Printable sand must become a usable mould
Foundry sand suitable for conventional moulding is not automatically qualified for 3D-printed moulds. Binder jetting builds successive layers and deposits binder in the areas corresponding to the digital part. The material therefore needs to support layer preparation, bonding and mould behaviour during pouring.
The Ministry of Industry’s profiles identify Tanger-Tétouan-Al Hoceïma as a region with a substantial industrial contribution, particularly in automotive activities 1. This provides context for component manufacturing and material qualification projects. It does not establish that a particular operator has a mould printer, or demonstrate local consumption of printable sand.
NIST describes binder jetting as an additive manufacturing technology family 2. A foundry project must qualify a specific combination: sand, binder, equipment, parameters and geometry. Printing a shape is the first stage; the cast component remains the final decision.
1. Separate loose sand from printed material
Loose sand feeds the printer. Printed material is a network of grains and binder, with its own porosity and curing condition. A suitable sand distribution does not fully describe strength or permeability after printing. Examine these properties on specimens prepared with the selected process.
Qualification therefore involves two connected records. The first describes received material: batches, grading, moisture and relevant characteristics. The second describes transformation: preparation, layers, deposition, curing and tests. A modification in either can change the result in the other. Records should preserve this relationship.
Retain reference sand and a printed reference when the programme provides for them. The first allows material to be re-examined; the second allows a process condition to be compared. A sand photograph cannot replace incoming inspection results or observations of the finished mould.
2. Compare grading with layer thickness
Layer thickness is a manufacturing parameter. Grain diameter belongs to the material distribution. Relate these quantities to printer requirements, but a simple equality or universal ratio cannot qualify the system.
Examine the upper part of the distribution and out-of-fraction particles. An acceptable average can hide grains that disturb layer formation. Ask the equipment manufacturer for the approved material range and parameters. Qualification must remain within that scope or document a new combination.
For comparison, retain the complete curve and preparation method. If material is sieved before testing, printed material comes from that prepared fraction, rather than the untreated commercial batch. The supply specification must then explain how this preparation will be reproduced during operation.
3. Define the ability to form a layer
A useful layer must be distributed consistently under the equipment’s conditions. Assess spreading with the relevant recoating and deposition arrangement. Observing flow outside the machine can provide a comparison, but cannot alone demonstrate printed layer quality.
Observe several surface areas and several layers. Identify streaks, accumulations and missing areas where they occur. An overall image can conceal a detail whose effects appear in fine geometry. Connect observations with settings and the batch used.
Do not classify every layer defect as a sand defect. Uneven distribution may also require examination of the device and its preparation. Isolate variables: use the same machine and settings to compare materials, then compare settings when investigating the process.
4. Examine the selected binder system
Binder and media combinations are not universal. ExOne states that its materials and systems are selected and qualified for casting applications 5. This manufacturer information supports identifying the material-binder combination, without treating advertised performance as a guarantee for another system.
Record binder type, any activator, sand preparation and storage conditions. A product intended for another preparation must not be assumed equivalent from a general chemical name. Qualification must examine the actual combination used in the printer.
Distinguish stated dosage from the quantity actually incorporated when methods express them differently. Explain the calculation convention and dry basis. An undefined percentage may describe product mass, saturation or a software setting that cannot be directly compared with a conventional mixing recipe.
5. Distinguish porosity from permeability
Porosity represents a volume of voids measured by a defined method. Permeability concerns the ability of these voids to transmit a fluid under test conditions. Void quantity does not describe all its connectivity. Structures with similar porosity may offer different flow paths.
Mitra and colleagues examine transport properties of printed moulds using tomography and measurements 4. Their work illustrates the value of relating pore structure to flow properties, rather than reducing qualification to overall density.
For an industrial programme, choose tests that answer the mould’s questions. Air passing through a specimen produces a measurement under its protocol; it does not automatically reproduce every gas or pouring temperature. The result remains useful when preparations are compared consistently.
6. Qualify strength and handling delay
Assess printed specimens at a defined time after manufacture. A result obtained after a long waiting period does not demonstrate the strength available when a core is actually extracted and handled. Qualification should include practical removal from the build volume and handling steps.
The Materials study compares printed and conventional furan systems through mechanical, permeability and thermal tests 3. It supports considering several prepared-material properties. It does not establish one recipe or minimum strength for every mould.
Record specimen geometry, loading method, elapsed time and curing conditions. Do not directly compare strength obtained by one method with another method carrying a similar name. Connect the result with actual loading and the acceptance criterion for the component concerned.
7. Check printing orientations and positions
The process constructs layers within a build space. Examine orientations and positions relevant to the geometry. Placing every specimen in the same location leaves part of the consistency question unexamined. The manufacturing plan must identify positions.
Prepare specimens with the same parameters, distributed according to the selected programme. Preserve the relationship between each specimen and its location. If results vary, material, deposition, waiting time and position can be examined without reconstructing information afterwards.
This article does not assume that all machines produce identical anisotropy or gradients. It proposes checking this question for the system studied. A conclusion restricted to a known orientation is more useful than an assertion of uniformity based on one specimen.
8. Examine details rather than overall shape alone
Choose a test part containing useful details: walls, passages, difficult extraction areas and junctions. A simple shape may emerge successfully while a thin detail remains fragile. Qualification must reproduce manufacturing difficulties that justify the project.
Document loose-sand removal and post-printing operations. Closed geometry may require a particular removal or circulation strategy. Examine the digital design together with the process, rather than only the final model image.
Dimensional inspection must identify reference points and project tolerances. A printer’s advertised figures do not automatically become the results of a particular part. Measure relevant details on the actual preparation and retain deviations, even when the overall appearance seems satisfactory.
9. Include thermal behaviour in the programme
Room-temperature strength does not fully describe behaviour in contact with metal. Preserve alloy, pouring conditions and relevant prepared-material results. Changing sand or binder may require renewed examination of this combination.
The Materials study also examines thermal deformation of tested systems 3. Its practical relevance is to distinguish pre-pouring strength from behaviour under thermal loading. Apparatus-specific values should not become universal industrial instructions without justification.
Where possible, examine the mould or core after the trial. Relate observations to component results: surface defects, residual sand, deformation or another identified criterion. Connecting material, transformation and defect adds more value than an isolated component photograph.
10. Compare more than maximum strength
Adding binder or modifying a layer can change several properties together. Assess strength, gas flow, surface and casting behaviour as a whole. Choosing the highest mechanical result can leave the usable-mould question unanswered.
Prepare a limited matrix with a known reference and necessary variants. Identify studied factors and factors held constant. If geometry or alloy changes, record a new qualification stage rather than treating its result as directly comparable with the previous campaign.
Present relevant differences and selected compromises. A preparation may be acceptable for a short series but insufficiently documented for another production rate. Validation scope must describe what was tested, without turning a feasibility demonstration into a regular-production guarantee.
11. Example: distinguishing fraction from process
Imagine two prints using the same sand batch but different layer thicknesses. This is a proposed reasoning example, not a Minerallum measurement. If strength and surface finish differ, the first conclusion concerns two preparations of the same material, rather than two sand qualities.
To examine grading effects, then prepare characterized fractions and use a plan compatible with the printer’s operating range. Identify necessary parameter changes. If each fraction requires its own settings, the decision concerns qualified combinations, rather than an isolated material property.
This distinction helps purchasing teams specify requirements. The file should describe the sand characteristics enabling the selected combination and the preparation steps making it reproducible. A supplier can receive a precise material enquiry; a size range alone cannot define all process settings.
12. Compare build volume and cycle time
Total time is more than advertised deposition speed. It includes steps needed for a usable part: preparation, construction, curing, extraction, cleaning and additional operations. Keep the same boundary and geometry in an economic comparison.
Do not confuse bound material with loose sand. A build box contains an arrangement of parts and unbound material. Identify what is used, recovered or rejected, with reuse rules actually qualified for the system.
Do not promise automatic savings because a mould is made without a conventional pattern. Cost depends on geometry, part quantity, materials and operations. The technical programme prepares this comparison with defined quantities and stages, without inventing local prices or production capacity.
13. Separate specimens for layer, binder and geometry
A strength specimen and a flow specimen do not necessarily serve the same purpose. The first reproduces a defined loading condition; the second provides a flow path and faces prepared according to the protocol. Using an irregular mould fragment to replace these tests mixes the effects of material and geometry. Prepare specimens in the manufacturing file, with their reference marks, rather than selecting available fragments after printing.
To study a layer’s effect, first retain the material and binder command. Then check whether binder deposited per unit volume remains comparable. Changing thickness changes the number of passes needed to build the same height. An identical software setting therefore cannot demonstrate identical printed composition. The comparison must explain what the setting maintains and what it actually modifies.
To study binder, compare preparations with identified distributions and geometry. Observe cohesion, edges and airflow together. A friable edge and low overall strength are not independent proofs of a grading defect: both can arise from insufficient bonding. Conversely, a rigid specimen can conceal gas-flow difficulties that emerge only during pouring.
The geometry specimen must include details whose cleaning can be inspected. An open passage permitting inspection does not fully describe a closed cavity that is difficult to empty. Choose the shape for the future component’s requirements, with an explicitly planned loose-sand removal operation. After cleaning, distinguish retained loose sand, a wall damaged during extraction and a dimensional error already present before that operation.
The programme becomes a sequence of decisions: check the layer, the bound material, the cleaned detail, then the cast component. If a stage fails, returning to its specimen avoids changing the whole recipe simultaneously. This organization does not replace equipment instructions; it makes their effects observable for the project studied.
14. Validate material through a cast component
The final stage connects tests with representative manufacturing. Retain moulding parameters, mould finishing and pouring conditions. Component inspection should examine characteristics that justified the project, using a known method.
If an anomaly appears, separate hypotheses: material, printing, geometry, coating or pouring. Printed specimens and retained sand permit certain stages to be revisited. Traceability supports identifying a cause rather than simply accumulating documents.
Our silica-sand page complements the material file. For 3D printing, the final decision concerns sand integrated into a qualified system, capable of producing the expected mould and component. Layer consistency, pore structure, strength and manufacture must all retain a place in validation.