| | | Enhanced Straightness Tolerances If your application requires improved straightness tolerances, we can supply Models with straightness tolerances approximately one-half of the nominal values given previously. We individually select, measure and certify UniSlide Assemblies. Wear Resistance The standard aluminum alloy dovetail base and low friction polymer pads of the slider provide excellent performance as a bearing manufacturer material combination. Unlike ball screw industrial slide mechanisms, no lubrication is required. Under light to moderate loads, sideways play caused by wear during the first 30,000 cycles of operation will be approximately 0.00015 inches. Wear after that is reduced, to approximately 0.00005 inches over the next 50,000 cycles. Sliders are equipped with adjustment screws to compensate for wear, if necessary. For harsh environments and/or a higher number of cycles, UniSlide Assemblies with hard coat anodized ways are available. For clean room environments we recommend electroless nickel plating. Magnetic Properties We can make linear positioners with very low or no ferric (iron) content. UniSlide base and slider assemblies are made from aluminum alloy. Most lead screws are 303 stainless steel. The exceptions are the double and quad lead screws which are electroless nickel-plated cold rolled steel. We can also substitute brass lead screws for some models. Brass lead screws are only offered in standard | | |
| | | grade accuracy. In a few models with small steel parts, no nonmagnetic replacements are available. For further information please contact the factory. Base and Slider Lengths Standard and maximum base lengths for all models are listed in the specifications for each model. Custom base lengths are available on special order. Slider lengths available are only those listed in the model specifications. Vacuum Applications UniSlide Assembly's patented dovetail bearings give it certain advantages over other designs. They have been used in a myriad number of environments from outer space to vacuum chambers. The necessity for modification depends upon the so-called hardness of the vacuum and other specific requirements. Velmex can supply assemblies that are free of grease and oils. However, for critical applications the assemblies should be cycled in an outgassing chamber to remove residual contamination. Search web site for "vacuum" for more details. Back driving the Lead Screw Models with 5 or 2.5 pitch lead screws (codes W2, W4, P5 or P2.5) can be back driven by the payload. See Lead Screws for additional details. Scale and Control Lever Position The control lever for Rapid Advance units is on the right hand side. Printed and engraved industrial scales are on the left side as shown in the drawings and photos in this catalog. Scale numbering | | always progresses toward the knob end of the unit — i.e., the largest numbers on the scale are closest to the knob. Control levers, top plates, thumbscrew locks and verniers can be mounted on the alternate side on special request. If requested, the scale can be mounted on the right side of the unit, with the largest numbers going away from the operator. For models with the base mounting holes located off the center line, holes begin at the bearing block end with the first hole to the right of the lead screw. See Dimensional Drawing for series of choice for details. Material Substitutions Material substitutions for drive nuts, lead screws and thrust bearing are possible. Drive nuts are available in brass, oil-impregnated bronze, and, for high temperature or radiation applications, in Vespel. Thrust bushings can be manufactured from Vespel. Alternatively, thrust bearings made with polymer raceways and cages, and stainless steel or ceramic balls are also available. Brass lead screws are available in a limited pitch selection. | | |