twin and earth cable we've all used it and we'll possibly pull in thousands of meters throughout
our working life but what are the secrets behind the manufacturing process in order
to find out i took a trip down to doncaster cables so we're going to guide you through the process of
manufacturing twin and earth and the first stage of that process is to get our eight millimeter
copper rod and we're going to draw that down into all the different wire diameters that we need
in our production facility so this is eight millimeter in diameter not cross sectional
area and this is what all copper in electrical cables starts off as you can see that the copper
will come off of these four to five ton packs so most the packs are four tons some are five tons
and it'll get fed into the machine and then we draw that down so each part of this machine
gradually makes the copper diameter smaller and you can see that as we open this up so the eight
millimeter rod is coming straight into the machine in the middle and then it will get to a die these
are diamond tipped dies industrial diamond not the expensive diamonds that you get for rings um
and then each die will draw the copper down so it goes from eight millimeters to seven millimeters
for example then it goes through another die which is seven millimeters to six millimeters
and then as it goes through the whole process it's gradually getting smaller and smaller
um until we get to the end and we have what we call a finishing day and that is the final
diameter wire that we want this larger wire drawer that we do that we have will draw down
to one millimeter in diameter anything else gets put through the second wire drawer that
we've got on site so there's the finishing die there at this stage the copper is what we call
work hardened so the copper's become quite brittle this second part of the machine is softening that
copper up so it goes through annealers and high pressure steam tubes to clean it back up again
and our operator is just inching this through before running at full speed which you can see
now and as we come on to this take-up drum we're actually running at about 30 meters per second
and you can see how that's going onto the drum each one of the drums in this machine
is probably carrying about two tons after the wire drawing stage of the process we need compound
and this is what insulates and sheaths the cables so we have our own thermoplastic pvc
70 degree compound plant on site these silos are storing all the raw materials so in here we have
resins fillers stabilizers and oils and these will get fed into the compound plant itself and
we have a really high tech weighing system the weighing system will weigh out to the recipes
that we've created and they're all bespoke based on our recipes and how we want our cables to be
and then they come through and drop down into the mixing bowl before they finally extrude it
we have a secret recipe pvc compound for our twin and earth which makes it super soft super supple
and when you come to terminating your cables it then makes it a lot easier for you to to terminate
in comparison to some other cheaper less lesser quality products the other extrusion lines on site
use a pellet form of pvc so this pvc comes through the extruder and you can see the blades that are
spinning around at high speed they're chopping the pvc that we've made into little pellets
and we then need to cool those pellets down before we can put them into storage for the
other machines to use the pellets are pumped up to these conditioning chambers so the first one
is rotating the pellets round so they don't stick together then the second one it cools
further before finally they get dropped into the storage bins and then the pumped around
site to all the different smaller silos that we use one millimeter 1.5 millimeter and two point
five millimeter square twin earth uses a class one conductor which is a single solid strand
four millimeters and above then move to a class two conductor this process is what
we'd use to create a class two conductor there's seven individual drums of copper
that we've drawn in the wire drawer they are then fed through this machine and they're all
tensioned before they come into a face plate where we can start to form the circular shape of a class
ii conductor we're going to open this machine up and show you how this process works so
inside this machine there's a large drum this drum rotates and it pulls the copper wires from those
individual packs onto the drum all of the twisting motion comes from this carbon fiber bow so the
individual seven strands go around this bow and this whole bow rotates and spins around the drum
and that's what puts the twist into the copper this can rotate about 1200 twists per minute
when it's at full speed so going back to the story of the twin earth that we're watching we're using
class 1 conductor so this single solid wire is going to come from this payoff stand and then
we follow it down the line and it's going to come to the extrusion head so as it goes through this
process we're constantly measuring the cable as it's manufactured so we measure there at the blue
box the diameter of the copper wire and then the compound granules that we've made are melted back
down again we add the colorants of blue in this scenario and we're insulating that bare copper
with blue pvc so this pvc is about 180 to 200 degrees celsius and before we put this onto a
drum to transfer it to the next stage which is sheathing we need to cool this core down
we use water baths so as the cable goes through this water it gradually gets cooler and cooler
there's then a final water chamber where it rotates around lots of wheels
you can see it coming out of this final wheel it then goes through another measuring system which
is measuring the diameter of the insulation but also the concentricity of the copper then
there's a high voltage spark test to ensure that the cable has no defects and no pinprick holes
and then finally it goes on to these big drums where we can store about 50 000 meters of core
ready to be shed at the next stage these cores are all left and stored on the factory floor
and then when we're ready to actually sheet them we'll take a blue and a brown and a
bare earth wire from the wire drawer and we'll thread that into the machine
the cores then come through our our talc unit our chalking machine so that we can coat it when
the line's running and then the operator will feed these into the back of the extrusion head
through the point and the die uh and the point is what holds the cores in place and the bare
earth wire in place and then we can cover it with the shape of the die machine starts up
we pull a purge valve so that the molten pvc is now coming onto the cable this is now colored grey
the wheels that we've just lifted up are applying the marking so there's actually an indent wheel on
there which is embossing doncaster cables england onto the outside of the sheath now that line's up
and running we can see the blue the brown and the cpc coming into the cable and it's very important
before we go in there that we put as much front chalk as we possibly can into the cable
you can see the amount of chalk going on and you can always tell i don't cast the cables to an
earth compared to some other ones by this fact you should come home covered in white like a snowman
the rest of the extrusion process is very similar to the insulation line so we now have to cool the
product down before we put it onto the bolt drum it's 180 to 200 degrees celsius again and if we
don't do that the cable will stick together so as we go to the take-up there's an accumulator
wheel we have a dual take up on this machine like most for other extruders so the machine
is constantly running once it's set up so because we've shown the setup of this machine we now need
to transfer onto a new drum you can see the blue and brown cores on the old one
the operator will fasten this cable to the base of this drum before he starts it up and then once
he's started up the drum will run to about 10 000 meters and then we have a bolt drum that we can
take to final testing and then final winding so what we do like to see in our 20th cables is lots
of white french chalk which you can see here we do a strip check and you can see how much chalk
has worked its way around those cores and the earth wire final high voltage testing
so we have two high voltage testing chambers so we're now going to show you the high voltage test
procedure on this three core and cpc so we need to strip the cable back at both ends and then
we need to connect up each core and the high voltage test procedure will test each core to
every other metallic component in the cable at 3000 volts so we close up the test chamber area
and then we make sure that all the interlocks are in place because it is a high voltage the machine
is then set for different cables so this twin earth is tested at 3 000 volts for five minutes
the test equipment ramps up to 3000 volts before the duration timer starts and we can see that that
five minute clock is now reducing and then at the end of the test we count that down then it will
ramp down the machine then does analysis on the performance of the cable and if everything is good
it will bring up test completed successfully so the drum is identified as high voltage past and
this can now transfer onto the final winding stage final winding stage for twin and earth is fully
automated we're winding it about 300 meters a minute so every 20 seconds we're getting 100 meter
reel of twin and earth coming off this machine the machine has a dual winding head so while it's
winding on one side it is wrapping the reel on the other and this allows us to process the cable
more efficiently so this winding machine is super accurate it measures to one centimeter and all of
our reels are wound at 100 meters as a minimum and they'll be between 100 and 101 meters on a reel
the machine has an automated labeling system which puts all the relevant information on regards cpr
and the product details and then the conveyor belt system finally ends up at a robotic arm where the
cable is lifted up and stacked onto a pallet in the formation that we'd like the final stage that
we need to do is then to wrap the pallet once it's full and then we can process this into the
warehouse and ready for dispatch to our customers so we pride ourselves on manufacturing the highest
quality product and looking after our customers and our facility in doncaster we're manufacturing
about a million meters per week of high quality british made cable but what about manufacturers
that like to cut a few corners this cable drum here we labeled as the ugly cable if you want
to see some of the corners that those type of companies can cut check out the video just here