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Breaking it down – Limits and Fits in Inventor / HSM

In this article, I’ll explore a workflow for utilising the Limits / Fits tools in Inventor, to maximise the benefits of using an integrated CAM system for precision machining. To start off with though, I’m going to explain a bit about Limits / Fits for the uninitiated.


When a particular design calls for a precise fit between two components, every engineer I know usually pulls out his/her copy of Machinery’s Handbook (or Boundy) and looks up the table of Limits/Fits. Inventor has these fits built in, so as long as you know what you’re looking for, it will put the correct tolerance limits on dimensions in the drawing environment, for you, once you have specified the appropriate fit. A slightly lesser known feature, is that tolerances can be used in the modelling environment as well. These model dimensions can then be retrieved and placed on the drawing.

Limits / Fits

For those of you who may not have dealt with Limits / Fits in a CAD environment, you typically dimension the part with a nominal dimension, and then specify a tolerance by listing upper and lower limits for the specified quantity. This allows the machinist a range to work within, that ensure the correct clearance or interference between the two components, regardless of whether he/she is at the upper or lower limit.

The limits/fits that everyone uses today, were conceived a long while ago, by clever people who are now probably long dead. Their age doesn’t make them any less useful today.

Broad fits categories

  • Clearance – There is always a gap between the 2 components, regardless of whether each part sits at it’s upper or lower size limits.
  • Transitional – Depending on where each part sits between upper and lower limits, there may be a gap between the two components, they may be identical in size, or material may even need to be deformed/displaced to fit them together.
  • Interference – There is always material required to be deformed or displaced in order to get the parts to fit together.

Within those categories, sub-categories of fits are often described using descriptive names such as “Loose-Running,” “Close-Running,” or “Sliding.”

You can choose to base the fit on either the hole or the shaft, and the codes for the fit are either upper or lower case to designate this.

Now obviously, if you have a range of possible sizes for the shaft, and a range of possible sizes for the hole, then there are an infinite number of permutations between the extremes. To deal with this, we often just look at the best and worst case scenarios and decide if they are suitable.

If the hole diameter is at the upper limit, then the component (with the hole in it) has less material than one with the hole diameter at the lower limit. In other words, a bigger hole removes more material. Conversely, a shaft whose diameter is at the upper limit has more material, than one whose diameter is at the lower limit.

So we have two combinations which form the extremes of the fit between these two components. The first is the biggest possible shaft in the smallest possible hole, and the second is the smallest possible shaft in the biggest possible hole. In a clearance fit scenario, they give the smallest possible clearance, and largest possible clearance respectively. We call the first scenario the “maximum material condition,” and the second, the “minimum material condition.”


If we have, say, a pin that needs to fit into a boss, but slide in a smooth fashion and remain co-axial to a high degree of accuracy, we may choose a Close Running fit. This has corresponding codes of H8/f7 in the hole basis system, and f8/H7 in the shaft basis system.

We’ll be using the hole-basis system, which means that the nominal size lies on the lower limit of the hole diameter. Another way to think about this, is if we have a perfect hole, exactly at the nominal diameter, then we will have to remove material from the shaft to get a clearance fit.


The nominal diameter is 50mm, and the H8 limits for that size give a range of 50.000mm to 50.039mm. This means that if the finished part comes out anywhere between these values, we would consider it a “pass” and it will give the desired fit when the shaft is inserted into the hole, as long as that is within it’s acceptable range too.


The nominal diameter is 50mm, and the f7 limits for that size give a range of 49.975mm to 49.950mm.

So when the parts are assembled, you can see that there could be a maximum clearance between them of 0.089mm, and a minimum of 0.025mm, depending on where the individual components sit within their tolerance range.

So how do we represent this information in our CAD model, and how do we go about conveying this information to the machinist you ask? Good question, I’m glad you asked….

Well, the way it has generally been done for as long as I know of, is that components are usually modelled or drawn at the nominal size. Tolerance notes are then added to the dimensions on the drawing, to show the machinist the acceptable range for dimensions of the finished component.

Toleranced DimensionAn example of a nominal diameter dimension with a fit code, and size limits

This is all well and good if the machinist is making this component by hand, and can adjust the size to suit, but what if we want to control a CNC machine using the modelled part? We can’t just toolpath everything at exact size, otherwise fits won’t work. Sometimes CNC operators adjust the offset parameters in the machine control to cut slightly bigger or smaller, but this is not a very good way to manage things. Even worse is hand-editing the machine code, as it gives opportunity for error and is slow.

A skilled machinist can definitely achieve very high accuracy on manual machines, but usually it is a case of removing material until close to size, and then taking a series of small cuts, with measurements in between, until the finished size is reached.

With CNC machines, this is not an easy or efficient process to use, as you have to wait for the program to complete, then create new code or make adjustments, before starting a program again. A much nicer way to work, is to have a good program, that you know will produce a part of the required dimensions.

So how do we create a model that can be toolpathed to give exactly the required result?

This is where the fun stuff starts. In Inventor, when you specify a value for a parameter, you can click the little arrow to the right side of the input box and select “Tolerance.” This will bring up a dialog that allows you to add tolerance information to the parameter.

Inventor Tolerance SettingsThe tolerance settings for an Inventor Parameter

By changing the “Evaluated Size” you can change where in the tolerance range, the actual model sits. You have 4 options, shown below.

Inventor Tolerance DialogThe tolerance dialog – What the various options do

So you can have the model represent either the maximum material condition, minimum material condition, nominal size, or half way between upper and lower limits. This gives a great deal of flexibility for use in the CAM environment (Inventor HSM), but also for visualising the fits, which I’ll show in more detail below.

When creating the CAM program, the software uses the actual geometry of the solid, to calculate the toolpaths. If you model it at the nominal diameter, then the CNC machine will machine it to close to the nominal diameter. I say close because all machines have some degree of error.

If however, you pick a tolerance that is at least twice the known potential machine error, then by selecting the “Median” value for the “Evaluated Size” option in the tolerance box, your finished part should end up within tolerance, because the toolpath will be calculated on the median value.

To illustrate what I mean, have a look at shaft diameter in the model, with each of the “Evaluated Size” settings selected:

Options to give maximum material conditionUpper Limit (Click to zoom) Options to give median material conditionMedian (Click to zoom) Options to give Minimum Material ConditionLower Limit (Click to zoom)

Proving it out

To prove it out, I created the following turning toolpath in HSM, with the “Evaluated Size” option in the model set to “Lower Limit.”

Turning Toolpath

I then posted the code and inspected the X-axis coordinate of the final cutting pass (i.e. the finished diameter.)

G-Code Example

I hope this has given you some ideas for utilising the Inventor tolerance capabilities in a machining context. I think it’s a really neat way to keep the manufacturing information inside the CAD model, and helps to create a richer digital representation of the component that is being manufactured.

Until next time…

The more things change, the more they stay the same?

Just before I went on vacation Jonathan Landeros (Inventor Tales) posted a great article about old technology vs. new technology – how new doesn’t always mean better. It should really be about picking the right tool for the job. On my vacation the family and I went away for 7-days to Prince Albert National Park (Waskesui) and I left my computer(s) at home. I still had my phone, so I wasn’t completely disconnected, but with no laptop at my disposal it left me lots of time to think and contemplate things.

What I ended up thinking the most about was my day job and the current technology at use. What I mean from this is that we are not adopting new technology and processes, we’re not even evaluating or considering most of them. Why is that? and is this ok? I also though about the current “rut” that I was starting to feel, from a technology standpoint. Which is odd as I never have considered myself bleeding edge, but I’ve always felt that I’ve had a good handle of what was going on….. but now? I’m starting to feel left behind.


So what “new” technologies am I thinking about? The Cloud [social, mobile, analytic, big data], Robotics / AI / Drones, Electric Power, 3D Printing / Additive Manufacturing, New Materials, IoT (Internet of Things), Easier more integrated access to CAD / CAM / FEA / Visualization, and the the blurring of lines between BOM / PDM / PLM / ERP / MRP / CRM / add acronym here. There is also generative design and many other unbelievable things happening.

There is also the change in how business is being done… crowd sourcing, crowd design, open source new-shoring, …. and the blurring of what’s public and what’s private. What does Intellectual Property (IP) really even mean anymore?

Change happens, and hopefully when it happens its a good thing. At my day job what really changed things for us was the acquisition of an electrical vehicle manufacturer. This has made us look at how we do things differently, and how we can approve. The status quo is no longer the status quo, which is good as one never wants to become stagnant. The new mine being built in the province has mandated 80% electric use for machinery and equipment, with a clear goal to exceed this. What an opportunity for us!

As you can see I was thinking about a lot! But also note that not everything is new, some items have been around for years but are just now becoming mainstream.


I’m going to embark on a series of posts exploring each of these trends and the new technology. I am far from the expert which I think makes it great as there will be plenty of opportunity for feedback. What has worked? What are you looking at? How are you approaching it? I want to explore how to approach the new technology from an individual personal and professional aspect as well as why companies may or may not look at the new tech.

For this series we’ll use an example company “ACME Mining Equipment”, that I’ve made up, but I don’t think is that dissimilar to a lot of small to medium companies. Here’s their profile:

ACME Mining Equipment is a  company that primarily manufactures, repairs, and services underground mining equipment. The company started as a custom machine / fab shop over 35-years ago. They have one facility and around 150 employees. They have a very small, but very loyal customer base, many whom we’ve done business with for over 35-years. ACME (or AME) is classified as a small, engineered-to-order, manufacturer (at least as far as ERP companies classify things) as they customize just about everything that goes out the door to meet their customers requirements. The customization is what separates ACME from their bigger competition that just pushes “boxes” out the door.

  • ACME is an Autodesk shop – through-and-through – they use Inventor, AutoCAD Electrical, AutoCAD Mechanical, Vault Professional, Simulation Mechanical, and even have a few seats of PLM 360 floating about.
  • They make things from purchased items and steel (laser / plasma cut profiles & standard structural shapes). Welded or bolted together
  • Although they have some CNC capabilities, most of the programming is done by hand on their NC machines (for various reasons – I’ll explain more later)
  • Communication with the customer is done mainly via the phone and email. Outside of quotes, sales order confirmations, and manuals very little other types of documentation are exchanged.

Keep watching the site!

All imagery from GRATISOGRAPHY

DMLS: 3 Reasons Why You Should Jump in Now

Recently, we discussed the history and processes associated with Direct Metal Laser Sintering. Maturity in the technology of 3D printed metal, and Carl Dekard’s SLS patent expiration have spurred a new surge of research. I want to point out 3 reasons why you should get involved with this technology now…or really soon:

  • The Materials
  • The Innovation
  • The Ground Floor Opportunity

EOS Sintered Part in Metal Powder Residue

Stainless steel powder residue being removed from EOS DMLS “3D Printed” part (Courtesy of Solid Concepts).

Reason 1: The Materials

In the last 8 years I have witnessed the expansion of materials being offered by SLS machine vendors. The following is the list of metals that EOS machines are prepared to use commercially:

  • Aluminum AlSi10Mg – Light weight
  • CobaltChrome MP1 & SP2 – High heat and Strength
  • MaragingSteel MS1 – Hardness
  • NickelAlloy HX – High heat and strength
  • NickelAlloy IN625 & In718 (Inconel) – Moderately high strength and heat
  • StainlessSteel GP1 & PH1 – Corrosion resistant steel applications
  • Titanium Ti64 & Ti64ELI – High strength and light weight

These materials are robust and in some cases can take temperatures as high as 1200 °C. EOS’ thinner powder application has increased sintered densities to ~100% in almost all cases.

A materials comparison chart is available in our Engineering Notes section for your benefit, sourced directly from EOS and Solid Concepts.

Morris Technologies Swirler Printed from SLM

Morris Technologies’ combustor swirler (Courtesy of EOS GmbH)

Reason 2: Innovation

General Electric and NASA are spending a lot of money and time innovating the additive metal processes including DMLS, and how ‘3D printed’ parts can be used. GE made a brilliant move by acquiring not only the DMLS and EBM technologies in 2012, but also by purchasing Morris Technologies, one of the most experienced service providers.

“Our ability to develop state of the art manufacturing processes for emerging materials and complex design geometry is critical to our future”

Said Colleen Athans, vice president and general manager of the Supply Chain Division at GE Aviation in a press release.

To further reinforce the point about the fitness of the additive manufacturing of metals, I offer this statement, taken from one of GE’s Leap program announcements:

“Fuel nozzles additively manufactured from direct metal laser melting are 5X stronger that previous nozzles with 5X fewer brazes and welds”. Applications such as these will push engineers and manufacturers to be competitive by either developing better alternatives, or jumping headlong into additive manufacturing.

GE SLM Printed Fuel Nozzle

General Electric’s DMLS printed fuel nozzle (courtesy of GE)

Competition Breeds Innovation and Cost Reduction

Expanding adoption of this technology is spurring materials and machine technology improvements. The choice is becoming which tool fits my needs better instead of which tool is cheaper.

My discussions with Solid Concepts indicated that cost was tied to production speed, rather than mass. The cost of a 400 – 1000 Watt laser running adds up. Morris Technologies provided a comparison of DMLS and EBM wherein they compared EOS’ M270 and M280 DMLS machines with Arcam’s A2 EBM machine, and the run-time cost relationships thereof:

  • EBM and DMLS appear to be mostly tied to run-time
  • Newer A2 and M280 machine runtimes and costs were almost identical
  • Older M 270 was 2X slower at almost 2X cost.

Morris Tech’s paper is being mirrored on D&M Engineering Notes, as website is gone.

Additive Manufacturing Providers

The following list was compiled during my web based research, as well as discussions with vendors and service providers; it is by no means complete or exhaustive.

Machine Manufacturers

DMLS – Hands down EOS GmbH.

EBM – Arcam is the provider (and to the extent of my knowledge the originator) of the EBM technology. They hold multiple global patents on the process.

SLM – SLM Solutions is the lead dog in this industry, and seems to have been the initiator of the manufacturing solutions in this process.

Experienced Providers

Solid Concepts, a Stratasys company in Texas – SLS, DMLS, machining, molds, and more.

Their experience and assistance with information relating to the DMLS materials and high temperature applications was invaluable and is referenced in this article. Kent Firestone, a former project manager at DTM is the company’s Vice-President of Additive Manufacturing.

Solid Concepts 3D Printed Metal 1911 Gun Components

Solid Concepts manufactures world’s first functional ‘printed’ steel 1911 .45 caliber handgun.

Morris Technologies in Ohio – SLS, DMLS, & EBM

Note: Morris Technologies may be out of commercial business after the GE purchase

Directed MFG in Texas – SLS & DMLS

TurboCAM Aero in New Hampshire – DMLS and just about everything!

New Blood

After the recent expiration of the SLS patent in January of this year, various DMLS start-ups and initiatives have begun. People are bringing new ideas together to reduce the size and expense of the DMLS process, and bring the technology to the forefront and make it more accessible.

Reason 3: Ground Floor Opportunity

One of my favorite speakers, Simon Sinek discussed the “Law of Diffusion of Innovation”, where he noted “the early majority will not try something until someone has tried it first”; we all get that. If you listened to that discussion, you know he went on to define the gap that lies between those ‘early adopters’ that want to be on the cutting edge, and the ‘early majority’.

We stand in that gap right now.

The ‘Innovators’, people like Carl Deckard and companies like EOS, have laid the additive manufacturing of metal ground work. The ‘Early Adopters’, such as Morris Technologies and GE, have paved the way to successful adoption of the technologies.

Now it’s your turn.

Innovation and cost stabilization will increase alongside adoption. As the technology advances, new thoughts and applied sciences will evolve better processes, far beyond DMLS. The main factor driving adoption at this time will be light-weighting of components due to previously impossible part geometries. DMLS (and other additive processes) will be the way to go. Those companies that become entrenched (and more importantly, experienced) now will be the ones that engineers will turn to for expertise in the upcoming years.

As you move to invest in this process, whether as an end consumer of components or a service provider, it would be wise to develop a good relationship with a DMLS provider experienced in developing applications for your industry. Consider their advice before completing your designs or buying equipment, it will help you avoid many pitfalls and save you a lot of heartache.

Note: Beware of which machines a company is using. If they are using older machines, your bill might look similar to having a taxi driver taking the long way to your destination.

My Closing Thoughts

We believe that successes in design and manufacturing are provided through passion and imagination. Additive manufacturing is the next step in the evolution of metals manufacturing, and a very powerful one at that.

D&M Early Concept Combustor

Our R&D turbine and combustor’s upper target temperature is >1000 °C. DMLS’ high temperature Inconel and Cobalt have been essential in making the design possible, by providing a realistic safety margin as we work through the fluid dynamics involved in reducing those wall temperatures. (Early prototype of combustor at right is an example where additive manufacturing is the only method of production)

We can build components far closer to ideal design parameters than was ever possible before; and at reduced scales that are impossible to mill and turn. The other really cool and truly inspiring part of the equation, is so many components that needed to be manufactured separately and assembled, can now be ‘printed’ as a single unit. Cooling channels and fuel systems can be integrated in truly creative ways.

DMLS, SLS, EMB, and SLM are only the beginning. Now that certain patents have expired, we should see some incredible advancements in cost reduction and new ways to build safer, lighter, and cheaper components… without the waste we associate with manufacturing in the past.

If you want to be on the cutting edge of component engineering, and are looking for the opportunity, here’s your sign.

Pacific Thunder 2012 gets jump start at Osan

(Courtesy of SSgt. Sara Csurilla)


Eos GmbH and Solid Concepts have been quite helpful in numerous areas of my DMLS research. I want to extend this as a personal note of appreciation to their respective companies, and all the resources that they provided, as well as their research and professionalism in the field of metals manufacturing technology.

Additional sources include:

Carl Deckard’s key SLS patent

Arcam Electron Beam Melting website

Renger’s (Morris Tech) EBM vs. DMLS comparison pdf

University of Texas at Austin article “Selective Laser Sintering, Birth of an Industry”

Selective Laser Melting on Wikipedia article “Direct Additive Fabrication of Metal Parts and Injection Molds”

General Electric acquisition of Morris technologies news release

3D Printing Industry ( “Many 3D Printing Patents Are Expiring Soon: Here’s A Round Up & Overview of Them

Tyre kicking SOLIDWORKS Model Based Definition

With the release of Solidworks 2015, Dassault Systèmes threw in a little gem, a new product offering focusing on 3D documentation and annotation called Solidworks Model-Based Definition, or Solidworks MBD for short. Here’s the official blurb…

“SOLIDWORKS MBD is a completely new product with powerful new tools found in SOLIDWORKS 2015.  MBD provides an integrated, drawing-less manufacturing solution for SOLIDWORKS 2015.  With these tools, you can define, organize, and publish 3D Product Manufacturing Information (PMI) and 3D model data in industry standard file formats.”

“SOLIDWORKS MBD defines 3D PMI such as dimensions, datums, geometric tolerances, surface finishes, welding symbols, bills of material (BOM), callouts, tables, notes, meta-properties, and other annotations within the SOLIDWORKS 3D environment. The process is both intuitive and interactive and helps multiple people within the supply chain understand the design without the need for 2D drawings.”

Solidworks MBD Screen Shot

Image from

The Paperless Office

When I was going through tech school in the mid 90’s we were witnessing the phasing out of pen plotters and digitizers along with the introduction of mid-level 3D modeling software like Solidworks, Mechanical Desktop, and the kickass 3D animation behemoth known as 3DS Max…. all on the Windows operating system, if you could believe it! The talk, not only by my instructors, but in the industry as a whole, was of the “paperless” office… no printing, no paper, no stale drawings on the shop floor, terminals everywhere, and the machine operators viewing, using, and marking up the drawings right from their mills and lathes. Sounds great right? Fast forward 20 years and although a small percentage have reached the paperless office, the majority in the manufacturing realm are still pumping out paper drawings at a feverish pitch, probably resulting in more paper now than 20-years ago.

The concept of documenting and detailing the 3D model is not a new concept. The idea is to forgo 2D drawings and replace them with the 3D model containing all the dimensions and annotations required to manufacture the component. I remember seeing this demoed in the late 90’s (I don’t remember by who though), it showed very well, it got people excited, but it was much too soon for its time. Fast-forward to 2012-2013 and Autodesk played with the idea with their 3DA add-in for Inventor (was available on Autodesk Labs). Autodesk was excited but found a collective “meh” from the intended audience based on the feature set presented to them. Noone really jumped up and down with excitement, Autodesk didn’t get the warm and fuzzies, so as far as I can tell its a dead Autodesk development (for now).

Now comes Solidworks MBD, which focuses on electronically delivering product and manufacturing information (PMI) in 3D, using the 3D Model Based Definition (MBD) and other metadata to no longer use 2D drawing views and paper-based drawings…. “drawing-less manufacturing

What is PMI?

Product and manufacturing information (PMI) is the act of creating all required manufacturing information and annotation on the 3D CAD model. This information is then used down-stream in processes like CAM, but also for viewing by other non-CAD people and departments without requiring access to the originating CAD system (hence drawing-less). What’s important with PMI? Its not just the model with some dimensions. The 3D views contain geometric dimensions & tolerances (GD&T), 3D annotations (like text and leaders), Surface Finish, and meta data (BOM, material, volume, mass, etc).

Why are we not all doing this?

Bataan Amphibious Ready Group, 2014 Deployment

Image courtesy of U.S. Naval Forces Central Command/U.S. Fifth Fleet via Flickr

Why isn’t PMI widely accepted? There are many reasons why people continue to print drawings on paper and many who claim they will hold those paper drawings until the day they die. Some of this reasoning I’ve experienced at work, many I’ve seen first hand during my days as an Autodesk reseller. Here are the challenges many face when trying to implement PMI or will face with Solidworks MBD.

CHALLENGE #1 – The Older Generation.

There is still a generation of machinist, welders, fabricators, and so on that are just not comfortable with a computer and would succumb to shear panic if forced to use one, as opposed to a paper drawing. These are the people whom read the newspaper every morning (not digitally), who read paper books, and have a flip phone from 1995. There is nothing wrong with this, its just what they know. They are extremely good at their jobs, its just a huge leap for them to remove the paper and go digital. Along with this mentality are the people who claim you can’t properly review a document on a computer screen, that it must be printed to properly read and understand.

CHALLENGE #2 – infrastructure.

Manufacturing plants and shop floors are plagued with older computers (DOS, Windows 95, etc) or no computers at all. In some cases its just because nothing else was required, in some cases its what’s required to communicate with the existing equipment. Other infrastructure issues include zero or limited network connectivity and no WiFi. If there isn’t a computer (or smart device) connected to the network, its difficult to see something. Also many manufacturing areas are not always clean; its not always easy (or convenient) to protect a monitor from flying weld splatter.

CHALLENGE #3 – Vendors & Suppliers.

Paper is universal, so are PDF’s of Drawings and DXF is almost universal. Distributing PMI style information to outside sources can prove difficult. Do they have the right software? are they capable of using it? Can they easily integrate the information into their lasers, plasmas, and other equipment? This is a struggle for many organizations, not just with sharing PMI, but 3D CAD data in general.

CHALLENGE #4 – Customers demand specific deliverables.

What if the deliverable is AutoCAD drawings? Solidworks or Inventor solid models and drawings? The customer is always right, right?

CHALLENGE #5 – Signed Contract Documents.

There are still many situations where a physically signed drawing is a requirement for a contract, very difficult to achieve with PMI.

CHALLENGE #6 – Historical Copies.

Will we still be able to access our PMI models in 30-years? What if Dassault goes out of business? What if Solidworks MBD does not gain traction and they drop it? What if the internet is a fad? What if Terminator or the Matrix becomes reality?  There is much doubt, not just about  maintaining the electronic data, let alone how will it be accessed in 30+ years. I was once at a shop where they showed me a paper drawing from the 1920’s which they pulled out of archives, to manufacture as per there customer’s request. They had not manufactured this component in over 70 years!

What makes Solidworks MBD different?

I’ve only seen Solidworks MBD on YouTube, and it looks slick, very well thought out… but doesn’t everything new? Why would Dassault introduce this when no one has succeeded before?

I think Dassault is playing a hunch here. The industry is changing… quickly, and they want to be out in front. 3D Printing, social-media inspired design & collaboration, the internet of things are all being thrust to the forefront. This is not your father’s or grandfather’s manufacturing anymore. With Solidworks MBD its a bit of “if you build it, they will come“. Provide the tools and let people take it and run with it.

With Solidworks MBD they answer many of the challenges listed above.

  • Solidworks MBD supports industry standards Military-Standard-31000A, ASME Y14.41, ISO 16792, and DIN ISO 16792. Maintain the MBD at the same level of standard you do your 2D Drawings.
  • They chose to support  many viewable file formats, but the key ones being their own widely used and accepted eDrawings format, as well as the defacto standard for sharing information PDF. Especially with 3D PDF’s, who doesn’t already have Adobe Acrobat installed?
  • Its easy to use.
  • The final deliverable looks good.

Will it be enough?

In Conclusion (for now)

We are working to get our hands on it, to try it out for ourselves. Once we do I’ll post a follow up to this article, where I will actually review the product.

For now, take a look at your own organization, could you implement Solidworks MBD and remove paper drawings? If not, let us know why by posting a comment. If you are already using a form of PMI post a comment and let us know what.

Ft. Walton Machining: Company Profile

Ft. Walton Machining – a company profile

I had the opportunity a few years ago to visit Ft. Walton Machining and to meet its owner, Mr. Tim McDonald Sr., a great business man with some amazing toys: One amazing machine facility, and one really cool WWII-era T-6 Texan training aircraft. Unfortunately I didn’t get the opportunity to spend more time with him before his passing in 2010.

I decided to return to Ft. Walton Machining, for a better look at the equipment and teamwork that makes company so successful. It really is an amazing company and has built an incredible reputation that has landed them some of the best contracts in multiple industries. Timothy McDonald Jr., runs the operations center, and agreed to see me and show me around.

Ft Walton Machining Front View

General Profile

Ft. Walton Machining was founded by Mr. McDonald in 1997. Since then it has been housed at 2 locations, and has increased from 35 employees to more than 210 team members at this time. The company houses more than 50 machine spindles, including fifteen 5-axis milling stations. They supply major corporations regularly with various components, including names such as Boeing, Gulfstream, Locheed-Martin, NASA, various military units, oil production companies, and more. The most exciting contract that I was permitted to mention was that Ft. Walton Machining is the largest supplier of F-35 airframe components in the world. Awesome!

The 65,000 SF Manufacturing facility is divided by process as follows:

  • CNC Milling
  • CNC Lathe
  • Electrical Discharge Machining (EDM)
  • Engineering
  • Fabrication
  • Finishing
  • Lean Manufacturing
  • Quality Assurance
  • Waterjet
  • Welding

One thing I learned since my last visit was that the company has purchased another facility in order to expand its materials finishing division. Now that location handles 100% of the finishing, giving more room to the machining facility, and streamlining their overall process.

The 42,000 SF Material Finishing Division facility is composed of process divisions as follows:

  • Anodizing
  • Assemblies
  • Chem-Film
  • Passivation
  • Prime & Paint
  • NonDestructive Testing (NDT)

This new addition includes a conveyor drying paint line, a gas curing oven, paint booths, and a PLC controlled custom chemical finishing line.

Manufacturing Walk Through

After I hefted out from under the enormous non-disclosure agreement the company’s kind receptionist ‘encouraged’ me to sign, I was issued a guest pass, and reacquainted with Timothy McDonald, Jr., who took the time to chat with me about this article, and to furnish some background on the company that I didn’t know. McDonald is the Program Manager, as well as the company’s Secretary/Treasurer.

It is difficult to get a grasp of the scope of the facility without a map; it’s huge. It’s not to the magnitude of say the Lockheed facility in Marietta, with cars on roads with named streets inside the oversized building, but you could spend a week at Ft. Walton Machining trying to figure out where everything is. A fun question to ask is, “what’s beyond that wall over there?”  The answer was usually “more!”

Immediately I happened upon these beautiful oil well drill drive shafts. 4’ long and 8” in diameter, with the finest looking bearing journals. I asked about the processes involved and was surprised to find that while the entire part was turned, the journals were not ground. McDonald went on to explain that they are roller burnished, using a peening-like process that rolls the journals into submission under great pressure [30,000 psi], delivering superior bearing strength and trueness. McDonald noted “As you can image, being a mile down a hole, the components will experience a great deal of vibration. That ultimately converts into fatigue stress and cracks, and this process extends the life of these shafts significantly.” I was however not permitted to take one home. That’s my kind of art!

Ft Walton Machining Oil Well Drill Shafts

The precision on the drill shaft turning and burnishing is held to 0.0005 in.

McDonald continued “If something goes wrong down in that hole, it costs $4 million an hour to pull that drill. That’s when feelings start to really get hurt, so you have to make sure your product is spot-on correct.”

As we moved, what I could observe was numerous aircraft parts including flight critical components for C-17’s aircraft and CH-47 helicopters. I was escorted through all the departments and given time to chat with the team members. We discussed everything from manufacturing processes to strategies, most of which could not be mentioned in this article. One topic that was approved was the oil drilling components, which turned out to be really interesting as well. The team explained, in detail, the ingenious strategies used in oil well drilling, as well as the processes used to manufacturing these tools. It was pretty awesome.

I found a dedicated team of individuals that know their machinery and products. When engaged about different approaches to specific components and techniques, everyone was eager to share their experiences and methods used to successfully get the components out the door. Everything from their adoption of High-Speed Machining to advanced materials was discussed; where things worked and where they didn’t. When I’d ask about the tolerances of a component feature, the technician’s would stop to explain what these were, and various strategies that paid off in maintaining them.

Ft Walton Machining Haas CNC Mill  Ft Walton Machining Milling

The two silver boring bars in the turret are 2 in. solid carbide DeVi bars. These are tuned to bore chatter free at extended depths. I just priced them out at over $2000 USD each, plus inserts. Pricey; I’ve never used one, but the industry swears by them. “We had Iscar make us a 4 in. slam drill that will chew metal like you would not believe. It took us 4 months to get it. It will pop a 4 in. hole, 5 in. deep in about 5 minutes. That’s a massive insert.” McDonald said. The technician pulled the turret down for me to inspect. “The savings were instantaneous.”

Ft Walton Machining Iscar Drill on Lathe

Ft Walton Machining CNC Water-Jet  Ft Walton Machining Inspection

While discussing the merits and problems with waterjet, McDonald mentions, “we used it once to cut 8 in.-thick titanium. We called the manufacturer and asked how it could be done. They said you couldn’t do it; that presented a challenge. It took 28 hours, but when talking titanium at 80 bucks a pound, it was worth it in the end.”

I was able to inspect some beautifully crafted components. High precision, small components and very large scale multi-process assemblies. Unfortunately I was only permitted to show a small sample for the sake of security.

Ft Walton Machining Multiple Processes

This Navy ship exhaust duct was one component that was extremely tedious to manufacture. The processes involved include sheet metal fabrication, water jet, welding, and finish machining. The mating flange surfaces have to be flat within 0.005 in. The team welds the processed components first, and then after substantial blocking, the custom jigs are removed, and the flanges are surface milled within tolerance.

Another really nifty gizmo was the Iscar Matrix tool vending machine. Sounds funny, right. Instead of Twinkies, this cool cabinet dispenses inserts. The team members enter their employee password, and then scan the scan bar on the job order. The Matrix is tied in with the ERP system, and after the scan is made and the insert is selected, the cost of the insert is automatically applied to the project for cost analyses. The vending machine then unlocks and opens the appropriate drawer. “It’s like a giant Pez dispenser”, one technician said. McDonald added “When the last insert is removed, an email is sent to the tool crib notifying them that the drawer needs to be restocked. We never run out of inserts this way. These are used throughout the industry in various ways, we use them for inserts… and subsequently the occurrences of having ‘missing’ cutters has dropped dramatically.”

Ft Walton Machining Medical Parts  Ft Walton Machining Medical More Parts

McDonald escorted me through every area of the shop. As we passed by their Blue Streak department, I pointed to the sign and asked about it. He told me that department is comprised of machines that are ready to work with low volume to handle their client’s emergency needs. This way when a problem arises, they don’t have to shut down an operation to accommodate the need.

As we were wrapping up the tour, Glenn Larson, Ft. Walton Machining’s software guru caught up with us and we began discussing some CAM issues and strategies in parts as McDonald took us by components and tooling. We looked at their R&D changes to the AccuView contact lens palettes (my wife wears those!), and the intricate detail required to accomplish their needs.  Moving along we passed by a FARO portable CMM unit and the discussion turned to inspections, and how they use it when they can’t check the parts in the QA Lab. They mentioned that a laser scanner can be attached to the unit and McDonald added “We are quite interested in light scanning, it’s the next wave and the direction we are going”.

I wanted to give their Haimer Power Clamp a try. The unit heat expands the milling collets in order to fit the tooling inside, and then cools the collets back down which clamps the tolling down tight. No screws, no clamps. McDonald said it absolutely kills the runout associated with collets. They showed me one application where they needed a small diameter tool in this arrangement. They had a tool, heat shrunk into a collet, heat shrunk into another, and into another.

After making it to the QA lab where all the components are inspected, the pair noted that the part being inspected had a variable radii developed in Autodesk Inventor with some special love from Glenn Larson’s team added in. McDonald noted, “Once we’re done welding, we verify the positions before adding that bottom fillet radii in the mill. The top surface has a 0.002 in. tolerance and is a bit tight to hold throughout on a mill. What we’re going to do is make a special arbor on the lathe; we’ll mount two of them to it to counterbalance, and turn the top profile. This part is very complex in the sequencing we had to go through, but I’m happy with it thus far.” The two were confident [if not a wee bit squeamish], as they reflected on the prospects of the final surface turning process. That’s a lot of time and money invested in a process that only gets more difficult and precise. By the time of this article, they should have completed that process. I’d love to hear how it went.

One thing I found odd but didn’t inquire about was that the company doesn’t do any plasma spray buildups. They outsource the process to favored companies when needed.

My thoughts

I always enjoy hearing about the progress of this company ever since I first met them and toured the facility years ago. Their continued expansion and successes have stemmed from staying on top of the technology, knowing the trade, thinking far beyond the norm, and building exceptional relationships. I never think twice about referring companies to them to handle any component manufacturing needs.

It’s an awesome team and facility, and I’m going back as soon as they get over my excitement during this past visit.

Check back in soon for the follow-up interview article with Tim McDonald and Glenn Larson, and their discussion about the company’s successful transition to CATIA.

What Makes A Maker?

The “Maker Movement,” I’m sure you’ve all heard of it, but what exactly is it? I don’t know if there’s actually an official definition, but I think of it as the tinkerers and hobbyists of the past, with access to a whole lot more knowledge and technology thanks to the internet. Now even this is a very broad definition, but I guess you could split it up again into a couple of big categories. Those that make for themselves, and those that make for, or with others.

Maker Faire Image - Pixel ArtCredit: Scott Beale / Laughing Squid

It has always blown me away at just how many people are happy to selflessly contribute a huge proportion of their free time to sharing things they’ve learnt with others, for free, using the internet. I consider myself to fit into the “maker” persona, but I often feel the guilt of just how lazy I am when it comes to sharing my knowledge with others. I owe a lot of what I know, to the internet and the people who contribute their knowledge, but yet I give so little back. I made a conscious decision earlier this year, to try to rectify that, and that’s when I started writing articles for Design and Motion. My wife and I live a pretty busy lifestyle, so while the fortnightly posts can occasionally become a bit of a chore, the sense of satisfaction I get when I finally hit the “publish” button is a magical thing. Kind of like that one shot you hit in your last terrible round of golf, which felt so good that you know you’ll be back to play again. This to me, is the essence of what fuels the maker community. People get satisfaction from sharing what they have made with others.

Now there is a dilemma that often arises here, when you want to move from making for fun, to making for money. Many have battled with the balance of how much to give away, versus what they should protect and sell. Creative Commons and the open-source movement had, and still has many scratching their heads, wondering how on earth a business can give something away for nothing, and still make money.

One topic that I often think about, is the future of makers. If we go back in history, humans went from being fairly self-sufficient makers, to fairly dependent non-makers. We outsourced our making to mass-production. If the futurists of today are correct in their predictions, self-making on a massive scale will return to the mainstream and the industrial revolution will effectively be reversed at some point. So my question is this:

What should traditional manufacturers do, to future-proof their businesses?

I don’t have an answer for this, so I thought I’d put it to the maker community from Autodesk, along with some of my other questions.

When I was a student, my visions of my future self always placed me in someone else’s company, designing things to be made for someone else. It turned out, that I have ended up spending a fair chunk of my career so far in self-employment. I often wonder how things would be different if I had focused my energy as a student, on working towards being my own boss. The reason I say this, is with today’s channels for dissemination of information and knowledge, along with incredible accessibility to technology (you can buy just about anything online), small scale manufacturing for a large market is a very real option to make a living. The internet allows people that have “the knack” to learn more about anything they want to, purchase just about anything they need, and sell their ideas, products or services to a potentially huge number of people.

So another question:

What should we be doing to equip today’s students, to go down the path of being a maker, regardless of what sort of scale it ends up being on?

I believe that teaching students to digest and assess information critically, regardless of source, is just as important as sharing knowledge of particular topics. Ask just about any ex-student how much of what they learned in their studies, they actually use in their jobs. Most will say very little. Now don’t get me wrong, I believe that all knowledge is valuable, whether you use it or not. With increasing variety and specialization though, the most valuable skills are being able to learn new things quickly, whilst maintaining rational thought and critical reasoning.

I spoke above, about the satisfaction that can be gained from sharing knowledge with others, which comes naturally for many makers who are proud to show off their creations. The other big maker satisfaction though, is simply just the satisfaction in creating something. Typically, when making something for one’s self, the end result is often a prototype of sorts. Something which was made with the materials that were readily available, using methods that were not necessarily very efficient, but which got the job done eventually. Even though the end result was not arrived at in the most efficient way possible, the satisfaction was still gained. When moving from making for one’s self, to making for others, efficiency quickly moves to the forefront. In my experience, a lot of tinkerer types don’t have a natural ability to find efficiency, or a desire to replicate their making in any kind of volume. Bear with me here, I do have a point, and I’ll get to it eventually.

A few years ago, I was discussing entrepreneurship with my uncle in a broad sense, and various examples of companies came up. We discussed how they differed and what we liked and disliked about each. He told me of a theory he had about a formula for a successful business. He mentioned “the 3 guys (or girls)” that need to be involved. Here they are:

“Ideas Guy”

Ideas Guy never settles for status quo, he is always finding better ways to do things, and constantly frustrating his friends with his practical solutions to everything. “How has no one thought of that before!?” is a common statement from his friends. While he is always asking why something can’t be done a better way, he doesn’t often know exactly his solution will be achieved.

The Ideas GuyThe Ideas Guy (Credit: Sebastiaan ter Burg)

“The Geek”

The Geek is a detail guy. He agonises over technicalities and details and is sometimes mistakenly perceived to be negative or a party pooper, by finding technical problems with proposed solutions. Having said that, he’ll expend a huge amount of energy overcoming the challenges to make an idea work.

“The Other Guy”

The other guy is a very flexible persona who can sell sand to a Saharan, but also has a good feel for legal matters.

Now obviously this is a rather flexible arrangement that could have different numbers or types of people with different strengths. The key however, is that to commercialize a product, you really need a team.

So how do you go about finding this team?

Makers are an interesting bunch, some of them manage to play both the Ideas Guy and The Geek. These guys are off to a head start and often manage to get themselves started using a crowd-funding platform like kickstarter or Indiegogo to get their product off the ground.

For others, they may naturally have the team in a group of people they know, and can quickly get to work turning their elegant solution for a problem they had, into a solution for others who are willing to pay for it, in similar ways.

The vast majority however, are the lonely makers, who make for themselves, quietly share their knowledge/recipes/instructions fairly inconspicuously through blogs and forums, and only dream of one day being able to sell their product. It’s this group that I believe we need to help the most, as students, to find their team.

This brings me onto an idea that I had which would somehow combine the various aspects of commercialization of an idea. We already have great resources for makers, in a number of areas:


You can learn about just about anything online. Whether you’re browsing a maker website like Instructables to learn how to replicate someone else’s idea, or studying towards a degree in a classical subject like physics through an online university, there is no shortage of knowledge that is accessible for free. logoInstructables – a website dedicated to makers


Autodesk are blazing trails when it comes to giving away design software for free, to allow anyone to explore their ideas in an almost limitless number of ways. While all Autodesk software is available to students at no charge, others are even free to anyone. Products like Fusion360 (free for enthusiasts), let people create 3D digital models of their ideas, simulate them, and even run machine tools to create the physical end result. GrabCAD is another company that has provided an amazing free platform, which allows people to share their digital models with others. Why design a certain sub-component yourself, if someone else has done it for you?


If you can’t get access to machines to bring your ideas to life, why not build a machine yourself? Many websites have are dedicated to open-source designs for machines which can be used to make just about anything. Components for making things are also readily available through a huge number of maker-focused websites. An example of this is BuildYourCNC.


Turning prototypes into saleable products requires money, and borrowed money for unproven ideas can be hard to come by through traditional channels. Online crowd-funding platforms like Indiegogo make fundraising for commercializing good ideas relatively easy. Potential customers effectively fund the development of products they like the idea of themselves.

So what’s missing?

“The Team” of course. While sites like allow companies to quickly find freelancers for contract work, I’m yet to see a site whose primary focus is in getting The “Ideas Guy”, “Geek”, and “Other Guy” together to commercialize a great idea. I’m not usually the Ideas Guy, but there’s my idea. Can someone please make it happen already….?

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