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Velmex Products in Vacuum Environments

Velmex dovetail stages have been used in a myriad of environments from outer space to vacuum chambers. Modification of the assembly depends on the hardness of the vacuum and other specific requirements. Material substitutions can be made for specific applications. Two areas of concern are heat and contamination.

Heat concerns
Heat from friction between the lead screw and nut cannot dissipate into the surrounding area. This is of particular concern for motor-driven stages, if the lead screw RPMs are high and the unit is in continuous operation. Substituting a brass or Vespel drive nut may be necessary. In addition, motor induced heat can also be a problem.

Contamination concerns
Contamination is another issue. Sources of contamination include Delrin drive nuts and thrust bearings (UniSlide Series A15 and some A25 only). For light or medium duty, all stages can be run without lead screw and dovetail way lubrication which precludes contamination. A small amount of vacuum compatible lubricant (Fomblin® Y VAC3) is applied to the thrust bearings.

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. The table below lists outgassing characteristics of Rulon PTFE and Delrin.

Rulon bearing pads are attached with a thin layer adhesive which is oven cured for 90 minutes at 325 degrees Fahrenheit. The amount of material used is small and the bake out helps to minimize outgassing.

OUTGASSING DATA*

Material % TML % CVCM % WVR

Rulon 123® (bearing pads)

0 0 0.01

UniSlide and XSlide Delrin® AF drive nuts

0.33 0.02 0.07

Delrin® thrust bearings in all UniSlide Series A15 and some Series A25 Versions

0.28 0.02 0.13

EC 2290 epoxy

0.12 0.15 -

UHMW

0.06 0.01 0

Vespel® drive nuts

1.09 0 0.38

*Data from NASA Reference Publication 1124, rev. 3, 1993, Outgassing Data for Selecting Spacecraft Material.


Data sheets and/or information links for each of the materials can be found on our Compliance page.

Environmental Preparation

Basic low-level vacuum prep would entail degreasing, addition of blind holes and using a vacuum-compatiable grease. Higher-level vacuum preparation could involve the basic prep, plus possible material substitutions and other modifications to the stage.

Velmex positioning devices can also be modified for specific applications such as food processing or medical applications, as well as address non-magnetic requirements.

Please talk to a Velmex Application Engineer, if you have a vacuum or other special environment application. To create vacuum-capable or special application Velmex UniSlide®, BiSlide® or XSlide™ Assemblies, we need to know the vacuum TORR rating, your outgassing tolerance and the environment that the slide will be subjected to.

  • Velmex Assembly Material Substitutions
  • UniSlide® Assemblies
  • BiSlide® Assemblies
  • XSlide™ Assemblies

Material substitutions/modifications
The table for each Velmex brand outlines the material substitutions and modifications that can be made to the various assemblies.

UniSlide® Assembly Material Substitutions and Modifications
Component UniSlide Series Standard Material Substitute Material Modification, if any

Drive nut

All UniSlide Series

Delrin®

Brass, Vespel®

Substitute

Bearing pads

A40, A60 and B90 Series

Rulon PTFE bonded with adhesive

UHMW or Vespel®

Secured with screws, not adhesive.

Bearing pads

All UniSlide Series

Rulon 123 bonded with adhesive

Rulon bonded with epoxy (A15-A25 Series) or screw on pads (A40 - B90 Series)

Use 3M 2290 Epoxy. GSFC3495

Lubrication on lead screw and ways

All UniSlide Series

Lithium grease

Vacuum compatible lubricant

Omit all grease. Substitute your lube.

Blind Holes

All UniSlide Series

Standard fasteners

 

Add bleeder holes. Use vented screws.

Knob

A15, MA15, A25 Series

Plastic/rubber

Aluminum knob

Vent aluminum knob

Knob

All other UniSlide Series

Aluminum

 

Vent aluminum knob

Engraved Knob

Graduated knob models

Wax filler in engraved lines and numbers

 

Omit

Scales

Graduated knob and Scale and Vernier models

Normally attached with adhesive

Fasten with screws

Omit adhesive

Limit switches

All UniSlide Series

PVC insulated wire, plastic cable clamps, glue, plastic switch

Check with Application Engineer on potential substitutions

Omit

Thrust bearings

A15, MA15 Series and some A25 versions

Delrin®

None

Use A25 Series with SS Ball bearing

Thrust bearings

All except A15, MA15 Series and some A25 versions

Pre-greased radial, steel ball bearing

 

Degrease radial ball bearings

Surface finish

All UniSlide Series

None (Standard aluminum finish)

Electroless Nickel or Black Anodized

None

Motor

All Motor-driven UniSlide Series

Standard motors offered

Vacuum compatible motors. (Purchase by customer)

None

 

BiSlide® Assembly Material Substitutions and Modifications
Component Standard Material Substitute Material Modification, if any

Drive nut

PET Polymer

None

Bearing pads

Rulon 123 bonded with adhesive

Rulon bonded with epoxy

Use 3M 2290 Epoxy. GSFC3495

Lubrication on lead screw and ways

Silicone oil

 

Omit all oils

Blind Holes

Standard fasteners

 

Add bleeder holes. Use vented screws.

Limit switches

PVC insulated wire, plastic cable clamps, glue, plastic switch

Check with Application Engineer on potential substitutions

Omit

Thrust bearings

Pre-greased needle bearings

Vacuum grease

Degrease & grease with vacuum compatible lubricant

Surface finish

Black Anodized

Electroless Nickel

Replace with raw aluminum

Motor

Standard motors offered

Vacuum compatible motors. (Purchase by customer)

None

 

XSlide® Assembly Material Substitutions and Modifications
Component Standard Material Substitute Material Modification, if any

Drive nut

Delrin®

Brass, Vespel®

Substitute

Bearing pads

Rulon 123 bonded with adhesive

Rulon bonded with epoxy

Use 3M 2290 Epoxy. GSFC3495

Lubrication on lead screw and ways

Silicone oil

 

Omit all oils

Blind Holes

Standard fasteners

 

Add bleeder holes. Use vented screws.

Knob

Aluminum

 

Vent aluminum knob

Limit switches

PVC insulated wire, plastic cable clamps, glue, plastic switch

Check with Application Engineer on potential substitutions

Omit

Thrust bearings

Pre-greased needle bearings

Vacuum grease

Degrease & grease with vacuum compatible lubricant

Surface finish

Black Anodized

Electroless Nickel

Replace with raw aluminum

Motor

Standard motors offered

Vacuum compatible motors. (Purchase by customer)

None