Bringing a product to market is challenging. Designing a product with automated manufacturing systems in mind can reduce complexity, streamline the entire process and save you money.
We know how challenging it is to build a product and to bring it to market.
It requires the combined efforts of many people from a variety of disciplines –design, engineering, quality, supply chain, manufacturing and more. Those experts use tools and methods (operational standards, manufacturing guidelines, business excellence guide-lines ) which drive processes efficiencies and reduce the pain points along this journey.
Since the greatest impact on the product performance & cost is its design, we would like to provide a few guidelines for an important subject – the design for assembly.
Design for assembly is one category in the DFx – Design for “x”, where “x” stands for:
Cost, Reliability, Manufacturing, Quality, testing, Maintenance, environment and more.
There are plenty of guidelines for each category, many of them are available online. The balance between the “x” categories is a gentle one – and in many cases they affect one another. For example, to simplify an assembly process, an engineer wishes to combine 2 parts using additive-manufacturing method. But if the result is a much more expensive part, then the gain cost is negative. So a structured-holistic process is required in order to perform the right cross-functional balancing.
In this article, we chose the “design for assembly” as a holistic approach, which is part of what we do here in Launchpad – We want to help customers get to their products much faster, and to use advanced manufacturing and assembly processes to get there.
Considering assembly and integration aspects of products at early phases of the design will improve down-stream processes, will minimize labor costs and will reduce the time and energy it would take to utilize assembly automation.
We will provide a few guidelines with reasoning, and would love to hear your opinion, if this is helpful and what other information would be of interest to you.
1. Keep it simple and minimize
Minimize the number of parts in the product assembly - combine parts by using alternative manufacturing methods. In many cases sheet-metal, molding and additive – manufacturing offer great solutions for parts combinations. During the production this will simplify the assembly, and will make the supply chain easier (a flatter BOM).
An example – if one type of screw can be used across the product, this will simplify production settings and change over time of tools.
Minimize the type of materials and finishes - this will affect supply chain, manufacturing methods and movement of parts to and from finish facilities (painting, other). During the production this will simplify the tooling and settings of the assembly line.
Minimize the number of assembly steps.
Minimize the number of sub-assembly orientations, as the product being assembled. The preferred method of assembly in many cases, is the vertical-stack, bottom-up, in which parts are stacked one within or on top of the other. Gravity helps in this case. If other assembly directions are required (non vertical), try to keep the movement of parts as simple as possible. This will help both operators and machines in case of assembly automation.
Avoid adjustments and tuning of parts.
Use standard, off the shelf, available components. By doing this, you have higher chances of getting the parts within their specs and tolerances and getting them at the lowest prices. Getting components in their specs, is a key contributor to a successful automated assembly.
There are great online digital catalogs which offer a huge collection of standard items, including all of their technical properties, and their CAD files. Websites like McMaster Carr for mechanical components or Digi-Key for electrical and electro-mechanical components.
3. Remember that someone or something needs to assemble your product
Adding features like tabs, slots and chamfers will make the assembly self-aligned, and will prevent incorrect assembly of parts. This is most beneficial for manual assembly.
Parts need to be handled, lifted, grasped. Parameters like dimensions and weight, surfaces for contact, lift or grip should be considered. Else, additional tasks would be added to the manufacturing process – like orientation, fabrication of special tools, and organization of parts prior the assembly. Leave free areas for adequate tool clearances.
Try to avoid parts adjustments or alignments in the assembly process
Assure visibility of parts and components – this is important for both manual assembly – operators will assemble much better if they can see what they assemble, and vision systems could capture images for machine controls or QA.
Avoid tight tolerances – both in parts manufacturing and in the assembly, where tolerances are “stacked-up” and in many cases will prevent the parts from being assembled.
Reduce number of parts, Self-alignment, parts securing during assembly (avoid movement).
Dimensions of parts: handling, positioning, assembling.
Design for Automation Assembly
Automation assembly brings many values and advantages – it improves quality by the repeatable-predictable characteristic of a machine, reduces tedious labor and potential health risks of employees, and can improve capacities and throughputs.
Most of the DFM/DFA guidelines are relevant to automated assembly.
For automation to work – products need to be designed for assembly automation or they need to have friendly automation features in them. These will include handling of parts, lifting, orienting them for pick & place applications. Parts handling can be mechanic, by Vacuum, Magnetic, Electrostatic.
Grippers & tools clearances should be considered for parts and assemblies/sub-assemblies, as the tools need to retreat out of the assembly area. Symmetrical parts are typically easier to make and to handle or feed into assembly machines
If parts don’t need to be secured or clamped during the assembly - that is a huge advantage for the simplicity of the automated assembly. It is particularly challenging to balance or to secure parts to one another when using automation.
Today’s computer vision systems are advanced, flexible and intelligent. They can drive machines by image processing. Hence, visibility of parts, sub-assemblies and related features are critical factors for as automatic assembly, guidance, measurements, and inspection. Adding visual features (fiducials) can help to simplify the computer vision application.
In most cases automation does not work well with flexible parts…they are challenging to grab and to manipulate. So these should be avoided when assembly automation is considered.
Below are two more examples of automatic assembly processes.
Automated Screw Driving
There are plenty of automated screw driving solutions, at a variety of features and prices. From tabletop machines to in line automated systems. In order to enable a robust automatic system, the bellow should be taken into consideration:
Fasteners selection (type of screw, screw head) – match the right tip to the right head.
Fastening parameters (torque, angle, speed profile) – these parameters are fully controlled.
Top to bottom screw driving is the easiest and most common method to drive fasteners, but bottom-up or angled screw driving are available as well. They will require more advanced methods of presenting the screw to the desired location. These can include “blow feeding”, which can work only with certain screws.
For clean environment processes, screwing should be done with a vacuum suction to avoid the spread of particles.
When using a screw presenter and a pick & place method, there are 2 main options: picking the screw by the tip using vacuum or the tip is magnetic. When using the vacuum method, avoid round heads.
Material dispensing, like glue, has unique process requirements which should be well defined and qualified, as they have direct effect on the strength of the adhered surfaces and their appearance.
Know the physical properties of the material (viscosity, curing methods and time…) – this will affect the type of dispensing method, equipment and systems to be used – what controlled environments are required (temperature, humidity).
Clearances are also required, to allow the dispensing tip and related mechanism to reach to the location where the material needs to be dispensed.
Product CAD Design Recommendations
Here are simple guidelines which will make processes like assembly analysis and simulations more efficient.
Build each part as symmetrical as possible to the "ORIGIN" point.
Each part should be oriented "FRONT, TOP, RIGHT PLANE" exactly as it will be located in the actual assembly.
Verify that sketches are either unambiguously defined or are “fully defined”
Items in the assembly file should be attached to one another just as they should be assembled in the real product.
The assembly file should contain all of the items that will be used for the real product.
By following these guidelines, we can assure important information regarding the parts and the assembly can be transferred automatically to applications like simulations, renderings, manufacturing-systems and procurement.
Manufactured parts properties should be populated (i.e – material, finish, tolerances)
Purchased items should be given a part number identical to the vendor part number
Following these guidelines will considerably reduce the complexity of manufacturing, and as a knock-on effect will speed up your process of selecting a manufacturer for your product.
Launchpad is developing the software, hardware and AI tools to dramatically speed up the manufacturing of low and medium volume products. Please get in touch with us at firstname.lastname@example.org if we can help you, or sign up to our newsletter to stay up-to-date with our developments