What Drives Machining Cost?

The Engineering Corner blog delivers perspectives from 35 Years of CNC Machine Expertise

“Save time and money with these simple machining tips”

The Design Process,

So, you have an application that requires a new design or possibly an existing design that needs to be revised.  This is the most critical stage of any components beginning; here is where you determine the material, tolerances, finishes, plating, marking and specific requirements that will ensure your innovative design is a success.  Over the years part features and expectations have grown in leaps and bounds; along with this so have the costs of machined parts.  At Tamshell we are trying to bring back some simple reminders to help keep costs down and production capabilities up.  Below we will try to break down each criterion which drives up the costs of machined components, whether the material is Plastic, Aluminum, Brass or Bronze; these simple reminders will ensure your components can be produced at feasible costs.

Please feel free to discuss any questions that you may have regarding the topics below.  Tamshell has an experienced staff available to assist you any phase of your project.   Aside from material recommendations, we can also help with manufacturing capabilities as well.  We look forward to hearing from you and hope that you find this information helpful.

Material Selection Process:

This is probably one of the most critical steps when looking to save costs on machined components.  Not only does the material itself account for most of the costs, it also controls what type of features can be designed into the component itself.  We see so many new designs where producing the component is not achievable due to the material itself of the features that are designed into the component.  So when choosing the correct material you need to consider the following:

  1. What is the most basic material that will work for my application? This is an important question because if you select an over-engineered polymer for your application, you have already driven up the costs.  You need to consider all physical properties to make sure that the material you choose will work.  Don’t just design on previous success stories.  Choosing Vespel, PEEK over a generic commercial grade material does not always work best; especially when it comes to saving costs.
  2. Will this material hold up to the tolerances and requirements that I am designing into the component? This question is often overlooked when designing a new component or switching from one material to another.  It is very important that you keep in mind the machinability factor of a material.  The best way of ensuring this is to work directly with Tamshell during this process.  We will ensure that each tolerance and feature is capable of being produced.  We will also ensure that the costs associated with this are kept to a minimum.
  3. Do I have the correct specification? So often in the plastics industry, the incorrect specification is given.  Always be specific when calling out a material specification, make sure that it is not a resin specification.  Make sure that the data you base your selection on is not resin data; look for finished shape data.  So often testing is not able to be performed in accordance with the specification being called out.  Also, don’t get caught with single-source suppliers of materials.  This will narrow your options down and make it impossible to double source materials.  This drives costs up as well as causes issues with supplying the material.
  4. Another costly mistake is calling out the wrong shape or form of material. So often we see “sheet” called out in a spec when the component being manufactured should be produced from the rod.  Yes, in some cases the physical properties of sheet vs. rod vs. tube may vary; just make sure that you consider the shape of the finished component so that half of the costs in producing the part are not due to wasted material or production time.

So, keep in mind that when deciding on a material for your application it is best to partner up with someone that can help you through the entire process.  At Tamshell we work directly with the manufactures of all materials and can ensure you that we will provide an unbeatable service from start to finish.

Tolerances:

This is definitely a topic that needs to be taken seriously.  As we mentioned above tolerance over the years have been getting tighter and tighter, just as much as the inspection equipment to check parts has been getting more and more precise.  Tight tolerances can drive the cost of a component up significantly either by the tolerance itself or by the material and tolerance together.  By this, we mean that if you choose to hold +/-.001 on Teflon; you are going to have to pay significantly more than; say machining it out of PEEK.  Each tolerance has to be considered when paired with each individual material.  Another cost driving factor is the difference in time it takes to machine a part with +/-.001 compared to holding +/-.0002.  Are the machines and tooling capable of producing these types of tolerance and dimensions? The answer is yes, however, the time it takes to produce these types of features is significantly different.  Not only in machine time but also in inspection time and method in which the dimensions are checked.  The simple rule of thumb is to make sure that tight tolerances are applied when needed and make sure that the material itself is capable of achieving this tolerance.  When at all possible stick with basic tolerance, or standard tolerance which is located in the basic tolerance block of the drawing.  Trust us, in the long run incorrectly tolerance drawings will cost you both time and money, not only in producing the parts but also internally with inspection issues.

When designing a new component or revising an existing application feel free to contact a specialist at Tamshell and see what type of costs saving ideas we can provide.

Finishes:

Finish requirements on machined components have become a big concern for OEM’s around the world.  The standard 32 – 63 RMS finish from years back seems to have fallen by the wayside.  Unfortunately, along with this came higher prices due to the tight finish requirements that we now see on machined parts drawings.  It is important to remember that the better the surface finish, generally the slower you need to manufacture parts.  Not only does the machining process slow down but inspection time also increases due to the methods that need to be used to inspect the parts.  At Tamshell we have some of the best quality equipment on the market that allows us to inspect tight tolerances and finishes; however, when designing a part keep in mind to only require what is needed to make the part function.  Sometimes a callout for a smooth surface finish does not always guarantee that the part will last longer or seat better.  Another huge factor when trying to save money is making sure to select a material that will allow the surface finish that you require to be produced.  Speak with someone at Tamshell regarding any surface finish questions that you may have.  We may be able to save you time and money when it comes down to selecting the right material as well as the correct surface finish for your application.

Marking Methods:

Please keep in mind that all marking methods or plating methods don’t work equally across the board.  Choosing the correct marking method for your finished component could save time and money.  A couple of the highest costs for marking are actually machining the marking on the component and engraving.  The reason these are so much more costly than other methods is that it takes time to program these features as well as actually producing the part with the marking.  Other options for marking may include laser marking, etching, ink marking and stamping.  These options tend to take less time and are much more affordable.

Broken Edges vs. Sharp Corners:

Technically speaking this is not a huge problem when machining parts.  However, depending on where the callout is on the component itself is going to be the determining factor in driving up the costs for the finished component.  It is important to remember that broken edges, chamfers or radiuses called out on both sides of a component may require secondary operations.  If possible try to determine if a simply broken edge performed by a deburring operation will do.   This will save time and money in the long run.  Also, when requiring sharp edges make sure you lay out the parameters in which the feature will be checked.  Often we find issues with inspection methods on sharp edges or burr free requirements.  Always consider the magnification level at which the parts must be checked as well as what equipment will be used.  This will reduce a number of rejections received from your suppliers which in the long run will save costs.

Tamshell can help with new applications in regard to machinability and cost saving ideas.  Please feel free to contact one of our experienced sales representatives directly.

Burr

Want vs Need:

What do I want versus what do I need?  This is often an issue that we all run into whether it be for design purposes or in our personal lives.   It’s simple, don’t overdesign something that in the long run will not be manufactured to your requirements.  At Tamshell we take pride in our quoting process and ensure that all requirements are addressed one by one.  We don’t just slap a price on a job and hope for the best; in the long run, this wastes time for you and us.  So, keep in mind every detail that gets placed on a drawing will be considered during the manufacturing process.

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