Data Checks

Detail Design

Sooner or later the conceptual work will lead to the need for detailed design drawings. Yes, still drawings in this world of 3D data, as not everything can be embedded in the 3D model! It is also the place that issues such as tolerances, material specifications and finishes can all be recorded.

How well a design works will need to draw on this information and particularly in the case of tolerances can be the difference between working and not working.

“Saving time” by not controlling this additional information usually results in delays and mistakes or worst case, assumptions being made.

As we have progressed from the days of paper drawings to the use of a single data set that holds the design information and is used directly for manufacture, so our reliance on the accuracy of this information has also increased.


The number of checks that used to exist in the progression to manufacture has decreased, whilst the consequences of the data being wrong have increased, compounded by the expectation of ever shorter timescales.

The old adage of “garbage in garbage out” still holds true, we can just do it faster!


The need for drawings
If you have spent hours, days or weeks building the CAD models for a new design, you will have thought about many issues that will confront whoever comes to put the design into manufacture. The drawing is the opportunity to capture and convey that information such that the manufacturer can understand your intent quickly.


What is therefore needed on the drawing?

  • material
  • surface coating/finish/texture
  • thread details
  • areas that should be free of ejector pin witnesses such as sealing faces
  • predicted gating locations
  • control dimensions
  • tolerances
  • specific packing requirements
  • and anything else deemed important or that could be cause for rejection.

Most of these are self explanatory, however a few are worth elaborating on


Control Drawings
Plunkett Associates works directly from the 3D cad model whether in a neutral format (STEP or IGES) or a native format from Solidworks. So when it comes to needing a dimension, the reference is the cad model and not the drawing. This becomes more important when dealing with mouldings due to draft, and it frequently not being clear on a drawing where the dimension point is taken from.

That acknowledged the cad model will not give a tolerance. Thus we work from the cad model plus a control drawing that does not seek to specify every dimension, in the way that would be necessary for manufacture, but just specifies and tolerances the critical features for the product to function. Everything else is under a blanket tolerance and controlled by the cad data.With the cad data taking precedence it is usual to see a note on the drawing to this effect.


Many cad packages will allow the modelling of threads, which in the case of 3D printing is just as well as the threads can be built in by the process avoiding the need to post tap. However, when it comes to machining, the thread is put in with a tap. What is required in the cad model is the tapping diameter and a call out for the thread type, pitch and depth. Modelling the correct tapping diameter is crucial as in many instances it will be incorporated early in manufacture with the thread form being applied later. Clearly the wrong diameter leads to a scrap part unless it can be inserted to salvage it.


Most applicable to mouldings where multiple textures can exist on a single part, it is important to define the applicable areas. Closely associated with this are “no go zones”, ie areas that must be free of ejector pin marks due to seals etc. Since this can define the whole way a part is tooled, it is critical information and needed early in the quoting process.

The most common texture is specified as a Vdi finish and relates to the roughness of an EDM’d surface post machining. The other end of the scale is a mirror polish, used on tooling when producing optically clear parts, or used to offer a contrast in moulding

Be the first to hear our latest news

  • Plunkett Associates worked on the design and production of titanium frames for an artificial heart valve where precision and consistency was paramount. Communications were efficient and productive with concepts readily incorporated into the final design, and suggestions for improvements all highly appropriate. The quality of the end product was ideal and I have no doubt that I will use the advice and expertise of Plunkett Associates again.
    David Wheatley, Wheatley Research Ltd
  • “Doing business with you has been an absolute pleasure. You have made my goals a reality. You have been patient, helpful and above all, responsive. Best service that I have experienced in ages. I consider Plunkett Associates to be an integral part of my business plan moving forward.”
    Jet Cooper, Sculptor
  • Thanks for the present that arrived this morning, as promised. Parts look first class, as always.
    Jon Todd, Design Manager, PHS Group
  • Plunketts developed a solution that met our precision requirements at a cost significantly lower than alternative manufacturing approaches we had investigated
    Nick Skaer, CEO, Orthox Ltd
  • Plunkett Associates have excellent breadth of experience, work with high quality partners and have a flexibility that we have found enables challenges to be met successfully, cost effectively and in a timely manner.
    Nick Skaer, CEO, Orthox Ltd
  • Interestingly, people who look at it in its own right with little knowledge of what it does, just like it! It’s tactile and it looks good…
    Tim Collings, Operations Director, Troika Systems Ltd
  • To create such a consistent quality finish in chrome was an amazing achievement and the prototypes really gave our stand the wow factor.
    James Clark, Group Commercial Director, The Airdri Group
  • I can’t recommend Tim and his team highly enough. We ended up with a design which can be produced and assembled quickly, efficiently and reliably, in volumes that make sense
    Simon Leggett, Director, Olivewood Technology
  • Kirintec were thrilled with Plunketts. They made a complex process simple and we were just amazed at the lead times achieved. Plus, every single deadline was met without any drama.
    Penny While, Marketing Director, Kirintec
  • Plunkett Associates truly offer a complete turnkey solution with Speed, Effectiveness and Precision.
    David Harden, Director, Enica Ltd
  • Thanks to Plunkett Associates flexible, bespoke and cost effective service I was able to produce the objects that I had originally had in mind.
    Simon Ryder, Artist
  • Plunkett Associates have a fantastic supply chain, work with all sorts of production processes and will always do their utmost to solve a problem.
    Naim Audio
  • We always know exactly what we’re getting and we know we won’t be let down on quality, price or lead times.
    Mark Williams, Research and Development Director, Johnson Safety Products
  • "With their simple to understand language, willingness to go the extra mile and approachability, Plunkett Associates were a great partner for our company. We couldn’t be happier with the results of our project. (A working prototype that they got right first time, by the way). Thank you!"
    Carolina Ballon-Forrester, Director, Kittyrama Ltd
  • “We use Plunkett Associates because we want someone we can trust, that knows what they’re talking about, has all the contacts, will provide reliable advice and feedback and will get the right result for us.”
    Jim Copestick. Design Manager, Thorlux Lighting
  • “Accuracy, finish and delivery all first class.”
    Andrew Peters, JMDA Ltd
  • “We were really surprised at how quickly they turned round such a high quality prototype and the parts certainly proved their worth. They were of high enough quality to provide a fantastic visual representation and to undergo rigorous testing."
    Stuart Wilson, Design Director, TRT Lighting
  • "Tim's experience, expertise and supplier base have been fundamental to us getting this project off the ground."
    Sam Pearce, Jelly Products Ltd
  • Plunkett associates always find a solution. Whatever we need to prototype, they have a great grasp on the technologies available, costs and lead-times so we get the right solution tailored to the project needs. Have always delivered and never let us down.
    Naim Audio

Get in Touch with us for your Prototyping, Machining and Tooling & Moulding requirements…