design project, you might say, “I’m doing development.”

But what are you developing? What remains unresolved? What will your next sketch or model help you decide?

Knowing the name of a phase is useful. Understanding its purpose helps you move forward.

The design process connects an identified need to a proposed solution through Needs Analysis, Idea Conceptualisation, Development and Prototyping. Research supports all four, while evaluation helps you judge what to keep, change or investigate further.

Two versions of my pen holder. A physical test revealed a limitation and prompted further development.

Needs Analysis: what is worth changing?

Investigate a person’s activity and the situation in which it happens. What are they trying to do? What gets in the way? What could become easier, safer or more appropriate?

Observe, ask questions and study existing arrangements. Check whether your explanation fits what actually happens. A proposed product such as “a phone holder” tells us little until you explain who needs it and why.

Your investigation should establish a worthwhile design opportunity. A design brief expresses the intended outcome; research helps you develop specifications that state what the solution needs to achieve. These can be revised as your understanding improves.

Idea Conceptualisation: what different approaches could work?

Explore possible ways of fulfilling that purpose. Sketch alternatives, borrow useful principles from existing products, combine features and use simple mock-ups to investigate promising thoughts.

For a hypothetical pen-storage project, a pocket, a clip and an elastic loop offer different ways of retaining the pen. Drawing the same clip in several colours gives you appearance options, but does little to explore alternative ways of holding it.

Compare your concepts with the user’s needs and the design specifications. Choose a promising direction for reasons you can explain.

Development: how will the chosen concept work in detail?

A promising concept still contains unanswered questions. Development is where you work through them.

How large should the opening be? Where will the user place their fingers? How do the parts meet? Which material and making method suit the intended use?

You still generate alternatives here. The difference is their purpose: you are resolving particular features of a chosen concept and bringing the decisions together into a workable whole.

Use sketches, measurements and models to check your assumptions. A change to one part may affect another, so keep checking the assembled design, its appearance and its use. Resolve enough detail to make the prototype with a clear intention.

Prototyping: what happens when the proposal becomes physical?

Make a working version that allows you to investigate the proposed solution in use.

Earlier models may have answered individual questions about size, access or movement. The prototype brings the developed decisions together so you can examine how they perform as a product.

Test it against the intended use and specifications. Record what happens, including limitations. Making something successfully does not, by itself, show that it meets the user’s need.

A test can reopen a design decision

In my clipboard pen-holder project, I began by sketching the pen’s cross-section and a holder around it. The sketch helped me think through the grip before printing.

Sketching the relationship between the pen and its holder made the proposed grip easier to examine. Click to enlarge.

The first print held the pen during light handling. However, a nudge on the unsupported section could dislodge it.

That finding sent me back to development. I doubled the gripping section’s length and added slots to the mounting plate.

The revision responded to something observed. Whether it provided sufficient retention still needed checking through use; a longer grip’s appearance alone could not establish that.

This is why research and evaluation belong throughout the process. Measuring the pen informs the design. Testing its retention provides more information. Evaluating that information tells you which decision needs attention next.

Your journal should record those connections as they happen: the question, the evidence, the decision and the resulting change.

Before moving on, be able to explain what you have found out, what you have decided, and what still needs resolving. Let that understanding guide your next action.

The phase names follow the official secondary D&T design model. This is an independent teaching resource, not an officially endorsed publication.

#DesignProcess #NeedsAnalysis #IdeaConceptualisation #DesignDevelopment #Prototyping #DesignAndTechnology #DesignEducation #DesignJournalSOS

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Good Design: Usefulness, Appropriateness and Appearance

A product can look attractive and still be frustrating to use. It can work perfectly on a table and become awkward the moment someone needs to carry it.

So when you say a design is “good”, what do you mean?

Three questions help you give a more useful answer: Does it serve a worthwhile purpose? Does it suit the user and situation? Does its appearance support the intended experience?

A dog bringing a note: the form gives an ordinary holder a recognisable story. The note and pencil still need to be held effectively.

Usefulness: what does it help someone do?

Start with the intended purpose. A note holder should keep a note where it can be seen. A pencil holder should keep a pencil available when it is needed.

Naming those functions is only the beginning. Can the note be inserted easily? Does it stay in place? Can the pencil be picked up without disturbing everything else?

These questions turn “it works” into something you can investigate.

Usefulness can also involve enjoyment, reassurance or a pleasant experience. As discussed in designing with purpose, a playful product can have a legitimate purpose. Be clear about what it is meant to achieve, then look for evidence that it achieves it.

Appropriateness: does it fit this situation?

A design may perform its basic function and still be unsuitable for a particular person or place.

Imagine a holder that keeps a note upright but occupies most of a small desk. Its holding function works. Its overall size makes it inconvenient in that setting.

Or imagine one that looks tidy when empty but becomes difficult to reach into when filled. The empty product gave an incomplete impression of its suitability.

This is why I keep asking students to draw the items inside their proposed holders, in proportion. Include the person and surrounding space when they affect use. A holder drawn on its own can hide problems with size, access and arrangement.

Appropriateness connects the design to the user's activity, abilities and preferences, the objects involved, and the environment. It also includes practical matters such as safe handling, cleaning and storage where these are relevant. Find out which matter in your project instead of adding the same general statements to every design.

Appearance: what does the form communicate?

Appearance includes shape, form, proportion, colour and texture. These choices influence how a product is perceived and can help someone understand how to use it.

In my dog note and pencil holder, the idea of a dog bringing its owner a newspaper gave the form a connection to its function. The mouth became a place to hold a note. The form told a small story.

That connection gave me a reason for choosing the dog profile. It did not, by itself, prove that the holder would work.

I first explored holding paper with simple blocks and curved slots. Later, I developed the dog form and made printed versions. The mouth gap needed further adjustments so that the paper would be held more effectively.

The attractive concept and the working detail both needed attention.

Whether someone likes that appearance is another question. A playful dog may suit one person's desk and feel out of place on another. Ask the intended user and consider the setting. Your own taste is a starting point for investigation.

Develop the three together

I often ask students to focus on function first. A simple block can help you investigate how something will work without getting distracted by styling.

That is a teaching focus. As you develop the design, every change needs to be considered in relation to the whole product.

Changing the dog's profile may change the space available for the pencil. Enlarging the body may improve storage while making it too bulky for the desk. Altering the mouth for a stronger visual expression may affect how the paper fits.

Sketch, model and test these relationships. After a change, check the product again with the objects it holds and the person who will use it.

Before calling a design good, explain what it achieves, why it suits its intended use, and how its appearance supports that purpose. Then show the evidence.

#DesignUsefulness #DesignAppropriateness #ProductAppearance #FormAndFunction #UserCentredDesign #DesignAndTechnology #DesignEducation #DesignJournalSOS

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Designing with Purpose: Needs, Users and Meaningful Change

When you propose a design, I want to know three things: what are you trying to change, who is it for, and why is that change worth making?

Your answers give the project its purpose. They also give you something to return to when you research, sketch, develop and test your ideas.

Without that clarity, it is easy to spend weeks making something and still struggle to explain what it achieves.

Organising pencils, extending their usable life, and storing the extended pencils: each change has a purpose.

Begin with the change you want to make

Consider this proposal: “I want to design a phone holder.”

It tells us what you intend to make. But we still know very little about the reason for making it.

Who will use it? Where? What will they be doing? What is difficult or unsatisfactory about the current arrangement?

For example, imagine someone following a recipe on a phone while preparing food. They need to see the instructions clearly, keep the phone away from spills, and use the available worktop space sensibly.

Now there is a situation to investigate. A holder might help, but its usefulness depends on whether it improves that particular experience.

The intended change gives the object a reason to exist.

A design opportunity can take different forms

Students often think they must discover a problem that nobody has ever solved. That expectation can make finding a project unnecessarily difficult.

There are several ways into a worthwhile design:

• Resolve a difficulty: help someone do something they currently struggle to do.
• Improve an existing solution: make an activity easier, more comfortable or more appropriate for a particular user.
• Explore an alternative: find a different way to achieve a familiar purpose.
• Develop an inspiration: use something observed in nature, a product or an everyday situation as the starting point for a useful or engaging outcome.

These directions can overlap. What matters is being clear about the intended outcome.

A project designed for enjoyment is a legitimate design challenge. So is an improvement to an ordinary task. Be honest about which you are pursuing. If the purpose is fun, explain the experience you want to create. If the purpose is practical improvement, explain what should become better.

Calling an idea “innovative” does not explain its value. You still need to show what changes for the user.

A small improvement can have a clear purpose

In an earlier project, I made a holder that kept classroom pencils organised and ready to use.

As the pencils became shorter, another need emerged. They still had usable graphite, but their remaining length made them increasingly awkward to hold.

I made pencil extenders so the shortened pencils could continue to be used. Then came another question: how should the pencils fitted with extenders be stored?

That led to a further holder.

Pencil extenders keep short pencils usable. A separate holder keeps them organised.

The important point is the connection between each change and the situation that prompted it. Organising pencils, extending their usable life and storing the extended pencils each served a recognisable purpose.

Design opportunities can emerge as people use something. A completed solution can reveal the next worthwhile improvement.

Understand the person and the situation

A user is more than a label such as “students” or “elderly people”.

You need to understand the activity they are carrying out, the objects involved, and the environment in which it happens.

The same object may work well in one situation and poorly in another. A storage solution suitable for a permanent desk may be inconvenient for someone who packs everything away after each lesson.

Observe what happens. Ask questions. Look at existing solutions. Check whether your explanation fits the evidence.

If you find a product that already addresses the need, study it. You may discover that it is suitable as it stands. Or you may identify a specific limitation worth improving.

Either finding is useful. Research helps you judge whether your proposed change is justified.

Before you proceed

You should be able to explain:

• Who the design is intended for.
• What they are doing and where.
• What you want to improve, enable or create.
• What evidence supports that intention.

You do not need to have the final solution worked out. You do need a clear enough purpose to guide your next investigation.

Designing with purpose means being able to explain why the change matters—and later demonstrate whether your design achieves it.

#DesignPurpose #DesignNeeds #DesignOpportunities #UserCentredDesign #DesignProcess #DesignAndTechnology #DesignEducation #DesignJournalSOS

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Free Sennheiser XS Lav Microphone Clip STL: Flat Base & Snap-Fit Design

Want to 3D-print a holder for your Sennheiser XS Lav microphone? The flat-base STL is FREE. Download the free flat-base microphone clip on Gumroad for personal or classroom use, then add your own adhesive hook-and-loop fastener to mount it where you need it. The phone-overhang option shown below is available in a separate paid bundle.

This small clip also makes a useful design lesson you can hold in your hand. For my Sennheiser XS Lav USB-C microphone, two measurements shaped the fit: a 6.5 mm gripping diameter and 5 mm of available gripping length. The detail that keeps it in place is where the cradle ends.

3D Rendered photograph: An overhang printed bases for an iPhone with case.

Physical photograph: two printed bases for different mounting preferences.

Why the snap-fit clip must pass the midpoint

Matching the diameter gives the microphone somewhere to sit. Retaining it needs another detail: the sides of the cradle must extend above the circle’s horizontal centreline.

A semicircular cradle ending at that line leaves an open path upwards. It can support the capsule, but provides no geometric snap retention. Extending the lips beyond the midpoint makes the entrance narrower than the diameter being held. The lips flex apart during insertion, then recover around the capsule to resist it lifting out. That is the basis of the “click-in” action; an audible click is not guaranteed.

I used a nominal 6.7 mm cradle bore around the 6.5 mm gripping diameter and a 240° wrap. The 5 mm gripping length keeps the cradle within the available cylindrical section. Diameter, opening, wall thickness and material flexibility work together to determine the fit.

CAD drawing: the cradle wraps beyond the centreline to form a retaining opening. Click to enlarge.

This follows the same habit I discussed in sizing a design around an accessory: start with the object that must fit, then build the surrounding form. The steel rule positioning block provides another example of a small retaining detail changing how parts meet.

Flat base or phone-overhang mount?

The free flat-base version is a straightforward starting point if you prefer choosing your own mounting position. It offers a 15 × 10 mm mounting surface for users who prefer adhesive hook-and-loop fastening, such as Velcro. The fastener is supplied separately; its thickness and adhesion need to suit the chosen surface.

Physical photograph: the flat-base clip with the microphone seated.

The overhang version is my preference. It clips over the phone edge and adds rounded internal gripping ribs for extra hold. This version was designed around my 11 mm phone-and-case thickness. A different case can change the contact, flexibility and grip, so measure yours before printing.

Physical photograph: the overhang base and microphone cradle.

CAD drawing: rounded ribs narrow the phone channel to provide the intended grip. Click to enlarge.

Both versions have been printed, and the photographs show the microphone seated. Check the fit gently on your own print, keep the acoustic opening and phone controls clear, and inspect for cracking or looseness. Print material and tolerances still matter.

Get the free flat-base STL—or choose the phone mount

To try the design, choose Flat Base V3 — Free on Gumroad and enter US$0; a tip is optional. The download includes the STL, a print-and-fit guide and a personal/classroom licence. If you prefer the phone-edge mounting option, the US$3.99 bundle includes both the overhang and flat-base STLs.

Want to sell physical prints? Choose the corresponding commercial option: US$11 for the flat base or US$14.99 for both designs. Each allows up to 100 physical clips in total; the bundle shares that allowance across both designs. Designer credit is appreciated but optional. Digital files may not be resold or shared under either licence.

Get the FREE flat-base microphone clip STL on Gumroad

For design students, the lesson is practical: do not simply record a critical dimension. Explain what it controls. Here, a diameter establishes the seat, a length defines the available contact, and the lips above the midpoint create the retaining geometry.

#SennheiserXSLav #MicrophoneClip #SnapFitDesign #CriticalDimensions #3DPrinting #DesignAndTechnology #DesignJournalSOS

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3D-Printed Steel Ruler Positioning Block: 45°/90° Marking & Critical Dimensions

A marking tool can look finished long before it works as intended. With a steel rule positioning block, the question is not only whether the body presents 45° and 90° edges. It is also whether the rule sits where you expect when you bring the tool to a piece of wood.

That small question shaped Version 4 of my 3D-printed positioning block.

Physical photograph: the printed V4 block with a steel rule inserted.

Combining two useful functions

I began with a compact block that offered two common reference angles. The 90° face helps when a line must cross a board squarely; the 45° face offers another familiar layout direction. This is an example of the Combine step in SCAMPER: putting related functions into one tool, then checking whether they still work well together. It is the same question I explored when combining functions in another printed design.

The steel rule is the working edge, so the printed body needs to position it reliably. A printed thumb screw pushes from one side. The exterior reference faces then meet the edge of the workpiece while the ruler remains available for marking.

Physical photograph: the body and matching printed screw.

A small dimension changes the contact

In Version 3, the rule rested on a seat against a straight shoulder, with the screw contacting its opposite edge. The CAD section below makes that arrangement visible. It established the basic relationship, but it also drew attention to the rule's upper edge: a flat shoulder does not place a lip above it.

V3 CAD section: screw, ruler and flat shoulder before the retaining change.

Version 4 adds a 2 mm-high, 2 mm-deep undercut with a 45° internal face along that shoulder. The rule tucks beneath the lip; the existing screw has enough extra travel to press it toward the sloping face. The screw trough was extended by 2 mm to make room for this movement. This is a digital design result, not a claim of measured holding force.

The number that matters first is the thickness of the actual steel rule. The CAD checks considered rules from 0.3 to 1.0 mm thick. Within that range, the geometry gives 1.7 to 1.0 mm of insertion beneath the lip. The 2 mm dimension describes the retaining recess, not a typical rule thickness. This follows the same principle as modelling the accessory before sizing the product around it.

V4 CAD section: the 45° lip and its relationship to two ruler thicknesses.

Physical photograph: the printed profile. The photograph does not measure grip strength.

Function and finish belong together

The body remains about 80 × 55 × 18 mm, with a 45° diagonal reference face, a 90° face and a round finger opening. The softened outside corners and edges carried forward from Version 3 make the form look more resolved and feel less abrupt. I kept the functional junction at the rule seat crisp, because rounding that point would change the contact with a thin rule. In a design drawing, form, function and critical dimensions should support one another rather than be treated as separate concerns.

V4 CAD drawing: body envelope and the two workpiece-contact faces.

Physical photograph: one reference-face orientation at a workpiece edge.

Physical photograph: an alternative layout orientation.

The V4 download includes the body, matched thumb screw and a thread-fit coupon. The printed thread is a custom pair, so I would check the coupon first, inspect the retaining lip in the slicer, then test the assembled tool with the particular rule and workpiece before making a project mark. The supplied photographs show a printed example; they do not establish marking accuracy or long-term retention.

Download the Steel Rule Positioning Block V4 files on Gumroad.

Small details such as the rule's thickness, a two-millimetre recess and a carefully kept sharp contact edge decide whether combining useful features becomes a useful tool.

#SteelRule #MarkingGauge #SCAMPER #CriticalDimensions #3DPrinting #Woodworking #DesignAndTechnology #DesignJournalSOS

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3D-Printed Chocolate Bar Coaster: Shape Borrowing in Product Design

Sometimes a useful design begins with a familiar shape.

Look at a chocolate bar and you immediately recognise its repeated grid. The divisions invite you to break it into smaller pieces, but they also give the object rhythm, proportion and character. I borrowed that visual language for a simple household product: a 3D-printed drinks coaster.

The result is a square coaster that still reads as a 3×3 chocolate bar, while each feature has been adjusted to suit a cup rather than confectionery.

Physical photograph: two separately printed square coasters in use.

Borrowing a shape without copying its purpose

Shape borrowing is a useful design method for students. Begin with a recognisable object, identify the visual features that give it identity, and then adapt those features for a different function.

The challenge is deciding what to retain. Copy every detail and the new object may become a novelty with little practical value. Remove too much and the reference disappears. In this case, the square outline and repeated divisions were enough to communicate “chocolate bar”. Colour was optional: the orange and white prints still make the borrowed form readable.

For this coaster, the important borrowed feature was the chocolate bar’s grid. Two horizontal and two vertical grooves divide the 100 × 100 mm square into nine equal-looking panels. The grooves are only 2.4 mm wide and 0.8 mm deep, so the pattern remains visible without cutting the coaster into separate sections or making the surface unnecessarily difficult to print.

Physical photograph: the shallow 3×3 grid preserves the chocolate-bar identity.

Physical photograph: the same geometry remains clear in a different filament colour.

Turning the borrowed form into a coaster

A playful, practical coaster inspired by a 3×3 chocolate bar. The raised circular rim helps position a cup and contain minor condensation, while the flat underside keeps the print simple and support-free.

The circular area creates a clear relationship between the square coaster and a round cup. It has an 85 mm flat seating envelope and a 91 mm upper opening. The gently blended transition avoids an abrupt internal corner, while the raised perimeter gives the cup a visual position on the coaster.

The overall height is 7.4 mm. Underneath, the coaster is completely flat. This gives it a broad contact surface and allows it to be placed directly on the print bed without supports. Rounded outer corners and softened edges also make the square form less severe in the hand.

These decisions also offer a useful lesson for design students. An attractive idea still has to be resolved in three dimensions. The cup needs a suitable seating diameter; grooves need enough depth to remain visible after printing; and the base needs sufficient material below those grooves. Form, function and manufacture therefore develop together rather than as separate stages.

CAD view: the grid, circular recess and square outline form one continuous part.

CAD drawing: the 100 × 100 mm body surrounds an Ø85 mm seat and Ø91 mm upper opening.

CAD section: a flat underside and shallow surface details enable support-free printing.

Two ways to print it

The download includes a single-coaster option and a plate arranged for two separate coasters to print sequentially on a compatible Bambu Lab P1S. With the tested PLA profile, the slicer estimates approximately 1 hour 5 minutes and 53.5 g for one coaster, or 2 hours 5 minutes and 107.3 g for the two-coaster sequential plate.

The sequential arrangement passed the stock P1S slicer-clearance checks, but I have not physically printed the complete two-coaster plate. Printer owners should confirm toolhead clearance, plate placement and print order for their own machine before starting a sequential print.

Slicer evidence: two independent square coasters arranged to print one object at a time.

Because the supplied profiles are intended for PLA, avoid placing very hot cookware on the coaster. Material choice and temperature resistance should always match the intended use.

Download the 3×3 Chocolate Bar Coaster files on Gumroad

This small project shows that playful form and practical manufacture can support each other. Shape borrowing supplied the character; careful dimensions, shallow details and a flat underside made that character printable and useful.

#ChocolateBarCoaster #ShapeBorrowing #3DPrinting #ProductDesign #DesignAndTechnology #DesignJournalSOS

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3D-Printed Sandpaper Holders: Flat & Rounded Sanding Blocks for Small Projects

Small pieces are often the most awkward to sand. A loose strip of sandpaper may seem convenient, but it can fold, slip or simply follow the movement of the fingers. This makes it harder to keep a surface flat, produce a consistent chamfer or follow a controlled curve.

I originally designed a compact flat sandpaper holder to give a 30 mm abrasive strip a firm, predictable backing. I have now added a second holder with a long, gradual convex face. The fastening idea is shared, but the two tools serve different purposes.

Photograph: the flat and rounded holders show how changing the backing shape changes the sanding task.

One fastening idea, two sanding surfaces

Both holders use a removable rear clamp and a large printed thumb screw. The abrasive strip passes over the working face and is held at the rear. When it wears out, the screw can be loosened and the strip replaced.

The important design decision is the form beneath the abrasive. Sandpaper alone is flexible; the holder controls how that flexibility is used.

The flat holder: keeping flat work flat

The original holder has a rigid flat backing and an 80 x 30 mm footprint. It is useful for small flat faces, controlled chamfers and edge refinement where the intention is to preserve a straight or planar surface.

With loose sandpaper, fingertip pressure tends to concentrate in small areas. The paper can also curl around an edge and round it unintentionally. A flat holder spreads pressure over a defined face and gives the hand a more stable reference.

Photograph: the original flat holder assembled with a 30 mm abrasive strip.

For chamfering, hold the work securely, mark a guide line and maintain a steady angle. Light, counted strokes make matching edges easier to compare. The tool improves control, but the accuracy still depends on the user's judgement.

The rounded holder: following gradual inside curves

The second holder replaces the flat working face with a long convex profile. It is intended for broad concave surfaces, shallow inside curves and gradual transitions that a flat block cannot follow. Its narrow nose can approach tighter areas, while the wider part of the curve provides a larger sanding surface.

Photograph: the side profile reveals the gradual convex face and narrow nose of the rounded holder.

This is a useful lesson in matching a tool to the geometry of the intended result. A flat block helps preserve flatness. A curved form supports the abrasive while allowing it to contact a concave workpiece more evenly. Neither shape is universally better; each is selected for a different outcome.

Photograph: the assembled rounded holder, rear cap and hand-tightened printed screw.

A shared clamping system

The rounded holder uses the same custom printed screw interface as the flat design. Its main body, rear cap and thumb screw are separate parts, making the clamping action visible and easy to understand.

Photograph: the rounded body, removable rear cap and matching thumb screw separated for assembly.

Both holders accept 30 mm-wide strips. About 175 mm is a sensible starting length; fit the strip, confirm its path and then trim if required. Tighten the screw by hand only. The thread is a matched printed pair and is not intended for a standard metal M10 fastener.

Photograph: comparing the compact flat holder with the longer rounded profile.

Printing considerations

The flat holder is supplied in support-free STL orientations and includes a thread-fit coupon. Printing the coupon and screw first allows the thread fit to be checked before the complete tool is made.

The rounded body needs selective removable support beneath the rear retaining rails. The cap and screw print without support. A prepared Bambu Lab P1S 3MF is included with the download. Its slicer estimate is approximately 1 hour 58 minutes and 40.25 g of filament, including purge and support; actual results will vary with printer, material and settings.

CAD view: the rounded holder body and cap measure 80 x 30 x 30 mm, with an 88 mm overall length including the screw.

Slicer evidence: selective support is confined to the rear retaining rails.

The flat holder has been physically printed, assembled and function-tested in PLA on a Bambu Lab P1S with a 0.4 mm nozzle. The supplied photographs confirm that the rounded holder has also been printed and assembled, and its 3MF has passed slicer checks. Its sanding performance, paper retention, support-removal quality and durability still need further physical evaluation.

Sand effectively and safely

Start with a grit suited to the amount of material that must be removed, then move progressively to finer grits. Test the chosen holder on scrap before working on the project. Secure small workpieces, wear appropriate eye and dust protection and stop using any printed part that cracks or allows the abrasive to slip. PLA can soften in high heat, so do not leave the tool in a hot vehicle or near heat-producing machinery.

The files are available separately for each holder, or together as a discounted set:

Download the Flat or Rounded 3D-Printable Sandpaper Holder on Gumroad

A simple holder does not replace skill. It gives the hand a backing shape that makes the intended result easier to judge and repeat. The flat and rounded versions show how one small change in form can produce two distinct workshop tools.

#3DPrintedSandpaperHolder #HandSanding #WoodworkingTools #3DPrinting #WorkshopSkills #MakerEducation #DesignAndTechnology #DesignJournalSOS

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From Portable Fan to Speaker Holder: SCAMPER, AI and 3D Printing

A portable fan, a rattan pattern and a small Bluetooth speaker became the starting points for this project.

I wanted to design a holder for my Xiaomi portable speaker, with its circular grille seated flush at the top. The process brought together several ideas I often discuss with students: observing existing products, using SCAMPER, developing a form and checking whether it can actually be made.

It also gave me an opportunity to build an AI-assisted workflow around a real design problem.

Photograph: the printed holder with the speaker fitted.

Begin with the object you are designing for

Before developing the holder, I examined the speaker from different directions.

Front

Back

Side

Photographs: each view reveals information that a single picture cannot provide.

The speaker measured 52 mm in diameter and 24 mm thick, with a mass of 66.2 g. These figures became design constraints.

The diameter and thickness informed the receiving socket. The mass mattered because the speaker would sit high above the tabletop, towards the front of the holder. Its position needed to be considered together with the base.

Inspecting the details

Measuring the mass

Photographs: record dimensions, mass and access requirements before modelling.

For students, this is a useful habit: connect every measurement to a design decision. A measurement becomes valuable when it helps determine what to make.

SCAMPER: combine, adapt and modify

The main form came from a portable handheld fan. Its upright body and curved head suggested a way to raise the speaker and orient it towards a listener.

I combined this with a rattan-inspired pattern to develop the holder’s surface.

Form reference

Pattern reference

Supplied design references: the fan informed the overall form; the rattan informed the pattern.

This is Combine in SCAMPER: bringing selected characteristics together to serve a new purpose.

Adapt followed. The area corresponding to the fan outlet became a socket for the speaker. The woven appearance became a pattern of openings in a printed shell, with shallow patterning over the closed base.

Modify helped develop the proportions, speaker orientation and base.

This follows the approach in my earlier post on concept borrowing and idea development: identify a useful characteristic, then develop it for the current design situation.

There is no need to force every SCAMPER letter into one project. What matters is explaining how a prompt changes the idea and why that change is useful.

Early CAD preview: the combined idea becomes a model that can be inspected.

Develop the form through specific revisions

I wanted the speaker’s axis tilted 20° above horizontal, aiming it towards a listener seated above desk level. This was a positioning intention; improved listening performance would need evaluation.

The early model also had an awkward interruption around the back of the bend. I returned to the fan reference and requested a continuous circular section flowing into a seamless curve.

CAD comparison: refine the transition while retaining the intended speaker angle.

I subsequently removed the rectangular access openings so the rattan pattern continued across those areas. This improved visual continuity, but also restricted access for cleaning out supports and handling the speaker.

CAD comparison: removing a feature introduces consequences as well as visual changes.

The developed holder was 160 mm tall, with a 60 mm body diameter and a 120 mm diameter, 5 mm thick base. The wider base addressed the raised speaker’s position. Physical stability still belongs in the evaluation stage.

Front view

Rear view

CAD views: inspect the design from several directions, including surfaces hidden in the presentation view.

As I explained in combining ideas and further refinements, combinations need continued development to become practical solutions.

How I built the AI-assisted workflow

I organised the work into a repeatable sequence:

Measure and photograph → provide references and constraints → generate a model → inspect → revise → check print preparation.

I used Codex to help generate and revise the model, prepare previews and check the geometry and slicing. My role was to establish the requirements, judge the results and give specific feedback.

For example, identifying an interrupted rear contour and requesting a seamless curved transition gave the revision a clear target.

For students using AI, preserve this reasoning in the design journal. Show the input, the result, the issue you noticed and the change you requested. That record makes your contribution visible.

Appearance also affects manufacturing

The perforated body needed consideration during print preparation, particularly around the tilted head and speaker socket. The saved support preview shows where temporary structures were generated.

Slicer preview: plan how supports will be removed as well as where they are needed.

I also explored a smooth, hollow alternative while retaining the main dimensions.

The reviewed patterned project had an estimated print time of 6 hours 17 minutes. The smooth version was estimated at 3 hours 57 minutes—approximately 37% shorter. These were slicer estimates with retained process settings; the changed geometry and base colour coverage both affected the comparison.

AI-generated visualisation guided by CAD previews—not a photograph or dimensional drawing.

Bring the learning back to evaluation

The finished photograph shows the speaker fitted into the printed holder. A fuller evaluation should ask:

• Can the speaker be inserted and removed conveniently?
• Does the holder remain stable during ordinary handling?
• Is charging access manageable?
• Does the orientation suit the intended listening position?
• Are the patterned appearance and printing time a worthwhile trade-off?

Teachers can use this sequence as a design-journal exercise. Ask students to identify what they borrowed, explain each modification and propose a test for each important requirement.

A convincing design journal shows how decisions develop—and what evidence is still needed to judge the result.

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