Swiss machining

- Mar 28, 2017 -

Now that you have the facts in front of you, here's how to tell if Swiss machining could be right for this requirement.

 

Check 1: Is the outer diameter right for Swiss?

Swiss screw machines come in an array of sizes, but all are designed for relatively small parts. Typically the machine "size" refers to the maximum OD that can be fed into the machine. While you might be able to machine a .25" OD part on a 1.25" OD Swiss machine, you'll probably get better cycle times, and therefore lower costs if you were to use a .393" or smaller Swiss screw machine. Our company has Swiss machines that are 10 mm (.393") , 20 mm (.787") and 32 mm (1.25") to help optimize the part to the equipment. Many parts can be made on all three platforms, but there is always a most optimal platform.

Check 2: How many parts do I need now and in the future?

Swiss machining requires CNC programing, set-up and tooling to make any new part. Some machining companies build this into the price per part and others separate it on a separate line item. Either way, there is a cost for getting started with any new part. In our experience, that cost typically ranges from $100 to $1200. As the quantities go up in a given production run, the price per piece typically goes down (to a certain point.) Is this an early-stage prototype and you expect the design to change a lot? Maybe Swiss is not your best option. However, if you think this will go to production in the thousands, or even millions, Swiss machining may be right for you. 

Check 3: What are the features on this part?

Generally speaking, the more complex the part, the more likely that it's a good fit for Swiss turning. Features like slotting, knurling, splining and milling various shapes can usually be performed in one program, so that the parts is made complete right off the machine. If it's a simple straight pin with a concentric feature, like a slot for an O-ring, it's possible that less expensive equipment can make the parts. In the case of an extremely complex part, only a Swiss machine shop engineer will be able to tell you if they have the tooling capability to do everything.

Check 4: What material is called out on the print?

CNC Swiss equipment is able to machine a wide arrange of materials. However, if lead-time is a major factor, then material availability may be important to you. If you haven't heard of the material called out on the print, it's a good idea to do some basic research it just to see if it's readily available in bar form.  Typically 12' long round bars in an oversize outer diameter is the raw material needed to make Swiss parts. If price is a key driver, and there's some flexibility with materials, then consider the machinability of the material. For example, stainless steels like 303 and 304 are easier to machine than 316 stainless. 

Check 5: What are the tolerances?

All the features on the print or model should specify the tolerances required. If the tolerances are relatively tight, for example, +/-.0005" or even +/-.001, CNC Swiss turning may be your best option. Wide tolerances, like +/-.005" combined with simple features and high volumes may indicate that other kinds of machining could be more cost effective. Again, if you have any questions about what tolerances are possible, contact the Swiss machine shop.

Check 6: What are the finish requirements?

A common finish "as-machined" is 32RMS (.8 microns) off a Swiss screw machine, though a wide range is possible. The higher the number, the rougher the finish. If a finish requirement is relative high (a fine finish is not required) and the volume is high, again, Swiss machining may not be the best option. If the RMS is very low, additional grinding and/or polishing may be necessary. For more information on surface finishes.


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