Atlas_Copco_Pocket Guide_TurboTight_UK__.pdf - Atlas Copco
Atlas_Copco_Pocket Guide_TurboTight_UK__.pdf - Atlas Copco
Atlas_Copco_Pocket Guide_TurboTight_UK__.pdf - Atlas Copco
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<strong>Pocket</strong> <strong>Guide</strong> to <strong>TurboTight</strong> ®
Contents<br />
Page<br />
1 Introduction ..................................................................... 4<br />
1.1 <strong>TurboTight</strong> ® simplified ............................................... 4<br />
1.2 Background ................................................................. 4<br />
1.3 Why is it now possible to use <strong>TurboTight</strong> ® ? .............. 5<br />
1.4 Theory ......................................................................... 6<br />
1.5 In practice .................................................................... 6<br />
2 Key benefits of <strong>TurboTight</strong> ® ........................................... 7<br />
2.1 How are cycle times reduced? .................................... 8<br />
2.2 How is reaction force reduced? ................................ 10<br />
2.3 How come set-up is so easy? .................................... 10<br />
2.4 How does <strong>TurboTight</strong>® provide energy savings? ... 10<br />
3 Ergonomics ...................................................................... 12<br />
3.1 Letting the tool absorb the reaction force ................. 12<br />
3.2 Less heat development .............................................. 13<br />
4 Accuracy .......................................................................... 15<br />
5 Clamp force ..................................................................... 16<br />
6 Relaxation ........................................................................ 18<br />
7 Residual torque ............................................................... 18<br />
8 Torque scatter ................................................................. 19<br />
9 Where to use <strong>TurboTight</strong> ® ............................................ 19<br />
10 Recommendations relating to <strong>TurboTight</strong> ® ................ 20<br />
10.1 <strong>TurboTight</strong> ® and tool extensions ............................. 21<br />
10.2 The limitations of <strong>TurboTight</strong> ® ............................... 21<br />
10.3 How to set up <strong>TurboTight</strong> ® ..................................... 23<br />
10.4 <strong>TurboTight</strong> ® and the customer ................................ 26<br />
10.5 FAQs – Frequently Asked Questions ...................... 27<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
3
The inertia of the car traveling uphill<br />
is used to offset the torque from<br />
the engine and help stop the car at<br />
the top. Similarly, <strong>TurboTight</strong> ® uses<br />
the tool’s inertia to counteract and<br />
minimize the force transmitted to the<br />
operator’s hand and arm. Thus, the<br />
end of the tightening feels soft.<br />
4 POCKET GUIDE TO TURBOTIGHT ®<br />
1. Introduction<br />
1.1 <strong>TurboTight</strong> ® simplified<br />
<strong>TurboTight</strong> ® is a new and revolutionary tightening strategy<br />
that dynamically reads joint stiffness during a tightening cycle.<br />
It calculates the energy needed to reach the target torque and<br />
regulates the tightening speed to provide the tightening energy<br />
required to ensure reliable accuracy. Reaching the target torque<br />
causes the regulator to stop the motor and the tightening is<br />
complete.<br />
In simple terms, <strong>TurboTight</strong> ® can be compared to a car traveling<br />
up a hill to a parking lot. The driver regulates the speed<br />
with the gas pedal and uses the brakes to stop the car immediately<br />
on reaching the target parking lot.<br />
Thus, a tightening can be controlled at a higher speed than<br />
ever before. One of the main reasons for this is an improved<br />
sampling rate between the controller and the tool.<br />
1.2 Background<br />
<strong>TurboTight</strong> ® has been patented as a new and innovative power<br />
tool control tightening strategy. It was developed to improve<br />
operator ergonomics and thus increase operator comfort.<br />
<strong>TurboTight</strong> ® is fast and, because it uses the inertia of the tool,<br />
the reaction force to the operator is minimal, delivering the<br />
best ergonomic behavior during tightening. The ergonomic
Fast Ergonomic Low impact Accuracy<br />
goal is to let the tool absorb the reaction force. The aim was for<br />
the operator to experience a similar reaction force as with air<br />
tools, i.e., a clutch tool feeling on hard joints.<br />
In parallel with the improved ergonomics, tightening accuracy<br />
was maintained at the respective system levels. Tensor STR<br />
using <strong>TurboTight</strong> ® will deliver ±5% and Tensor ES will deliver<br />
±7.5% accuracy (over 6σ).<br />
<strong>TurboTight</strong> ® is extremely easy to set up. In fact, it can be described<br />
as a “set and go” tightening strategy.<br />
1.3 Why is it now possible to use <strong>TurboTight</strong> ® ?<br />
The Power Focus 6 Series uses an advanced technology compared<br />
to the Power Focus 4000. It has higher sampling, communication<br />
and calculation rates in both the Power Focus and<br />
the tool. The increased processing speed between the Power<br />
Focus and the tool, the optimized algorithm and the tightening<br />
knowledge <strong>Atlas</strong> <strong>Copco</strong> has gained during the past 10 years<br />
has helped us to develop this revolutionary tightening strategy.<br />
<strong>TurboTight</strong> ® is a high-tech tightening<br />
strategy that makes the tool<br />
operator’s job more comfortable,<br />
reduces cycle times and speeds<br />
up production. It took <strong>Atlas</strong> <strong>Copco</strong><br />
specialists 10 years to develop<br />
based on extensive know-how and<br />
experience.<br />
With <strong>TurboTight</strong> ® the torque reaction<br />
is so small that the operator can<br />
hold the tool in one hand without<br />
experiencing a jerk at the end of the<br />
tightening. This is particularly true in<br />
the case of hard joints.<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
5
Example: Signal sampling rate, Power<br />
Focus 4000 vs. Power Focus 600/6000<br />
Series.<br />
Sampling frequency on Power Focus<br />
600/6000 controllers is considerably<br />
higher than on the Power Focus 4000.<br />
This enables <strong>TurboTight</strong> ® to calculate<br />
when the correct final torque is<br />
reached and stop the tool in the shortest<br />
possible time and with the lowest<br />
possible reaction force.<br />
6 POCKET GUIDE TO TURBOTIGHT ®<br />
Power Focus 600/6000<br />
Power Focus 4000<br />
1.4 Theory<br />
The innovative idea behind <strong>TurboTight</strong> ® is to control the<br />
speed of the motor so that the rotational energy E r of the motor<br />
is equal to the energy E t which is required to complete the<br />
tighten ing to the target torque. To calculate the energy required<br />
to fasten an ideal linear joint, <strong>TurboTight</strong> ® needs to know the<br />
final torque and the tightening angle, or the target torque and<br />
the torque rate. The rotational energy can be calculated from<br />
the rotor inertia and rotor speed.<br />
1.5 In practice<br />
<strong>TurboTight</strong> ® is activated after the joint has been brought to<br />
snug tightness, but not tightened to the target torque. The snug<br />
level is detected by a torque threshold (rundown complete),<br />
which is manually adjustable. After the snug level is reached<br />
the torque rate k starts being calculated.<br />
The torque signal from a real tightening analysis contains<br />
mechanical and electrical noises and many other kinds of<br />
disturbances. Also, in handheld applications, operators<br />
constantly move tools during a tightening sequence.<br />
Since all the disturbances tend to distort the torque measurement,<br />
the torque rate k is automatically filtered during the calculation<br />
phase. Using the filtered k value the speed is always<br />
calculated and adapted to the condition of the joint.
2 Key benefits of<br />
<strong>TurboTight</strong> ®<br />
Reduced cycle times<br />
<strong>TurboTight</strong> ® optimizes the tightening speed to achieve the<br />
fastest possible tightening that still ensures reliable accuracy.<br />
The results are:<br />
• Possibility to remove bottlenecks,<br />
• Possibility to rebalance assembly lines due to increased<br />
cycle rate,<br />
• Less heat development, a cooler tool during operation.<br />
Reduced reaction force<br />
With optimized tightening speed, the torque builds up faster,<br />
reducing the amount of force transmitted to the operator’s<br />
hand.<br />
The results are:<br />
• Reduced operator fatigue and thus reduced<br />
risk of injury,<br />
• Improved operator comfort during tightening,<br />
• Reduced need for reaction absorbing devices in<br />
certain situations, thus less cost and reduced<br />
tool weight.<br />
Torque<br />
Rundown<br />
complete<br />
Torque<br />
Final torque<br />
40 Nm<br />
Snug tightness<br />
5 Nm<br />
∆ Angle<br />
Target<br />
torque<br />
Torque rate =<br />
∆ Torque<br />
∆ Torque<br />
∆ Angle<br />
Angle<br />
Angle<br />
<strong>TurboTight</strong> ® is activated<br />
after the joint has been<br />
brought to snug tightness.<br />
After the snug level is<br />
reached the torque rate<br />
starts being calculated.<br />
Ergonomics are improved since less<br />
muscle force is required from the<br />
operator’s arm to counteract the<br />
torque reaction.<br />
With <strong>TurboTight</strong> ® , tightening times are<br />
cut by 0.6 seconds per bolt. After only<br />
100,000 tightenings, the time savings<br />
will be 60,000 seconds, equivalent to<br />
an amazing 16 hours! This enables the<br />
production line to be rebalanced for<br />
optimum flow.<br />
Tightening<br />
angle<br />
Avoid<br />
bottlenecks<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
7
8 POCKET GUIDE TO TURBOTIGHT ®<br />
Easy set-up<br />
<strong>TurboTight</strong> ® is designed to be extremely easy to set up.<br />
In most cases, you just need to set the target torque and you’re<br />
ready to go. Exceptions are discussed in the following chapters.<br />
In such cases please contact your local <strong>Atlas</strong> <strong>Copco</strong> Tools<br />
representative for support.<br />
The results are:<br />
• Time savings during set-up,<br />
• Less time and money spent on training,<br />
• Work rotation enabled.<br />
Sustainability<br />
Using <strong>TurboTight</strong> ® results in shorter tightening cycles. This<br />
in turn means less heat development and thus a cooler tool.<br />
It also helps to reduce energy consumption and prolong tool<br />
lifetime in high-cycle environments.<br />
2.1 How are cycle times reduced?<br />
<strong>TurboTight</strong> ® controls the motor speed to achieve the fastest<br />
possible tightening without excessive overshoot. Comparing it<br />
to a traditional Two Step strategy, <strong>TurboTight</strong> ® runs faster for<br />
a longer period.
<strong>TurboTight</strong> ®<br />
Two Step<br />
Speed (rpm) Torque (Nm)<br />
Speed (rpm) Torque (Nm)<br />
t<br />
t 2 . t<br />
In the examples above you can see that <strong>TurboTight</strong> ® reaches<br />
the target torque after the time [ t ]. The Two Step tightening<br />
strategy takes more than twice the time [2 · t ] to reach the<br />
target torque.<br />
As the graph at the top<br />
shows, with <strong>TurboTight</strong> ®<br />
the tool runs fast throughout<br />
the tightening cycle,<br />
yet reaches the target<br />
torque at low speed.<br />
Thus, the reaction force is<br />
minimized.<br />
Final torque<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
9
The perfect <strong>TurboTight</strong> ® partnership<br />
– the controller is the brain while the<br />
tool supplies the inertia.<br />
10 POCKET GUIDE TO TURBOTIGHT ®<br />
2.2 How is reaction force reduced?<br />
<strong>TurboTight</strong> ® uses the tool’s mass moment of inertia to reduce<br />
the reaction force transmitted to the operator. The increased<br />
control of the motor in combination with the fast dynamic<br />
regulation enables the tool to minimize the reaction force from<br />
the tightening.<br />
2.3 How come set-up is so easy?<br />
<strong>TurboTight</strong> ® is a strategy that controls the motor speed based<br />
on the actual torque rate and the remaining torque of the joint.<br />
Since all these parameters are dynamically calculated during<br />
the tightening, the only user input required is the target torque.<br />
2.4 How does <strong>TurboTight</strong> ® provide energy savings?<br />
Since 2010 <strong>Atlas</strong> <strong>Copco</strong> has been ISO 14001 certified, ensuring<br />
the planning, execution, control and optimization of continuous<br />
improvement processes for all <strong>Atlas</strong> <strong>Copco</strong> Industrial<br />
Technique products.<br />
If we compare the energy consumption of a Power Focus<br />
4000 running a Tensor ST tool with a Two Step set-up, with<br />
the energy consumption of a Power Focus 600/6000 running<br />
a Tensor ES/STR tool with <strong>TurboTight</strong> ® , we get the following<br />
result.
Thanks to <strong>TurboTight</strong> ® energy consumption will decrease<br />
by 10% due to faster tightening cycles. In general the losses<br />
during a tightening can be reduced by speeding up the tightening<br />
phase. But remember the big savings come from standby.<br />
This pie chart illustrates a “normal” user case<br />
with a specific tool size and a specific number<br />
of tightenings/minute. It does not apply in<br />
all cases.<br />
32%<br />
Standby<br />
Tightening<br />
Rundown<br />
8%<br />
60%<br />
Energy Consumption = Standby +<br />
Rundown + Tightening where:<br />
• Standby represents 60%<br />
• Rundown represents 32%<br />
• Tightening represents 8%<br />
Tools using <strong>TurboTight</strong> ® make light<br />
work of tightening.<br />
<strong>TurboTight</strong> ®<br />
10% energy<br />
savings.<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
11
With <strong>TurboTight</strong> ® there is less heat<br />
development and the tool is cooler<br />
and more comfortable to handle.<br />
Pull a sheet of paper out from under<br />
a glass of water with a sharp jerk and<br />
the glass stays on the table. Pull it out<br />
slowly and it takes the glass with it.<br />
This can be compared to <strong>TurboTight</strong> ® ,<br />
where the glass is the tool and the<br />
hand is the tighten ing cycle. When<br />
the final torque is reached there is no<br />
jerk transmitted to the operator since,<br />
due to the fast tightening speed, the<br />
weight of the tool absorbs the reaction<br />
force.<br />
12 POCKET GUIDE TO TURBOTIGHT ®<br />
3 Ergonomics<br />
3.1 Letting the tool absorb the reaction force<br />
The force from a handheld tool acting on the operator is called<br />
the reaction force. The reaction force can be counteracted either<br />
by the inertia of the tool or by the operator’s muscle force.<br />
One of the main goals of <strong>TurboTight</strong> ® was to reduce the reaction<br />
force force by letting the tool’s inertia absorb most of the<br />
reaction force. This is achieved by increasing the tightening<br />
speed.<br />
The tool inertia’s ability to counteract reaction force depends<br />
on:<br />
– Speed of rotating parts during tightening,<br />
– Inertia of the tool – tool weight,<br />
– Joint characteristics – a hard joint has a faster torque buildup<br />
and will be tightened in a shorter time.<br />
The operator’s ability to counteract the reaction force depends<br />
on:<br />
– His/her muscle strength, posture, age and gender,<br />
– Reaction time.<br />
There is a time span where the tightening is too slow for the<br />
inertia to absorb the reaction force or too fast for the operator to<br />
build up muscle force in a controlled way. A tightening in this<br />
region will feel jerky and uncomfortable.<br />
A tool using <strong>TurboTight</strong> ® should be held less firmly. This will<br />
improve the ergonomics even further by reducing the static<br />
load on the operator.
3.2 Less heat development<br />
Also contributing to good ergonomics, with <strong>TurboTight</strong> ® , since<br />
the tool works faster, it does not consume as much energy<br />
during a tightening cycle. As a result, there is less heat development<br />
and the tool is cooler and more comfortable to handle.<br />
When you work with <strong>TurboTight</strong> ® ,<br />
you can hold the tool in a relaxed<br />
grip and you don’t need to prepare<br />
yourself for a jerk caused by the<br />
torque reaction at the end of the<br />
tightening.<br />
With <strong>TurboTight</strong> ® the tool inertia<br />
takes the strain by absorbing the<br />
torque reaction.<br />
Depending on muscle strength,<br />
posture, age and gender, the torque<br />
reaction from a tool can put stress<br />
on the operator. <strong>TurboTight</strong> ® enables<br />
tightening to be performed comfortably<br />
even in less accessible places,<br />
such as overhead.<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
13
From snug to final torque, Turbo-<br />
Tight ® ensures a smooth and<br />
comfortable tightening cycle for the<br />
operator.<br />
Soft joint<br />
Hard joint<br />
360° 50°<br />
A soft joint reaches target torque at<br />
360° and a hard joint at 50°.<br />
Example of an ergonomic chart for a<br />
Tensor ETV STR tool. A soft joint has<br />
weaker ergonomics.<br />
14 POCKET GUIDE TO TURBOTIGHT ®<br />
Torque<br />
55<br />
50<br />
45<br />
40<br />
35<br />
30<br />
25<br />
20<br />
15<br />
Excellent<br />
ergonomics<br />
Please consult our tightening experts to find out if<br />
<strong>TurboTight</strong> ® is the optimal tightening strategy for<br />
your specific application.<br />
Acceptable<br />
ergonomics<br />
10<br />
0 50 100 150 200 250 300<br />
Joint angle<br />
Weak<br />
ergonomics
4 Accuracy<br />
When running <strong>TurboTight</strong> ® the accuracy may decrease compared<br />
to a moderately tuned Two Step tightening. However<br />
the tool is still within its accuracy limits. This means for<br />
Tensor ES ±7.5% over ±3σ, and for Tensor STR ±5.0% over<br />
±3σ, according to ISO 5393.<br />
When tightening joints with a stiffness of around 70°<br />
and below, the speed might need to be reduced due<br />
to overshooting or inaccuracy problems. This always<br />
varies with different tool types, surfaces and friction.<br />
Accuracy<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
15
Clamping<br />
force<br />
Different types of bolt. The large<br />
friction radius of a flange screw may<br />
cause a higher clamp load.<br />
When tightening fasteners with a<br />
large friction radius, such as flange<br />
screws, the coating melts. This causes<br />
“aquaplaning” under the head, resulting<br />
in a decrease in friction.<br />
Example of a customer-specific<br />
Application Analysis Report. For more<br />
information, please consult your <strong>Atlas</strong><br />
<strong>Copco</strong> representative.<br />
16 POCKET GUIDE TO TURBOTIGHT ®<br />
5 Clamp force<br />
Empirical studies with a selection of bolt types with various<br />
coatings, e.g., zinc flake or nickel, and without any temperature<br />
sensitive lubricants, indicates that by using <strong>TurboTight</strong> ®<br />
there will not be a difference in clamp force compared to<br />
traditional tightening strategies such as Two Step.<br />
Coatings and surface treatments such as wax, grease, paint,<br />
Teflon, etc., may reduce friction due to increased temperature<br />
caused by a higher tightening speed. Due to the high tightening<br />
speed of <strong>TurboTight</strong> ® , the heat build-up in contact surfaces<br />
will reduce the friction, enabling higher clamp force.<br />
If the geometry of the fastener is beneficial, i.e., if the friction<br />
radius is large, as in flange head screws, the coating melts<br />
and causes a kind of “aquaplaning” under the head, resulting<br />
in a decrease in friction. The underhead friction decrease<br />
will result in a greater tightening angle leading, in turn, to a<br />
higher clamp force.<br />
On the other hand, if the friction radius is smaller, as with<br />
inner hex screws, for example, there is a risk of penetrating<br />
the coating/surface treatment, which would result in metallic<br />
contact between the screw and the joint.<br />
This can cause local welding between the surfaces as a result<br />
of higher friction. Since more torque is consumed under the<br />
head due to the higher underhead friction, the clamp force<br />
will be reduced compared to the same tightening carried out<br />
at a lower speed.<br />
ADVANCED FASTENING TECHNOLOGY<br />
Test parts – bolts and screw joint<br />
Test equipment<br />
Seven different bolt types were tested. 30 pcs of each type were available.<br />
Technical Report<br />
Type Technical report<br />
Title <strong>TurboTight</strong> tests on VW bolts measuring Clamp load and Residual torque<br />
Prepared By A. Roloff<br />
Approved By<br />
Revision 4 Last Modified 2012-11-01<br />
Summary<br />
The intention with this investigation was to see if there is a significant difference in achieved Clamp<br />
load and Residual torque in a screw joint when tightened at different tightening speeds / tightening<br />
strategies. The question is if the coefficient of friction is affected of the tightening speed and if the<br />
answer is yes, how?<br />
Seven different bolts from VW were tested in a test fixture.<br />
Three different bolt coatings were available:<br />
b140: No information available<br />
t647: Zinc-flake with lubricant<br />
r677: No information available<br />
- PowerMACS Classic system with a QMX50-15RT was used to create reference tightenings<br />
results.<br />
- PowerFocus 6000 system was used with two different tools, one ETV-STR61-50 and one ETV-<br />
STR61-40.<br />
- The test joint is built up with a load cell that has an internal “nut” (a threaded part made of<br />
- MC900 Transient recorder with an IRTT torque hardened angle inline steel). transducer The screw and joints a RS-Technologies<br />
effective clamp length is built up with steel spacers and the flat<br />
load cell.<br />
metal bar (called the under head material) with drilled holes according to standard. See the<br />
picture below:<br />
1 2 3 4 5 6 7<br />
- As a reference, a fixtured QMX nutrunner controlled by a PowerMACS Classic system tightened 5<br />
bolts in two steps with the speed 200 and 20 rpm. The torque in the first step was set to 20% of the<br />
final torque.<br />
- Next, 5 bolts were tightened to the same final torque with an ETV-STR61-50 or ETV-STR61-40<br />
controlled by a PowerFocus 6000 using the <strong>TurboTight</strong> strategy (using the Quickprog function).<br />
- All tests were repeated on three different under head materials. Raw Aluminum anodized Aluminum<br />
and raw steel. The same threaded hole was used in all tests,<br />
- The relation between tightening torque, Clamp load and residual torque varies almost +/- 10% for<br />
these combinations of bolt types, bolt coating, under head material and tightening method/speed.<br />
See Table 4: The measured results are first recalculated to the same tightening torque level and then<br />
the quotes for Clamp load, Residual torque and Residual Torque/Load between the QMX and the<br />
STR are calculated.<br />
- No significant difference in Clamp load or Residual torque could be seen in the results that<br />
could be explained by a speed dependant friction coefficient.<br />
NOTE: The bad results in the two points below are probably explained by the use of a “High<br />
noise tool”. The ETV-STR61-50 that was used was of the old version that had some problems<br />
with electrical noise in the torque transducer signal. The intention with this investigation was<br />
not to evaluate the torque scatter from the STR machine and therefore it hasn’t a major<br />
influence on the Clamp load and the Residual torque comparisons.<br />
- A torque “overshoot” with up to 20% could be noted with the ETV-STR tests and the torque scatter<br />
was significantly higher compared with the QMX tests. The torque scatter is based on 5 values which<br />
makes the absolute results very uncertain.<br />
- Another observation was that the average torque and the torque scatter measured with the inline<br />
reference transducer were lower than reported from the PowerFocus 6000.<br />
<strong>TurboTight</strong> tests on VW bolts_4.doc Page 2 of 15<br />
<strong>TurboTight</strong> tests on VW bolts_4.doc Page 1 of 15<br />
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<strong>TurboTight</strong> tests on VW bolts_4.doc Page 4 of 15
The <strong>TurboTight</strong> ® strategy is not suitable for applications<br />
where Torque-Angle strategies should be chosen to deliver<br />
an accurate clamp load. Some customer requests might need<br />
a thorough joint analysis to assure the optimum tightening<br />
parameters.<br />
Please keep in mind the possible risk of high speed<br />
tightenings like <strong>TurboTight</strong> ® affecting the clamp load<br />
value to the bolt for a certain torque value (as given<br />
in recommendations from screw manufacturers and<br />
standardization committees). There may be a risk of<br />
tightening the screw beyond yield.<br />
If you need to investigate the clamp load status of a bolt,<br />
please contact <strong>Atlas</strong> <strong>Copco</strong> for more information.<br />
Fasteners such as inner hex screws<br />
have a smaller friction radius. Thus,<br />
there may be higher friction leading<br />
to higher temperature under the<br />
head, which could cause a decrease<br />
in clamp force.<br />
The impact of the size of the friction<br />
radius of different fasteners on the<br />
heat generated during tightening<br />
can be compared to different sized<br />
frying pans. There is a faster build-up<br />
of heat in a small frying pan. In the<br />
large pan the heat is dissipated over<br />
a larger area.<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
17
When the joint surface is magnified,<br />
ridges and hollows become visible.<br />
18 POCKET GUIDE TO TURBOTIGHT ®<br />
6 Relaxation<br />
When the surface of the joint is magnified, what appears to be<br />
a smooth surface actually consists of ridges (or asperities) and<br />
hollows. Partial plastic collapse (embedding or settlement) of<br />
the surface results in a preload loss or relaxation. This preload<br />
loss is time dependent but occurs over a very short time and<br />
can be measured in milliseconds.<br />
If the tightening occurs over a short period of time, the preload<br />
loss will be greater compared with if the tightening occurs<br />
over a longer period of time. For <strong>TurboTight</strong> ® some relaxation<br />
has been observed and the higher the speed the more relaxation<br />
can occur.<br />
However, the relaxation observed from experiments shows<br />
that, comparing <strong>TurboTight</strong>® with a Two Step tightening<br />
strategy, the relaxation of the clamp load will increase by less<br />
than 4%.<br />
7 Residual Torque<br />
Tests with a selection of bolts have not shown any significant<br />
difference in the clamp load or the residual torque by using<br />
the <strong>TurboTight</strong> ® strategy. The bolts were surface treated with<br />
coatings such as zinc flake or nickel and the bolt surface was<br />
not waxed, oiled or coated with grease or any other lubricant.<br />
In some cases, with bolts with a small friction radius, such as<br />
inner hex bolts, measurements have shown that the residual<br />
torque can increase by up to 20%.<br />
The reason for the residual torque increase is that as the contact<br />
surface cools down, the coefficient of friction increases.<br />
There may be local miniature welding in areas where the<br />
temperature during rundown was high due to the increased<br />
friction. The miniature welding will increase the residual<br />
torque – the weld has to be cracked.
8 Torque scatter<br />
In some applications a small increase in torque scatter<br />
has been noted. In particular, very hard joints cause<br />
higher torque values or torque overshoots. This is<br />
because the tool needs a minimum time of 12 ms<br />
between the snug level and the final torque to be able<br />
to regulate in order to deliver accurate torque.<br />
9 Where to use <strong>TurboTight</strong> ®<br />
<strong>TurboTight</strong> ® can be used where higher cycle speed is required.<br />
In some cases, it can be used to improve operator ergonomics,<br />
although the tightening of “softer” joints will have a tendency<br />
to feel slightly more jerky. It is always advisable to test the<br />
behavior of the tool in real customer applications.<br />
Please consult our tightening experts to find out if<br />
<strong>TurboTight</strong> ® is the optimal tightening strategy for your<br />
specific application.<br />
The tool needs a minimum of 12 ms<br />
between the snug level and the final<br />
torque to be able to regulate in order<br />
to deliver accurate torque.<br />
When using <strong>TurboTight</strong> ® on a soft<br />
joint the reaction force is greater than<br />
with a hard joint and the tightening<br />
may feel slightly jerky.<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
19
It pays to use the right tool for the<br />
job. If you use, for instance, a 70 Nm<br />
tool on a 35 Nm joint, the result will<br />
be less ergonomic behaviour. The correct<br />
choice would be a 40 Nm tool.<br />
What should you focus on when<br />
choosing a tool? Optimize your tightening<br />
operations by choosing the tool<br />
with maximum torque closest to your<br />
application torque.<br />
20 POCKET GUIDE TO TURBOTIGHT ®<br />
10 Recommendations<br />
relating to <strong>TurboTight</strong> ®<br />
As a rule of thumb and as explained in the previous<br />
chapters, <strong>TurboTight</strong> ® is optimal for joints exhibiting<br />
a joint stiffness between 70° and 270°, depending on<br />
tool size. See graph on page 14.<br />
When choosing a tool with <strong>TurboTight</strong> ® the size and speed of<br />
the tool and the joint stiffness will affect the performance. A<br />
higher tool speed will create a feeling of a joint being harder.<br />
Ideally Tensor ES/STR tools will work best close to the maximum<br />
recommended tool torque.<br />
Customer tool recommendation example<br />
A joint with a stiffness of 120° and a specified torque of<br />
35 Nm should be tightened with <strong>TurboTight</strong> ® to obtain the<br />
main benefits of improved productivity and ergonomics.<br />
Given Looked for<br />
Joint stiffness = 120° Angle tool needed<br />
Final torque = 35 Nm ± 2 Nm Tool size = ?
Use of an over dimensioned tool<br />
An over dimensioned tool may deliver a bigger spread in<br />
overall accuracy in the application. Tools with a higher torque<br />
range than the torque required for <strong>TurboTight</strong> ® have a bigger<br />
spread because the torque reading takes place in the lower area<br />
of the torque transducer’s reading range. Using the tools in the<br />
lower torque area will always increase the torque scatter.<br />
10.1 <strong>TurboTight</strong> ® and tool extensions<br />
When a tool extension or any other accessory is used between<br />
the tool and the socket it can cause a decrease in torque accuracy.<br />
Tests conducted by <strong>Atlas</strong> <strong>Copco</strong> show a small decrease in<br />
accuracy when the target torque is close to the tool’s maximum<br />
torque. Torques in the lower region of the tool’s torque range<br />
show a greater decrease in accuracy.<br />
If the use of an extension or any other accessory cannot be<br />
avoided, apply the following rules:<br />
1. The accessories should be as stiff as possible, e.g., thick,<br />
short extensions are better than long, slim ones.<br />
2. If possible, use supported accessories, e.g., extensions with<br />
ball bearings.<br />
3. Use the tool close to its maximum torque.<br />
10.2 The limitations of <strong>TurboTight</strong> ®<br />
Since <strong>TurboTight</strong> ® calculates at which point the tool has to be<br />
stopped and as even the fastest possible sampling rate between<br />
the controller and the tool will have limitations, <strong>TurboTight</strong> ®<br />
will not be suitable for all joints.<br />
On very soft joints with more than 270° joint stiffness<br />
the tool will still be unable to deliver optimal ergonomic<br />
results, since the soft joint condition will increase<br />
tightening time, thus increasing the reaction force to<br />
the operator.<br />
On hard joints of less than 70° the tool may have<br />
insufficient time to find the torque rate and to regulate<br />
the motor to the requested torque level. The result will<br />
be an overshoot. <strong>TurboTight</strong> ® needs at least 12 ms<br />
between the snug torque level and the final torque<br />
level.<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
21
T (Nm)<br />
Tensor ETV STR.<br />
Joint 2 Joint 3<br />
Joint 1<br />
Angle<br />
(degrees)<br />
Joints 1 and 2 have the same k factor<br />
but different target torques. Joints 2<br />
and 3 have the same target torque<br />
but different k factors. Joint 3’s k<br />
factor is half that of joint 2.<br />
Tensor ETV ES.<br />
22 POCKET GUIDE TO TURBOTIGHT ®<br />
<strong>TurboTight</strong> ® was designed to be used for torque tightenings.<br />
<strong>TurboTight</strong> ® cannot be used in tightenings where bolts have<br />
to be tightened to a certain angle.<br />
Other components, such as washers, O-rings, etc., will<br />
distort the k factor of a joint (torque rate), leading to<br />
a wide variation in the k factor during one tightening<br />
sequence. Thus, suddenly the k factor will no longer be<br />
linear. This will cause misbehavior of the <strong>TurboTight</strong> ®<br />
algorithm, resulting in incorrect target torque values.<br />
<strong>TurboTight</strong> ® only works with Tensor ES and Tensor STR<br />
tools operated by Power Focus 600 or 6000 controllers.<br />
Using a Tensor STR tool with a Power Focus 4000<br />
will not allow the use of Tensor STR tools with Turbo-<br />
Tight ® (see Table 1 below).<br />
Hard joints and soft joints<br />
Joint “hardness” is defined in figures as the “torque rate”, i.e.,<br />
the tightening angle necessary to achieve the recommended<br />
torque, measured from the snug level. The torque rate can<br />
vary considerably for the same diameter of screw. A short<br />
screw clamping plane metal components reaches the rated<br />
torque in only a fraction of a turn of the screw. This type of<br />
joint is a “hard joint”.<br />
A joint with a long screw that has to compress soft components<br />
such as gaskets or spring washers can require several<br />
turns of the screw or nut to reach the rated torque. This is a<br />
soft joint. The two different types of joints behave differently<br />
when it comes to the tightening process.<br />
System combinations allowing the use of <strong>TurboTight</strong> ®<br />
<strong>TurboTight</strong> ® PF 600 PF 6000<br />
Tensor ES OK –<br />
Tensor ST – –<br />
Tensor STR – OK<br />
Tensor STB – –<br />
Tensor DS – –<br />
Tensor SL – –<br />
Table 1.
Always consider a joint failure<br />
or a tool error which can cause a<br />
sudden unexpected reaction force<br />
and possibly injure the operator.<br />
Please consult our tightening<br />
experts to find out if <strong>TurboTight</strong> ®<br />
is the optimal tightening strategy<br />
for your specific application.<br />
<strong>TurboTight</strong> ® and safety<br />
Please remember to avoid using <strong>TurboTight</strong> ® in applications<br />
outside its limitations (see pages 24 and 25).<br />
<strong>Atlas</strong> <strong>Copco</strong> recommends using <strong>TurboTight</strong> ® within<br />
the same torque limits as for other, slower tightening<br />
strategies.<br />
10.3 How to set up <strong>TurboTight</strong> ®<br />
It is very easy to set up <strong>TurboTight</strong> ® . Use the<br />
Power Focus 600/6000 controller with the<br />
<strong>TurboTight</strong> ® quick programing function.<br />
The quick programing will be suitable for most<br />
joints selected. However there might be cases where<br />
<strong>TurboTight</strong> ® delivers lower residual torque values or<br />
torque overshoot.<br />
If the auto set-up does not deliver suitable residual torque<br />
results, the following steps are recommended:<br />
<strong>TurboTight</strong> ® set-up with<br />
Power Focus 600.<br />
<strong>TurboTight</strong> ® set-up with<br />
Power Focus 6000.<br />
Power Focus 600 and Tensor ES.<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
23
Due to its shape, the spring washer<br />
slows down the last part of the<br />
tighten ing cycle until the washer<br />
flattens out with a jerk. From this<br />
point the final part of the tightening<br />
takes place at high speed. The jerk is<br />
reflected as a peak or “knee” in the<br />
graph below.<br />
Torque<br />
Snug<br />
Knee<br />
24 POCKET GUIDE TO TURBOTIGHT ®<br />
t<br />
What to do if residual torque is too high<br />
1. Look at the bolt coating to determine if it could influence<br />
the torque overshoot.<br />
2. Determine if additional joint components, such as gaskets,<br />
sealings, glue, etc., are used with the joint.<br />
3. Tighten with the tool used previously and measure the<br />
residual torque with an STwrench. Note the residual torque<br />
value.<br />
4. Tighten with a Tensor ES or Tensor STR tool using Turbo-<br />
Tight ® and measure the residual torque with an STwrench.<br />
5. Compare the residual torque check value from the tool used<br />
in step 3 with the residual torque check from the Tensor ES<br />
or Tensor STR tool.<br />
6. <strong>TurboTight</strong> ® works best with tightenings with a fairly linear<br />
torque rate. If a knee should occur close to snug level, try to<br />
increase the “rundown complete” level to above the knee. If<br />
possible, look at the torque traces over time and analyze the<br />
torque increase.<br />
7. Since the friction in a joint might have changed towards a<br />
lower friction coefficient, adjust the target torque accordingly<br />
to reach the needed clamp force. This always has to be<br />
agreed with the customer.<br />
8. If specific investigations are required, please contact your<br />
local <strong>Atlas</strong> <strong>Copco</strong> representative or <strong>Atlas</strong> <strong>Copco</strong> SEPO.
Table of influences<br />
Coatings or components Observations Result<br />
Wax Melts with high speed tightening Less friction under the head or in the<br />
threads, causing higher clamp force<br />
Oil Might burn away, which causes<br />
higher friction<br />
Grease Might burn away, which causes<br />
higher friction<br />
Table 2.<br />
Causing less friction or higher friction,<br />
causing higher or lower clamp load<br />
Causing less friction or higher friction,<br />
causing higher or lower clamp load<br />
Teflon Lower bolt friction coefficient Causing less friction<br />
Paint or lace Lower surface friction coefficient Causing less friction and causing<br />
relaxation after high speed tightenings<br />
Gaskets Element which softens joints Will relax after a high speed tightening<br />
has been performed<br />
Seals Element which softens joints Will relax after a high speed tightening<br />
has been performed<br />
Viscose glue Element which softens joints Will relax after a high speed tightening<br />
has been performed<br />
Adhesives Element which softens joints Will relax after a high speed tightening<br />
has been performed<br />
In the case of torque overshoot with hard joints<br />
Look at the snug torque. If it is set too high, reduce the snug<br />
torque assuring that the prevailing torque of the joint is still<br />
below the snug torque. The snug torque is expressed by<br />
the torque parameter when rundown is complete within the<br />
<strong>TurboTight</strong> ® set-up.<br />
If the tool still delivers torque value overshoots, take the<br />
following action:<br />
• Manually reduce the tightening speed in steps to reach<br />
accepted torque values,<br />
• Reduce the speed manually in steps and check the torque<br />
rate. When you have reached an acceptable level of torque<br />
accuracy you have reached the maximum possible Turbo-<br />
Tight ® tightening speed.<br />
In some cases the joints are so hard that the tightening speed<br />
has to be reduced to below 50% of the maximum possible<br />
tight ening speed. A lower speed might cause the tool to<br />
transmit a jerky feeling to the operator, thus reducing operator<br />
comfort. In this case <strong>TurboTight</strong> ® should not be used.<br />
Remember that more samples will<br />
deliver a better statistical result.<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
25
To ensure customer satisfaction,<br />
the customer and <strong>Atlas</strong> <strong>Copco</strong> must<br />
agree on using <strong>TurboTight</strong> ® in a<br />
specific application.<br />
26 POCKET GUIDE TO TURBOTIGHT ®<br />
To verify the consistency of joints please check in advance the<br />
residual torque of the bolt which has been tightened with the<br />
tool previously used in the application.<br />
After tightening with a Tensor ES or Tensor STR tool check<br />
the residual torque again and verify that the torque variation<br />
levels do not differ excessively from the values produced with<br />
the old tool. Variations of ±10% should still be considered as<br />
ok values.<br />
In the case of unacceptable ergonomic behavior<br />
on soft joints<br />
Increase the <strong>TurboTight</strong> ® tightening speed as much as possible.<br />
If the tool behavior is still not acceptable ergonomically,<br />
<strong>TurboTight</strong> ® cannot be used in the application. Use a Two Step<br />
tightening strategy instead, or torque arms or other reaction<br />
devices.<br />
10.4 <strong>TurboTight</strong> ® and the customer<br />
Please consult our tightening experts to find out if<br />
<strong>TurboTight</strong> ® is the optimal tightening strategy for your<br />
specific application.<br />
If you need support, please contact your local <strong>Atlas</strong> <strong>Copco</strong><br />
Tools representative.
10.5 FAQs – Frequently Asked Questions<br />
No. Question Answer<br />
1 Can <strong>TurboTight</strong> ® be used together with a<br />
software safety function?<br />
2 What is the torque accuracy for Tensor ES<br />
tools using <strong>TurboTight</strong> ® ?<br />
3 What is the torque accuracy for Tensor STR<br />
tools using <strong>TurboTight</strong> ® ?<br />
4 Why can <strong>TurboTight</strong> ® be used with Tensor<br />
ES and Tensor STR tools?<br />
5 What limitation does <strong>TurboTight</strong> ® have on<br />
hard joints?<br />
6 What are the main benefits of using<br />
<strong>TurboTight</strong> ® ?<br />
7 Which surface treatments will influence<br />
the clamp force of joints, tightened with<br />
<strong>TurboTight</strong> ® ?<br />
8 Will <strong>TurboTight</strong> ® have an influence on the<br />
relaxation of tightened joints?<br />
9 Can <strong>TurboTight</strong> ® be used with Tensor STR<br />
using Power Focus 4000?<br />
10 Can Tensor ST tools be retrofitted with<br />
<strong>TurboTight</strong> ® ?<br />
11 Is there a rule-of-thumb regarding which<br />
joints <strong>TurboTight</strong> ® should be used on?<br />
12 Should <strong>TurboTight</strong> ® be verified on the actual<br />
joint if there are doubts about clamp force<br />
and ergonomic performance?<br />
*) This is valid for a correct <strong>TurboTight</strong>® set up<br />
There is no software safety function available<br />
for <strong>TurboTight</strong> ® .<br />
±7.5% over ±3σ *)<br />
±5.0% over ±3σ *)<br />
Because of the higher sampling rate between<br />
the controller and the tool.<br />
From snug to final torque there must be a<br />
minimum of 12 ms for <strong>TurboTight</strong> ® to function<br />
properly.<br />
Reduced cycle time, reduced reaction force,<br />
easy to set up, energy savings<br />
Coatings and surface treatments like wax,<br />
grease, paint, Teflon, etc.<br />
Yes, there might be a slight increase, since<br />
there is no stop time during the tightening<br />
sequence being carried out.<br />
No, since the Power Focus 4000 controller cannot<br />
support a high sampling rate.<br />
No, since Tensor ST tools cannot handle the<br />
required sampling rate.<br />
As a rough rule-of-thumb, joints should have a<br />
stiffness of around 70 to 270 deg.<br />
Please follow the advice in the <strong>Pocket</strong> <strong>Guide</strong>.<br />
Final judgement lies with the customer, and<br />
we should be clear about the characteristics<br />
of <strong>TurboTight</strong> ® .<br />
POCKET GUIDE TO TURBOTIGHT ®<br />
27
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© <strong>Atlas</strong> <strong>Copco</strong> Industrial Technique AB. All rights reserved. No part of this publication may be reproduced without the prior permission of the copyright holder.