Request a quote

Cast spare parts: wooden model, fully molded casting or printed casting?

Nowadays, anyone who needs cast parts as spare parts has several options to avoid these problems. A good understanding of all the possibilities helps in an emergency, but also simply in selecting the best process for the respective application.

The three main procedures at a glance

The traditional way via the wooden model

Full mold casting with polystyrene models

The “Printed Casting” process

All three main methods have advantages and disadvantages that can be skillfully exploited. Here we provide a brief overview to help you make a decision.

By the way: There are also interesting hybrid methods in between, which we will also address in this article.

The procurement of cast spare parts comes with specific problems, such as:

  • No drawings are available.
  • There is no wooden model.
  • The wooden model was from a supplier that no longer exists.
  • It is particularly urgent, as the missing spare part causes downtime.
  • There are improvements to the original part.

    • Three casting processes, in fast-forward

    In hollow mold casting with a wooden model and in full mold casting, the mold is created by shaping a model of the future casting in sand. The wooden model is molded out again to create a cavity. The polystyrene model used in full mold casting usually remains in the mold and evaporates during casting.

    Casting mold production with 3D sand printing does not require a model at all. The cavity is created by building up the sand mold layer by layer from a bed of sand, which is produced on the basis of CAD data of the casting as in an inkjet printer (instead of ink, a binder is applied layer by layer).

    Hollow mold casting with wooden model versus solid mold casting

    A wooden model can be used several times and offers very high dimensional accuracy and precision. If a wooden model for a spare part is already available and intact, this is the quickest method – as long as it can be cast quickly where it is. If no pattern is available, the disadvantages of hollow mold casting with a wooden pattern usually outweigh the advantages: Pattern production is expensive, so it is only worthwhile from a certain number of pieces; molding requires mold chamfers and complex molds and cores to reproduce the cast part. Certain geometries are simply not possible, complexity is expensive. The lead time is long (weeks to months).

    Hollow mold casting with wooden model versus solid mold casting

    With full mold casting, the model is milled from a solid piece of EPS (expanded polystyrene). This is quicker (usually 1-2 weeks) and costs less (around a fifth of the cost of the wooden model). As the polystyrene model does not have to be molded, there is no need for bevels; undercuts and more complex geometries are possible. Since some work steps are also eliminated during casting preparation compared to hollow mold casting, casting is also around 20% cheaper. Models can be easily modified until shortly before casting. As the model can only be used once, the wooden model pays off from a certain number of pieces (if other factors such as start-up times and design freedom do not play a role). The EPS that evaporates during casting leaves behind residues that affect the surface quality. A larger machining allowance must be taken into account, especially on the top side of the casting. Due to the softer pattern material, a casting tolerance one degree higher must be selected.

    “Especially for the production of spare parts, 3D sand printing also offers potential for continuous optimization of the component.”

    Tweet

    When is 3D sand printing worthwhile for spare parts?

    3D sand printing (or “printed casting”) combines the speed, flexibility and design freedom of full mold casting with the precision and dimensional accuracy of castings produced with a wooden model. It is hollow mold casting without a pattern. The elimination of the pattern means no demolding, no polystyrene residues, no pattern costs, and allows even greater design freedom than full mold casting with minimal start-up time (no pattern construction phase!).
    For the production of spare parts in particular, 3D sand printing opens up potential for the continuous optimization of the component: better use of materials through bionic structures, functional integration of component parts, etc.
    The speed advantage of 3D sand printing continues even after casting. The precision of the mold can directly produce the final contour of the cast part – even without machining and with very good surface quality. This means that the spare part is ready for use more quickly.
    What limits 3D sand printing is the print space of the 3D sand printer, which restricts the size of the printable shapes. The length of this “job box” is generally the largest dimension and is usually between one and four meters.
    Compared to full mold casting, the costs of the technically superior 3D sand printing must be considered individually and are sometimes cheaper, sometimes more expensive, depending on the component.

    Hybrid casting processes?


    3D sand printing itself is a hybrid process of 3D printing and traditional casting. However, there are also other hybrids between the three main processes, which open up additional possibilities depending on the problem. These include demolded full-mold casting (the polystyrene model is removed from the mold), which can be used to avoid polystyrene residues, and 3D sand printing of cores and other mold elements for molds otherwise created with a model. In borderline cases, it may be worth considering these.

    “As the cost differences between full mold casting and 3D sand casting vary depending on the component, it is worth starting with 3D sand printing as an option, especially for smaller castings.”

    Tweet

    Conclusion

    If the wooden model for a required spare part is already available and nothing needs to be changed on the casting, hollow mold casting with a wooden model is the quickest and cheapest method (however, model storage costs should be taken into account for rarely required or very large spare parts).

    If no wooden model is available, full mold casting and 3D sand printing are the better alternatives for small quantities. Both are fast, although 3D sand printing is somewhat faster and also more accurate. As the cost differences between full mold casting and 3D sand casting vary depending on the component, it is worth starting with 3D sand printing as an option. Especially as cost estimates for printed castings can be obtained much more quickly.

    3D sand printing also allows a “virtual wooden model” to be stored, which enables a precision sand mold to be created at any time, but also allows changes to be made. The sand mold can be created anywhere there is a 3D sand printer. Compared to the wooden model, this expands the circle of potential suppliers.

    Spare parts on demand are available online at castfast.de – with instant quotations and delivery date forecasts for urgently needed cast parts. Helps even when there’s no fire!

    verfahren_02-min

    Interested in trying it out?

    The CASTFAST calculator provides an instant price, delivery date and CO2 footprint based on key data and/or CAD file

    Calculate instant quote
    Share the Post:

    Related Posts

    Production & Casting
    Our company
    Resources
    Legal matters
    Youtube Linkedin

    © 2025 All Rights Reserved.