concrete formwork Recess former
Precision-engineered penetrations, ducts and openings from CAD
Formwork blockouts keep the space in the precast element free where there is subsequently to be no concrete: for conduits, connections, sleeves or assembly openings. Mach-3D manufactures them according to your geometry – tapered for reuse or as lost formwork.
As of September 2026
In short: A recess former is a placeholder in the formwork that creates an opening in the concrete element. Standard dimensions are available as catalogue items. As soon as the opening is inclined, conical, combines multiple apertures or is only needed twenty times, the printed former becomes worthwhile: it is created directly from the CAD geometry, without a moulding tool.
Content
Wherever a pre-cast concrete element has to accommodate something later on: pipe and cable penetrations, connection pockets for reinforcement, assembly and transport openings, drainage channels, recesses for built-in components. If the opening is not cast in at the same time, it has to be drilled or chased out later. That costs time, weakens the reinforcement and rarely looks neat.
Standard geometries such as round sleeves or rectangular boxes are available from specialist suppliers. It gets difficult with anything that is not in the catalogue: angled penetrations, openings with changing cross-sections, multiple apertures at a fixed distance from one another, or bodies that have to fit precisely between two layers of reinforcement.
We will decide that together before production, as material, wall thickness and price depend on it.
| Execution | When useful | What that means |
|---|---|---|
| Reusable, conical | identical opening in many parts, demoulding access provided | draft angle, smooth surface, robust material such as PP or PA-GF |
| Multi-part, dismantlable | undercuts, long channels | The body is divided into segments in the concrete and pulled out individually |
| Elastic | small undercuts, structures | TPU body can be pulled out where a rigid one would break |
| lost formwork | closed cavities, no access, one-off piece | thin-walled printed, remains in the component or is destroyed |
For standard round sleeves in large quantities, this is Catalogue part unbeatable. For large, simple volumes, cut EPS cheap, but the surface remains rough and the body is used up after one casting. The printed void formers it is the choice when the geometry is not in the catalogue, dimensional accuracy matters, or the same body is to be used multiple times. Many plants use all three alongside each other.
You send a STEP, STL or a dimensioned sketch of the opening. We check mould release, suggest design and material, and quote the price. For simple bodies, the 3D printing calculator the price immediately. Manufacturing takes place in Altenholz near Kiel, in single pieces measuring up to 900 × 900 × 1000 mm.
3D-printed recess formers bridge the gap between off-the-shelf products and expensive custom tools. They are produced directly from the CAD geometry, starting from a single piece, optionally reusable or as lost formwork. Anyone who plans for draft angles, buoyancy, and fastening from the outset avoids drilling and chiselling in the finished part.
Send us the geometry of the opening and the planned quantity. We will get back to you with a proposal for execution and a price.