By conducting an objective analysis of chip removal processes in material machining, abrasive waterjet cutting machine, as an additional or unique alternative, opens up completely new perspectives. Discussions and developments in the area of chip removal work are aimed at producing parts with an optimal finish with a machine that has the highest possible speed and requires minimal setup time. The key word to achieve greater competitiveness within the international market in a highly dynamic integral production.
Thus, today multi-axis milling machines for 5-sided machining enjoy the same prestige as lathes, with which high-quality milling can be performed by integrating an additional B-axis, or milling machines that can perform considerable turning jobs thanks to a fast rotating CNC circular table. Other keywords in this combination are high-speed chip removal or the use of highly dynamic linear drives on the travel axes. Indeed, when trying to optimize the tools, there is practically no aspect of the process that is not examined to the last detail by the heads of the development departments of the companies and the corresponding colleges or institutes.
However, there is still a specific aspect that no one has stopped to consider: The possibility of broadening horizons. How many times should you insist on the idea that a clearly profitable process combination will always achieve great success? In addition, it should be pointed out that waterjet cutting was not originally developed for its application in the field of turning and milling, but for the field of stone, glass or sheet metal machining.
However, some resourceful professionals in the industry already know the possibilities of this insightful strategy and have begun to exploit them. With this, the first of the (economic) advantages consists in the use of the material, because instead of acquiring costly cuttings that can be used as blanks in chip removal, the water jet allows to work with the appropriate standard format. And instead of a rectangular or circular waterjet cutout, blanks can be machined almost to the final contour when there is no different standard for the surface of the edges, for example when an out-of-the-box accuracy is not required of water jet cutting and not exceeding tenths of a millimeter.
If this aspect weren’t stimulating enough in itself for chip removal professionals, there are still other significant advantages when it comes to material application. As it works from standard formats and the water jet cutting as a cold process does not generate any kind of changes in the texture, in the first place the blanks can be inserted in an adequate way on the existing surface. Second, depending on the circumstances, it is also possible to integrate a second blank in the geometry of the blank itself. In addition, waterjet cutting offers the possibility of counting not only exterior geometries but also internal geometric elements such as drilled or hollow holes.
Adding all the possibilities together, this means that at best, when edge quality and precision are within the capabilities of waterjet cutting, the machine produces final work pieces that could not be processed. With the same speed and perfection with any other milling machine or lathe on the market. However, generally the work of a piece is divided between the water jet and the chip removal: in the first process the rough cutting is carried out beforehand, and then, in the cold cutting, the chip removal is done. In charge of finishing the pieces. The question about the division of tasks, that is, what operations each process performs, can be answered very quickly with objective consideration.
That is to say, it can be derived in the first instance from the economic and timing results that become evident especially in a profitability comparison. Take as an example a batch of ten units of side plates whose original manufacturing procedure would be milling. Thanks to the box option of the waterjet cutting installation, the material costs alone, compared to the milling results, are already 40 percent lower.
In addition, when making a direct comparison it is revealed that for the use of waterjet cutting, in addition to a perfect use of the material, other factors must be taken into account, which result from the basic advantages of the process:
- Great flexibility
- Short installation times
- Great material flexibility
- Machining without tension
- Low tool cost
- Multilayer cut
- Using multiple cutting heads
As an initial situation in the example calculation for both orders, there is a DXF file with the geometry of the piece with an aluminum base. For each calculation, the real time of production of the ten parts was considered exclusively, including programming, preparation and machining. The result was surprising. While with milling, just 42 minutes were invested for programming and adjustment, with waterjet cutting the order was completed in 32 minutes with one tool and in a work sequence. Instead, the chip removal professional required seven different tools and nine piecework sequences; I also spent 104 minutes in the operations required to change parts, which adds up to a total of 146 minutes to place the ten parts on the workbench.
During this direct comparison, it was not taken into account that, once this process was concluded, the deburring of the pieces was still necessary, while the pieces cut by waterjet left the machine already finished. The fact that the proper device was required for the milling process was also overlooked. It should not be forgotten that the operator of a waterjet cutting installation, firstly, does not require a level of qualification as specific as that of a milling machine, and secondly, he does not intervene as much in the process, as he does not replacement of blanks will be necessary. In short, a reduction in personnel costs is experienced as less operator intervention is required.
This indication already points out what a subsequent calculation makes clear: saving water is not only the fastest process in many cases, but, despite involving a greater investment in the technology of the device and, consequently, an increase in the hourly rate is by far the most profitable process. Thus, the user of a vertical machining center, in an example calculation (high-wage country), a representative order of ten pieces costs 131.70 euros, while the user of a waterjet cutting installation spend only 79 euros for the same order.
All the more surprising is the comparison with a waterjet cutting system with two cutting heads. In this case, the cost of the order amounts to 53 euros. And if an installation with two heads with a changing table is used, the order is only 48.40 euros. Even compared to a milling machine equipped with automatic parts change, where the order costs 88.50 euros, all of the above are aspects that any professional in chip removal should consider. Especially in view of the advantages that waterjet cutting offers:
- Economical, despite the high acquisition cost
- Cost coverage for small batch production thanks to minimal setup costs
- Increase in turnover and profits thanks to two-head machining
- No need for any additional devices and no specific training required
- Tool storage and maintenance costs are zero
- Possibility of prototype mechanization, learning, etc.
- Increase in turnover and income through optimal use of the tool and less material consumption
- Increased competitiveness even in small batch machining
- Shorter lead times – flexible ordering, no need for additional training or devices
- Reduction of salary and personnel costs.
Other aspects to consider: Despite all the possibilities that waterjet cutting offers, this technique also has its limitations compared to chip removal. Thus, the level of precision and the fall of the surface that reaches the cutting by jet of water do not get to equal the levels reached by means of the milling or the turning. In the same way, the water jet does not allow working in three dimensions or cutting blind holes or threads. However, the waterjet offers much more than what the chip removal professional could ever think and demand of this technique. Often, when applying this type of two-dimensional machining techniques, it is worth consulting the service provider in the field of waterjet cutting: It costs nothing to ask, but it does not cost you the fact of not applying the optimal procedures.