|Abssac Newsletter : October 2014|
do not require the finite accuracy of the ground ball screw equivalents, but are still required to reliably transmit an axial load with a high degree of accuracy. Using the traditional recirculation of the balls within the nut housing, a typical ball screw may be 90 percent efficient, versus 50 percent efficiency of a lead screw of equal size.
Precision rolled ball screws achieve accuracies of C7-20 (that’s 50 microns per 300mm of cumulative lead accuracy - 20 microns of axial backlash).
Ball screws that have been formed by a grinding process are used where acute linear accuracy is paramount within the application. We offer a quality program of diameter and lead combinations with a variety of ball nut styles.
Precision ground ball screws achieve accuracies of C0-0 (that’s 0 microns per 300mm of cumulative lead accuracy - 0 microns of axial backlash).
So if you are a user of ball screws give us a call to see how we can make your requirements heard.
It is not often you come across a product that is breaking the boundaries of design and performance on what is probably one of the oldest energy storing devices known to man. However, the machined spring, justifiably holds that claim.
How the machined springs are actually manufactured is a very closely guarded secret but as the name suggests, whether the spring is destined for compression, extension or torsion use, it is literally machined from a solid piece of material.
Why machine a spring?
The machined spring provides enhanced performance simply not available from wound spring designs. The most common configuration is the single start spring, which consists of a single continuous coil element, starting at one end and terminating at the other end, much like its wire wound counterpart. However, uniquely we can offer a double start or indeed a triple start spring which has two or three intertwined continuous coil elements, still within the same single part construction. In effect, this puts multiple independent helixes in the same cylindrical plane.
Multi-start springs have many advantages. When applied to compression and extension springs, a single start spring provides a reaction force plus a moment. On multiple start flexures, all internal moments are resolved within the spring itself, which translates into excellent compression or extension parallelism. Multiple start spring configurations also significantly unify the
lateral bending and lateral translation forces and moments around the springs circumference given a lateral deflection. Double and triple start variants make the loading points irrelevant on the radius of the spring but increase the accuracy of parallelism. Multiple starts as high as five have been employed to unify the lateral reaction forces of machined springs.
Machined springs can provide very precise, linear deflection rates because virtually allresidual stresses are eliminated. As a result, there are no internal stresses to overcome before deflection occurs, which again can be the case in the wire wound spring. (Normal rate accuracy is +/-10% but we have obtained +/- 0.1% for the more demanding applications)
Applications to date have beennumerous and in all types of industry.
Abssac has recently aided the design and reliability of a compression spring control mechanism that originally involved the amalgamation of four separate parts. Those being a wound compression spring, a machined spring seat, which incorporated a captivated ball bearing and finally a machined top hat attachment complete with a M5 locating thread. An additional issue with the original design was that the customer had to batch test the wound springs before assembly for dimensional accuracy and performance. All of these parts were sourced from separate suppliers and then assembled at the customer’s factory.
Satellite roller screws
If you are involved with linear applications you might be interested in the Satellite roller screw program.
Different to a ball screw, roller screws employ matched rollers to rotate (or satellite as the product name suggests) around the screw during actuation, instead of ball bearings. By the nature of the design there is an immediate increase in the physical amount of contact points on the screw that can support the load compared with that of the same diameter ball screw.
The result is that static load can be 3 times greater than that of ball screws and their
lifespan is 15 times longer. The many points of contact also give a satellite roller screw greater rigidity and shock tolerance than a ball screw without a compromise to friction or efficiency. Lastly, satellite roller screws can rotate significantly faster and support much greater accelerations than ball screws as there is no recycling of the ball bearings. In fact, a roller screw mechanism can handle twice the rotation speed of a ball screw.
It is also possible to supply planetary roller screws with smaller leads compared to ball screws. As the lead is a function of the pitch of the planetary roller screw, the lead can be very
small (0.5mm and even less). The lead can be chosen and supplied without any geometrical changes of both the screw shaft and the nut body. In a ball screw the lead is limited by the dimension (Outside Diameter) of the bearing ball, which is a standard feature.
The ABSSAC satellite screw product has two standard designs directly aimed at replacing less effective ball screw designs. There is also a full design capability of the standard satellite screw program which continues to “upgrade” linear designs around the world.
For further details on satellite roller screw please call Chris Cattle
Be clever and amalgamate your end attachments
The hidden potential of expanding how a shaft coupling physically connects within an application, which is often left to standard grub screw or locking clamp, can enhance the overall efficiency of an application. With Abssac’s Heli-Cal beam coupling product, customers have been able to take their standard coupling designs to the next level, by incorporating features into the original shaft coupling design. In many cases, the final shaft coupling design is normally an amalgamation of separate parts that include such items as external gears, splines, threads and tangs. However, most importantly, it enables the design engineer to achieve far greater usage from one item in the total machine which inevitably leads to greater efficiency. How the standard shaft coupling connectability is enhanced, is really up to the designer. Abssac is so confident with the products success rate that in many cases it offers a free sample for the customer to test and evaluate. Ms Stacey Taylor at Abssac says, “When you consider the Heli-Cal beam couplings capability as a shaft coupling and then add this ability to integrate the design engineers own end attachment ideas, you have a formidable product combination that other coupling manufacturers can not supply.”
The perfect shaft coupling for highly dynamic applications
We Give a Schmidt !
The extreme shaft offset capability combined with a small D.B.S.E. (distance between shaft ends) makes the Schmidt-Kupplung quite unique. Interestingly, its modular construction allows both torque transmission and radial offset capacity to be optimized for each application. It is possible to accommodate a parallel shaft offset of 275mm in an overall shaft coupling length of 284mm! (Offset Plus V3300 series). No other shaft coupling design can provide the parallel shaft offset to overall length ratio.
Call Peter on 01386 421005 for further details.
Power Screws & Nuts -
Abssac not only supplies high precision lead screws but also a range of medium to heavy duty industrial leadscrews. Continuously stocking up to 3 meter lengths of lead screw diameters of 12mm, 16mm, 20mm, 22mm, 24mm, 30mm, 36mm, 40mm and 50mm in both right and left handed formats. The POWER SCREWS are available in both Steel and Stainless Steel and can be supplied with a large selection of round bodied flanged or non-flanged Bronze matched thread nuts from stock.
Abssac can also supply the screws machined to print for easy connection to a range of in stock thrust and pillow block bearings as well as linear slides. Additionally, we supply weldable square, hex and round steel nuts and Abssac is also offering a free cut to length service on all the screws.
Call Phil on 01386 421005 for further details.
3mm diameter miniature lead screw & nut
Leadscrews under 5mm in diameter can be a challenge to the cold rolled screw forming process, but with nearly 30 years of experience, Abssac successfully met the challenge when asked to supply a new medical application. In fact Abssac was able to go further than the customer required by offering a 3mm diameter stainless steel trapezoidal thread form with a 1mm lead holdnig a run lead tolerance of .0.5mm per 300m. This saved both cost and space. In an effort to reduce operational drag and improve efficiency further, the lead screw was then coated with Teflon to make a very low friction linear assembly. The final part measured 30mm in length and is supplied complete with a machined journal for motor formed the basis of the design within an automated micro syringe device. Abssac was able to supply the parts on below budget and has also exceeded reliability and performance demands set by the customer.
We talk the torque
Stand Number D10
Come and meet us
Abssac’s innovative products have been incorporated into a plethora of engineering projects for well over 30 years. Our rotary, linear and specialist products go the distance for a wide range of customers engaged in areas as diverse as mechanical engineering, research and development, aerospace and defence, medical equipment, nuclear physics, printing and engraving, scientific instrument design and surface analysis, to name a few. Why not come and discuss where our unique products can help in your applications.