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3D printed PLA mold for concrete casting

Hi, a new project and I’ll be adding to the documentation coming weeks. I hope it gives you useful information or inspiration.

Usually for casting concrete a wooden form is made which is filled. For simple shapes that’s easy, but some shapes are hard or time consuming to make of wood. I wanted to try this already for some time, so I decided to make a 3D printed mold. Interesting study project but for such a simple shape way over the top 🙂

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This is what I want to make: a sign for use at competition days at my athletic club

(Tion Herfstloop)

We thought of a simple wooden cross with a weight (three tiles or a bag filled with sand) placed on it, a bucket filled with sand (or concrete). It has to be transportable, not too heavy, and it will be decorated (painted).

Rather simple, and it could well be made quickly without any problem. But for learning I’ll use 3D printing. The added value might be: nice shape, own logo, durable.

Questions:

-How thick should the mold be

-Will the concrete release well? Release agent or grease necessary?

-How many times can it be used.

-Aluminium or Portland cement ? Alu is much faster and fine for details. Portland is cheap.

A block with a center hole for a post, 2 handles to pick it up easily and two holes to put a rope through.

These parts would form the sides of a wooden mold. However, I abandoned this idea of separate parts and adjusted the plan for 3D printing the mold.

The 3D print design. The walls are still 9 mm thick, remnant of designing for wood 9mm.

The resulting shape. Looks nice to me. Print it

27 hours printing.

Settings: 0,20mm Standard @BBL A1M (Bambuslicer):

0.2mm layer height, 15% fill, , gyroid.

Nozzle: 0.4mm.

PLA: Basis PLA (Bambu), printed at 100% speed.

The next print ( the shape to form the opening for the hand) I printed at 160% (ludicrous). It turned out well.

Next: sanding before appling a coating.

K120 sanding paper, primer spray paint, 2 coats applied

I bought this material:

Gietsteen (casting stone). You can also use aluminiumcement mortar with sand. Alu cement is not sold everywhere like portland cement. I found it at sculptors supply store Beeldhouwwinkel. Others that have it: Keramikos and Hazelaar. 20 kg costs about 40 euro, transport 12,50 euro. That is much more than 25 kg portland ( around 8 euro / 25 kg mixed with sand (3x 25 kg, less than 10 euro). It better looks awfully nice for such a price. Bought it anyway. If this works well there will be follow up projects.

https://www.beeldhouwwinkel.nl/nl/caltra-gietsteen-standaard-snelwerkend-801

For the through holes I use a PE tube around a metal rod, so I can remove it easily: just pull it out, it is flexible and does not stick to concrete. Metal tubes or wooden rods might get stuck. Then you have to do a lot of work to get them out and keep the mold intact.

For the big hole I cut a 2-piece foam core with the hotwire cutter (smoother than with the belt saw), made a 2-piece foam core (might be easier to remove than a 1-piece core). Taped around it to keep it together. I can, I suppose, remove this core quite easily with a piece of metal, a screwdriver or other sharp tool. We’ll see 🙂

The mold parts. Now: applying release agent ( bekistingsolie (NL), Schalol (GE) ). Oil or vaseline can also be used as well but is not recommended as it may stain the concrete. I found a jerrycan with still 3L in it at Marktplaats for a very reasonable price. That will do for many molds to come.

A thin coat of oil applied, 1 liter is good for 20 -30 square meter, that means a layer three times as thin as a paint layer, so apply sparingly. I applied it with a dry-ish brush and removed excess with a paper towe

Cement and water. Ready to go

Mixed. Now tapping against the bucket with a stick, to get the air out

I waited 5 minutes before casting, following the instructions. But it set very fast, I could hardly poor 80% into the mold and it got to stiff already. Probably too hot today (over 25°C). So I quickly prepared another batch, mixed, did not wait 5 minutes this time and still it set very quickly. But now I succeded to fill the mold to the rim and hit it gently with the plastic hammer to get the air out and level the surface. Even filled a couple of small test molds. Covered it with wet cloth and a plastic bag to prevent that the concrete dries out. Tomorrow we’ll see how it ended up. Will it release properly, will there be a visible separation between the first and the second cast? I must go home now and not have a look (and rip the fresh concrete apart)

Ok, some positive and some negative points:

1 cast came out easily,

2 tubes and center hole worked out well

3 overall shape and weight are convenient

but:

4 shrink cracks,

5 characters were damaged

6 casting in two times gave an ubly joint

next cast:

Working at lower temperature or using a slower setting cement so I have enough time to fill the mold in one time

adding sand against fracture

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marble run 2026 drawings and manual

(you can also download the files from github here)

Manual for the workshop (German)

murmelworkshop manual duits 5 20260716Downloaden

workshop manual Nederlands

knikkerbaan workshop manual nederlands 5 20260716Downloaden

Making the schablone:

Cut the PDF with a laser cutter or print them on paper and cut them with a knife and scissors. use cardboard of about 0.5 – 1 mm.

Alternatively they may be 3D printed.

straight track schablone:

schabloon rechte goot karton 20260708Downloaden

curved tracks and support schablone:

mal bochten en pylon 920260630Downloaden

Using the schablone:

copy the lines on 200- 300 gram paper, using a ballpen, which gives suitable folding lines. when tracing: skip the triangles, they are only ment for holding the schablone together. draw / cut a straight line

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Marble run maker in residency

Augustusburg, june – july 2026

I have been invited as a maker in residency in Aufweiterflur in Augustusburg, close to Chemnitz in Germany. A major objective was giving workshops marble run here and also representing AWF at the Chemnitz maker fair. And also collaborating with other makers at Makers United (link to Makers United 2026 here)

I developed a marble run made of paper. Trial and error and interaction with children was part of designing. The first ideas of the marble run were very much rooted in smoothly running tracks made of wire, or referencing the German – Ertzgebirge toy tradition. For example here: spielzeugmuseum-seiffen

Very nice things, but I wanted to create something else than the than marble runs that are available on the market (not so easy though!). Why? A couple of reasons: some need specialized tools to construct them. Or require much work. Or are just expensive. I would like to connect to the German toy making, but still had to find out how.

Paper

Paper is a material that I like a lot, and it can be worked with quickly. So it felt comfortable to follow this paper road and see what could be done with that material for a good workshop, wherever it might go.

Ultimately i arrived at a very simple solution: two curved tracks, a straight track and a support that can be combined. All made of easily available, either new or recycled, paper. It runs with standard glass marbles. It requires nothing more than scissors, a pencil and some tape. Optional were bamboo or paper sticks and (ready made) 3D printed supports for the tracks that fit on the sticks. For drawing the tracks I produced schablones, cut with a laser (optionally with a scissors and a knife) and I also printed these

The shapes are included in the workshop manual (aimed at instructors) and all are available digitally here as well as on Github.

The sticks and supports turned out to work well. The support design is not perfect ( too stiff), but it is used successfully anyway. An improvement may follow later.

You can find the support 3D design (VV2-TPU) here on Github, you can download and print it, or improve it (keep me informed!) yourself.

Other marble tracks were also prepared (more about them here). These use 3D printed supports and wire ( either ABS , bamboo sticks or rattan; a natural fiber). Building them requires more time and dexterity than the paper tracks. Most of all, they are more permanent and components can be used over and over again in new marble runs. Built marble runs now reside in the AWF garden and are used frequently by children. It obviously is not necessary for them to build a new marble run from scratch. Much of the fun is playing with a marble run, not only building it.

Looking back.

And, did I connect to the tradition of toy design? 
Specifically, Erzgebirge toy design? 

Frankly, not really. 
But I did connect to toys and toymaking, when you ask yourself: 

What is a toy (for)? 

If there is a specific goal, I would put this on the first place: 

Make children (and also adults) explore, cooperate, try for themselves, get interested, learn not to give up.....

That, rather than making a nicely looking toy (even though that certainly helps a lot in accepting the toy), is what unites toys all over the world. Not a design-goal maybe or something to advertise on a website, but certainly a deeper understanding of what toys mean and what they can do.  The good thing is: you get it because you are working with it. 

I have this result now and kick it into the world. It is not perfect and it is limited in its use but it works and it broadened my understanding of marble runs.

Gluck auf!
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To AI or not to AI?

In my work as a designer and fine artist, AI is being regarded in various ways. As a useful helper, a horrible cheater, and a grabber of jobs. Should we deliver ourselves to it? Withstand it, endure the agony?

How to handle this? Indeed an old question

My own first results in using AI were mixed, a bit of all the above. It is a very useful help in Google searching, and it can write Grasshopper code for my Cad program. It also can code for Arduino, also a time saver. But a question (or better: prompt) to write a setup for an AI study group produced thirteen in a dozen results and ignored the scope and purpose of such a group. Something a human, experienced user would not miss. Or was it inexperienced prompting?

In my work for the Art Union (Kunstenbond) I notice AI being used frequently already, for better or for worse. Animations are made using AI, writers illustrate their books in a certainly not uninteresting way. That’s nice. Musicians are afraid to lose work and income because of the huge volume of songs on the playlists that are AI-generated and deprive them of their income. That’s not nice.

One thing is sure (for now) : AI does not have an intent. And it does not understand your intent either. You are the one who has to guide AI to where you want it to go. Not the other way around. Be aware of that. Always ask yourself: is this what I need, want, desire, or have to do.

Good prompting will definitely help you a lot and guide AI into interesting ways. Especially in the routine work like searching, coding. But can it compose a good song? Probably that still is your job. Expect a lot, but not everything, and stay awake.

This post will be expanded in the coming weeks. I will give some examples of AI use in a more professional design context, as that is what interests me. Think: developing packaging, coding Grasshopper. Probably also some useful links to books, sites, examples.

Personally, I don’t care so much about a flawless drawing made by AI. I’d rather go out into the field with a sketchpad myself. And I don’t feel that I have to surprise my family with a song that I made for them. They know I cannot sing or compose and nobody gives a damn.

If you are interested, feel free to email me. Direct reactions on this post, however, are blocked to avoid spamming.

January 25th

Some experiences with AI.

An weird example: a lawyer who produced a lot of material we had to read, that we found incomprehensible, but nevertheless had to react upon. Every reaction and request for explanation was followed up with more, longer letters. It ultimately ended up in court. The judge, obviously better informed and experienced than we were didn’t need much time to implode the bullshit. At the end of the court he asked the lawyer (who lost his case completely), asked whether he used AI because not a single part of what he had written was founded anywhere.

Fast forward: if you don’t master the subject AI can deliver wildly varying results. And you lack the understanding, intuition or experience to be aware of it. That is a very dangerous part of AI. It can be rubbish and you don’t notice it. It may also have been a strategy, flooding us with letters that caused a huge amount of work for us, time that could be used better. Luckily we could hang on and indeed went to court. Others may not be so fortunate and simple be destroyed by this barrage of bullshit.

Another one: I asked an approach for a workgroup about AI, how to start it. A list came out that appeared quite understandable and useful. But what AI missed completely, and what a human advisor could (would?) have sensed was the reason why we wanted to start such a group. A simple human question would have made clear that our question was not to the point. The answer looked good, but missed the point completely.

The rule to understand AI seems to be : garbage in , garbage out. But if you know what you’re talking (prompting) about, usefull answers can follow.

So the next step will be: test AI in an area where i have some knowledge: design, art. And see if ” prompting like a pro” indeed has much extra value.

For now the working hypothesis is: AI is not more, but also nothing less, than a tool, that you have to master to do something useful with it.

February 13th.

Much work on the house of the inventor, little time for AI. That’s why i prefer this “static site” above instagram or whatsapp. I can pick up the text where I left it. i can add thinngs, edit the text afterwards. or even: find it back. A pitfall is that text gets too long and that it lacks a theme, focus.

maybe we could say: information is followed by knowledge. And knowledge is followed by wisdom.

AI is organised information. But it lacks wisdom.

July 13th

I see many programmers use AI very intensively and, as they say themselves: very productive. It look so promising. But do I really want to program at all? I worked with Arduino, Grasshopper, all interesting, but my work is much more satisfying for me when I’m building, tinkering, doing physical work, sawing a board of wood. Coding gives me a pain in my lower back, a headache, and never the satisfying feeling of feeling at home in my own work. Maybe I better outsource it, cooperate with other persons who are much better in it than I ever will be. Add my solution or idea for an interesting frame, material. We’ll see. I hear so many expectations, but i just don’t know. I do know i don’t like to sit behind a screen whole day, coding, programming. But it helps me a lot translating or searching the internet.

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Home of inventor Edwin Dertien

Edwin Dertien is an inventor. He asked me to help him for his coming exhibition in Oyfo , Hengelo, to build the house of the inventor, filled with many of his ideas, inventions, constructions. We’re still building, it is work in progress (January 2026)

What about using boxes and stacking these? We can make an interesting ” labyrinth” with surprises, hidden corners and so on. I developed the boxes for Diets present, but they are, like some kind of Lego or Meccano, also good for this design. And we can make the walls of transparent material (” kanalenplaat” : lexan sheet as used in roofs) so it will not be a massive, closed box but inviting instead.

The rendering looks good, but will it work?

First build. Made extra boxes and an outline of the house. Now we can change easily. This will result quickly in a useful assembly. We can change it, make pictures, discuss it easily.

Architects say they “discipline” their idea. Which means with an idea in mind the possibilities, opportunities of a layout of the building (here: the set) can be explored quickly. That is exactly what we aim to do with this 1 to 10 scale model

Jan. 9th:

Dummies of the objects in the model so we can check if we have enough space. And also wheelchairs should have access which limits the width of the paths.

Material will be 18 mm plywood. It is heavier than 9 mm but we need the stability. And building, and later, disassembly, will be easier and cheaper because we can use screws instead of connectors that require more precision and use nuts and bolts

construction of the boxes. i use a mold in the front of the box, it works quick and exact.

finishing the edges with the router

inspecting how light works in the box

Edwin Dertien checking positions of the boxes. Does it work?

Assembling the first portal. Will it bend, is it straight? It is going well, nice architectonical shapes that also have some intimacy. And strong enough to build with.

jan 31th

building proceeds. 30 blocks is a lot, so help from Ruud Steltenpool is welcome

The old projection / TV case fits in the 60 x 60 x 60 box

How to assemble the real set? Lifting 2 connected boxes to about 3.5 m elevation should be done safely. Fortunately there is an old, but still partly functional lifting beam, right above the location. This will be very helpful.

The roof at Oyfo, Hengelo, where it will be build. That looks promising. Even two more beams to hoist the blocks. That saves a lot of work.

Edwin is already filling the first boxes with his robots and furbies

Friday Feb 8th: we’re assembling in Oyfo!

making a grid for the placement

edwin and Ruud put the blocks on their place, i do the coordination with the plans in my hand, good for a 67 year old guy🙂

a lifter, very useful and it saved us a lot of hoisting

Today, Februari 7th, is a rest day, we made good progress yesterday. Tomorrow we finish the details and Edwin can start to fill the boxes. I will make a construction plan for the “envelope” that gives an outline of the house. We did already have an idea what it should be like. But we waited until we actually had the boxes stacked so we could walk through and have a good look.

It’s getting there. We made a big decision: we skipped the house shape around the blocks. For various reasons. The most important: what would it add? Would it work? Especially in this already “noisy” visual place. We had our doubts, as it already looks good. More is less in this case. So the red pencil scratched through it. I think it was a good decision

Opening

Thursday 19th of Februari opening of the exhibition at Oyfo

Floris Hazemeijerstraat 300, Hazemeijer Hengelo, Hengelo, NL

https://duckduckgo.com/?q=oyfo+techniekmuseum&atb=v403-1&ia=web&iaxm=maps&source=places

It’s open! You can visit the expo now

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Diets present

Members of Intervocaal Enschede assembled and decorated the boxes

Diet Gerrits, leaving director of Intervocaal, would get many presents . I was asked to help them to make some kind of box or construction to put the presents in. My goal was to give the choir members something they could build themselves.

A plywood box was designed with connectors, giving freedom to build. A bit like Lego

The frog is the symbol of Intervocaal

Every box contains a present. Enough to keep Diet busy for a while.

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Chemnitz Maker advent

I was invited to join the Maker Advent in Chemnitz in December 2025.

I worked on the Schwibbogen, last summer I designed these in Lossnitz, but I wanted to add candles. So I did some experimenting in Enschede to make it reliable and safe. No messing around with fire!

But we don’t work (much) in the mines anymore (well, not in the Oremountains). Nor with hammer and pick. We use robots instead. So i used these forms for my new Schwibboge.

I made various designs of Schwibbogen. Dutch, robotics, circular, simple cut out…

When we ran out of precut decoration, creativity got a new chance. Make your own Red Tower.

When also the arches ran out, they blasted off….

It is a tough job not to go with the traditional flow, especially when that can be purchased so easily and comply to how schwibbogen should look: recognizable symbols and pictures, unpainted wood. Tradition on the edge of becoming a cliché mass product? Sit down and do it yourself, become a maker!

That became even more obvious later in Lossnitz. A Led schwibbogen with the traditional theme had to be assembled, this attracted much attention. But it also demanded some basic maker skills: soldering, assembling.

Satisfaction

And this may look very traditional, but the printing is done using Tetrapack cartons for printing, and there is a laser engraving on slate. Don’t be afraid of the old symbols and tradition, but look for openings and possible connections they offer. It was nice to work in the crowded maker place, one working with textile, another with the laser.

Traditional themes are useful to reach out, and from there you can proceed and combine. And also appreciate the old tradition itself deeper.

By the way: the elderly textile-ladies were very, very capable of working with the soldering iron. So precise and with rock steady hands.

All together now: slate tradition (background), robotics, Gluck Auf, modern Led candles (with remote control), and the Xmas angel and Bergman. And lasercutting, I’d almost forget to mention that.

The miners’ parade in Lossnitz

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Pathmos vredesstalletjes

Samen met een aantal mensen uit de wijk Pathmos een bouwplaat gemaakt. Het was bedoeld om in Pathmos achter de ramen te zetten en een lint van vredesstalletjes door de wijk te maken. De bewoners konden in een aantal workshops hun eigen model bouwen. Het oorspronkelijke ontwerp kwam van Tom van de Linden. Ik heb er een paar aanpassingen aan gedaan zodat het in een workshop gebouwd kon worden en heb daarna de productie uitgevoerd. In totaal zijn er zo’n 170 gemaakt welke door kinderen en volwassenen zijn gebruikt

setjes in de laser

led-theelichtjes kunnen er van achter in worden gestoken

workshop

Voor Anke, Tom en Ismael een kleinigheidje als bedankje gemaakt voor hun inzet.

workshop in de Boei, wijkcentrum Pathmos

Figuurtjes om de vredesstal mee in te richten

de Pathmosprinses met haar vriendjes om haar heen

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Maker Days Eindhoven

this weekend in Eindhoven , Maker Days 2025. I prepared a new Schwibboge. For Eindhoven and Brabat in general music as the theme seemed appropriate to me.

for me, as a stage designer, a schwibboge is a small theater, and what happens inside can be perceived as a small-scale play. Once you look it this way, it is more than a Christmas decoration.