Swiss Versus Conventional CNC Machining

Swiss CNC machines were originally developed to produce the high precision parts used by the famous Swiss watch industry.  While often associated with high volume production and costly tooling charges, in fact they are an excellent solution for long run high precision machining work.

The machined part in this image is suitable for both conventional and Swiss machining. Our machines can handle parts not smaller than this one, at roughly 0.81 in diameter and 2.75 inches long.   The volume of the part is low —50 pieces per month.  A part like this would typically be source machined on conventional CNC machines.  Let’s review the part itself, processed through conventional CNC machines, processed in a Swiss-style CNC, and re-imagine the potential cost reduction and quality improvements of low volume Swiss-style CNC machining.

It contains a variety of machining operations needed to complete.  It requires turning operations to reduce the diameter and create the threads on one side.  It will need milling to create the cross holes and hexagon pattern above the outer threads.    While the part envelope and features make it a candidate for a swiss-style CNC, the lower volume may guide one towards conventional CNC machines.

Let us imagine a manufacturer with a standard CNC lathes/turning centers and a four-axis CNC machining center as it could consolidate both the turning and milling operations into one set up making for efficient conventional CNC machining.  The raw bar would need to be cut to either part length.  It is possible that a manufacturer has a bar feed system on their CNC lathe and would feed through the chuck.  Most likely the bar would still need to be cut to fit the feeder and have bar ends not able to be pushed or pulled through the chuck.  A second turning operation in the same lathe or another would be required to complete the part.  The part would then go to the 4 axis machining center to mill the hex and drill the cross holes.  In summary, to produce the part would require a saw operation and two setups on a CNC lathe, and the set up of a 4 axis CNC machining center.  If the manufacturer had older technologies for their CNCs, the number of machines, setups, and fix turning required would increase as well as costs.

A Swiss machine is physically smaller than a conventional CNC machine as they were developed to produce smaller parts.  They also can machine on multiple axis.  Macfab has up to 9 axis Swiss-style CNCs.  In place of chucks, they utilize guide bushings and collet systems allowing for high speeds and lower runout parts.  A Swiss machine with guide bushings works by advancing the part out as turning and milling parts are machined; however, the part runout is directly affected by the runout of the bar material.  As a result, bar stock should be centerless ground. Newer Swiss machines also can switch to a collet system and can use standard bar material with much better control over part runout.  The collet systems are typically for shorter parts, whereas the traditional guide bushing machines are capable of running parts up to 24” long with slightly more efficient cycle times.

This animated part could be completed in one setup and a single fluid operation, whereas If the same part is made in a conventional CNC, it would present challenges with the orientation of the cross holes to the hex at an angle.  Furthermore, the number of cross holes drilled is an odd number making the angular alinement to the hex even more critical.

As Swiss machines are designed for high volume production, bar feeding integrated, and with less scrap as all operations are done in the same setup.  The collet design has high part rotation speeds for shorter cycle times with improved accuracy.  As the Swiss machine produces the hex, the machine can quickly establish the orientation of the cross holes without additional fixturing or probing time.  Macfab’s investment in virtual manufacturing allows for offline programming of our Swiss CNCs making them an economical option for lower volume precision parts.

Can you imagine your lower volume parts being made on a Swiss-style CNC?  Let Macfab’s creative engineers turn these visions into shorter lead times, lower part cost, and higher quality.