Jena Tec Systematic Multi Head Spindles

The Systematic Multi Head range now exclusively manufactured by Jena Tec provides a wide range of engineered solutions for High Productivity Machining. Our experienced engineers can design or retro-fit our multi head components into your machining centre to maximise the productivity demands of today's environment, offering you time and cost savings in the manufacturing process.

Jena Tec Systematic offer single or multiple heads for block boring, drilling, tapping, reaming, indexing rotations and W axis slide motion. Using gear or belt drives, Jena Tec Systematic can custom design a unit to your specification utilising standard, ISO, BT or HSK tooling.

For information contact the Jena Tec team on +44 (0)1623 726010 or email at sales@jena-tec.co.uk

Jena Tec Miniature Ballscrews Deliver High Precision and Low Drag Torque

Jena Tec Miniature ballscrews can be manufactured from 6mm diameter with 1mm pitch with exacting precision grades less than 6 microns over the stroke length and very precise drag torques of 0,002 to 0,005 Nm. Jena Tec experiences a wide range of demanding customer applications in the fields of medical, aerospace actuation and instrumentation. Customer specifications vary depending on the use of the ballscrew and Jena Tec designers know how to accomodate important parameters such as motor torque, long life lubrication, low noise, elevated temperatures and extended life time calculations into specifying a product that fits for each request.

As well CF53 controlled case depth or through hardended material, Jena Tec can accomodate materials including aerospace standard and corrosion resistant materials in their range including those suitable for vacuum applications.

All Miniature ballscrews undergo rigourous testing to ensure compliance with drag torque and accuracy requirements on our well equipped test facilities in Jena.

For more information on the miniature ballscrew range, contact Jena Tec on sales@jena-tec.co.uk or +44 (0)1623 726010.

Jena Tec Raydent coating extends linear rail life

Developed in Japan in the 1960's and well proven in industry, Raydent coating is a proprietary technology deposited by low temperature electrochemical bonded chrome ceramic particles diffusion bonded to provide a layer up to 1mm thick on the surface of the metallic substrate.

The Jena Tec SBC range of linear rail uses this proprietary technology to great effect for corrosion protection making it suitable for corrosive environments, food grade applications and clean room standard machinery such as that used in semi conductor manufacturing.

The method of coating deposition ensures no hydrogen embrittlement takes place while a high degree of elasticity is maintained in the coating such that even while the steel substrate is flexed and placed under repeated external deformation or bending, the coating maintains its appearance and performance and is free from flakes, chips and cracks which may appear in other anti-corrosion treatments such as chrome or nickel plating.

Tests conducted on linear rail within materials testing institutes showed that for a variety of tests, SBC rail Raydent coated outperformed alternative electro chemical methods with no evidence of rust whereas traditional coatings such as chrome plating corroded significantly. Raydent was effective in concentrated sulphuric acid environments, sodium hydroxide and salt water spray tests with no evidence of degradation.

Specially treated to order, the Jena Tec SBC Raydent treated range provides a superior lifetime performance in excess of 10 years.

For information contact the Jena Tec team on +44 (0)1623 726010 or email at sales@jena-tec.co.uk

Jena Tec SBI Linear Rail offers 40% increase in capacity

The SBI range available from Jena Tec provides multiple benefits compared to those offered by the competition in relation to low noise, high rigidity and load coupled with a smooth movement and self adjusting mechanism. Increase of load carrying capacities of up to 40% can be achieved compared to standard block and rail systems.

Compared to conventional linear rail cross sections, the SBI range is approximately 10% lower in height with a wider through section of nearly 20%. Its improved lower cross sectional centre point offer greater structural rigidity, improved straightness during manufacturing and therefore a higher level of straightness in application which benefits the customer for smooth running. Heat treated to HRC60 the SBI range is extremely stable and shorter cross sectional areas mean grinding time and plastic deformation are reduced.

Similarly, Linear blocks are constructed from a hardened steel rigid structure with the same lower cross section centre as the rail and slightly longer block length meaning a greater number of balls with a smooth circular angular motion. This improved track profile and angle results in a smoother and quieter operation.

Standard across the range of SBC products is the heat and chemical resistant end plate with moulded return systems and a self aligning retained designed to ensure the end plate is correctly fitted in line with the main steel block. Despite an increased load carrying capability the additional length attributable to the SBI range is approximately only 3-4 mm longer than standard types dependant on carriage model made possible by an improved end plate design. When considering the advantage of 40% increase on load, the additional length is very modest.

Upper and bottom retainer plates fitted to each block ensure that loose steel balls are eliminated as well as skidding and poor rolling performance within the load zone. Additionally, this benefits the cleanliness of the block by preventing ingress of foreign substances. Advocating a simple design philosophy, the SBI retainers are snap assembled and self aligning. The moulded return plate contributes to the smooth running operation of the SBC range as well as keeping running noise low.

The SBI range achieve this through an improved contact angle of 52% versus the industry standard of 53%. The lower radius of curvature provides a broader contact surface compared to the relevant ball size possible and therefore improves the rigidity.
The improved angular ball re-circulation system with 4 row 2 point contact and 45 degree angular orientation ensure that excellent rolling performance is maintained with low noise even at all grades of pre-load.

For further information, contact the Jena Tec sales team at www.jena-tec.co.uk or on +44 (0)1623 726010.

Jena Tec MF option linear guides keep going and going...........

Expensive lubrication systems become a thing of the past and for machines without lubrication, Jena Tec's SBC MF series linear rail option extends the life and performance of your linear system by a significant factor.

The MF Lubricating Seal now offers longer life for SBC Linear Rail Systems, eliminating the necessity for periodical greasing. The MF Unit contains high quality ,grease filled fiber seals which will guarantee total surface lubrication and long maintenance free bearing life. The polymer housing containing the surface contact seals are tolerance matched to the guide rail to ensure perfect sealing and smooth motion.

MF Seal Units are grease filled and the lubricant is contained , spread and absorbed by the fiber seals. Using grease rather than oil ensures that the lubricant is retained within the MF seal units for a much longer working life than oil would remain. The grease used would be compatible with most standard industrial grades recommended for use in bearing blocks and provides excellent thermal stability and water proofing characteristics.

Tests conducted by SBC show a clear advantage of MF type seals, despite a modest increase in overall length through the slim line design of the fiber seal housing. Results show that for a standard theoretical distance life time calculation of a heavy pre-loaded guide block that the distance for an MF type under heavy load can be increased by 40% up to a 1000Km with no sign of degradation or wear affecting performance or accuracy. For light pre-loads the life extension can be up to a factor of 10 times. Even then replenishment with new MF end caps is a very simple straightforward procedure to give a further period of un-interrupted service.

For more information, contact the Jena Tec team on +44 (0)1623 726010 or email sales@jena-tec.co.uk or visit http://www.jena-tec.co.uk/

Intelligent GMN UHS Spindles from Jena Tec UK

In addition to our own manufactured range of high quality B&T customised spindles for milling, turning, boring and grinding, Jena Tec represents a high quality German brand GMN Nuernberg in the UK market for high speed and high frequency machining spindles.

In this issue, we've provided some detail information about GMN's capability in ultra high speed grinding spindles. Conventionally supplied by air bearng spindles which have some limitations and disadvantages in terms of cost and running efficiency, GMN's UHS series provides a robust oil lubricated grinding spindle for exceptionally high speeds up to 250,000RPM coupled with an exacting stability and geometric tolerance. A minimised oil/air dosing system means just the right amount of lubrication gets to the spindle and reduces maintenance and running costs throughout the life of the spindle.

Jena Tec's automation division can offer the UHS series from GMN including integration or retrofit to existing machines. If you would like to discuss how we can offer you the advantage of higher speed and better process performance from your grinding machine, then give our UK office a call on +44 (0)1623 726010 or by email to sales@jena-tec.co.uk

Intelligent Spindles from GMN**

Processing small internal diameters with optimum cutting speeds requires high rotational speeds. New GMN spindle ball bearings with very high speed characteristics permit 250,000 revolutions per minute, for instance, with comparatively high spindle rigidity and load capacity. Optimized lubrication of high speed spindles offers great potential for increasing performance. Furthermore on-demand minimal lubrication lowers oil consumption and increases service life. In future integrated data loggers will monitor the condition of the spindle, store the operating parameters and guarantee high availability. GMN has a long track record of supplying a wide range of high frequency spindles of up to 180,000 rpm. However, around two-thirds of the spindles supplied for internal grinding operate with maximum speeds in the 30,000 to 90,000 RPM range.

250,000 RPM for small bores
To operate efficiently, a machine tool spindle must have the appropriate load capacity, rigidity and dynamic run out. In order to guarantee these characterisitcs even for extremely high speeds, the GMN development department was faced extraordinary challenges. Breaking points are reached due to the high centrifugal forces, a compact design has to ensure subcritical operation with sufficient distance to the first critical speed, high precision hybrid ceramic bearings have to be designed specifically for the demands of high speed spindles. These challenges were met wth the the help of current advances in motor technology and the use of further developed GMN spindle ball bearings. It is now possible to efficiently grind small internal geometries with up to 250,000RPM. The GMN grinding spindles used for this purpose have a comparatively large and rigid mounting and a powerful sychronous motor. Consequently, they are not only suitable for special applications at maximum speeds but can also be used flexibly and efficiently in a relatively large rotational speed range.

Integrated lubrication module
These days, ball bearings with permanent grease lubrication or oil/air lubrication are predominantly used in machine tool spindles. Yet both methods have their disadvantages which can be overcome by an innovative micro-dosing system combined with appropriate lubrication strategies. Compared with today's oil/air lubrication method, a significant reduction of the lubricant quantity necessary can be achieved and the systematic performance limits of grease lubrication. I.E. Limited usable life of grease at high temperatures and speed, are to be exceeded. Minimizing lubricant quantities makes ecological and economic sense. It facilitates the inegration of an oil reservoir in to the spindles and ideally requires no more external components. The problems associated with waste oil disposal are also defused. Operating costs of machine tools can exceed acquisition costs several times over if calculated over a normal life cycle. These costs are therefore a decisive factor for many users when making an investment decision. An integrated lubricant cartridge means that high maintenance external components can be dispensed with. The lubricant reservoir only needs to be replaced at relatively long intervals. An almost instant dosage of lubricant ensures that the adjustment of the lubricant quantity matches demand based on the exact measurements of the bearing. This increases reliability and efficiency of the bearing and reduces the quantity of the lubricant needed.

Third generation spindles for machine tools
Spindles are also becoming more and more intelligent. Miniaturised electronics which are integrated in the spindle stores the sensor signals, processes them and reports any exceeding of critical values to the overall machine control system. Important operating data can be accessed during the entire running time of the spindle and can also be analyszed with regard to optimising the process, machine and spindle. In addition, the aim is to go for bearing condition monitoring and consequently early damage detection,based on these intelligent systems is possible. Evaluating temperature sensors, position sensors and vibration sensors will increase precision and productivity of the production process. Additional sensors, on the other hand, harbor the risk of reducing the availability of the spindle system further, therefore, as few additional sensors as possible should be employed and for the time being, a more intelligent analysis of available signals should be aimed for.

** Reproduced from an article by Dr. Bernd Moeller, Head of Engineering Spindle Technology Division at GMN Paul Mueller Industrie GmbH & Co. KG in Nuernberg, Germany.

For service and support on design, selection, repair and replacement of spindles from GMN in the UK from Jena Tec go to www.jena-tec.co.uk or call our UK office on +44 (0)1623 726010

Principles of Ballscrew Repair

Principles of Ballscrew Repair

What exactly does happen to a ballscrew when it fails and what are the principles and procedures to repair a ballscrew from a company such as Jena Tec?

The most frequent cause of failure of a ballscrew is either loss of pre-load or rough running typically characterised by a fault flagged by a CNC control system of a machine tool or dimensional inaccuracy or poor surface finish. This in turn is caused by gradual degradation of the ballscrew surface through metal to metal contact of the re-circulating balls to the hardended metal surface of the ballscrew shaft. This repeated contact over an extended period of time leads to a worsening of the ballscrew surface and ultimately erosion and wear.

Lubrication can therefore have an obvious impact on the lifetime of the ballscrew as well as protection from debris from the machining processes. Over time as a machine condition worsens, axis covers and bellows can be damaged and allow machining debris to enter the ballscrew nut even through wiper seals. Over lubrication can also be problematic particularly with grease lubricated systems where too much lubrication can cause pressure on the ballnut return system causing the tube to literally burst with excess grease.

The second most frequent cause of ballscrew failure is catastrophic failure due to an exceptional shock load, which is more commonly recognised as a machine crash. The abrupt excessive load and rapid decceleration from a machine crash can cause buckling of the ballscrew shaft and damage to the ballnut itself including splitting some of the re-circulating balls within the ballnut meaning even if the machine runs afterwards the ballscrew will very quickly fail after a short period of running.



Typical Ballscrew Failure Points

A - Metal Fatigue & Wear to Bearing Surfaces
B - Surface Brinelling
C - Wear & Damage to Balltrack
D - Loss of Squareness to PCD
E - Ball Wear/Breakage
F - Loss of Pre-Load
G - Shaft Bent
H - Damaged Threads
I - Uneven wear over Balltrack
J - Poor System Concentricity
K - Wiper Seals Worn Leaking Lubricant
L - Excessive Backlash
M - Return Mechanism Worn/Broken

The good news is that for routine wear, a ballscrew life can be extended for a further period of service by a very straightforward procedure of repair of the ballscrew by a company such as Jena Tec. Firstly, the ballscrew is checked for its initial condition, this includes checking its free running condition and the "as received" pre-load or drag torque. The ballscrew then undergoes a 32 point healthcheck to check the major points contributing to the ballscrew performance. You can see some of the major areas of inspection referred to above.

After extensive cleaning and checking, the ballscrew, if repairable, is polished along the length of the ballscrew track and undergoes ultrasonic cleaning of the ballnut coupled with high pressure washing to remove baked on grease and grime. The ballscrew assembly is then re-built with oversized micron graded precision ball bearings to achieve a satisfactory level of pre-load along the length of the ballscrew according to DIN specifications.

The unit is then put on extended test and Jena Tec facilities include the ability to document and test the ballscrew running performance on motorised testing rigs. Where a ballscrew passes, a complete documented test report is provided for the customer detailing the received condition and the pass criteria with drag torque graphs and certificates of conformance. Based on Jena Tec's expert assessment, the unit is warrantied with recommendations for the customer on the extended life period.

While many claim to offer ballscrew track re-grinding, Jena Tec advise that due to a weakening of the induction hardened surface and also the cost to re-grind, that in most cases it does not make economic sense to re-grind the ballscrew track form. It is however feasible to re-furbish bearing end journals by hard chrome plating or metal spraying and then re-grinding with a precision universal grinder to exacting bearing fit tolerances. Fixing thread forms are always checked, cleaned and re-furbished where possible as well as wiper seals, fixing key ways and a variety of related small details.

What happens when the ballscrew is not in a repairable condition? Not all is lost, as most ballscrews can be repaired to give a shorter extended life, but in this instance Jena Tec would not offer a warranty but strongly recommend the customer buys a new replacement unit. Jena Tec's extensive stock of precision ground, rolled and whirled product means that we can offer a matched replacement sometimes within the same working day to provide an OEM quality replacement ballscrew.

This means that Jena Tec has the ability to support not only your repair requirements but also your spare parts backed up by our highly trained linear motion technicians, high stock levels and capable precision machine shop.

Typical makes and types of ballscrew repaired by Jena Tec include;

THK NSK Steinmeyer Mannesmann
Hiwin PMI ABBA Comtop
20th Century TCM Blis Berger Bosch
SKF PSI Saginaw Nook
Rockford Nachi Thompson IBL Star
Shuton Iperanga Korta LSI
Barnes American Ballscrew Warner Electric


For service and support on design, selection, repair and replacement of ballscrews and linear motion from Jena Tec go to www.jena-tec.co.uk or call our UK office on +44 (0)1623 726010