Formeur de treillis

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What this makes

Three parts: the net, and the two halves of the press it is formed in.

The net is flat: the outline of whatever you upload, printed as a solid rim with the whole inside filled by a thin printed mesh. It prints flat on the bed in minutes, with no supports and no overhangs, because at this stage it is still a sheet.

The press is a matched pair, the way press-formed mesh is made. The cavity is a block with your shape sunk into its top, and a shallow pocket around the opening that the net's rim drops into. The plug is the same shape standing up on a flange: you turn it over and push it into the cavity, and the hot net is caught in the gap between the two, which is exactly one net thickness wide all the way down. Both are generated from the same traced outline as the net, so all three always match. These are the parts people otherwise have to model in CAD.

The shape arrives after printing. Warm the net with a heat gun until it goes limp, press it into the cavity with the plug, and it stretches into a curved net that holds its shape once it cools. The rim is printed taller than the net on purpose, so the outline stays stiff while the middle gives way.

How to press-form it

  1. Print the net in a material that tolerates heat: PETG or ABS. PLA works but softens across a much narrower window and goes brittle if you overshoot. Print both press halves flat side down at a high infill, 40% or more: you are going to lean on them. The mesh has so little heat in it that the press does not need to be heat-resistant; PLA is fine for the two halves.
  2. Stand the cavity opening up on a board. It does not need vent holes, whatever the vacuum-forming guides say, because a net is already full of holes.
  3. Drop the net into the pocket on top of the cavity, flat (bed) side down. The pocket is cut to the rim's outline, so it locates the net for you and nothing has to be centred by eye.
  4. Warm it slowly and evenly with the heat gun, kept moving, from 15 to 20cm away. You are aiming for limp, not glossy. Once it shines you have gone too far and the struts will thin out and snap.
  5. Turn the plug over and push it straight down into the cavity until its flange sits flat on the block. That same flange clamps the rim in its pocket, so the outline cannot lift while the middle stretches. Hold until it is cool to the touch, which takes under a minute. Let go early and it springs partway back.
  6. Lift the plug out and the net with it. The wall angle is what makes this possible: straight sides would be gripped by the net as it shrinks. The side that was on the print bed is now the smooth outside of the shape.

A closed shape from two halves

For a ball, an apple or any hollow ornament, tick Two halves that fit together. You get a second net, the mirror image of the first, and each formed half is a bowl whose open side is the top of its rim. The front net has short pins standing up off its rim and the back net has a hole straight through its rim at each matching spot, so the two bowls close rim to rim and the pins press into the holes. A drop of glue makes it permanent; without it the halves come apart again, which is handy if you want to fill it.

Form both nets in the same press, flat (bed) side down both times. The plug's flange has a hole over every pin, so it still sits flat on the front net. If your outline is not symmetric the back half is a genuinely different shape, and the download includes a second, mirrored press for it; the sidebar tells you when that happens. The pins need a frame at least 3 mm wide.

Settings that decide whether it works

SettingWhat it changes
Mesh thicknessThe forming window. Around 1mm softens quickly and evenly. Much thicker and the rim reaches forming temperature before the mesh does.
Cell sizeHow closely the mesh follows detail. Fine cells drape over a curve; coarse cells bridge across it and leave flats.
Strut widthHow much stretch each strand survives. Two to three nozzle widths, so every strut prints as solid extrusion rather than a thin under-filled line.
Frame widthHow much the outline resists the heat: a narrow rim distorts along with the mesh, which is occasionally what you want. It also moves the press, because the shaped part starts where the rim ends, so a wider frame gives a smaller shape and stretches the mesh further.
Form depthHow far the mesh has to stretch. The mesh gains area going into the press and every bit of that comes out of its own thickness, so a printed 1 mm mesh can arrive at 0.9 mm or at 0.4 mm depending on the depth and the shape. The sidebar warns you as soon as it drops under 0.6 mm.
ShapeHow hard the stretch is, at the same depth. A cone hugs the flat and barely stretches anything; a plateau drags the mesh over a rim and across a full flat top and asks the most of it.
Wall angleHow easily the cooled mesh lifts out of the press. Three degrees is the floor; more is safer on a deep form. A cone has no slider for it: it closes to a point, so its angle comes out of the depth and your outline, and the sidebar reports what it built.

Common problems

The mesh tore while I pressed it

Either it was too cold in places, or the struts are too thin for the amount of stretch. Warm it for longer at a greater distance so the heat reaches the middle of the sheet, and raise the strut width or the mesh thickness a little.

The rim warped along with the mesh

Too much heat aimed at the edge. Work the gun over the middle and let conduction do the rest, and raise the frame width or height so there is more material holding the outline.

It sprang back flat after I let go

Released too early. The part has to cool fully under pressure. A quick pass with compressed air or a damp cloth over the pressed mesh sets it in seconds.

The mesh will not come off the form

The wall angle is too shallow for how deep the form is. A cooled mesh shrinks onto whatever it was pressed over, and only the taper lets it slide off. Raise the wall angle, or lower the depth. On a cone there is no wall-angle slider, so lower the depth or switch to a dome.

The struts snapped near the top of the form

Too deep a draw for that outline. The mesh has to cover more area than it started with, and all of that comes out of its thickness. The sidebar warns you when it drops under about 0.6 mm, which is where the struts snap instead of stretching. Lower the depth, raise the mesh thickness, or pick a shape that closes in less sharply.

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