Product category:
Subcontract machining and assembly services
News Release from: Unicut Precision | Subject: Unicut Precision - CNC multi-axis turning
Edited by the Manufacturingtalk Editorial
Team on 30 April 2003
Machining solution was a burner for gas
fires
It was the capability of subcontract machinist to provide single operation turning solutions that took some 20 per cent out of the price of gas fire burner heads and ensured total consistency.
It was the capability of subcontract machinist Unicut Precision to provide single operation turning solutions that took some 20 per cent out of the price of gas fire burner heads and ensured total consistency throughout the batch of components that won the Welwyn Garden City subcontracting company initial contracts for 60,000 parts from Seagas Industries Leicester based Seagas was formed in 1971 and is the sole manufacturer and patent holder of a safety pilot supervision device for decorative flame effect coal and log gas fires found in many households throughout the UK
This article was originally published on Manufacturingtalk on 27 Apr 2004 at 8.00am (UK)
Related stories
Subcontractor invests in systems integration
To raise productivity a small precision parts machinist has invested some GBP 25,000 in an integrated central communications and production management system.
No blues sung at subcontract machinists'
Such has been the upsurge in the fortunes of Unicut Precision that July and August have set record sales and profit levels for its precision sub-con tract machining business.
It is also a stockist for gas valve, thermocouples, thermostats and cooker burner assemblies.
Says manager Donal Heffernan: "We combine some 30 years of expertise in gas fires and cookers and can provide a pre-CE certification consultancy and testing service to gas equipment developers and importers.
This means we are totally involved with performance requirements of gas appliances." Prior to switching to Unicut for its stainless steel burner heads and injector bodies, the company sourced them from two different factories of one supplier.
Further reading
Big order led to new machine purchases
Following the winning of a 12 month contract for three million components from an American fastener company, Unicut Precision immediately ordered two CNC sliding head automatic lathes.
Latest sliding head autos reduce costs
Subcontractor, equipped with latest sliding autos, can demonstrate howit can considerably reduce cost, improve quality and consistency of a machined parts in difficult materials.
Machine tool investment pays off for subcontractor
Unicut Precision's investment programme in the latest mill/turning technology has paid-off enabling the company to meet market changes and as a result grow sales by 18 per cent during 2003.
Due to their production capability, each of the sub contractors had to produce the parts using multiple operation techniques involving relocation in jigs and fixtures in order to drill and mill the various secondary features.
The problem created by this production technique was the lack of consistency over the batch of parts.
For Seagas, consistency is one of the most critical elements when it comes to supervising the pilot burner flame and it has to overcome any differences on test results between one burner and the next as it is assembled and tested on a special purpose machine.
As Donal Heffernan outlines: "We found because Unicut uses Citizen CNC sliding head automatic lathes to single operation mill/turn the various features in the stainless steel burner head and the brass injector body, into which the burner head is clinched on assembly, any variance in the parts throughout the batch is eliminated.
Also, with the single operation machining techniques, Unicut was able to take 20 per cent out of the production price for the two components." As Unicut's methods of production ensure the relationship of features to one another is guaranteed, geometric positioning and size variation are never a problem.
Donal Heffernan follows on to explain how he now has under precise control the determining factor in ensuring the installation of the pilot burner assembly is trouble free.
The 10mm diameter stainless steel burner heads are produced at Unicut in two main types with a 0.9mm wide burner slot in the end, which is set at either 90 deg or 45 deg to the centre line of the part according to the application required.
The slot is milled in the Citizen M20 in cycle to break into a main 4.5mm diameter bore.
A separate 2mm diameter air feed hole is also drilled which is critical because any size variation influences the level of noise emitted from the pilot burner.
Both the positioning, depth and width of the burner slot are also important because any difference in the dimensions or shift in geometric relationship alters the burning pattern of the flame.
The brass injector body is produced out of 12mm A/F hexagon material and is machined on the 13-axis Citizen M20 at Unicut from both ends in a single operation.
Within the cycle, a 1 mm deep 1.5/1.6mm wide slot is milled across one of the flats and an aeration hole of between 2.8mm and 4mm diameter drilled according to the type of gas being supplied.
These holes break through from the outside flat on the bar material into the central bore in the body.
Each end of the body is machined simultaneously using the main and secondary spindles of the Citizen machine with several internal bores and counterbores to tolerances of 0.1mm.
However, depth tolerances must be held within +0.05mm with square corner bottoming to each bore.
At the other end, an M10 thread is tapped for a pipe connection but most critical, is a 70 deg included angle taper that acts as a venturi to increase the speed of the gas flowing into the burner head from which the slot fans out the ignited gas to enable the thermocouple to monitor the flame.
All drilled holes have to be totally burr free and smooth so as not to disrupt the gas flow and clean edges have to be maintained in order to prevent the ignited gas clinging to the thermocouple.
If this occurs it can lead to lengthening the time to shut off the flame.
According to Donal Heffernan, the working relationship between himself and Unicut's two directors Jason Nicholson and Charles Kenny was ideal to develop out the machining process for the two parts.
To which Charles Kenny adds: "The Citizen M20 is so flexible in its programming and tooling set up that we could experiment with different slot arrangements, have them tested by Seagas for burn pattern and flow and then adjust positioning or size for the next prototype part.
To this method of working Donal Heffernan confirms: "Unicut were able to understand immediately what we required.
Then, once the samples performed the way we wanted, they simply pushed the button and produced the 60,000 burner components in a single batch." Indeed, the goods inwards inspector at Seagas confirms his sample assessment across the batch demonstrated a level of consistency he had never seen before.
"When the assembled burners are 100 per cent tested prior to despatch, rejection of burners is so minimal, it is no longer an issue," concludes Donal Heffernan.
• Unicut Precision: contact details and other news
• Email this article to a colleague
• Register for the free Manufacturingtalk email newsletter
• Manufacturingtalk Home Page
Search the Pro-Talk network of sites
