Understanding Large Assemblies

The term “large assembly” means different things to different people, so how do we define a large assembly? Large assemblies are not defined by the number of component or physical properties, rather they have two primary characteristics. An assembly is considered large if:

  • It uses all your system resources
  • It hurts productivity

These characteristics can be further divided and be caused by many of the following traits:

Physically large

  • Requires some sort of layout or other engineering input to properly position all the components.
  • Has so many components that their management, calculation, and memory requirements are large enough to be a detriment to productivity

Complex

  • Has many parametric relationships
  • Has a large number of mates.
  • Taxes your computer resources.
  • Contains a large number of different components that need to be managed and can slow down the processing speed of even large, fast computers.
  • Has imported data that has to be located and loaded.
  • Has geometric complexity that is difficult to rebuild

Requires best practices for large assembly design not only at the assembly level but also the part and drawing stage of work.

Uses multiple systems or disciplines.
These could include:

  • Mechanical components
  • Custom components
  • Toolbox parts
  • Library parts
  • Weldments
  • Routed systems
  • Components from outside vendors and subcontractors
  • Customer files

The truth is not bigger and better hardware can fasten assembly performance but the slow performance is a combination on many factors in design.

Slower performance can be seen in following areas:

  • Opening, Closing & Saving time
  • Rebuild time
  • Creating drawing
  • Rotating, panning & viewing
  • Inserting components
  • Switching between parts, assembly, drawings
  • Mating, etc…

Major performance issue arise from modeling practices than any software or hardware issues.

  • Things under solidworks control is 20%, they are bugs, algorithms, code efficiency.
  • Things under user control is 80% as,
    - Software and data management option and setup, fail to plan things in most efficient way affects performance.
  • It’s good to buy solidworks certified hardware or equivalent for maximize performance.
  • Best modeling practice needs to adapt to guide your work by avoiding lengthy modeling processes.

Slower performing assemblies are accumulation of many small fixes there is no easy fix for such assemblies. Fact is when solidworks models starts running slow user wants to jump to bigger and faster computer which is waste of money for keeping nonprofessional drivers on board. With proper strategy of design root cause can be controlled to low problematic end irrespective to how good your computer may be (I am not against powerful Pc’s but against wrong practices).

Best Design Practice

Its important to know how thing in Solidworks background is working.

Effective modeling parts

  • Proper origin
  • Easy build features
  • Removal of in-context relationships
  • Removal of circular references
  • Simplified versions

Effective modeling assemblies

  • Subassemblies orginazition
  • Proper level of detail
  • Proper mates

Reducing information loaded into memory

  • Quick open
  • Light weight
  • Large design review
  • Simplified configurations
  • SpeedPak
  • Draft quality drawings

Data sharing (Must for designers)

  • Access to all necessary files
  • Access to most current version
  • Make changes to files with responsibility
  • Protect from others to overwrite files.

Things to consider while creating large assemblies

File management

  • All design team members of project needs access to files as required
  • Protect files from accidental overwritten from non design team members
  • Ensure file properties/metadata are filled correctly

Don’t allow to create situations where parts, assemblies, & drawings are stuck down by,

  • Inability to locate files
  • Working on the wrong version file
  • Modeling problems
  • Hardware problems
  • Network problems

Produce parts, assemblies, & drawings efficiently

  • By using in-context features at design as appropriate
  • Breaking in-context relationships & the problems of part origins
  • Sharing data between engineering, manufacturing, & design team without any problem
  • Its ideal to limit configurations to two to three at component level
  • Design simplified parts
  • Ideal to use parasolid bodies or simplified parts for library or purchased parts and assemblies

There is no quick fix method for slower large assemblies therefore significant methods and steps need to follow while designing to improve large assemblies.

Design plan and file management for large assemblies

Planning and File Management

  • Understand the need to plan ahead when creating large projects.
  • Understand the key elements required in a data management plan.
  • Understand the benefits of a file management system such as PDM.

Large Project Design Planning

The more complicated a design, the more planning that needs to be done before the first part is created. Failure to plan and have everyone using the same methods can result in lost data, long rebuild times, and higher costs due to problem resolution.  The planning of a large assembly follows the same general rules as any large project: you need to plan ahead and have structured progress. Some things to consider when starting the project:

  • Have an understanding of the approximate size and makeup of a typical data set.
  • Because you will be dealing with large data sets, develop a strategy before you start to model the parts and assemble them.
  • Decide which tools and techniques you will utilize to make your assembly as manageable as possible,
  • Determine which of the two primary techniques you will use:
  • Skeleton model technique for large assemblies, usually used for machines, plant-t designs, paper processing allows visualizing and selecting important interfaces at all sub-assembly and even part levels.
  • Master model technique Usually used for consumer products as ducts, car body, and the like, allows using complex surfaces as the base for components , Results in many multi-body parts.
  • Decide how you are going to name parts and handle revisions.
  • Each file name should be unique. Are you going to use intelligent part numbering or dumb part numbering?
  • What will the revision scheme be and how will revisions be captured in the files?
  • What is the workflow for documents?
  • How are in-context relationships going to be used and managed? Keep in-context relations as simple as possible and keep to one master model where feasible.

Efficient large assembly design is a combination of many smaller things that when combined, can make a big difference. You must have a disciplined modeling, assembly, and drawing technique. Plan before starting work, as the time to react is not when there are 15,000 parts in the assembly.

How to Implement a Strategy

The way you will implement and enforce the strategy should be part of the strategy development. Things to consider when implementing your strategy for the design:

Document the approach

Procedures that are not written down can be more easily misunderstood and varied.  The time required to properly document a plan is less than the rework time (and cost) caused by people not following the plan.  Having written documentation of procedures also allows for accountability when members of the team deviate from the plan.

Make it readily accessible

No matter how good a plan is, it is useless if the people that need the information cannot see it. Have it posted on the engineering intranet, or on some common location where it can be easily viewed by the entire team.

Communicate with users

Make sure the procedures are discussed at planning meetings. Stress the consequences of not following the plan. Remind people of the procedures as soon as any deviation is noted.

Document templates and document level settings

Have everyone use the same templates. Well—designed part, assembly, and drawing templates can save time by automatically filling in required data directly from the models. Document templates also set the document properties to insure consistency between all the members of the design team.

Custom properties

Custom properties can be very useful as they can be automatically read and used to fill in data in bills of materials (BOMs) and forms in the PDM system. They can also be used as search criteria to more quickly locate files by helping to filter components during “advanced selection” to aid in assembly visualization and performance. Many custom properties can be included in the document templates to make it easier to include all the properties that are required for the project.

System-level settings

System-level settings can make a significant difference in system performance. Provide guidance to the design team on setting these.

File Management

File management can help to save significant time during the design process. File management is a topic that needs to be decided on early in the process and is not something you slowly ease into. The methods and procedures need to be determined, implemented, and enforced if you are to gain any benefit. Starting a project with the idea that you can just start designing, naming and storing files without a well- thought-out procedure is a recipe for disaster. It takes much less time (and costs less) to plan the process and rules, than it does to fix the problem afterwards.

Managing and Sharing Data

To set up and manage files it is important to start with a set of goals. So, what are our goals when managing our files? These are some general goals that are usually included:

  • Multiple users must have access to the same files.
  • Users must be prevented from overwriting each other’s work.
  • Everyone must know what the current version of each part is.
  • Different work styles must be accommodated.
  • Files need to be stored for maximum productivity by keeping them stored locally.

Product Data Management

While a single engineer or designer may be able to organize, store, and keep track of changes without a data management system, as soon as a second engineer is added, some form of data management is necessary.

Data management is a prevention, not a cure. Some people will resist using a PDM system because they think that it is too hard, or they don’t want to learn something new, or they feel that it takes too much time, among other reasons. Yet, they are also the ones complaining when they can’t find all the files for the assembly they are working on because someone moved them, or their latest changes were overwritten by an older version of the same file when someone else saved the file on top of their work. There are several product data management systems on the market from workgroup level through enterprise, so the method or product you choose can be matched to the size of your data and budget.

The bottom line is that you need to manage your data efficiently either by using a PDM system or through manual brute force. Not managing your data is costly in time, money, and human frustration.

Goals of Data Management

When selecting a data management method or system, you should keep in mind the goals of any data management system. They are to be able to do the following:

  • Search and find referenced files
  • Easily create bill of materials listings and locate where files are used
  • Enable collaboration and change control
  • Track revision history and provide secure vaulting

SolidWorks File Structure

The SolidWorks file structure is a single point database. This means that each piece of information is stored in only one file. Any other file that needs that piece of information must reference the file where it is stored rather than copy the information into itself. This means that SolidWorks creates compound documents by establishing external references.

External References

External references are the links between documents. There is no separate database to list the references. Instead, a pointer in the file header lists the referenced files and their location. These are absolute references, in other words, they are a complete path such as D:\myfiles\bracket.sldprt.

Where Used

There are no reverse file pointers in SolidWorks. While an assembly knows what files are used in the assembly, the individual components do not know that they are used in that assembly. This presents a management problem when modifying files that may be used in different assemblies. Data manager PDM systems keep track of these relationships, which makes it easier to determine the effects of changes to parts. Without a data management system, SolidWorks Explorer can be used to locate “where used” relationships; however, this can be slow as it must literally search through all the files in the specified search paths to determine if there is a reference.

The Manual Data Management Method

If you have a PDM system, how are you going to manage all the files for your large project? Different companies have tried different methods, but they generally reduce to two primary methods.

In the first method, all files are stored in a central location. Users open the files across the network from the central location as needed and save the files when done making changes. SolidWorks collaboration options help to prevent multiple users from having write access to the same files at the same time.
There are several problems with this method:

No history

Any history as to changes, or who opened or saved the files, must be kept manually.

No revision or version control,

Tracking revisions must be done manually. Methods such as appending the revision to the file name are sometimes used and can cause additional file management problems.

Easy to violate the rules

There is nothing to stop users from copying files to their local drives to speed up their work, but this in turn violates the rules of only one person having write access to a file. If you are not strict with all users, someone will break the rules at the worst possible time and cause a loss of data.

Opening files across a network

Opening files across a network is a sure way to reduce productivity. With the large number and size of the files, network bandwidth can significantly slow the opening, saving and closing of files. Most PDM systems cache files locally on the user’s hard drive to speed open and save times.

Search

Without a PDM system, searches are left to SolidWorks and Microsoft® searches, In the second method, files are stored in a central location and users copy the files they need to their local workstation. After making changes, they save the files back to the central location. This ls the “Wild West” approach as nothing in the system enforces the rules. All control is lost except for what can be done through procedures enforcement. Whoever saves a file back to the network location last, overwrites the previous version, even if the last saved file is older than the file it is overwriting.

SolidWorks Workgroup PDM

As the name implies, this PDM system is made for workgroups at a single location. Depending on the size and structure of the design team, SolidWorks Workgroup PDM may be used, but generally the size and makeup of the design teams that are required for large projects call for an enterprise solution.

One key difference between SolidWorks Workgroup PDM and an enterprise solution is the single vault structure. if your design team works in multiple off-site locations, SolidWorks Workgroup PDM is not the best solution, as connectivity requirements would require excessive time to check files in and out of the vault.

Some key features provided by SolidWorks Workgroup PDM

  • Revision control
  • Single workflow
  • Tracks all changes to the files
  • Can store any type of file
  • File access is controlled through permissions

SolidWorks Enterprise PDM

With very large file sets, SolidWorks Enterprise PDM is usually the best choice for file management. SolidWorks Enterprise PDM uses an SQL database and can replicate the vault to multiple locations so that data can be synchronized regularly to avoid delays due to network bandwidth or slow internet transmission speeds. As the vault is stored as an SQL database, searches are fast.

Some key features provided by SolidWorks Enterprise PDM.-

  • Both revision and version control
  • Multiple revision schemes
  • Multiple workflows
  • Tracks all changes to the files
  • Can store any type of file
  • File access is controlled through permissions
  • Can provide notifications of changes

The Choice

The decision to use PDM is up to end users & companies requirements, as without PDM any data loss may significantly effect productivity and increase cost of system and of training the users.