Hey guys, I created this script for a bench, and I want to precast concrete for each piece. My question is: how can I create one mold that works for all the pieces, or maybe if this is not going to work, how can I control these sizes to make 4 or 5 molds that work for all of them? How can I make the voids parts of my design solid if I want to make them as wood pieces for a comfortable bench? I attached my file below.
Got you, but what about the void spaces? How can I make them as a solid pieces to make them wood? I want to make it real and comfortable bench, one piece of concrete and one piece of wood.
Ah, I didnāt know what you meant. Filling the voids with wood is easy in CAD (in theory), more difficult to build than attaching āslatsā to sit onā¦ Easy to write the CAD, more difficult for the computer to handle so many pieces in SDiff - 1.2 minutes and it failed, perhaps because of the holes?
Tried again without the holes, still laboring. Are you sure these 51 pieces will work in CAD, being so thin? Tried doubling their thickness and using only half as manyā¦ SDiff still fails. It often fails when surfaces are coplanar. Tried Scale several times to make the sweep smaller. Iām getting bored nowā¦ 2.2 minutes and looks terrible.
Not sure what else to try? Maybe Offset Curve instead of Scale to avoid coplanar faces. Reduced section count to 30 and set thickness to 0.03 - takes 22.1 seconds and looks OK. Trying reduced offsetā¦ works but still without holes. Added the holes back but now the wood fills the holes. Enough for now, filling the voids with wood doesnāt sound like a good idea to me.
I remember spending a lot of time working with someone on a parametric bench with āslatsā to sit on, connecting the sections - but canāt find it.
P.S. Might work better to make the sections connected with pipes, then fill the voids with foam?
This demonstrates an important detail that likely contributes to the difficulty SDiff had in getting the āvoidsā between extruded pieces. It is a simple technique that can be useful in many contexts.
This is a top view of the extruded pieces āOff-centerā from the PFrames, as I left them yesterday:
This shows them āCenteredā on the PFrames by moving them backwards half of their thickness using a simple expression on the same vectors used to extrude them; the Move āTā input:
See the difference? Smoother. SDiff still wonāt be happy trying to subtract extruded pieces with flat edges from a volume created with Sweep but it may help.
As a general comment, I hope you are thinking through all the details of building such a bench. None of the three section curves you provided look good to me for a bench? And as I said, building the void volumes from wood could be quite complex. If the bench is installed outdoors, it must drain water!
I donāt know if this can be useful in the current situation, but as Iām passing by, the Brep.CreateBooleanDifference is MUCH faster than regular Solid Difference component.
Your last file seems to work fine without any of those anyway.
The last two files arenāt using SDiff to get the voids. This is yesterdayās version ācā retrofitted with the āCenteredā option. It works better and with smaller Offset āDistanceā values. SDiff takes 19.1 seconds with an offset of 0.002, but more than a minute with an offset of 0.001. Still, it looks better and is more accurate so is better.
I wish Iād thought of these things yesterday. The best way to get the voids is applying the offset to one set of extrusions that are discarded (ignored). SDiff has no problem at all subtracting the oversized extrusions from the swept volume. 11.4 seconds.
The pipes and optional holes (through extrusions and voids) are added in the white group. The only way to see the holes is to turn off preview of the pipes.
The beauty and fascination of these structures is due, in part, to their changing cross-sections. You had that in your original code (sweeping through three different section curves) and gave it up for āone mold that works for all the piecesā. However, two significant build complications remain:
Building voids from wood.
Using pipes to connect and align all the pieces.
If you really intend to build this bench, practical considerations must influence the design. And again, this does not look like a comfortable bench shape to me?
I still can change the cross sections and the entire design of the bench when I start the fabrication phase (to be a comfortable bench). I know that I will face a lot of challenges but what is you suggestions instead of using wood in the void parts? Also if I did them wood, what do think of the best way to fabricate them? Especially that they are not the same in the sizes and coordinates?
Attach āslatsā to sit on, like the images from Max Allstadtās work. They will shed rain water.
Use foam to fill the voids that can be trimmed and shaped when it hardens.
My point exactly! Not easy to build by hand or even CNC.
Your model shows the difficulty of using pipes. Not easy to slide all the extrusions and voids over them and they werenāt required for your model so why use them for the real thing?
Maybe you could use flexible tubing that would be easier for assembly, then once all the extrusions are positioned correctly, fill the tubes with the same foam used to fill the voids? There are many products available and Iām no expert in using them, but here is just one example:
Urethane Pour Foam Overview
This two-part liquid, expanding rigid urethane foam is a closed cell, pourable foam, which will resist the absorption of water.
The densities shown refer to the weight per cubic foot of expanded foam (12" x 12" x 12").
Once fully cured this foam can be laminated over with any type of polyester, epoxy or vinyl ester resin without melting.
This product can be poured in multiple layers with excellent bonding between layers.
16 LB Density Urethane Foam
Common Applications: This 16LB density foam is essentially as hard as a rock, you would need a hammer in order to make any dents in this product. Can be used for sculpting or the casting of objects that require superior toughness and strength.
Figure out a way to wrap the completed concrete parts in heavy cardboard (ramboard) or some other flexible, durable material, and then pour concrete in place to fill the voids. maybe use some sort of thin removable filler/form material on the inside of ramboard so that the void-filling concrete is slightly recessed, like 1/4". then finish with stucco to get it super smooth. Contrasting color might work well.