The final component of the SquareTech system is the holding of the workpiece.
The 90° indexing fixture accepts the Matrix pallet and drawbar from System 3R. The pallets can be either manually loaded and indexed or integrated to a fully automated manufacturing cell.
The following options are available for mounting of the workpiece
Directly to Matrix pallet.
To a reference system.
To a manual vise.
To a magnetic chuck.
Mounting directly to Matrix Pallet
The workpiece can be mounted directly to the Matrix pallet (approx 5” diameter) utilizing a series of predrilled holes. The pallet is also available in a 6” automation ready version which allows for custom hole layouts for specific applications.
Larger sub-plates are easily implemented for custom mounting, jigs, etc.
Mounting to a Reference System
Many facilities are already using System 3R, Erowa or Hirschmann referencing systems. Already-mounted components can be used by mounting the preferred referencing system manual chuck to the face of the Matrix pallet. The Matrix pallet is still used for the indexing function.
When the squaring procedure is finished, the pre-mounted components can be moved to the next process.
Mounting to a Manual Vise
Two styles of manual vises apply themselves well to SquareTech
The self-centering style of vise has many jaw options available to satisfy various part geometries. The repeatability of location of these vises is 0.002” on center. Most applications will use a sacrificial portion of the workpiece for workholding then remove that section when the process is finished.
The precision toolmaker style of vise requires a workpiece with parallel sides, in order to function properly. This vise also only allows for centering in one direction. The benefit is that workpiece location will repeat exactly and squareness to the indexing feature is predetermined.
Mounting to a Magnetic Chuck
While selecting a magnet chuck, careful consideration must be given to the size, shape, type of material and process to be applied to the workpiece.
Two styles of magnetic chucks apply themselves well to SquareTech:
Permanent magnetic chucks are a cost effective solution for use in this application.
The benefit here is that only one workpiece surface is utilized for part holding. Many sizes and shapes are available with varying holding performance. In general the limiting factor most situations is that the part is smaller than the magnetic chuck contact surface. This limits the access to the workpiece.
The ultimate solution when magnetically holding a workpiece is the use of an electro-permanent magnetic chuck, which has be specifically designed for workpieces mounted on its centerline.
This magnet concept was originally applied to conventional milling applications only. Its unique characteristics allow the use of top tooling. Top tooling is a consumable plate which allows the transfer of magnetism to the workpiece. The top tooling can be machined away until a pedestal of material is remaining which is undersize of the workpiece, giving full access for machining.
Top tooling is removable and can be reused on repeat jobs or refashioned to fit new workpieces. Recent advancements in surface coating applications to top tooling have resulted in holding performance doubling.
This is an application driven area. These magnets have successfully completed jobs with part sizes below 1 sq. in to over 100 sq. in.
Accuracy: Total indexing error is less than 2 arc seconds, creating a true 90 deg index. As an example grinding four sides of an 8” by 8” block will result in a block which is Square & Parallel less than 0.0001” TIR.
Repeatibility: Ensured by use of System 3R reference.
So how does the SquareTech Indexer actually measure up in the real world?
We tested it. Here are our results.
Results of SquareTech Precision Test
The SquareTech system was used to surface grind 80 pieces of fully annealed 1018, initially rough milled square within 0.001”. The workpiece size was 8”x8”x1 ¼”.
The goal was to be able to have a resultant accuracy of 0.0001” square and parallel. The surface grinder we used was a two year-old Okamoto ACC1224EXB. Measurement results are considered accurate within +- 0.000010” (ten millionths).
All four sides of the blocks were ground on the fixture. These measurements are total squareness and parallelism of all four sides. Results are summarized as follows.
The average is ½ of the maximum value, with the mean value falling below the average, which shows that the majority of the measurements were toward the lower values.
Another way of looking at this is as follows:
85% of the parts were within 0.000050”
35% of the parts were within 0.000025”
This shows the accuracy of the system in a production environment. Remember we are measuring processed parts, so we are also dealing with the errors in grinding; we are not just indexing and measuring.
The above errors result in a total indexing accuracy below 2 arc-seconds.
An easier way to look at it is linear error based on part size.
Conclusion: High Precision Confirmed
Our tests show that our our SQUARETech High Precision 90° Indexer has a total indexing accuracy below 2 arc-seconds in a production environment.