Monday, March 30, 2009

Lots of sparks

The feedwire from my heatingcoil broke today. It's a double wire of the same kind as the coil itself, it's more like a thin strip. The end of the coil is folded between the feedwire and fused together. An attempt to fuse them again with the spotwelder that we have here resulted in a rain of sparks and evaporated wires...
Now I've build a spotwelder in the lathe. One elektrode in the chuck and one in the tail stock. The elektrode in the tailstock slides in a PVC bush for the insulation, a spring behind the elektrode presses it towards the chuck-elektrode. A powersuply will provide the current to weld, I hope 10 amps will do the trick. Pictures of the welding will folow.

Friday, March 27, 2009

Too hot and rising...

I found a piece of insulation material after searching the entire building. It's glassfiber with a sheet of aluminiumfoil. After wrapping it around the barrel I was curious how hot the barrel could get.
So I turned up the amps to 2.2 A at 24 volts. At 380 degrees celsius it was still climbing but I thought that was hot enough because some smoke was coming out of it and I don't trust the Celeron at these high temperatures.
I started experimenting with extruding HDPE and ABS, it works. Now the tweaking starts to get an optimal flow of material.

The Celeron turns out to be a very good solution. It's very easy to work with, it handles a bit like wood. When you turn it on a lathe I do advice to keep a vacuumcleaner next to it to prevent the machine from getting covered in a layer of yellow dust.
The thermalcouple reeds a temperature around 160 degrees celsius IN the material, just under the surface where the heaterbarrel (260 C) is attached. So I would stop spending money on PEEK, Celeron is cheaper and stiffer. It is possible to cut a thread but with frequent loosening and fastening I would advise to use metal inserts.

Some more good luck came to me today in the discovery of a stack of various thermalcouples. The shipment is dated from 1983 but I don't really care as long as they work...! After that I found a 30V/3A powersuply that works better than the one I was using.
It turns out that when you know where to look (usually places where no one ever comes) you will find lots of 'forgotten' equipment, parts and tools that come in handy in some way.

Now my weekend starts...I can't wait till monday...


Yesterday I went with a group of students and teachers to the Solitaire. This is a ship from the company Allseas wich is specialised in laying pipes on the seabed. These pipes are upto 60 inch in diameter (!) and can be laid to a dept of 2700 m! The ship is in fact one big pipe welding factory wich welds sections of 12m into one big pipe that slides of the stern of the ship and is held by big tensioners wich can tow 3x300 metric tons. Quite an extruder in a way...

The pipe makes a S-shaped curve and lands on the seabed. It's as easy as that ;)

The ship was in a dok in the Rotterdam harbor for major maintenance and we had permission to fotograph anything we wanted during the tour trough the entire ship. Briljant! Underneeth a couple of shots to give an impression.

Start of the main firing line in the bow.

End of the main firing line in the stern with a view on the stinger

The main firing line goes over the length of the whole ship (300 m) and consists of a line-up station, 5 welding stations, 3 tensioners, a none destructive test station and a seeling station.

The stinger guides the pipe into the first S-bend and extends the ship with 150 m.

A 'small' pipe in an opened tensioner. The pipe is covered in concrete to make it sink and to protect it.

A view from the aftbridge. In the back you can see the stinger. The crane (one of two) on the right is used to hoist pipes on board. The ship is almost constantly resuplied wit new pipes while at sea. There are two bridges, one for normal sailing and one for pipelaying.

Wednesday, March 25, 2009

I like it hot...

Today I assembled my test heater. The goal of this heater is to try some different shaped heaterbarrels and nozzletips. The heater consists of a brass tube with the wire from the soldering iron wound around it. An aluminium nozzle and heater channel are placed in the tube and closed in by a bolt. In this way it's very easy to switch between different nozzles and barrels to see wich shape gives the best result.

As thermal insulator I used a piece of Celeron (aka Tufnol or hard linnen). I didn't expect to much of it but I just had to try because it was there. The specs say that it can resists temperatures upto 160 degrees celsius. Surprisingly it held out very well in my first test, the contact surfaces of the brass and stainless flanges became 200 degrees celsius.

The backside. It shows the stainless flange and the bolt that holds the inserts in place. The rod sticking out of the nozzle is a thermal couple connected to a display.

The frontside. You can see the coil from the soldering iron with the mica sheets between the coil and the brass.

The inserts. The nozzle has a 0,3 mm hole, the drill is next to it. Sweet isn't it? The hole trough the barrel inserts hasn't been drilled yet.

The connection of the heaterwire glows because of high resistance. Even without insullation, to keep the heat inside, the display of the thermal couple read 300 degrees celsius... As expected, the 50W from the soldering iron is a bit overkill. I'm planning to shorten the coil.

The testfacility. Unfortunately the ordered polymers didn't come in today so I haven't actualy been able to extrude yet...

Monday, March 23, 2009

Cheap 'insolution'

I think I did a nice discovery by taking an old soldering iron apart to its core.

This is a minor edit due to the fact that I just read Nopheads blog about his attempt to use a soldering iron (should have done my homework better). Off course I couldn't have expected that no one would try to use a soldering iron but by taking it apart further I found some components that are very well reuseable in a self build heater barel. This would solve the problem Nophead had with the jamming plug.

It turns out that this soldering iron is build up in the folowing order:
-steel tube that holds the tip
-Mica sheet for electrical insulation
-heatingwire (NiCr ? it seems the same as a toaster)
-another layer of Mica sheets
-outside tube of the iron

The Mica makes a very good electrical insulation wich makes it posible to place the coil nearer to the heater barel and so providing a good thermal conduction to the filament.
You can adjust the temperature gradient along the barrel by varying the pitch of the windings.

On the picture I marked the places to cut the outer tube with a plain pipe cutter like plumbers use. This iron comes from a soldering station with a regulated temperature so there is also a thermistor installed in the inner tube.
The advantage of the Mica is that you can controll it better than puty beacuse you can see what you're doing. Also , you can take it apart as often as you like.
I think cheap-ass soldering irons make a good source for heating wire, Mica sheets and if you're lucky thermistors. Altough I understand from Nopheads attempt that the type of thermistor isn't the right one.

I'm not sure if Mica is called the same in english as in dutch. So to be sure: Mica was used in stead of glas in old stoves with coles. It's yellowish, brittle and it can withstand high temperatures. I only know this from stories because this was before I was born... ;) SO if anyone knows more about the material (perhaps where to buy it...) I would like to hear.