Gene Zak

Areas of Research

Laser Welding of Plastics

Laser transmission welding is a relatively new joining process in which laser energy is used to melt polymer at the interface between laser-transparent and laser-absorbing components. Past work (2003) in collaboration with Prof. Bates (RMC) and Prof. Kontopoulou (Chemical Engineering, Queen's) examined the effect of diode laser speed, power, beam area and weld pressure on the meltdown, microstructure and weld strength of T-joints made from unreinforced nylon 6. The results showed that meltdown increases strongly with line energy and is also affected by beam area and weld pressure. For the range of parameters selected, the strength was observed to depend largely on the ability to make welds free of local stress concentrations and degraded material.

Laser Machining of Ceramics


Laser machining has been applied for many years as an alternative to conventional machining methods for hard-to-machine materials. Laser machining is a non-contact technique, with no tool wear and no cutting force applied to the machined material. For these reasons it is well suited for ceramics due to the extreme hardness and brittleness of these materials. The above characteristics make machining of ceramics using conventional techniques very difficult, expensive and often impossible. Ceramics are most commonly formed by casting the shapes directly (which is can be inaccurate due to shrinking during the firing process) and/or diamond grinding, which is slow, expensive and limited in the shapes that can be created. Laser machining allows direct shaping of the fired ceramic, bringing with it the potential of building a wide variety of shapes with high accuracy.

Past work has been carried out in collaboration with Prof. Krstic (former director of CMACN). Laser machining parameters were studied (2004) to optimize the laser machining of pockets in aluminum nitride for high material removal rates and minimum surface roughness. The parameters were determined by machining single-layer rectangular pockets. Using a 10W Nd:YLF laser with a 3-axes motion system (part of the RLT lab facilities), a maximum material removal rate of 0.019 mm3/s and a minimum surface roughness of Ra=0.29 mm were achieved.

A versatile Laser Ceramics Machining System was designed and built as part of the former Centre for Manufacturing of Advanced Ceramics and Nanomaterials (CMACN). Together with a 6-axis motion system and two X-Y beam scanners, the system will feature three laser sources:

  • UV-frequency, 7-W diode-pumped solid-state laser (Coherent AVIA 355-7000)
  • 1,064 nm wavelength, 100W solid-state Nd:YAG laser (Lee Laser LDP-100MQ)
  • 10,600 nm wavelength, 250 W CO2 laser (Coherent K-250)

The system has been in operation since 2004.

Rapid Tooling and Prototyping

Rapid Tooling technologies offer the promise of quick and inexpensive fabrication of short-run and prototype tooling. This work deals with design and fabrication of injection mould insert produced via Laminated Metal Tooling process (LMT). Thin steel laminations are joined by an adhesive film and then cut by a laser. A small injection mould insert has been designed and built on the prototype LMT system . Successful injection moulding trials have been conducted.

Plastic Composites in Biomedical Applications

This was conducted with support of MMO and in collaboration with Bloorview MacMillan Children's Centre located in Toronto, Ontario.

Approximately 130,000 ankle-foot orthoses (AFOs) are prescribed each year in North America to children and adults with neuromuscular disorders to stabilize the foot and ankle and to improve their ability to walk. Currently, AFOs are custom manufactured using a multi-step labour-intensive process involving: (1) creating a plaster cast (negative) of the foot and ankle held in the desired position (2) casting a plaster mould from the negative and (3) using the plaster mould to vacuum-form a polypropylene AFO. The goal of this project was to develop a composite prepreg AFO that would be moulded in place directly on the leg and foot, safely using the client's body as the mould. The AFO would be partially cured at room temperature using visible light. A monomer system has been developed with no visible cell toxicity and a high vinyl group conversion. This research focused on optimizing the reinforcing material and the orthosis design and manufacturing process.