Monday, 24 October 2011

High Precision Horizontal Boring Machine

High Precision Boring Machine
Cranfield Precision has produced a high precision horizontal boring machine. The machine was designed and developed to meet a need for our parent company Cinetic Landis Ltd where there was no commercially available machine that could achieve the required accuracy over the 4m³ work volume.

The machine is designed as a high accuracy finish jig boring machine capable of multi-purpose machining functions such as; mill, drill, ream, face and bore in one set-up




Initial 3D CAD Concept





Tuesday, 18 October 2011

The Principle of Determinism

Precision Machine Tool
Precision Machine Design adheres to the fundamental principle of determinism. The principle of determinism is that machine systems obeys cause and effect relationships. The principle of determinism does not accept the word random, it suggests that nothing is random and at some level there is a cause for the observed effect.

The repeatability of a machine tool is not driven by some inherent and seemingly random limiting process. With the ability to measure all of the influencing variables we can aim to better control them and therefore produce a more accurate machine tool.

Layton Hale's PhD Thesis (10mb PDF) talks about the principles of determinism and that the list of variables that cause errors in machine tools is not so long that we can't control them.

Cranfield Precision has a proven track record of producing highly accurate precision machine tools that are designed and produced using deterministic techniques.






Thursday, 13 October 2011

Repeatability in Precision Machine Tools

Repeatable Machine Structure
Repeatability is one of the most important elements in precision machine tool design. The aim is to make a mechanical structure that is stiff and repeatable. Having a stable and stiff mechanical structure is the basis for a high precision machine tool.


Finite Element Analysis
of a machine element
At Cranfield Precision we design high precision machine tools with stiff and repeatable structures through advanced finite element analysis techniques and by obeying the key principles of precision machine design.


Once you have a stiff and repeatable mechanical system that will consistently repeat to a demanded position advanced control system and error compensation techniques can be applied to correct any measured errors. 


Precision metrology techniques are used to accurately measure machine error motions. The combination of a stiff repeatable structure, precision metrology and error compensation techniques produces a very accurate precision machine tool.

Monday, 3 October 2011

Error Budgets and Error Budgeting Techniques

An error budget is a method employed in ultra precision machine design that identifies the accuracies of individual machine elements and gives a useful value as to the over all machine accuracy. This technique can identify potential weak spots in a machine concept and be used to focus design effort into ensuring that every element of a machine tool is fully optimised.

6 degrees of freedom for a machine tool axis
Each machine element will have a potential error motion or influence in 6 degrees of freedom dependent on  the constraints in place.

Error budgets are used with a good deal of experience and where necessary previous results and test beds to prove a principle or concept.

Read more on error budgeting techniques here.

Monday, 26 September 2011

The 11 Principles of Precision Machine Design


The 11 Principles of Precision Machine Design were developed at CUPE - Cranfield Unit for Precision Engineering which ultimately evolved into Cranfield Precision. Development of the 11 Principles of Precision Machine Design and CUPE were lead by Professor Pat McKeown.

Cranfield Precision are world renowned for their expertise in designing and developing special purpose machines. Many new and existing world leading precision machine tools are still based on the 11 Principles of Machine Design which Cranfield Precision still utilise today.

The 11 Principles of Precision Machine Design
  • 1. Structure
  • 2. Kinematic / Semi Kinematic Design
  • 3. Abbe Principle
  • 4. Direct Displacement Transducers
  • 5. Metrology Frames
  • 6. Bearings
  • 7. Drives / Carriages
  • 8. Thermal Effects
  • 9. Servo-Drives and Control (CNC)
  • 10. Error Budgeting
  • 11. Error Compensation
Cranfield Precision has developed and improved upon each of these key principles and has also developed many new technologies that embody and advance these principles.

Read more on the 11 Principles of Precision Machine Design.

Saturday, 17 September 2011

Precision Machine Design

Cranfield Precision are specialists in Precision Machine Design. Cranfield Precision has a rich history of designing precision machines, born out of Cranfield University's Unit for Precision Engineering we fully embody the 11 principles of precision machine design as defined by Prof Pat Mckeown (former MD Cranfield Precision).
 Cranfield Precision has an extensive history in producing world beating precision machine tools dating back to 1968. The company was born out of Cranfield University's Unit for Precision Engineering and still has ties with the University and plays a central part in the Precision Engineering Industry.