Pete Schmidt

Altering a Magnetic Chuck for Custom Setup

Custom Solutions, Magnetic Workholding

Adding a fine pole top plate (top tooling) to an existing magnet.

When discussing how to choose a fine pole magnet vs a hard milling magnet, there are times when we want to combine the benefits of both. Here is a real-world example:

A customer wanted to build custom tooling into the top of a fine pole magnetic chuck for in their sinker edm.

The customer had it all planned out –

  • Four fine pole magnets palletized to EROWA
  • Each magnet would have its own pin layout for part locating
  • Jig grinding locations to press in pins in for work locating
  • Flushing holes drilled

The customer proclaimed, “This is all we do and it will work great.” I had a different approach to the challenge.

Here is some of the reasoning I took to show the customer how they could achieve the results they needed, while reducing costly tool alterations.

The Hermann Schmidt Approach

FPH on HSM Pin BackI am usually very against altering a magnetic chuck. Any mistakes or damage will result in a costly chuck rebuild and then another rebuild of the custom component.

So after a review of all the customer requirements first – then a review of the ideas they had on how to do it – we developed the following solution:

We used a fine pole top plate as a build basis for the customizing.  The top plate can be treated like a solid piece of material, and altered as needed.  Specific alterations were as follows:

  • Plate was ground parallel top & bottom, with 2 sides square to be used as referencing edges.
  • Flushing holes were added as needed.
  • Instead of jig grinding locations:
    • Tapped holes were added at the nominal location.
    • Set screws were inserted.
    • Locations were milled at the nominal location.
    • Once installed in the machine a female electrode was used to accurately burn the stop locations.
  • Thru holes were added for mounting to supporting magnet below.

A hard milling magnet was chosen as the base magnet so we could get the magnetic power through the top plate to the workpiece.

These operations were repeated for three other top plates, allowing for one base palletized magnet to do all of the work.

The Customer Benefits

By minimizing customization, and by building a more flexible tool set up, the customer received the following benefits:

  • Cost savings of 53%
  • Ability to build the fixtures themselves as they had no internal jig grinding
  • And, as expected, the part did change two years later and they had to change the top fixtures.

 

Customizing Precision Stainless Steel Chucks

Custom Solutions, Grinding, Mechanical Chucks

Much of our designs tend to lean toward the smaller side of things.  For example our 3 jaw chuck line has a version which will hold a .008” diameter part.

Well, we do go the other way.

This is a 9-Jaw beast with a capacity of 7 to 8 inches.  Sense of scale is that the thru hole shown is 8”.  Customer is a medical device OEM who needed to position parts on center within .0002” but the part diameters were ranging +- .050”.  This did it with tolerance to spare.

Custom 9 Jaw Precision Stainless Steel Chuck
Custom 9 Jaw Precision Stainless Steel Chuck Close Up

Other options are horizontal jaws instead of vertical jaws.

A die-stamping customer had parts with a cylindrically ground 30° taper almost 4” diameter at the base.  We took a standard design 3 to 4” capacity 6 jaw and turned the jaws 90°.  Now as the jaws close the work piece is forced down to a stop and centralized.

Palletizing Services – Considerations

Palletizing Service

Our product accuracy and reliability coupled with the repeatability of a referencing system allows for the reduction of set-up time and increased productivity from your machine tool. Mounting services along with the palletizing product designation guarantees that specific x-y-z locations are held.

When palletizing work there are many issues which should be considered:

Accuracy and reliability 

  • Most of our products are ground within .0001” of flat, square & parallel.
  • We are the designers, manufacturers and sellers of the products many which have a long history. Products are built for longevity
  • When you buy a Hermann Schmidt product, you are buying it for life.
  • Materials are chosen for the product’s operating environment. The heat treating requirement is set to maintain dimensional stability over time.

Repeatability of a referencing system

  • We offer dealer services for System 3R, Erowa, and Hirschmann.
  • These systems offer repeatability of 2 microns. Some subsystems within their offerings will deliver 1 micron or better repeatability.

Reduction of set-up time and increased productivity

  • Once we have a system that repeats, we can measure once and then trust it is returned to the same location.
  • This location is in reference to a master location initially used to set up the reference system receiver.
  • For example, we can reduce set-up time when we put a vise in the system. After initial set up we have established its location in x-y-z. The next time we run a job there is no set up as these values have been saved.
  • Workholding set-up for the next time has essentially become seconds.

Mounting services along with the palletizing product designation guarantees that specific x-y-z locations are held.

Now we put all of the above together with one added condition:

  • All products marked with the palletizing designation have mounting protocol to place x-y-z surfaces at specific locations
  • These dimensions are held over the life of the product line
  • This allows you to have a reference location in your machine that is flat, square, and parallel along with multiple units that have the same dimensions.
  • You do not need different offsets for different pallets minimizing error
  • You do not need to buy “matching” sets all at once. As your needs expand you can buy tooling to expand with you and it will all match.

 

Evolution of the Hermann Schmidt Stainless Steel Rotary Index Fixture

Spin & Indexing

Historically, grinding applications in the manufacturing industry used a rotary device for hand grinding pins placed either in a v-block or 5C Collet which was designed into the unit.  This is a dry grinding operation with the fixture being spun by hand.  The indexes were set up on a sine plate, indicated in and stops set.

This grinding operation  evolved to a motorized option, eliminating the need to spin by hand.  The motor delivers steady speeds so the operator can concentrate on grinding.  This is also done dry.

Further innovation came by manufacturing the same fixture in stainless steel with ceramic bearings. The stainless steel construction allowed indexing functions in the wire EDM.  The ceramic bearings resulted in a tool that could be used in all EDM operations as the ceramic bearings isolated the bearing race from electrical discharge.

Further development to use this unit while submerged opened the potential to also spin and burn in the EDM environment.  These solutions were always considered an add-on option.  The results were often limited due to the challenges of successfully submerging a small, high torque, high rpm motor.  Usually at best 2 of the 3 above requirements were met.

Hermann Schmidt decided to redesign the product to meet today’s new demands for a device of this quality and flexibility while also addressing the changing workforce that the industry is experiencing.

We see a trend where manufacturers tend to have fewer toolmakers and more specialty operators in an area.  As a result, broad-base experience is diminished and many employers make this up with more sophisticated systems.

Stainless Steel Rotary Index Fixture in the Grinding Area

In the grinding area the RIF-S improves on all abilities of previous products as follows:

  • Compactness of design maintained.
    Face diameter of 4″ and maintaining thru hole capacity of 1″ allows customers to use previously developed face tooling.
  • Ceramic bearings allow a higher preload without generating heat.
    Previously as a unit was spinning the ball bearings would warm and expand.  As a result lower preloads needed to be used.  The end result is tolerance on the spindle can be held tighter.
  • The output from the rotary encoder allows the setting of indexing stops without indicating a position on a sine plate.
    This is significantly quicker than previous products.  This also allows a less skilled operator to set up the fixture to toolmaker tolerances.  Output can be in either decimal or degrees-minutes-seconds, eliminating the need for calculations.
  • The unit is submersible.
    If flood grinding is required, the internal motor option allows spinning. The applications for this are usually seen in high-pressure oil type grinding or when flood grinding chromed materials.

Stainless Steel Rotary Index Fixture in the EDM Area

In the EDM area our RIF-S – along with optional high RPM internal motor – changes what has been previously available to the industry.  Many work pieces previously ground can now be EDM’d.  Tighter tolerances with smaller details can be manufactured with greater repetition of accuracy.

  • Compactness of the design allows flexibility of placement in EDM.
    Small size also allows easy movement from machine to machine.
  • Ceramic bearings isolate the unit from electrical discharge.
    This prevents the any damage to the bearing race during EDM. The ceramic bearings also allow for a heavy preload, maintaining high precision with heavier work holding fixtures and work pieces installed on the spindle face.
  • The digital readout allows setting of the indexes while the unit is installed in the machine and squared to the machine travel.
    Previously the unit would need to be uninstalled, indexes set up and reinstalled.
  • The high-torque and high-rpm internal motor gives precise control up to 1800 RPM.
    This combination has not been available until now.  The high torque is required so proper face tooling options can be utilized at the high rpm required on smaller diameter work pieces.

Flexible, Expandable Options

The face tooling options can be purchased as required by the customer when their needs change.  None need to be added to the spindle at the time of purchase.

Dovetail Fixtures: 4 & 5 Axis Workholding Solutions

4 & 5 Axis, Dovetail Fixtures

Loading material onto a Dovetail Fixture

Prepared workpiece being loaded into a Dovetail Fixture
Prepared workpiece being loaded into a Dovetail Fixture

Simple
Machine dovetail detail into the workpiece

Rigid
Workpiece is clamped into a solid shoulder resulting in high strength & distortion free holding

Part Access
Only a small clamping area is required to secure the workpiece. The fixture profile is minimized to allow for maximum machine tool access

Magnetic Top Tooling Examples

Magnetic Chucks

Pole Extensions

Pole Extensions for Magnetic Top ToolingSimple, mild steel blocks called “pole extensions” bolted to the chuck face can be used to lift the part up providing clearance for through drilling, edge milling and back milling.

These “pole extensions” can also be configured to facilitate part location, magnetic side grip for holding small parts, and clearance for through machining.

  • Applies to all styles of Electro-Permanent Chucks
  • One size magnet can accommodate various sizes
  • Transferring magnetism to side of part

Self-Shimming Support

Self-Shimming Pole Extensions for Magnetic Top ToolingSelf-shimming pole extensions are the ultimate solution for holding rough or deformed parts.

These blocks conform to the shape of the part when the chuck is “off.” Once the chuck is magnetized, the self-shimming pole extensions not only lock to the part, they also lock in position without deformation.

Warped plates can be machined flat and stepped parts can be machined without warping.

pdficon_largeMagnetic Top Tooling Options

Select the Best Magnetic Chuck for the Workholding Job

How To, Magnetic Chucks

Magnetic Chuck Types and Applications

Magnetic chuck design has evolved to maximizing work holding power while taking into account the application. The strongest magnetic chuck is not necessarily the best. Here are some considerations when selecting a magnetic chuck.

Permanent Magnet Fine Pole
Maintains a low magnetic penetration to the work piece. This allows for superior holding on thinner pieces. No negative effects on Sinker EDM operations near the surface.

Permanent Magnet Standard Pole
Maintains a deep penetrating magnetic circuit and is used to maximize holding power as the work piece is usually unsupported.

Wire EDM
The single pole design eliminates the potential for removed material to affect the cutting zone.

Permanent Hard Milling
Concentration of the magnet forces allows holding of smaller hardened pieces. Superior magnetic flux control allow rough and finish mill operations without buildup of chips in the cutting zone.

Electric Magnet
Most commonly found on surface grinder. Fairly inexpensive to manufacture while giving good holding power and variable settings.

Electro-Permanent Magnet
Incorporates the highest strength for the broadest range of work pieces. The use of top tooling creates 5 sided access and thru hole machining. The design allows palletization. No thermal growth allows for higher accuracy applications. The control allows variable power settings and demagnetization cycle.

Narrow Wheel Dressing – How Thin Can I Go?

Grinding, Wheel Dressers

To determine what wheel to use, under normal conditions, multiply the grain size by 3.

Example: Grain Size of A 100 Grit Wheel is .0068” x 3 = .0204”

Average Particle Size of Abrasive Grain

Grit Size

Inches

Microns

4

.2577

6848

6

.2117

5630

8

.1817

4620

10

.1366

3460

12

.1003

2550

14

.0830

2100

16

.0655

1660

20

.0528

1340

24

.0408

1035

30

.0365

930

36

.0280

710

46

.0200

508

54

.0170

430

60

.0160

406

70

.0131

328

80

.0105

266

90

.0085

216

100

.0068

173

120

.0056

142

150

.0048

122

180

.0034

86

220

.0026

66

240

.00248

63

280

.00175

44

320

.00128

32

340

.00090

23

500

.00065

16

600

.00033

8

900

.00024

6

L.A.

.00012

3

Other conditions such as wheel density will affect how thin a wheel can be made.
For example if you use a more open wheel structure a finer grit size will be required to achieve the same thickness.

Narrow Wheel Dresser

Narrow Wheel Dresser Operating Instructions

Grinding, How To, Wheel Dressers

At 25° the tool dresses the back of Grinding Wheel

This Narrow Wheel Dresser is designed to dress the sides of grinding wheels quickly to a very thin width. This method directs the pressure up into the wheel, not to the side.

The rate of stock removal and the width to be dressed are determined by the wheel structure, hardness, density, and grit size. The narrow wheel dresser will dress the sides of any width wheel to a specific size quickly and accurately.

This narrow wheel dresser has successfully dressed wheels down to .010″ with minimum wheel failure.

At 20° the front of the Grinding Wheel is dressed

To operate:

  • Set the narrow wheel dresser at 25-degrees to true up the back of the wheel.
  • Rotate the crank in counterclockwise direction and feed the wheel down.
  • Next, set the dresser at 20-degrees and rough-dress the front side down to 0.40″. Stock removal failure depends on wheel structure.
  • Dresser will easily remove 3/16-inch on one pass on most wheels.
  • To dress wheels below .040″, set dresser at 45-degrees.

For under .040″ , set dresser at 45°

We stock the replacement cluster diamond. SKU: NWD-DIA

 Download Operating instructions for NWD

 

Narrow Wheel Dresser

Custom Tool Solutions for Your Manufacturing Requirements

Custom Solutions, Magnetic Workholding, Mechanical Workholding, Workholding

Hor jaw closeupFPH on HSM pin front w part

AP_EML_CUST

Customers looking at our custom solutions area ask why there are no descriptions to the pictures.

We do special versions of our products on a continuous basis. Usually they are variations of a concept of our standard offerings or a special mounting of a standard tool.

We cannot show all we have done nor do we show our products being used. Different industries or different areas of the world use our products in unique ways. I have seen many of them but by no means all of them.

We are trying to show concepts and ideas to stimulate your mind and use us to accomplish your unique requirements.

Please ask us about custom solutions.

Many applications can be addressed by taking a standard product and altering it by size, orientation or material. This keeps cost down from a true full custom solution and provides you with a tool that has most of the engineering decisions already proven.

I invite you to call me so we can discuss your specific applications.

Why Doesn’t Hermann Schmidt Still Sell…

Custom Solutions, Workholding

NBIwPNM_webAP_EML_CUSTWe are often asked: “Why don’t you still build…?”

That list of tools still requested include angle plates, non-magnetic sine plates, edge finders, v-blocks, 123 blocks, squareness gages, etc.

Product life is not forever in this now fast-paced industry. Products have generally been dropped as stocking items when the market has indicated to us that we cannot support having items in stock at the price we need to sell them at.

That being said, we still regularly build angle plates, non-magnetic sine plates and 123 blocks for customers. Rarely is it price effective to have one built, but it is effective once quantities of three or more are needed.

Recent custom version tools include:

  • Angle plates
    • Special bolt pattern
    • Stainless steel
    • With integrated wire edm magnets
    • With System 3R, Erowa, Hirschmann referencing chucks installed
  • Non-magnetic sine plates
    • No holes in top plate for inspection
    • Custom size with spin fixture mounted
  • 123 blocks
    • Stainless steel
    • Custom hole pattern

Repairing Hermann Schmidt Tools

Maintenance, Rebuild, Repairs, Replacement Parts

Customers taking tools apart.

BTDR

This industry is filled with very good “I can fix anything” mechanics. But please pause before taking anything apart – It will only save you money.

We have many customers calling to ask if we repair our products. We do.

We fully support all of the products we currently sell and have many spare parts for non-current products. We offer full rebuild service including regrinding if required. We will sell you any spare parts we have and will also assist you with reinstalling those items.

We have been doing this for a long time and can make suggestions which will make your rebuild more successful.

If you don’t know what model number or what the name of the part is you need, send us a picture and we will identify it for you.

How to Maintain Your BTD Style Chuck

Maintenance, Mechanical Workholding

Maintaining your 3 or 6 Jaw Precision Stainless Steel Chuck.

BTDSQ12In the past year we have been getting more and more BTDs in that need significant cleaning prior to us figuring out what is wrong with them. The conclusion is:

You have to maintain the chuck better.

The chucks look newly cleaned on the outside when we get them. Do not waste your time doing this. Spend your time maintaining the interior of the chuck. Remember you or your company spend significant money obtaining this tool.

Precision Chuck maintenance tips

BTDRWhen you are done with your job, prior to all the material swarf has dried, you need to do the following.

  • Flush the chuck out with water in closed, middle and open positions.
  • If you have an ultrasonic cleaner use it.
  • Spray WD-40 or equivalent on interior of chuck.
  • Flush chuck again if you do not want WD-40 in your machine environment.
  • If you use any cleaner that you use in your machine on the chuck you need to flush the chuck out excessively.

If a chuck does not have swarf in it many times we see that the cleaner has dried on the chuck internally.

We have chucks in the field since 2003 that are used daily and have never needed rebuilding. Yours could be one of those also with just a little careful maintenance.

Selecting the Right Spin & Index Fixture

Mechanical Workholding, Spin & Indexing

Customers often ask us: “Which spin & index fixture do I buy?”

I have already discussed SquareTech, which is a specific solution for high accuracy 90° indexing.

We sell four other styles. Here is some information to help you decide the best solution for your application:

Flatspin – NBFS  NBFS

Mostly used for face grinding on a surface grinding or jig grinding ID/OD.

The unit also has 15° internal indexing stops. Manufactured from tool steel the spindle can be used in a wet environment with pressurization. This unit is sold motorized as a plain spindle without tooling. All face tooling options are available.

Flatspin Spin Indexer product info.

Grindit – NBG  NBG

A very all-purpose tool for spinning and indexing.

The unit has 15° internal indexing stops and adjustable stops for off angle locking and arc limiting. Adjustable stops are set by mounting on a sine plate and indicating the angle. Zero-null feature allows for adjustment of zero +- 8° off of index origin. Manufacture from tool steel the spindle can be used in a wet environment with pressurization. This unit is sold motorized with v-block and 5C collet capabilities. Other face tooling options are available.

Grindit Spin Indexer product info.

Indexer – NBI  NBI

Has all the attributes of the Grindit, but does not need a sine plate to set the adjustable stops.

Patented interlocking Vernier plates allow you to set the adjustable stops to 1 arc second accuracy quickly. The indexer can be left setup in the machine environment and adjustable stops can be moved in location. This model should be purchased if you are using non 15° stops on a weekly basis or less.

Indexer Spin Fixture product info.

Stainless Steel Rotary Index Fixture – RIF-S  RIFS

This is the next generation in small spin and index fixtures.

Manufactured from stainless steel, containing ceramic bearings in a fully submersible package allows the unit to be used in most manufacturing environments, Wire EDM – Sinker EDM – Grinding.

An internal rotary encoder allows you to set up to 45 adjustable stops within 15 arc seconds accuracy. This eliminates the need for setting up using a sine plate and re-verifies your index position every time. Output is switchable between degrees decimal and degrees, minutes, seconds.

This unit is sold as a plain spindle. Motor drive options are the external motor usually used for dry grinding or the internal motor. The internal motor is integral to the RIF-S body allowing for fully submerged operations. The direct drive motor allows for full control 5-1800 RPM and reversing. Indexing accuracy improves to 6 arc seconds.

Options available are:

  • EDM grounding system for ensuring continuity in the EDM environment.
  • Leveling head to add or remove taper from a workpiece.
  • Adapter to rotate spindle to vertical orientation.
  • All face tooling options

Stainless Steel Rotary Index Fixture product info.

Proper Set Up for Achieving High-Quality Flat Surface Grinding Results

How To, Magnetic Workholding, Maintenance

A high-quality surface grinder is, of course, critical to successfully grinding parts flat. However several basic areas should be addressed before effectively evaluating the quality of the surface grinder. Correct and precise set up procedures are necessary to achieve the best results of the grinding tool.

MCS6x6HSM1

Set up areas include:

  • Magnetic chuck installation and maintenance
  • Grinding wheel selection and balancing
  • Diamond selection

Steps for high precision flat surface grinding

Magnetic Chuck Installation and Maintenance

  • Grind the machine table flat. Grind deep enough to remove all rust.
  • Grind the bottom of the magnetic chuck. Grind so there is approximately .0002” of dish per 6” of chuck length.
  • Mount the chuck with a light coating of oil between the surfaces. Tighten the right hand bolts first and then just snug the left side bolts.

Important: The ground-in dish and just snugging the bolts on one side allows the chuck to move due to thermal changes – while minimizing changes in flatness.

  • Grind the top surface of the chuck
    • Set the chuck magnet to “on.” With a properly built chuck this does not matter, it should not matter if the magnet is “on” or “off.” However, to be safe, grind with chuck magnet “on.”
    • Always grind with flood coolant (if available) and use an open-structure wheel, in order to minimize heat buildup in the grinding area.
    • Use small down feed increments with frequent dressing to minimize distortion.
  • Schedule maintenance
    • These steps are done yearly in our shop as rust builds up between the chuck and machine bed.

Grinding Wheel Selection and Balancing

  • Select a wheel that will not introduce stress or heat into the work piece. Your wheel supplier should be able to assist you in selecting the proper wheel.
  • Wheel balancing is an important part of flat grinding. An unbalanced wheel will produce a poor surface finish and shorten the life of you spindle bearings.
  • Wheel balance should be checked during the life of the wheel as it will change as the diameter is reduced.

Diamond Selection and Set Up

  • As a rule of thumb, the minimum size diamond should be ½ carat per inch of wheel face.
    • Large diamonds dissipate heat better, last longer and dress faster due to more contact with the wheel.
  • The diamond should be set approximately 10° in the direction of the wheel location.
    • Minimize the shank length and mount as rigid as possible.
  • Dressing feed depth should be a maximum of .001” per pass. Use flood coolant if possible.
  • Rotate the diamond to a sharp surface whenever possible.

Improve the Return on Your Investment

Careful installation of your surface grinding setup is vital to get the precise results that the grinder and the workholding tools are designed to deliver. Following these steps will not only improve your flat grinding, your grinding tools will continue to perform as expected for a longer time.

The return on your investment in Hermann Schmidt tools to support your precision grinding operations will be far greater with careful set up and ongoing maintenance.

How to Properly Use a Magnetic Squaring Block / Chuck

How To, Magnetic Workholding

MSB6x61Using a magnetic squaring block (magnetic squaring chuck) is the most accurate and quickest way to square parts on a surface grinder. The magnet will hold the workpiece without distortion that will be caused by mechanical clamping, while release/clamp time is significantly reduced.

To get the finest results from a squaring block, correct setup is vital. Here are key steps in the process.

  1. Check that the magnetic chuck on the surface grinder is flat and nick free.
  2. Grind the first side of your workpiece flat.
  3. Mount the magnetic squaring block (MSB) with the on/off switch on the right side and hardened rail on the left.
  4. Place a support block near the lower left corner of the MSB.
    • We like to use a block with a button head screw in the top so the part rests on the top of the screw. The screw allows you to adjust workpiece height to extend beyond the top of the MSB.
  5. Turn on the magnetic chuck on the surface grinder
  6. To mount your workpiece, place ground side on against MSB. Slide the workpiece against the rail and down to the support block.
  7. Turn on the MSB.
  8. Grind the first side.
  9. Turn off the MSB.
  10. Clean both the workpiece and MSB.
    • We do not use the air hose here, we wipe the contact surface with our bare hand
  11. Follow previous steps, placing the last ground surface against the rail.

This will accurately square up the two sides you ground to the third side you located from. When removing the MSB from the surface grinder, care should be taken to not slide the MSB.

  1. After demagnetizing the surface grinder magnet, apply force at the top of the MSB to break any residual magnetism and surface tension
  2. Lift the MSB straight up
  3. Clean and oil the MSB

Get the Most from Your Hermann Schmidt Precision Tools

At Hermann Schmidt, we offer two models of magnetic squaring blocks. For most high-precision squaring operations, Our standard pole 6-inch Magnetic Squaring Block delivers a quick and extremely accurate method of grinding blocks square. Our 4-inch Fine Pole Magnetic Squaring Block is a fine pole, low profile magnetic chuck designed for fast and precise squaring up of smaller parts.

Following our guide to using magnetic squaring blocks will help you get the most out of your tools.

UPDATE:  Question was asked to see some setups.  The following is a couple of pictures of a work piece set up on the 6″ squaring block.  The top of the stop in the 123 block has a radius on it so the work piece is sitting on a point.

001  002

Magnetic Squaring Blocks

How to Choose Between Fine Pole Magnets and Hard Milling Magnets

How To, Magnetic Workholding

When comparing Fine Pole Magnets to Hard Milling Magnets in work-holding applications, it is important to consider these three key factors:

  • Specific application / manufacturing environment
  • Performance
  • Cost

Let’s look into how these two magnetic solutions compare.

Fine Pole Magnetic ChuckFine Pole Magnet (FPH*)

Manufacturing environment

The FPH magnetic circuit is designed specifically for the sinker electrical discharge machining (EDM) environment. It is also used in the grinding environment as it meets the performance requirements there.

Performance

The FPH allows for the EDM process to continue into the surface of the magnet if necessary without any re-burn due to materials staying in suspension. This is an area where the strongest magnet is not the “best” magnet.

Hard Milling Magnetic ChuckHard Milling Magnet (HSM*)

Manufacturing environment

The HSM magnet is designed specifically for the hard milling area. It has the highest strength of any permanent magnetic circuit. The HSM magnet generates a primary and secondary field which allows it to provide a strong holding force while not magnetically penetrating deep into the part, hence minimizing chip contamination in the cutting zone.

Performance

While this circuit does not penetrate deep, it does create a situation where use in the sinker edm should be avoided. If an electrode tip is within approximately .25” of the magnetic surface and you are in a situation where the length /depth ratio of the area is greater than 5, you can get reburn. As the electrode cycles the coolant is evacuated from the hole and some solids can stay in magnetic suspension. When the electrode returns to the hole, we can get depth & finish problems.

Note that while we recommend the FPH magnetic circuit for sinker EDM for the reason described above, Hermann Schmidt does have customers that successfully use HSM magnets just fine in the EDM environment.

Comparing Cost

Cost is always a consideration, especially when automated cells can easily exceed 20 palletized magnets.

The HSM magnets cost 30% more to build and it is reflected in the price. Many customers want just one type of magnet to do all the work. We believe that is usually not reasonable. At Hermann Schmidt, we build magnets for the manufacturing environment and do not recommend trying to make a magnet design work where it does not belong.

Choose the Right Magnetic Tools for the Environment

Between selecting between fine pole magnets and hard milling magnets, consider the manufacturing process and the performance requirements first. Once that is established, the cost can be factored in – with cost going well beyond the initial purchase price.

* Throughout this post we used our FPH and HSM abbreviations to match our corresponding product lines. When selecting the correct magnetic tool for your specific application from Hermann Schmidt, look for models with the matching designation.  If you have any questions about using the right tool for your application, please give us a call at 860.289.3347.

SquareTech: Presetting Workpiece on Center

How To, SquareTech

The workpiece should be delivered to the machine tool in a pre-centered orientation.

Workpiece Center PresetterThis presetter features reversible gage arms to allow workpieces up to 11” x 11” to be centered. It is compatible with System 3R: Macro, Macromagnum and Matrix systems.

The system is applicable to the following workholding solutions:

  • Magnetics
  • Direct to Reference System
  • Vises

The basic procedure is as follows:

  1. Measure workpiece with height gauge.
  2. Set up planar gauges to proper dimensions by using height gauge.
  3. Place planar gauges between workpiece and presetter arms.
  4. Align workpiece.
  5. Activate workholding mechanism.

This system allows for the centering and squaring of the workpiece within 0.002” quickly and efficiently.

Download PDF of this SquareTech article.

SquareTech: Mounting of Workpieces

How To, SquareTech

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

High Precision ViseTwo styles of manual vises apply themselves well to SquareTech

  • Self Centering
  • Precision toolmaker

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

Mounting Worpieces DiagramWhile 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.
  • Electro-permanent.

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.

Download PDF of this SquareTech article.

Please contact us with your specific application. The options in work holding are continuously improving. Applications which were impossible only a couple of years age are now common.

SquareTech High Precision 90° Indexer: Real-World Test

SquareTech

SquareTech Precision IndexerWe make great claims of the quality and accuracy of our SQUARETech High Precision 90° Indexer:

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.

Maximum Value 0.000060”
Average Value 0.000030”
Median Value 0.000025”

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.

SQUARETech_size_chart

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.

Download PDF of this SquareTech article.

The following video is a presentation of fully automated SquareTech grinding cell.

Next post in this series: SquareTech: Mounting of Workpieces

 

SquareTech Precision Indexer