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Avoiding buyer’s remorse – Get a test cut!

Choosing the right machine tool to purchase is a big deal. There's technical information to absorb, input from stakeholders to consider, and a budget to stay within. Different companies will have different evaluation criteria based on their specific machining needs. For some companies, fast production times will rank highest in the requirements list. For others, high precision will be at the top. Still others will look for a machine that allows them to handle a wider range of material types. Marketing materials and technical specifications will talk about cutting speeds, positioning accuracy, repeatability, pump pressures, etc. But how do you interpret all the data points in a practical way and apply them to the materials and part geometries your company is cutting or planning to cut? How can you make sure the machine you choose is the right one for your company's specific application and expectations? The answer is to get a test cut, or several, before making the final purchase decision.

With a test cut, you can analyze the performance of a machine cutting the specific material and part geometry your company handles. In the case of abrasive waterjets, you can see the edge quality of the finished part, how much time it took to cut and how much garnet was used. If you're present during the test cut, it's a good idea to time the entire process, including machine set-up and programming. Keep in mind the total time to process a part affects energy costs, manufacturing capacity, labor costs and consumable costs. If one machine is 10% faster than another, that 10% will probably have significant impact on total production cost and profitability. It's important to find out how easy (or not) it is to operate the machine and how well the various components, accessories and controller software work together.

Many machine tool manufacturers offer test cuts of your sample part files and material. Some will also let you try out their software for free. You can receive just the test cut time and materials data, the data plus the actual finished part, or be present during the test cut in the manufacturer's demo lab to watch the process. If you can't be physically present and want to see a real time demonstration of the software or even a test cut, video chat applications such as Skype make it possible to watch these from the comfort of your own office.

If you are in the evaluation stage of purchasing a new machine tool, your first step is to narrow your selection based on the size and type of materials you work with. Take the time to look at marketing materials, industry articles and comments from people who use those machines on objective Internet forums.

Next, contact the manufacturer or distributor for the machines on your short list and schedule in-person or virtual visits. Machine tool companies want to sell you their products and many will welcome you to visit their facility. In some cases, they may even work with other machine owners in your area so you can see a live demonstration. For these live demonstrations, be sure to ask if they have your particular material available to process. If they don't have your material in stock, ask if you can bring material with you. For example, if you're purchasing a machine to cut warped, cold-rolled steel, the demonstrations should be done on THAT material.

In advance of your visit, send a part file with geometry that is representative of what you want to cut with the machine. The effort required to set up a machine and program a part will likely be just as important as how the machine cuts. If you have to hire an Applications Engineer or buy new software in order to program your parts, then you certainly want to know that before you buy a machine. Make it clear that you want to see the machine being programmed for your geometry.

Finally, if you are viewing the test cut in real time, use a watch or timer and record how long it takes to set up your material to cut. Different machines use different methods to line up a cut. Time and record how long it takes to actually cut your part. Compare your measured cut time to the time on the controller. Some machines estimate the cut time based on straight line cutting, which can be off by as much as 15%. While this should not necessarily be a show stopper, you need to be aware of it.

Other parameters to take note of during test cuts done on abrasive waterjets are mixing tube size, orifice diameter, pump horsepower and abrasive size. A blog article on direct drive pump efficiency has more information on the two types of pumps used in the waterjet industry and the role of pressure and orifice size.

With test cut data gathered from various machine tool companies, you'll be in a great position to choose a machine that best fits your specific needs.

Get a free test cut from OMAX and receive a comprehensive parts cut analysis.

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