6 Ways to Check if Swiss Machining is Right for a Custom Machined Part
Is CNC Swiss Machining best for this part?
So, you have a print for a precision machined part that you’ve been told to source, and you suspect that CNC Swiss machining might be the best route to have it made. However, if you’re not a machinist, selecting a supplier with optimal machining capabilities can be a daunting task. Most machined parts can be made a number of ways on various types of equipment, but unless that equipment is a good fit for your part, you’re not going to get the best parts or price.
As a machine shop making custom turned parts, we speak to buyers and engineers everyday trying to figure out that magic fit for what they need made. It takes a wide range of experiences in machining to quickly ascertain the best kind of machining for a given material, quantity and complexity of part. Most shops specialize in a few types of machining and there’s not really a “one-size-fits-all” solution.
What you need to know: Here are some general things to consider. The more your part and requirement fit these criteria, the more likely it is that Swiss turning will be right for you. You’ll need to look at the print and both short-term and long-term quantity requirements to make a good judgement call. Be prepared to know:
- What is the largest outer diameter?
- What are different quantities that are needed both now and in the future?
- What are the features on the part?
- What material is the part?
- What are the tightest tolerances on the print?
- What are the finish requirements (if specified?)
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. See photos of parts to get an idea of what can be made.
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. Visit CNC Swiss Screw Machining for a more detailed list of materials and features possible.
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, check out this Surface Roughness Conversion Chart.
In summary, if you suspect Swiss turning could be the best option for sourcing your machined part, you should submit your print to a qualified Swiss machine shop for an engineering review and quote. For more general information on CNC Swiss Screw Machining at Pioneer Service, click here.