|
Project Info:
A manufacturer of
bulk drainage systems had an application where they were stick welding trench
drain grates manually. Their skilled welders would produce approximately
200 linear feet per 8 hr shift of various width grates. We saw an
opportunity to introduce robotic welding to their process to both improve
product production rates, and eliminate hazardous conditions for their
employees.
After consultation with the customer, we agreed on a tooling design, and chose the
Motoman Fabworld II cell as a base. We chose the Motoman UP20 6-axis arm
with the new XRC control due to the massive reach and the open-ended features of
the XRC control. We chose the Miller Autoinvision II welder for its
pulse-arc capabilities. We also chose the Tweco QTA air
cooled torch with custom nozzle / tip / diffuser combination for tight access. The initial goal was to produce 300 linear ft. per shift.
All tooling on this project was
custom designed using Solidworks 3D and Cosmos FEA analysis. The tooling
is fully automated using MAC valves, Destaco clamps, PHD slides and
Norgren cylinders. Every pneumatic device is monitored with reid switches
or proximity sensors. The tooling is fully adjustable to accomodate the
entire range of 30+ part sizes. All wear surfaces are user replaceable and
all high wear surfaces are constructed of heat treated tool steel.
Components in the tooling were precision machined using CNC lathes and mills,
and precision ground for flat mounting surfaces.
A MIG Spray-arc procedure was
chosen for this application due to a higher linear travel rate, lower weld
spatter, and less-complicated paramater adjustment than Pulse-Arc. This proved to be a critical aspect of the project.
Each part is loaded into a "Side A"
and "Side B" fixture. The fixtures are mounted to servo
headstock/tailstock positioners. Upon starting the weld sequence, the
fixtures are rotated into a position to allow a horizontal fillet weld, with a
minor negative angle.
The use of servo positioners allowed us to eliminate the need for a "vertical
down" weld that would be extremely difficult if not impossible in this
application due to the severe torch angles required. Each weld was to be
placed at a distance of 1" on center. Maximum number of welds on the
largest part is 144. The narrow 1" spacing made it particularly
challenging to fit a MIG nozzle and allow for for the weld to be completed.
Severe weld angles at the end of the weld sequence do produce a flow of hot
filler metal as the puddle is pushed out the back side, but penetration is
consistent through the entire length. Nozzle cleaning in this process is
critical as the 3/8" opening gets plugged easily to cause porosity. An
automatic torch tender is on the cell, but due to the extremely small nozzle
opening, the process is manual and must be completed after every part.
This was a successful project even
after a later delivery date than expected. It was an extremely
"programming-intensive" project requiring many hundreds of hours designing
programming structure for the over 30 part variations to be run on the tooling.
We developed a custom "step and repeat" program so that the operator can tweak
points at one datum location. This saved hundreds of hours in programming
and tweaking. The ROI on this particular machine was calculated to
be under 12 months, and our actual production rates are even higher than
originally anticipated.
*As an update to the project, we have chosen to utilize Motoman's new
Hyperstart
software. This allowed for up to a 20% cycle time savings!
Current rates at full production are over 400 linear ft. per shift.
This project demonstrates the
individual skill that Industrial Robotix can provide you. The entire
project was sold, concepted, designed, built, programmed, installed, and
debugged by Erik Shafer of Industrial Robotix.
|
