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Process Cleaning Magazine
© 2012
AMT-The Association For Manufacturing Technology
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PC FEATURE
The trend towards smaller cars and engines with reduced fuel consumption and emissions is leading to ever-stricter requirements for component precision,
and thus for component cleaning as well. On top of that, the increasing variety of models, engines and transmissions and shorter product life cycles has required increased fl exibility in manufacturing, which includes surface and component cleaning. Automobile manufacturers and their suppliers need top quality, highly flexible cleaning solutions that are also extremely cost eff ective.
Flexibility with Robots
Transfer units are designed for effi cient processing and cleaning
within very short cycle times (and, therefore, high throughput
values) for repetitive parts, not for high levels of fl exibility.
Modular cleaning solutions equipped with robots can be
integrated into the production line to increase fl exibility. Th ese
systems off er highly fl exible cleaning, high-pressure deburring,
and drying of complex components such as cylinder heads,
crankcases, transmission housings and clutch bell housings, all
with very short cycle times. When parts are changed over, or
in the event of a workpiece modifi cation, the robot’s motion
sequence can easily be reprogrammed with the help of a reachin
panel. Th ese robotic cleaning cells are off ered as compact
modules with integrated media treatment.
Th is concept was implemented by an automobile manufacturer
for fully automated intermediate and fi nal cleaning of seven diff erent cylinder heads. Th e central cleaning station consists of fi ve robot cells and is linked to the machining department, as well as to downstream processing. Each
cleaning module includes clean and dirty storage trays and its own autonomous controller. Th is way, cleaning cells can be removed from the grouping and set up at a diff erent location, and the setup provides redundancy in case a
cleaning cell has to be shut down for maintenance or due to a malfunction.
Cleaning in Action
When a cylinder head arrives at the transfer position, a central
loading robot grasps it and reads its data matrix code, which
provides information about exactly which part is involved.
Th e robot selects an available cleaning cell, places the cylinder
head onto the dirty storage tray, and electronically transmits
the component’s part code to the cleaning cell’s controller. Th e
component is cleaned by injection fl ood washing, a process in
which high-pressure water spray creates a whirlpool eff ect in the
chamber, rinsing chips and contamination out of hollow spaces
such as threaded blind-holes. Next, high pressure deburring
with a 300 bar water-jet begins outside of the bath. A cleaning
program writt en for the part surface and confi guration
and stored in the controller instructs the robot to manipulate
the workpiece to remove the burrs from critical areas in the
hydraulic fluid circuit. In cases where the standard waterjet
routine is not suffi cient to clear the burrs, specially designed
high-pressure lances are inserted into the workpiece’s hydraulic
fl uid channels. Aft er a rinsing operation and pre-drying, the
cylinder head is set onto the clean storage tray, where it will be picked up by the loading robot and placed onto the conveyor to
the vacuum dryer.
Batch Process with Solvent
Many automobile parts are cleaned as bulk goods or as
individually positioned items in batch processes using aqueous
cleaning agents or solvents. Th e high throughput within short
periods of time means that a smaller percentage of overall cost
is att ributed to cleaning the workpiece. But in order to achieve
cleaning results that fulfi ll the specifi ed requirements, the process
has to be set up with parameters to cover the spectrum of
part confi guration, the degree of cleanliness and type of surface
contaminants. Cleaning trial tests conducted at the facilities of
the system or cleaning agent manufacturer are the best way to
accomplish this.
A manufacturer of drive technology that produces synchromesh
mechanisms for the majority of large automobile manufacturers
chose this procedure. Depending upon the type of
vehicle, the cone synchromesh mechanisms can include up to
ten individual parts, and can include organic, carbon composite
and scatt er sinter materials. Th e company uses an in-house gas
nitriding system to fi nish the part surfaces, and this process
requires absolutely grease-free, dry parts. Numerous cleaning
trials with systems from various manufacturers revealed that
a cleaning system operated with Dowclene 1601 modifi ed
alcohol was the ideal solution from both a technical and an
economical standpoint.
Th e option to freely select parts movement during all process
steps allows the company to create its own cleaning programs,
which are matched to the respective task. Th e system is equipped with a post-rinsing unit, which allows for a second
cleaning operation with cleaning agent from a separate tank.
Furthermore, an ultrasonic cleaning module was also integrated
to ensure that non-ferrous metal particles from scatt er sintering,
graphite residues and partial contamination caused by machine
oil can be reliably removed.
Th e combination of a distillation unit and a residual distillation
unit also makes a signifi cant contribution to good cleaning
performance. Th e cleaning agent is continuously distilled
in these two units, and carried-over oil is removed from the
system immediately. As the cleaning agent fl ows from the parts,
it is fed through fi ltration systems that separate the particulate
contamination.
Th e synchronizer rings (with diameters ranging from 67.5 to
172 mm) are all handled by the same conveyor rods. Each batch
rack (washing basket) is equipped with various corresponding
mounting positions. In this way, each basket (with dimensions
of 670 × 480 × 300 mm) can be used for all synchronizer ring
sizes as they move through the degreasing process.
Saving Money in Parts Handling
Th e results, duration and cost of parts cleaning in batch
processes depend on accessibility of the parts in the workpiece
carrier, as well as the process technology and cleaning agent
being used. Cleaning baskets made of stainless steel round
wire assure that the workpieces are accessible by the cleaning
agent on all sides, that dislodged contamination is readily
fl ushed away, that the drying process is accelerated, and that
media carry-over is minimized. Th is leads to bett er cleaning
results in shorter periods of time, higher throughput rates and
longer bath service lives, and overall improved economy. More
and more frequently, the use of workpiece carriers designed
in a part-specifi c manner is required to adhere to specifi ed
cleanliness requirements. And not only can cleaning quality be improved with cleaning baskets that are ideally matched to the
workpieces, operating costs can be reduced as well. As a prerequisite,
in-house transport and subsequent packaging must
be taken into consideration in addition to part-specifi c and
cleanliness-specifi c requirements when designing workpiece
carriers. Appropriate design makes it possible to minimize the
number of manual transfer operations between the individual
manufacturing steps and/or fi nal cleaning. Th is reduces the
risk of parts damage and off ers considerable savings potential.
Th is strategy is employed by an international supplier to the automobile industry who procures two diff erent components from external production facilities in blister packs that contain 96 and 46 workpieces, respectively.
Component A is the external housing for component B. For fully
automated assembly, 48 pieces each of part A and B must fi rst be loaded
into a workpiece carrier, aft er which an adhesive, corrosion-protection coating is removed in a cleaning step. Th e parts are cleaned and transported in a workpiece carrier designed specifi cally for them. A special upturning adapter was developed to minimize the number of manual transfer operations required. Th e blister pack containing 96 pieces of part A is turned upside down into the adapter, which can be split in two aft er fi lling. Th e upturning adapter for part B is designed to receive 48 workpieces. Half of adapter A and adapter B are placed onto a frame, and the parts are then turned upside down into a workpiece carrier. Th anks to this solution, the workpiece carriers can be
fi lled with just fi ve manual operations. Relative to the manual transfer operations actually planned by the customer for this sequence, required eff ort has been reduced by 75%.
With careful planning and consideration, OEMs and their suppliers can
implement the latest cleaning and automation technology to improve quality
and increase fl exibility while minimizing expense. PC
DORIS SCHULZ has worked as a freelance journalist for more than 15 years. Her specialty is the fi eld of surface treatment, especially parts cleaning. She can be reached at ds@pressetextschulz.de.
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