Automated Feeding Technology: Loading the parts
AAE (Grauel) pushes technical boundaries. We provide high tech printing & assembly solutions. We support smart printing and manufacturing equipment with Industry 4.0 technologies and solutions. This series of articles provide background information on how these developments are supported.
In the last article about part feeding we reviewed the complexity of this process. Getting products from bulk to a ‘singulated’ (individual) and orientated position is not an easy task. A lot of aspects need to be factored in to introduce automated handling and transport.
Having overcome all those challenges, we will now look at the next “hurdles” to overcome for correct part automation, the actual loading of the parts into the printing or automation equipment.
Overview of feeding systems to automate product handling
In this article we will focus on the importance of the loading position for the parts (e.g., pick up position at the end of the transport line). For reliable operation of the automation system, this is an important aspect. We will look at different methods for motion (vacuum, servo controlled, etc.) and the use of grippers and their design.
The next important step to evaluate is the synchronization between all moving parts. This is where simulations can be used to verify and check the proposed operation. We will review the challenges the products offer for handling in the first paragraph. The different methods for positioning the parts will be reviewed after that. The third paragraph looks at the synchronization between the different moving parts after which high speed application and their unique requirements are reviewed. The last paragraph looks at vision supported positioning systems and their unique character.
Product Challenges in Transport
Products make a long journey from bulk storage to ‘singulation’ and orientation before they are placed in the printing or assembly machine. Assuming the parts made it all the way in a good and safe manner (without being recirculated too much in the feeding system), they need to be handled without disturbing the other parts, allowing them to be positioned correctly.
The large variety of the parts offers challenges in their journey toward the assembly machine. They also offer challenges in correct pick-up and positioning into the printing or assembly machine. The ultimate goal is to have a smooth transition from the loading track to the printing or assembly machine.
Example of a Product Range
Overview of various products, each offering dedicated challenges for the transport, singulation, orientation and pickup (to the printing or assembly machine).
Positioning and Handling Methods
A common way to isolate product(s), to ensure it is under no vibration and can be picked up accurately, is sometimes referred to as a “dead nest”. The part that needs to be picked up is pushed by the parts behind it and held in a static pocket. The other parts are then held into position by a clamping system preventing disturbance of the (front) part that is to be picked up.
Once the product is free from the other products, a handling unit will take the product and place it in the printing or assembly machine. The most simple and cost-effective solution is to use a pneumatic system.
An example is included below where products (white caps) arrive to the end position (all in the same orientation). The products behind them are held back and the ones in front are pushed down. They are then inserted onto the assembly machine (the caps will be screwed on bottles later in the process by a capping unit).
‘Dead nest’ combined with a pushing mechanism
The movement of the pusher is shown in the images, once the products are in place (left-hand side, the product to be pushed down is present behind the slider) they are pushed down into position (right-hand side). The operation can also be seen in this video on ‘Our Assembly Technologies: Capping’.
More Controlled Movements
When it comes to high speed and more accurate positioning, pneumatics solutions are less suitable. In these cases, mechanical (cam) based, servo-controlled, robot-controlled systems, etc. provide a better solution. Each of these types offer unique benefits but need to be chosen carefully (based on aspects such as speed, accuracy, maintenance, investment cost, integration, motion profile, etc.).
Especially when products require to be stacked on top of each-other in the printing or assembly machine (e.g., just before they are ultrasonic welded or require exact positioning), accurate handling is critical.
Image of a servo-controlled handler within a Grauel automation.
In the image above, a servo-controlled handler takes products from the loading position (left-hand side) and places these onto the printing & assembly system (combined system in this case). The products can be placed very accurately onto the system by this handling unit.
The unit that makes actual contact with the part is the next challenge. Obviously, the parts need to be grabbed correctly. This requires various factors to be considered such as product shape, part material, location where the part can be grabbed, orientation for placement, etc.
This is where the gripper design comes into view. The grippers are normally placed on the end arm of the handling unit and grab the product (sometimes referred to as EOAT, End Of Arm Tooling). It may take only one incorrectly grabbed part to cause the machine to stop functioning. An example of a gripper at the end of a handling unit is shown below.
Image of gripper within a Grauel automation.
The combination of gripper design and the full handling operation are critical aspects for good product handling. Both play a key role for correct product pickup and positioning.
Synchronization of movements
For the complete system to function correctly, the handling system (movement of unit and gripper) need to be synchronized with the printing or assembly system. All movements need to be done in time, it may just take one part to arrive a little late or early to stop the full printing or assembly machine. When multiple handling systems are present on a production line, the complexity becomes apparent.
Image of a handling unit within a Grauel automation.
The image above shows a handling unit taking a product (white part) from the loading position (left-hand side) and places it onto an index table (assembly machine). A dedicated shape is present on the index table to hold the part in place).
The correct product presence is verified to ensure it has been placed correctly; the sensor used for the detection is shown on the bottom right.
Simulations to verify operations
With the increased complexity in movement and the required synchronization between the various handlers, simulations can be used to verify the operation in an early stage.
For those interested in more information about simulations, please check out our article on Simulations & Virtual Reality, Digital Twins and Augmented Reality.
As an example, we can simulate the operation of a handling system for a ring type product. The ring type products travel down a linear track (left side in image) into a positioning unit (middle of image). The positioning unit is used to separate the parts and present them to a handling unit (scara robot). Since the (robot) gripper moves inside the handling unit, we must ensure that, during this time, the handling unit does not rotate. To verify this, we can introduce a signal “Gripper down / locked”.
We also want to be sure the product is grabbed (gripper closed) for which we need another signal (“Gripper Closed”). We can now move the products to a predefined position (we would need another signal for the assembly system to be in position).
Image of a Grauel automation with a scara robot implemented.
All parts need to work together in a synchronized way to ensure no damage to the parts, handling units or the machine occurs. A simulation can provide useful insight in the timing needed and the handling operation in general. For those interested in simulations, please check out our article on Simulations & Virtual Reality, Digital Twins and Augmented Reality.
High Speed Application
For high-speed applications, dedicated handling solutions are needed. This is especially true for continuous motion systems. These systems commonly use various dials (discs) that rotate at high speed.
For these types of systems, the loading position of the products needs to be arranged differently as this position is in constant motion.
When using a linear or vibrating linear feeding system, the position of the products cannot be guaranteed. This may result in misalignment of the parts not allowing correct intake or cause product to get damaged.
Image of a Grauel ‘continuous motion dial’.
The image above shows a continuous motion dial. Inserting products directly into the dial from the linear transport belt may prove to be a challenge (for reliable operation).
A dedicated solution may include the use of a worm drive. This unit takes products from the linear feeding system and transports them further in a controlled way. This allows the positioning and delivering of each product in a timely and accurately defined position.
Virtual representation of a WormDrive.
The image above shows an overview of a (basic) worm drive for syringe plungers. The distance and position of the products in the linear / vibrating feeding system (left) is not well defined as the transport depends on factors such as pressure applied by the upcoming plungers, dust and wear of the track, etc. The position in of the plungers in the worm drive is much better defined and contributes to better handling.
Vision Supporting Positioning
Robots are becoming more popular for product handling. They can provide complex movement and offer a great deal of flexibility. Especially when looking at creating modular and flexible automation, robots are a preferred choice. When combined with vision for robot guidance, a great deal of the separation and orientation can be accommodated by the robot.
Image of a vision guided robot.
The image above shows the option for product identification by a vision system (from the top). The robot can then be guided to the correct position. A second vision system may be included, looking at the products in the robot arm (EOAT) which can be used to provide information on the initial part orientation. Based on this result, the robot can execute the correct rotation / movement for the part to align with the assembly machine.
Stay tuned for more, coming up next month! In the meantime, please consider following Grauel, a brand of AAE, on LinkedIn for weekly updates and extra content.
‘Automated Feeding Technology: Loading the parts’, by Ivo Brouwer – Business Developer Production Automation at AAE b.v.