SF&G Calibration 

There are three distinct products within the SF&G product group

:Surfcom – surface finish measuring devices – described in the email history below

• Rondcom – there are two basic types of Rondcom – “roundness” machines and “cylindricity” machines 

• Rondcom measures:

• Roundness Machines: roundness, concentricity, coaxility, flatness (2D), etc. – the Z-axis or vertical column on these types of systems is not a datum axis – it is a positioning axis only.

• Cylindricity Machines: measure everything that the “Roundness Machine” measures plus straightness, cylindricity, rectilinear cylindricity, based on machine model R-axis straightness, etc. the Z-axis or vertical column on these types of systems is a datum axis.

• Calibration for roundness and cylindricity sytems is much different than the Surfcom product

• Contourecord – a Contourecord system is basically a 2D CMM.  A Contourecord is able to measure dimensions; radius size, location (X and Z), angle, distances, etc.  The Contourecord system is also able to measure roundness in terms of the form error on a radius, it can measure straightness on a line segment.  The Contourecord system is also able to perform an actual data to nominal data (CAD data) comparison – the software has best fit functionality to accomplish this task.  Etc.

• Note: we have “hybrid” systems that are able to measure both surface finish and contour in a single pass – Surfcom 3000 / 5000 / CREST – Surfcom 2000 

In terms of calibration differences for the Rondcom systems please see the following:

• Third party service providers in general (from my experience) are very limited on what they are truly able to do specifically with cylindricity systems.

• Our Rondcom products use air bearing rotary tables.  We use a master ball to verify rotational accuracy.  I did not mention above, but the Rondcom portfolio covers traditional bench top systems as well as large overhead spindle systems.  Table top systems will rotate the part that is being measured and the sensor will remain stationary.  With overhead spindle systems the parts are typically large (engine blocks, crankshafts, machined castings, etc.) and stay stationary on the table with the actual measuring sensor rotating around the part while measured the desired feature.  So rotational accuracy means verifying the accuracy of the rotary table on a bench top system and spindle accuracy on an overhead spindle system.

• On certain systems we are also able to map the rotational accuracy of the system using a “master ball” mapping fixture.  This allows us to further refine the rotational accuracy of the system through mapping.  The mapping fixture allows us to separate master ball roundness error from the actual roundness error of the rotary table.  No third party service provider is capable of providing this.

Note: if you encounter an overhead spindle customer using a third party there is absolutely no value to the customer.  Overhead spindle systems range in price from $200,000 up to around $650,000.  They are complex and require 

         Special / expensive gages to calibrate.

•  On cylindricity systems we use a “cylinder square” to verify the relationship between the centerline of the rotary axis and the datum Z-axis or vertical column of the machine. The relationship is the parallelism of these two axis.  Depending on the system we use mapping to fine tune – no third party will be able to map.  At best a third party can only attempt mechanical adjustment – without factory training this mechanical adjustment is not intuitive or easily accomplished – it will never achieve the result of mapping.

• Again on cylindricity systems, depending on the actual model, we will use an optical flat or Zerodur straightness master to verify Z-axis straightness or vertical column straightness.  Again we have the ability to refine through mapping

• On certain cylindricity systems we also verify R-axis straightness using an optical flat or Zerodur straightness master.

• We of course evaluate the system for mechanical integrity throughout the process of performing a PM.  We are able to address any deficiencies as found.

• The same comment regarding our Surfcom product applies here.  Our SF&G service technicians are factory trainied.

For most Surfcom systems third party providers will only use a roughness specimen to calibrate the system.  They will clean the system, but honestly after that there is not much else that they do.  Many customers accept this because third parties have some sort of accreditation (ISO 17025) and because of the limited service they provide cost is much cheaper. 

• This roughness specimen calibration is not a full system calibration and it is a user requirement to perform this on a regular basis regardless (the numeric result is only part of the result.  Surface roughness instruments use a 2um, 5um or 10um conical diamond stylus.  The diamond can become damaged or worn over time.  It is important to look at the roughness graph in order to see that there is even distribution of peaks and valleys about the mean line of the data.  If this is not the case there could be damage to the diamond or possibly damage to the actual sensor; loose pivot bearings, other).

• In general terms and for most Surfcom systems we will take things much deeper.  Some examples are as follows:

• We will of course use the roughness specimen or a step height master to calibrate
• We will verify the straightness of the X-axis datum (the machined way in the tracing driver of the system)
• On systems that include a scale in the tracing driver we will verify that the scale is set-up and counting properly
• We provide a full preventative maintenance on the system; thorough cleaning, lubrication where needed, any mechanical adjustments as needed

• We typically do not calibrate the Handysurf product in the field and typically the Surfcom 130A only when it makes financial sense for customers – meaning when they have other equipment / more capital type equipment that we will be calibrating at the same time 

• For Surfcom 3000 / 5000 / CREST (our laser based system) there are additional checks performed.  Laser power is an example as this can change over time – we use a Helium Neon laser tube and these deplete over time so it is critical to check power during a PM. 

• Note: it is also important to note that we are the OEM and have factory trained our service technicians who perform this work.