When you need a new CNC machine, either to replace an existing one that has reached the end of its life cycle or to expand production, you have to consider all the factors that impact productivity, output quality and economic viability. Ideally your new machine will be able to carry out tasks that you currently handle and add a few new functions.
The machine should be able to handle current tasks more rapidly or reduce associated labor costs. At the same time you don’t want to pay for features that you don’t need and are not going to use, and when considering your new machine, check whether there are compatibility issues with your existing CAD/CAM software. There are many such key factors and they can be grouped around three areas.
The material you usually use has a big impact on the selection of your new machine. The size of the sheets, the type of material and its thickness help determine the kind of machine you need. You also have to decide whether the new machine has to be capable of handling all of the jobs you usually carry out or whether you are buying it for a specific purpose and type of work. Once you settle on the material the machine has to work with, you can narrow down the possibilities.
The size of the metal sheets determines the table size of the machine. If the machine is to fabricate single parts or small numbers of parts from small sheets, a four by four-foot table might be enough. Large numbers of nested parts usually require four by eight or five by ten-foot sheets and the machine table has to be sized accordingly.
Once you settle on the material the machine has to work with, you can narrow down the possibilities.
The thickness of the metal is another key factor in selecting the type of machine. A punch can handle thin metal well but you may need a laser cutting machine to cut thick metal efficiently. You have to look at whether the jobs you are considering justify getting a heavier punching machine, a combo punch and laser machine or whether you should handle the cutting of heavier metal separately, possibly on another new machine or an existing machine. In any case, specifying the type of material the machine will handle lets you narrow down the kind of machine that you can consider.
The Type of Machine
The different types of machines available impact the speed at which you can fabricate sheet metal, the output quality and what kind of fabrication you can carry out. For example, water jet cutting machines are generally less expensive than laser cutters but are slower and the cut is usually not as clean. If the work you plan to carry out includes forming parts, you have to start with a punch.
You can use the punch for cuts, but it is slower than lasers. Combo punch and laser machines cover both functions, but you have to evaluate whether the extra cost is covered by higher productivity, better quality output or easier set-up.
When you have narrowed down the type of machine you have to look at part complexity, tools and turret capacity. Small numbers of simple parts require fewer tools and a lower turret capacity while large numbers of parts or complex parts require larger numbers of tools and more turret tool stations. If your work includes creating ribs to make sheet metal parts more rigid, a special tool like the Wilson wheel may be an appropriate tool and it can also carry out some cutting and forming. Once you settle on the type of machine you’re almost ready to make your purchase.
You can address the third group of factors that are important for choosing your new machine by reviewing the work the new machine has to carry out. The key factors here involve optimizing production with the type of machine you have chosen and ensuring that the new machine improves overall performance of your production facility. You want to minimize processes and procedures that are slow or costly and use the new machine efficiently.
A key factor in this evaluation is to examine the cost of labor versus the cost of additional automation of the machine. Automatic sheet handling can reduce costs and the amount of time a job takes. A sheet loader can automatically take up sheets of metal and place them on the machine table. An evaluation of the corresponding labor costs and any time saved can determine whether a sheet loader is an appropriate addition for your new machine.
Another automatic feature is parts chutes. Instead of fabricating parts that are held in place with tabs, parts are stamped or cut out completely and fall into parts chutes through trap doors in the machine table. The process can be faster than fabricating parts with tabs and the parts are finished when they leave the table. For tabbed parts, the tabs still have to be removed before the parts are ready and the cost for this additional process have to be evaluated against adding parts chutes to your new machine.
When you have settled on which new machine to buy, you still have to verify that your existing software is compatible with it and its automatic devices.
Some machine manufacturers include software with the new machine. Although this can be a tempting offer, it is generally not a good choice. Even if they “throw it in” with the purchase of the new machine, it can be a costly mistake in the long run. If this isn’t your first machine, then you probably have years’ worth of parts in the library in your current sheet metal software. Your programmers will have to learn and be trained on the new software, and in most cases, you will now have multiple support contracts to ensure all of the different software are running efficiently. Imagine the time it would take to now recreate/reimport all of those parts into the new software, compared to just getting another post processor from the current CAD/CAM and Nesting software and cross-posting all of your parts with ease. This alone would save incredible amounts of time and money for your company.
Source: Merry Mechanization
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