Tol-O-Matic System Compatibility - Industrial and Bearing Supplies

4. If screw-style is selected:
A. Select body style.
First evaluate the application’s load and support requirements
(consult performance and moment load charts for each body
style — see performance data on pages 74, 76 and 78. Next,
determine whether a standard or metric model is appropriate
then choose one of the following:
Cylinder— BCS: Cost and size effective for most moment load
and linear accuracy requirements. B3S: Heavier load capacity
with higher accuracy.
Slide — Load-supporting housing and bearings provide lower
friction, high load and moment-load capacity, improved torsional
stability, and greater linear-path accuracy over the life of the
actuator.
B. Select Screw Form and Nut Configuration.
1. Select Screw Form. Evaluate the application for accuracy,
backlash, smoothness requirements, and life, then select the
appropriate screw form:
Standard Rolled ACME Screw - Used with engineered solid
plastic nuts, this non-hardened screw has a pitch accuracy
rating of .005 in/ft. This combination is a cost-effective solution
for most requirements. An ACME thread with a solid
nut may reduce back driving in vertical applications.
Precision Rolled Ball Screw - Used with ball nuts, this hardened
screw has a pitch accuracy rating of .003 in/ft. This
combination provides higher thrust capacity and longer life
in continuous-duty applications.
2. Select Nut Configuration. Once the screw form is selected,
refer to Figure 1 then select the appropriate nut style
depending on backlash concerns.
SOLID
BALL
NUT Single Anti- Single Low-
Backlash
Backlash
Backlash (in) .007 .003 .015 .002
Backlash (mm) .018 — 0.25 0.05
Designation SN SNA BN BNL
Figure 1
B. Select Screw Pitch/Lead and Body Size.
Evaluate the application’s thrust, speed and stroke requirements
in relation to the screw capability curves. Refer to the
Performance Data charts of “Speed and Thrust vs Stroke” for
the screws available in each model size. The screw speed
charts (figure 2) and the chart of available models on pages 70
and 72 will help find a starting point for this evaluation.
SCREW SPEED (rpm)
If the screw size first selected is not adequate, move to the
next appropriate body and screw size and reevaluate. Repeat
this process until the correct screw pitch and body size are
identified.
Pitch/Lead - Lower pitch (higher lead) provides higher linear
speed, yet requires more drive torque.
AND
Body Size - Larger bodies provide more load support capability
and accommodate larger diameter screws. Larger screw diameters
permit higher rotational speeds, more thrust capability,
and allow the use of longer screw lengths.
SCREW SPEED • STANDARD MODELS
SCREW SPEED (rpm)
Conversion: Screw Revolutions/Minute to Carrier
Inches/Second for Various Screw Pitches (turns/inch)
3000
2500
2000
1500
1000
500
Conversion: Screw Revolutions/Minute to Carrier
Inches/Second for Various Screw Pitches (turns/millimeters)
3000
2500
2000
1500
1000
500
8 TPI
2.5 mm
5 TPI
5 mm
2 TPI
12 mm
1 TPI
0
0 5 10 15 20 25 30
CARRIER SPEED (in/sec)
SCREW SPEED • METRIC MODELS
25 mm
0
0 200 400 600 750
CARRIER SPEED (in/sec)
Figure 2
ACTUATOR SELECTION
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