## 1 Introduction
In terms of achieving a higher hole quality, lower tip angles were preferred combined with medium cutting speeds and high feed rates. A similar investigation was conducted on AlSi7 closed cell aluminum foam by [PERSON] et al. (2018). In their paper, cutting forces were separated between the crust and the heart of the foam. The non-porous nature of the crust provided higher penetration resistance, thus producing twice the thrust force of heart drilling. Finally, they concluded that neither cutting speed nor tip angle had a significant influence on the thrust forces during the drilling of either the crust or the heart of the foam. [PERSON] et al. (2018) used HSS and carbide drills with varied helix angles and 118\({}^{\circ}\) tip angles to machine powder metallurgy (PM) porous steel. Thrust force analysis of variance showed a 94% feed rate influence while tool type and cutting speed contributed 3% each. High heat generation associated with the drilling process causes high plastic deformations of workpiece materials which manifest as burrs protruding from the hole exit (2018). Excessive burr formation can negatively affect both dimension accuracy and product functionality (2018). Deburring is a time-consuming process whose costs, according to [PERSON] and [PERSON] (2018), can be as high as 30% of the entire manufacturing process. Identifying major contributing factors in burr formation could considerably shorten and cheapen porous material production and processing. [PERSON] (2018) identified chisel edge as one of the main causes of burr formation, as it produces up to 70% of the total thrust force. Thinning the chisel edge and frequent resharpening of the tool can positively affect burr formation. Investigating burr formation and thrust force on ATOMET 1001 steel parts, [PERSON] et al. (2018) noted an increase in thrust force and burr size with an increased feed rate. To reduce hole breakout, lower cutting speeds and carbide tools were preferred. Hole breakout is sensitive to tool wear; as noted by [PERSON] et al. (2018), drilling Distaloy AB using HSS drills caused larger breakouts owing to higher tool wear in comparison to carbide tools. Porosity in foam materials has severe detrimental effects on the tool, mainly in the form of excess heating due to low thermal conductivity and due to the porosity of the material that leads to interrupted cutting. Today's industries are focusing on increasing sustainability and reducing their carbon footprint. In the case of the metalworking industry, high tool consumption increases tool production, which leads to higher greenhouse gas emissions (2018). One way to greatly reduce tool wear is to introduce cutting fluids into the cutting zone to both cool and lubricate the tool and workpiece (2018). Other than reducing tool wear, [PERSON] et al. (2018) noted a decrease in burr dimension and occurrence rate during the drilling of nonporous aluminum 7075 alloys with cutting fluid present. However, as shown in Figure 1, implementing cutting fluids into the machining process comes with its own set of challenges, mainly in the form of added costs and environmental and health risks. According to the National Institute for Occupational Safety and Health (NIOSH), 1.2 million workers in the United States of America are exposed to cutting fluids annually [40]. Storage, filtering and disposal costs of cutting fluids can add up to 17% of the entire manufacturing process [41; 42]. Worldwide cutting fluid consumption is estimated to be more than 2 billion litters annually. As most cutting fluids must be diluted with water, the amount of waste cutting fluid is drastically higher [43]. Additionally, many skin and respiratory system illnesses are linked to long-term exposure to cutting fluids and their vapors [44]. The application of cutting fluids during the machining of metal foams is not advised as the fluid can get trapped inside the porous structure, which can lead to significant corrosion.