Control Engineering Europe – March 2019

Control Engineering Europe http://www.controlengeurope.com March 2019 21

ROBOTICS

are costs associated with the machine’s
downtime and the programmer’s
labour.
“If an end user is manually
programming a robot on the teach
pendant (online), they have to shut
down production in order to program
the part,” said Rob House, director of
sales at Octopuz Inc. “The benefit of
using offline programming is you can
be running production, and you can
program your next two, three, or five
parts offline in the software and then
once you are ready to start a new job,
you can just switch over the program
and then start your production again.”
OLP is best-suited for complex path
planning applications that require a lot
of points such as welding, trimming,
laser cutting, deburring, thermal
spraying, painting, laser cladding, and
additive manufacturing. OLP isn’t as
beneficial for simple pick-and-place
applications, assembly, packaging, and
palletizing. These applications still can
be programmed using offline software,
but users may not realise their return
on investment (ROI). It’s more cost-
effective to program manually if the
process has only four or five points.
“If you are spending as much time
programming in software as you do
with a teach pendant every single
time you have a new part, you are
no better off,” said Garen Cakmak,
senior director at Hypertherm Robotic
Software Inc. “For robots in a high-mix,
low-volume environment, software
needs to be easy.”
Improving ease of use is top priority
for these software developers. But
simulation and OLP are pointless if they
do not accurately reflect reality.

Calibrate and don’t deviate
For OLP to work, the virtual world must
match the real world. This means the
simulation must represent the physical
robotic cell accurately.
“The virtual environment in OLP
software has to be an exact replication
of the actual workcell on the shop
floor, which is not the case in most
situations,” said Helmut Ziewers, vice

president of digital factory solutions

for Cenit North America Inc. “The

deviations between a computer-aided

design (CAD) model and the physical

part associated with that CAD model

can be minor or significant, especially

in conjunction with less than perfect

tooling. We still see major issues

and people saying we can’t do this

offline, because of those deviations.”

However, those deviations are not

insurmountable. Calibration is critical.

“If we are off just a few millimeters

or centimeters, you can create as many

offline programs as you wish,” Ziewers

said. “They will never fit. We have

to know exactly how that robot was

set up on the shop floor, and there

must not be any deviations or else the

OLP won’t work. The toolpath, the

trajectory will always be off. This was

the case with Crown.”

Crown Equipment Corp.

manufactures powered forklift trucks.

Its Roding, Germany, facility has several

complex robotic welding systems with

external axes and multi-axis workpiece

positioners. Faced with production

bottlenecks caused by time-consuming

manual robot programming, Crown

Roding decided to explore if OLP was

feasible. Their journey was not without

a few hiccups. Some on the Crown

team were skeptical while others were

eager to try OLP.

Cenit was one of two suppliers

brought into participate in a

benchmarking study. Ziewers said

they took CAD drawings provided by

Crown’s automation integrator and

created the virtual robotic workcell

in their software. Based on those

drawings, they created the robot

program and ran it on the physical

workcell. But something was off. Cenit

engineers arrived on site to physically

calibrate Crown’s workcell.

“We found out what the differences

were, dimensionally,” Ziewers said. “We

applied those differences in our software

and then adjusted the offline program

based on the new setup in the virtual

world. This matched exactly the physical

setup from the shop floor, and the robot

program worked perfectly.!

Ta n y a M. A n a n d a n i s c o n t r i b u t i n g

editor for the Robotic Industries

Association (RIA) and Robotics Online.

This article originally appeared on

http://www.controleng.com

A collaborative robot is programmed offline, saving operators months of manual programming time

for this tedious railway maintenance process requiring hundreds of repetitive movements.

Courtesy: Hypertherm Robotic Software Inc./RIA