Answers to your questions
Who are the School Network webinars for?
School Network webinars are intended only for employees of secondary schools in Zagreb County.
Are the webinars free?
All School Network webinars are free and open to all employees of schools in Zagreb County.
Can I attend a webinar?
Yes, if you are a school employee. If you are not employed at a school in Zagreb County, the "Adult education" section offers webinars for anyone who would like to learn more about a particular technology.
Can participants ask the lecturers and experts questions during live webinars, and are recordings of past webinars available to watch later?
Yes, our webinars are usually designed to let participants take an active part. During live webinars (on platforms such as Zoom, Teams or similar) you can usually ask the lecturers and experts questions, most often through the chat or, in smaller sessions, through the microphone in the part of the session set aside for this.
Recordings are often made available to watch later in the "Webinars – video" category.
I am mentoring a student's final thesis in the CNC operator programme. Can we contact you for help and support during the work?
Of course – our CNC technology expert is available to help.
Feel free to contact us with any specific questions about programming, tool selection, machining process optimisation or technical documentation. Our team is ready to provide insight and guidance to help your student produce a high-quality, professionally sound final thesis.
Which material do you recommend if the printed product will be exposed to friction and wear?
For products exposed to friction and wear, we recommend materials that are resistant to mechanical loads, flexing and abrasion. Two suitable materials are:
TPU 95A (thermoplastic polyurethane) – especially in harder variants. Harder TPU (e.g. 95A and above) offers a good compromise between flexibility and wear resistance, making it suitable for parts that bend but are subject to friction (e.g. protective covers, wheels, low-load gears).
Printing requirements:
- A direct drive extruder is required (Bowden extruders make printing TPU difficult)
- Lower print speed (20–40 mm/s)
- Good bed adhesion and even temperature (e.g. heated bed at 40–60 °C)
Nylon (polyamide) – an extremely durable material with high wear and impact resistance, suitable for mechanically loaded parts such as gears, bearings, guides and similar.
Printing requirements:
- High extruder temperature (250–300 °C, depending on the type of nylon)
- Heated bed (60–80 °C)
- An enclosed chamber is recommended because of its tendency to warp
- Nylon is very hygroscopic, so the material must be dried thoroughly before printing
Both materials need extra care when preparing and calibrating the printer, but they give excellent results in applications where friction and wear are key factors.
I tried to print a vase, but after a while the water leaked out. Is it possible to print watertight models?
Yes, watertight models can be printed with FDM technology, but this requires careful tuning of print settings and the right choice of materials.
Why does it leak?
FDM printing builds the model layer by layer, so microscopic gaps can remain between layers and lines through which water can pass. This is especially likely with thin walls, a print temperature that is too low, too few perimeters, or a hollow model (e.g. with low infill).
How to prevent leaks and make a model watertight:
- Increase the number of outer walls/perimeters – at least 4 are recommended.
- Increase the number of top and bottom layers – at least 5 or more.
- Use 100% infill – especially for containers or vases.
- Increase the extruder temperature – better layer adhesion reduces the risk of leaks.
- Reduce print speed – allows the material to be deposited more precisely.
- Thicker layers – layers of 0.2–0.3 mm often "seal" the surface better.
- Post-processing – e.g. coating the inside with epoxy resin or a special waterproof lacquer for 3D prints can make the model fully watertight (e.g. Dichtol).
Materials such as PETG and ASA have better layer adhesion than PLA, which can also help make a model watertight.
I am thinking of buying an FDM printer. Which features should I pay attention to?
- Kinematics and axis configuration
The most common configurations are:
- Cartesian or bed slinger – the most common type (e.g. Ender 3): the print head moves along the X and Z axes and the bed along the Y axis. Reliable and easy to maintain.
- CoreXY – faster and more precise, ideal for higher speeds while keeping accuracy. Mechanically more complex, but suitable for more advanced users. The print head moves along the X and Y axes and the bed along the Z axis (height).
- Delta – uses triangular geometry and offers high speed and print height, but is more complex to calibrate.
- Open vs. enclosed printer (chamber)
- Open printers (e.g. typical hobby models): easier access, more affordable, good for PLA and TPU, but industrial materials are almost impossible to print.
- Enclosed/heated printers (with a chamber): allow the ambient temperature to be controlled, which reduces warping and enables reliable printing of engineering materials (ABS, ASA, PC, PA, etc.).
- Sensors and features that make printing more reliable:
- Auto bed levelling (ABL) – automatic bed levelling saves time and ensures a good first layer.
- Filament runout sensor – detects when the filament runs out and pauses the print.
- Power resume – resumes printing after a power cut.
- Direct drive vs. Bowden extruder – direct drive is better for flexible materials (e.g. TPU), while Bowden is lighter and faster for harder materials.
- Load cell (force/pressure sensor) – precisely measures the height and contact of the nozzle with the bed; used in advanced automatic levelling systems.
- Accelerometer – used for input shaping (vibration compensation), which reduces visual defects such as ghosting at higher print speeds.
- LiDAR sensor – used to scan the bed surface and check the first layer during printing (e.g. on Bambu Lab printers); improves reliability and levelling precision.
- Camera – allows remote monitoring of prints as well as advanced features such as error detection, time-lapse recording and visual inspection of layers and any deviations during printing.
- Other important features:
- Build volume – depends on the kind of projects you plan (e.g. 220×220×250 mm is standard, but larger printers offer more flexibility).
- Hotend and bed temperature – important for more advanced materials.
- Extruder type and supported materials – check whether the printer supports e.g. nylon, carbon fibre, flexible materials, etc.
In the end, the choice depends on your needs: a simpler open printer with basic features is enough for beginners, while for engineering and more reliable prints it is worth investing in an enclosed chamber, ABL and better mechanics (CoreXY).
Which measuring devices are available in the measurement laboratory, and can they be used for practical exercises?
The measurement laboratory of the Regional Centre of Competence Velika Gorica has several measurement and inspection systems:
Coordinate measuring machine (CMM) – used for high-precision measurement of geometric shapes and tolerances, with automatic generation of measurement reports.
3D scanner – used for high-precision measurement and quality control after production, as well as for reverse engineering.
Tool presetter – used to precisely determine tool dimensions outside the machine.
Renishaw system – integrated into the CNC machines and used to automatically measure tool length and diameter, set the workpiece zero point and inspect parts during machining.
Hand measuring tools – such as micrometers, calipers, dial indicators and depth gauges, used in basic practical exercises.
The measuring systems are available for practical exercises by prior arrangement with technical support.
Teachers and students may use the measuring equipment only after introductory training in its correct use and under the supervision of a responsible person.