BLOCK-HEAD® Operator`s Manual - Professional Instruments
Contents
1. 2 5R 3R 4R 4B Low Profile 4R amp 4B Load Capacity Ultimate Working Ultimate Working Ultimate Working Ultimate Working Ultimate Working Radial 60 Ib 30 Ib 65 Ib 32 Ib 100 Ib 50 Ib 100 Ib 50 Ib 100 Ib 50 Ib Axial 120 Ib 60 Ib 170 Ib 85 b 400 Ib 200 Ib 400 Ib 200 Ib 400 Ib 200 Ib Tilt 100 Ib in 50 Ib in 140 Ib in 70 Ib in 400 Ib in 200 Ib in 400 Ib in 200 Ib in 400 Ib in 200 Ib in Stiffness Radia 0 35 Ib microinch 0 5 Ib microinch 0 67 lb microinch 0 67 Ib microinch 0 67 Ib microinch Axia 0 5 Ib microinch 1 5 lb microinch 2 0 Ib microinch 2 0 Ib microinch 2 0 Ib microinch Tilt 1 0 lb in microradian 1 6 Ib in microradian 4 0 lb in microradian 4 0 lb in microradian 4 0 lb in microradian Error Motion Radia lt 1 microinch lt 1 microinch lt 1 microinch lt 1 microinch lt 1 microinch Axia lt 1 microinch lt 1 microinch lt 1 microinch lt 1 microinch lt 1 microinch Tilt lt 0 1 microradian lt 0 1 microradian lt 0 1 microradian lt 0 1 microradian lt 0 1 microradian Total Weight 5 Ib 7 25 b 19 Ib 18 Ib 16 Ib Rotor Weight 2 b 3 2 Ib 7 7 b 7 7 b 5 Ib Rotor Inertia 0 057 oz in sec 0 16 oz in sec 0 73 oz in sec 0 73 oz in sec 0 40 oz in sec Maximum Speed 15 000 rpm 15 000 rpm 10 000 rpm 10 000 rpm 10 000 rpm Air Consumption lt 2 scfm lt 2 scfm lt 2 scfm lt 2 scfm lt 2 scfm 4R 2 25 10R 10B 10R 606 23R Load Capac2. areas of contact These pads can bend the mating part if they are not flat Small area contact at a bolted joint can cause tilting by variable compression This may be useful for minute adjustments Clamping screws must be coaxial with the contact pads Absence of support between the pads will allow variable deflection as an off center load passes over The result is an apparent three lobed out of round condition that will vary in magnitude depending on whether the load is near a pad or an unsupported region In other words the structural loop is not elastically symmetrical Increasing the contact area will lessen this effect The inherent angular accuracy and stiffness of the spindle can best be obtained by full area contact with a flat and rigid structure Off center load Deflection is increased over unsupported region Optional Pneumo Lock Internal Plumbing All BLOCK HEAD spindles have internal crossovers which are normally open so that one inlet feeds both sides of the spindle The crossovers are blocked with screw inserts to separate the flow to the two sides of the spindle in the Pneumo lock version of the BLOCK HEAD spindle The inserts can be installed or removed in the field but it is preferable to set the spindle up at the factory to avoid introducing contamination to the internal passages below the integral filters When air pressure to one side of the BLOCK HEAD air bearing spindl
3. is made across the bearing surfaces Working load capacity is half of the ultimate load capacity Rotor weight must be included as part of total spindle load Axial and tilt loads are supported by the same bearing surfaces Consequently a load applied in one mode reduces the other mode proportionally High speed or high inertia applications require rotor containment Maximum speed is dependent on application Consult Professional Instruments for further information with regard to speed Technical Support If you have any questions about your BLOCK HEAD air bearing spindle or any other Professional Instruments Company product please contact us at Professional Instruments Company 7800 Powell Road Hopkins MN 55343 USA Phone 952 933 1222 Fax 952 933 3315 E mail pico airbearings com Website www airbearings com May 2000
4. the four holes nearest the rotor on the 4B stator Excessive tension in these holes will cause swelling of the thrust surface with up to 20 reduction in 8 8 ultimate load capacity Nylon set screws are installed as a reminder in e 1 these sensitive holes i Use 120 pound inches maximum torque on the 1 4 20 screws in the model 10B The relationship between the torque applied to a screw and the clamping force produced is complex and subtle Please refer to a threaded fastener user s manual for a more thorough treatment of the subject 1 Mounting Guidelines for Model 4R The round stator is especially designed for face mounting Each of the six stator holes is tapped 5 16 18 through and counterbored for a 1 4 SHCS from the other side The holes are alternately oriented so that each side has three tapped holes and three counterbores facing up Use 120 pound inches maximum torque on the 1 4 20 and 5 16 18 screws A 4 375 diameter pilot is provided on each side Use 4 3755 minimum pilot hole diameter Alternate inlet and gauge ports on the face of the stator allow plumbing directly through a mounting plate This leaves the 5 625 diameter clear and keeps hoses out of the way Three Point Mounting When a mounting surface is inconvenient to machine a three point contact mount may seem advantageous Several aspects should be kept in mind Three point support actually consists of three finite
5. BLOCK HEAD Operator s Manual Model 3R e Ze Model 10B Model 4B Professional Instruments Company 7800 Powell Road e Hopkins MN 55343 USA e www airbearings com Phone 952 933 1222 e Fax 952 933 3315 e pico airbearings com BLOCK HEAD Operator s Manual This air bearing is one of the world s most precise mechanisms It provides a convenient way to rotate a component without friction or error motion and with complete stability high stiffness and long service life It is easy to use but successful installation depends on careful attention to details in this manual it is also quite easy to abuse The keys to success 1 Clean flat surfaces 2 Clean dry air 3 Know your loads and forces If in doubt about any procedure in this manual or just for a word of encouragement call us We are generally available 7 00am 5 00pm weekdays and many Saturday mornings Warranty Material and workmanship are warranted for one year after seasonable acceptance by Buyer Latent defects are warranted on a prorated basis for the expected life stated by Buyer in Buyer s Purchase Order Professional Instruments Company i BLOCK HEAD Operator s Manual STOP Before you unpack this bearing feel it through the yellow plastic bag If it feels cold do not proceed with unpacking until it has warmed to room temperature This may take 24 hours Condensation forming on a cold unpressurized bearing will damage it Professional Instr
6. able of supporting double the greatest anticipated load Note that the bearing s load capacity varies directly with air pressure e The pressure may be reduced when the bearing is not being used By maintaining a flow of air through the bearing the interior surfaces are protected against contamination We recommend an uninterrupted supply of clean dry air as the safest way to keep a bearing on standby or in storage e The pressure may be turned off only after careful cleaning and drying of the bearing s exterior and installation of the rotor lock Air Bearing Start Up Procedure 1 Purge the air line with a brisk flow of air for at least one minute Confirm that air line humidity is below 85 Install the inlet line s as shown in the diagram below Partially open the regulator to purge the gauge ports Connect the gauge s and adjust the regulator for maximum pressure The bearing gauge should read within 5 psi of the regulator gauge A larger pressure drop may indicate an air line leak obstruction or constriction A model 4B will also show a pressure drop when its gauge ports are incorrectly used as inlets other BLOCK HEAD models have universal ports which may be used for inlet or gauge Note that any unused port must be plugged 5 Remove the rotor lock The rotor should now turn freely with just a finger touch If it shows any sign of stickiness let it stand for 24 hours at maximum pressure before attempting further diagnosis t
7. ap Especially do not use an air blast to dry the bearing Clean the bearing with a non residual solvent such as acetone or isopropanol Clean all accessible surfaces including the rotor s bore and any unfilled tapped holes Final cleaning with gage block cleaner can help prevent surface rust since the cleaner leaves a scant film of protective oil Do not overdo it Let the bearing stand for 24 hours at a reduced 50 psi pressure Turn off the air supply and remove the air line s Place the bearing into the special plastic bag as shipped with a fresh pack of desiccant Optional Place the bagged spindle into the shipping drum arranging the foam packing material as shipped Close the drum and seal it Storing an Air Bearing Spindle The spindle can be safely stored without air if it is first cleaned and dried Do not use a strong blast from a blow gun in an attempt to dry the bearing this air blast can drive liquid upstream into the thrust bearings even with 150 psi on the spindle The best insurance against liquid penetration is to keep at least 10 psi pressure on the bearing at all times Provisions should be made to keep the spindle pressurized with clean dry gas i e dry nitrogen anytime the main air system is being serviced If the outer surfaces are to be protected by a rust preventative oil take care that it does not accumulate near the rotors exhaust regions Put a drop of oil on a clean cloth and wipe off the spindle Do
8. d forth overlapping action is required to slide the last remnants of trapped particles out of the joint Keep in mind that a tiny particle will often act like a roller bearing traveling only half as far as the stroke When overlapping action is impossible such as when there is a central pilot it is necessary to provide wiper grooves which make it possible to displace micro particles by simple rotation The best surface finish for precise assembly is the eight microinch finish on the BLOCK HEAD spindle Finer finishes are more difficult to bring into full parallel contact because they are less able to absorb residual micro particles Coarser finishes make gaging the part s flatness more difficult Check crucial surfaces before and after assembly to monitor the quality of the bolted joints For example the top surfaces of the bearing s rotor outboard of the mounting bands have been ground in assembly and will typically display no more than 10 microinches runout Distortion of the plate is likely to be revealed by an increase in the indicator readings High Accuracy Fixturing Most items that are fastened to the spindle rotor must run concentric to the rotor axis within very close limits Standard practice is to wring the flange down to full parallel contact with the rotor s mounting band A sensitive indicator is then used to measure the concentricity of a reference surface The item can be readily adjusted to run true to whatever level is r
9. e is cut the rotor is locked against the thrust surface of the stator The holding force is enough for finish cuts in machining and grinding The axial motion is about 0002 5 micrometers and is essentially free of unwanted rotary motion The rotor must be stopped before the Pneumo lock is applied Never use the Pneumo lock as a brake Do not exceed 60 pound inches turning force at 150 psi spindle differential NOTE If a central screw is used on the work holding fixture it should be a 10 32 or smaller to keep the torque requirement low This will minimize the chance of inadvertently turning the rotor while tightening the screws Plumbing Select the direction of locking force The usual practice is to depressurize the side that carries the weight of the fixtures Locate the three way valve in a dry place It will draw a little ambient air into the bearing lines each time it is switched on We can provide a protective box if desired Use pressure gauges on both sides Install a pressure switch on the interrupted side Check for proper operation of the valve by noting gauge readings Rotor translates about 0 0002 when upper side is depressurized Normally open open pressure 54 NY e pressure switch 0 switch near side supply Access to crossover pressure switch supply Pressure Switch All motorized drives should have a pressure switch such as Whitman Controls type P119 to prevent accidental start up at l
10. e or a gage block stone Reclean with a small amount of rust preventative oil on a lint free cloth We use Rust Lick 606 which is available from Rust Lick Company 30 Endicott Street Danvers MA 01923 Tighten 10 32 screws uniformly to 80 pound inches or 1 4 20 screws to 120 pound inches after applying a small amount of grease on the end and under the head If the spindle is to be used for machining the unused mounting holes can be plugged with screws to keep out debris GF 5 Precision Ground Flatstones These stones have been ground flat on both faces with a diamond wheel The long sides are ground perpendicular to allow stoning up to a shoulder The ends are unground The stones are used to remove the swellings which surround the inevitable tiny nicks and dents found on any machined surface They are much like gage block stones but with a more aggressive cutting action The stone s porous structure allows asperities to penetrate far enough to be trimmed off When the raised area is reduced in height to about ten microinches the force is spread out between two relatively large flat surfaces and cutting activity substantially stops Proper application will avoid scratching the work and L will prolong the useful life of the stone e Prepare the work by locally removing large burrs with a file or an unground work stones together before each use stone Clean with solvent and tissue e Before stoning a workpiece rub the two stone
11. eads are clean and undamaged Observe the torque recommendations e Observe safety precautions Use adequate guards for high rotational energy applications e The pressure may be turned off only after careful cleaning and drying of the bearing s exterior and installation of the rotor lock Wet Environment Operation As long as a BLOCK HEAD spindle is pressurized the exhaust air serves as a seal against contaminants a pressurized spindle will operate well in a dirty environment under a flood of liquid or even submerged However a stream should not be directed at the exhaust region where the rotor and stator meet since contaminants could be forced upstream into the bearing For this same reason the bearing should not be cleaned with a blast of compressed air When the spindle is depressurized any moisture present at the exhaust regions will be drawn in by capillary action leading to sticky operation error motion loss of load capacity or bearing failure Before a spindle is depressurized it must be scrupulously dried paying particular attention to the areas where the rotor and stator meet If liquids are likely to come in contact with a BLOCK HEAD spindle we recommend fixture designs which incorporate non contact seal features such as labyrinth seals or capillary seals Professional Instruments offers a standard selection of such seals which will reduce the chance of bearing failure from liquid intrusion We have experience with
12. equired It takes a few moments to do this but it makes possible a higher level of accuracy than any pilot could provide Despite the high degree of roundness and concentricity of the rotor s inside and outside diameters they should not be used as piloting diameters A fit close enough to provide accurate centering is certain to distort the rotor leading to loss of the bearing s load capacity and accuracy In addition a tight diametral fit prevents the rotation that is necessary to wring the flange surface into proper contact with the rotor s mounting band Where manual centering is unacceptably inconvenient we can provide a piloting system as an option that will center fixtures to less than 50 microinches T I R We have had many years of experience with this system and we find no loss of accuracy after hundreds of disassembly reassembly repetitions It can be readily adapted to all sorts of chucks wheel mounts centers and fixtures Contact Professional Instruments for more details Spindle Drives Careful attention must be given to the drive train to realize the inherent performance of the spindle An ideal drive would transmit vibrationless torsional force with no radial or axial loads Flywheels For spin table work in jig grinding small holes a high inertia faceplate can store enough energy from a hand spin to go for several minutes This is the closest approximation of a totally non influencing drive Belt Drives For low pow
13. er applications a low tension drive employing a minimum cross section miniature V belt or Mylar flat belt can be used directly on a pulley attached to the spindle Note that belt tension contributes to total load on the spindle It is important that the load limit not be exceeded Consult the specifications for maximum working load capacity Belt tension should be slacked off when the air pressure is lowered for storage Do not overload the bearing by forcing the belt over the pulley during installation Keep the pulley overhang to a minimum As a rule of thumb the pulley should be within four inches of the center of the stator Drive requirements over 100 pound inches need fairly high belt tension A separate pulley support bearing with a coaxial coupling or alternately an idler pulley opposite the drive pulley can be used to carry the radial load A belt lift arrangement can be used to augment the radial bearing in the case of heavy loads Consult our Engineering Department for details Coaxial Drives A coaxial drive can be either direct from the motor or through a coaxial jackshaft In either case adequate couplings are required Off the shelf flexible couplings are often adequate for low speed low power jobs Attention must be given to the vibration characteristics of the motor drive package If vibration amplitudes in the low microinch range are required it is necessary to isolate the motor and drive train This can be done by separatio
14. he stickiness may be due to a minute amount of oil which found its way into the bearing by capillary action and must be cleared Never force the rotor to turn if it is sticky Test for stickiness by adding a slight imbalance to the rotor for instance a single 10 32 screw The rotor should oscillate several times before stopping 6 Reattach the rotor lock whenever the bearing is idling at low pressure or being stored or shipped without pressure The bearing will be damaged if it is rotated with insufficient pressure to support the load Normally open pressure Any of these 5 Any of these 4 ports can be gauge ports can used for inlet be used with any inlet port Normally open pressure switch Any of the 8 ports can be used for inlet Any of the 4 opposite ports Dryer Dryer can be used in Filter Filter conjunction with Regulator Regulator the chosen inlet port Air Bearing Shut Down Procedure Avoid bearing shut down if possible An unpressurized bearing is very vulnerable to damage by contamination An air bearing perpetually pressurized has the best chance of being trouble free if it is not overloaded its service life is virtually unlimited 1 2 By 02 Ov 2 Install the rotor lock Dry the bearing Use an absorbent swab in the corner where rotor and stator meet Do not push debris into the corner instead wipe away from the g
15. hole identified by the sintered bronze muffler Mounting surfaces should be ground flat to avoid distortion of the bearing surfaces and to realize the full stiffness of the spindle Mounting plates and fixtures are preferably made of steel rather than aluminum to minimize the possibility of distortion from variation in expansion rates due to thermal effects The degree of flatness required increases with the stiffness of the plate The mating surfaces should come into total area contact with only a few pounds force Heavy structures should be ground or lapped flat enough to wring to the stator As a rule of thumb figure 0 0001 per inch flatness for a steel plate 0 25 thick and 0 000 010 per inch for a steel plate one inch thick If in doubt check for full contact by lightly bluing one member Clean the mating surfaces and check for nicks and burrs with a GF 5 Precision Ground Flatstone or a gage block stone Reclean with a small amount of rust preventative oil on a lint free cloth Tighten the screws uniformly after applying a small amount of grease on the end and under the head Screws should have at least 0 2 engagement but they must not bottom in the hole Before installing the plate measure the length under the head with the screw finger tight It should be at least 0 2 less than the thickness of the plate 0 2 minimum Use 80 pound inches maximum torque on the 10 32 holes in the 4B rotor and stator except 20 pound inches maximum on
16. hould be checked by running the screw into the hole making certain that it runs in freely 0 2 5mm beyond the depth needed to clamp the fixture Good lubrication will provide more uniformity of screw tension Molybdenum disulfide powder or grease is very effective It should be applied under the screw s head and on its first few threads When two flat surfaces are to be bolted together the forces must be spread out to prevent localized distortion in other words multiple fasteners are best For example a flat plate attached to the rotor of the four inch BLOCK HEAD spindle with only two screws at 0 and 180 will bend the rotor 100 microinches out of flat adding two more screws at 90 and 270 will reduce the total distortion to less than 40 microinches When all 12 screws are used the stress is distributed so uniformly that the regions of high and low compression are no longer measurable Surfaces must be clean as well as flat Remove oily residue by wiping with tissue and solvent Remove burrs and particles by use of a model GF 5 Precision Ground Flatstone Wipe again with solvent on a lint free cloth and stone again as a final cleaning This cleaning process is recommended for every high precision bolted joint whether new or previously assembled The freshly cleaned surfaces should be brought into careful contact taking care not to bump or scratch them and then wrung together in the same way that gage blocks are assembled A back an
17. ity Ultimate Working Ultimate Working Ultimate Working Ultimate Working Ultimate Working Radial 125 Ib 63 Ib 400 Ib 200 Ib 400 Ib 200 Ib 600 Ib 300 Ib 1 500 Ib 750 Ib Axia 175 b 88 Ib 2 400 Ib 1 200 Ib 2 400 Ib 1 200 Ib 1 000 Ib 500 Ib 15 000 Ib 7 500 Ib Tilt 150 Ib in 75 Ib in 6 000 Ib in 3 000 Ib in 6 000 Ib in 3 000 Ib in 2 800 Ib in 1 400 Ib in 50 000 Ib in 25 000 Ib in Stiffness Radia 0 8 b microinch 2 b microinch 2 b microinch 3 Ib microinch 4 lb microinch Axia 1 0 Ib microinch 10 Ib microinch 10 Ib microinch 5 lb microinch 40 Ib microinch Tilt 1 7 lb in microradian 100 Ib in microradian 100 Ib in microradian 60 Ib in microradian 1 500 Ib in microradian Error Motion Radia lt 1 microinch lt 1 microinch lt 1 microinch lt 1 microinch lt 1 microinch Axia lt 1 microinch lt 1 microinch lt 1 microinch lt 1 microinch lt 1 microinch Tilt lt 0 1 microradian lt 0 1 microradian lt 0 1 microradian lt 0 1 microradian lt 0 1 microradian Total Weight 16 Ib 154 Ib 146 Ib 104 Ib 2 200 Ib Rotor Weight 7 b 72 lb 72 lb 42 Ib 1 400 Ib Rotor Inertia 0 77 oz in sec 36 oz in sec 36 oz in sec 27 oz in sec 245 oz in sec Maximum Speed 7 500 rom 1 800 rom 1 800 rom 1 500 rpm Application Dependent Air Consumption lt 2 scfm lt 3 scfm lt 3 scfm lt 4 scfm lt 10 scfm Load capacity and stiffness are approximately linear with air pressure Ultimate load capacity is measured when metal to metal contact
18. n of the drive from the spindle structure or by isolation of the motor in a resilient mounting We can provide motor drives which are spring isolated and friction damped sized for motors to about 1 5 horsepower Integral Motors The ultimate spindle drive technique integrates the frameless motor and the air bearing into a compact efficient package Noise vibration and wear typical of couplings and belts are completely eliminated The motor components are finish machined to precise geometries and assembled nicely concentric to the spindle axis this creates a uniform air gap in the motor for enhanced smoothness The motor is supported by the air bearing from one end only leaving space beyond the motor for an encoder a resolver a rotary union or the like Air cooling frequently suffices to carry off motor heat while water cooling is used in more demanding applications An integrated motor provides high power extremely precise speed control and speed stability The rotating mass is balanced to the limit of perception The result is a spindle that exhibits virtually no asynchronous error motion no vibration and no radio frequency interference Mounting Guidelines for Models 4B and 10B The spindle can be mounted vertically or horizontally on any of its six sides Alternate inlet and gauge ports allow mounting on the nameplate side If the nameplate side is covered an exhaust hole must be provided for the radial bearing airflow from the central
19. not force the cloth down into the corner where the outer diameters of the rotor meet the shoulder of the stator It is better to leave the corners dry than to over oil the bearing If the corner is dirty clean it with a cotton swab soaked with solvent Do not use a hard instrument like a screwdriver Fixture and Adapter Plate Mounting Do not disturb the 12 cap screws that hold the rotor s thrust plates to the shaft Do not attempt to drill additional holes in any part of the spindle The rotor mounting surfaces are ground flat and perpendicular to the rotational axis of the spindle to 0 000 020 Any stiff plate that is to be attached to the rotor should have comparable flatness The degree of flatness required increases with the stiffness of the plate The mating surfaces should come into total area contact with only a few pounds force Heavy structures should be ground lapped or scraped flat enough to wring to the faceplate As a rule of thumb generate 0 0001 per inch flatness of steel plate 0 25 thick and 0 000 010 per inch for a steel plate one inch thick If in doubt check for full contact by lightly bluing one member Screws should have at least 0 2 engagement but they must not bottom in the hole Before installing the plate measure the length under the head with the screw finger tight It should be 0 2 less than the thickness of the plate Clean the mating surfaces and check for nicks and burrs with a GF 5 Precision Ground Flatston
20. ontact This will crash the spindle if the rotor is in motion Working Load Capacity is defined as half the ultimate load capacity The 50 factor was selected to provide a reasonable margin of safety for most applications Cae xa d 20 200 pounds axial load 200 pound inches tilt load 400 pounds axial load e OO OK Pure tilt load as applied in our tester Z SS GR 100 pounds balanced 100 pounds radial radial load 400 pound inches tilt load BLOCK HEAD Air Bearing Spindle Specifications at 150 psi The BLOCK HEAD family of air bearing spindles named for their short blocky shape combine rotational accuracy with extremely high stiffness comparable with that of heavy duty ball bearing headstocks These spindles are suitable for accurate support of overhung loads and their unique combination of accuracy and stiffness makes possible direct machining to optical tolerances and finishes BLOCK HEAD spindles have been used successfully from less than 50 psi up to 200 psi and have shown no signs of instability They will operate equally well in any position over a wide speed range and in a variety of environmental conditions Add ons such as motors chucks mounting plates and custom tooling benefit from the correct nature of the BLOCK HEAD design Accessories can be close coupled tightly held and non distorting
21. ow pressure A lamp wired through the switch can give the operator warning even if a motor is not used Air to the switch should be taken from the spindle gauge port This will give actual pressure in the bearing even if the inlet line is pinched or the integral filter is clogged The switch should be set up with a normally open circuit contacts open on falling pressure Attachments Professional Instruments offers an extensive line of mounts couplings fixtures and adapters for use with BLOCK HEAD spindles many of which are available from stock In addition we would be pleased to quote on special order fixtures Load Capacity Air bearings get their load capacity from the change in pressure that occurs with the change in air film thickness as the rotor is displaced Pressure rises on the side that is getting tighter and falls on the loose side The strength of the restoring force depends upon the area of the bearing surface the pressure of the air and the efficiency of the compensation Note that the shape of the BLOCK HEAD rotor gives maximum bearing area for a given package size The bearings in a four inch BLOCK HEAD spindle have at least 100 pounds ultimate radial load capacity and 400 pounds ultimate axial load capacity at 150 psi Since load capacity varies directly with air pressure reducing the pressure by half will cut the load capacity approximately in half Ultimate Load Capacity is the load that causes metal to metal c
22. s together to remove or cut down embedded debris which could scratch the work e Slide the stones onto the workpiece with light pressure to avoid scratches from loose particles Small projections are easily felt if the work is clean Concentrate on the feel loose debris can be felt rolling around Stop immediately and reclean e Gradually bear down always working in the direction of the original grind lines on the work e Clean the stones by spray rinsing or ultrasonic cleaning followed by air workpiece blast Store in the original container to avoid misuse on rough work every scratch has burrs Air Bearing Care and Maintenance e Observe the humidity level and take action if humidity exceeds 85 e Use a rotor lock when not at maximum pressure Inadvertent rotation without air pressure will generate wear debris which will bind up the spindle This is particularly important during installation when several people may be working near the spindle Never rotate the spindle even a little without at least 50 psi pressure e Know your loads and forces Be sure the supply pressure is adequate for the load Never exceed 50 of the ultimate load capacity e Be sure the mating surfaces are flat clean and free of nicks and burrs Full accuracy and load capacity can be achieved only when the bearing surfaces are undistorted e Use proper length screws be sure the screw does not bottom in the hole because it is too long Be sure the thr
23. uments Company ii BLOCK HEAD Operator s Manual Table of Contents Air SUDPIY EE 1 Air Bearing Start Up Procedure 2 Air Bearing Shut Down Procedure ssssesssssesesrssrrssrrssrssrirssrrssrnssrnssrnssrnssrnnsrnnt 3 Storing an Air Bearing Spindle AAA 4 Fixture and Adapter Plate Mounting eseeesseeeessrnesssrrssesrnssrirnssrinnnsrnnnnsrennnsrennns 5 Model GF 5 Precision Ground Flatstones cc cccceececeeeeeeeeeeeeeeeeeeeeeseaeeeeeeeeeas 6 Air Bearing Care and Maintenance esseesseeeseesseeeseeeseestnurtnnstnnstnnnnnstnnsrnnennnenn 7 Wet Environment Operation 8 L w Re Indien EE 9 High AcCcuracy Fixturing esnias aa a innana a ian a iA 10 SPINS Dives a a a a as 11 Mounting Guidelines for Models 4B and 108 12 Mounting Guidelines for Model An 13 Optional PneUMO LOCK isisisi deariden iiaii iadi daaa iaa 14 Pressure SWITCI asrni a E e E a t 15 Linter CEET 16 Load Capacityuteu i ain aie Ae are TEE 17 BLOCK HEAD Air Bearing Spindle Specifications 0seeseeeeee ereenn 18 Technical Support gebuede ia anaana ania Ae EN 19 Professional Instruments Company jii BLOCK HEAD Operator s Manual Air Supply Air bearing spindles and slides require clean dry oil free air at adequate pressure e The relative humidity of the air at the bearing must be maintained at 85 or lower e The air must be free of oil tars resins and of particles larger than five micrometers e The operating air pressure should be cap
24. very demanding sealing requirements and will assist you in choosing the best design for your application Labyrinth Seal Capillary Seal 005 010 Stator Thrust Plate Low Distortion Mounting Our published accuracy specifications apply to the undistorted spindle carrying less than its maximum load In order to achieve the full potential accuracy of the spindle meticulous attention to detail is required in mounting the spindle s stator to the machine and fixtures to the spindle s rotor The spindle is provided with mounting surfaces that are flat to 20 microinches 0 5 micrometer mating surfaces must be similarly flat in order to maintain accuracy and load capacity If a mating surface is not flat enough the spindle will be distorted possibly enough that the spindle will have zero load capacity or even be locked Reduced screw tension will not compensate for out of flat mating surfaces which will be pulled into contact with an almost infinitesimally small force The relationship between screw tension and the torque used to tighten the screw is not at all precise since only 10 percent of the force actually stretches the screw the other 90 percent overcomes friction in the threads and under the screw head It is possible to have zero tension on the bolted joint despite high torque if the threads are rough or dirty or if the screw bottoms out in the hole To prevent this every threaded joint s
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