Being such a simple shape, with no extruder off moves, it came out perfect, just like my wife.
Tuesday, 4 November 2008
Black Heart
I made this tiny heart shaped box as a little gift for my wife's birthday.
Being such a simple shape, with no extruder off moves, it came out perfect, just like my wife.
Being such a simple shape, with no extruder off moves, it came out perfect, just like my wife.
Thursday, 9 October 2008
Pot black
Having tried green ABS and found it a bit disappointing, I had a go with black ABS and was even more disappointed. I got it to try and make objects a bit more aesthetically pleasing but it was even harder to get working than green and has aesthetic problems as well.
The temperatures seem to be the same as those for green, i.e. higher than I have used for plain, but it is harder to get it to stick to the raft and it de-laminates more readily.
To make it stick I had to make the first layer a bit lower than normal. With plain ABS I can have it at the normal layer height above the raft (filament diameter * 0.8) but with HDPE and green ABS I had dropped it 0.1mm. With black I had to drop it 0.15mm as 0.1mm does not stick enough and 0.2mm sticks too much. 0.05mm makes all the difference and has about the same effect as changing the temperature by 10°C.
Another problem is that the extruded filament is not smooth. Close examination reveals that it has small craters in the surface where it has out gassed. It is particularly noticeable when laying the thick filament for the first layer of the raft.
It could be the effect of water absorption but, as all my ABS is stored in the same room, I think it is more likely a volatile component of the black dye. Another effect is that if the filament is stretched while molten, so that it is drawn into a fine thread, then it looks like a string of beads. I think that is an indication the black dye does not mix well with the ABS.
Fortunately, for some reason I don't understand the crater effect is less noticeable when making objects.
These are Darwin y-belt-clamps, a nice small part good for a quick test. The small one is made with 0.3mm filament and shrunk by 3/5. As you can see it is far less shiny. All I can think is that is related to the fact the filament is being stretched more.
Another downside of coloured ABS is that ABS turns white if it is stressed. This shows up far more when it is coloured and particularly with black. Because the base of the object is weakly welded to the raft then it gets bruised when it is peeled off.
This is the bottom of another screw topped pot.
As you can see it has white highlights where the welds to the raft have been broken. One way of fixing it is to wave a hot air gun over it to relax the stress points. That also flattened the base, which was a little convex due to warping.
I expect rubbing it with a little solvent like MEK would also solve the problem.
I now have a little family of pots!
I would not recommend coloured ABS as the dye introduces more variables and generally seems detrimental to strength and aesthetics.
The temperatures seem to be the same as those for green, i.e. higher than I have used for plain, but it is harder to get it to stick to the raft and it de-laminates more readily.
To make it stick I had to make the first layer a bit lower than normal. With plain ABS I can have it at the normal layer height above the raft (filament diameter * 0.8) but with HDPE and green ABS I had dropped it 0.1mm. With black I had to drop it 0.15mm as 0.1mm does not stick enough and 0.2mm sticks too much. 0.05mm makes all the difference and has about the same effect as changing the temperature by 10°C.
Another problem is that the extruded filament is not smooth. Close examination reveals that it has small craters in the surface where it has out gassed. It is particularly noticeable when laying the thick filament for the first layer of the raft.
It could be the effect of water absorption but, as all my ABS is stored in the same room, I think it is more likely a volatile component of the black dye. Another effect is that if the filament is stretched while molten, so that it is drawn into a fine thread, then it looks like a string of beads. I think that is an indication the black dye does not mix well with the ABS.
Fortunately, for some reason I don't understand the crater effect is less noticeable when making objects.
These are Darwin y-belt-clamps, a nice small part good for a quick test. The small one is made with 0.3mm filament and shrunk by 3/5. As you can see it is far less shiny. All I can think is that is related to the fact the filament is being stretched more.
Another downside of coloured ABS is that ABS turns white if it is stressed. This shows up far more when it is coloured and particularly with black. Because the base of the object is weakly welded to the raft then it gets bruised when it is peeled off.
This is the bottom of another screw topped pot.
As you can see it has white highlights where the welds to the raft have been broken. One way of fixing it is to wave a hot air gun over it to relax the stress points. That also flattened the base, which was a little convex due to warping.
I expect rubbing it with a little solvent like MEK would also solve the problem.
I now have a little family of pots!
I would not recommend coloured ABS as the dye introduces more variables and generally seems detrimental to strength and aesthetics.
Monday, 6 October 2008
Brassed off
My first attempt at an extruder had stainless steel bearings and a stainless steel drive shaft, more by accident than anything else. I wondered at the time how the bearings would last compared to the recommended brass ones. Obviously stainless steel is harder than brass, but brass should have less friction, so less wear.
The first drive shaft got retired because the bearing lands were off centre. At the end of its life the bearings and lands were still in good condition.
I ran it from 10/07 to 01/08 but up to that point all I had made was lots of HDPE test shapes.
I replaced it with a plain steel shaft that I bought from BitFromBytes. That had the big advantage of being solder-able.
It worked well for a long time but eventually the bottom land on the shaft wore down so much that the pump halves closed together when using undersized filament (2.7mm).
The bottom land has worn down from 3mm to 2mm. The bearings show a little wear but still have some life left in them. This is after running 5lbs of ABS through the extruder.
In the last few weeks I replaced the shaft with a new zinc steel one and switched to brass bearings in an ABS extruder with HDPE filament guide. That worked well until I noticed the pump halves closed together again. When I opened it up I found that the brass bearings had rotated in the ABS, but they had also worn down a lot, considering the short time I had used them.
The drive shaft lands are still fine though.
So it would appear that the best combination is stainless steel bearings and a stainless steel shaft, but I would have to find another way of attaching the nut.
Most metal bearings I have recovered from old equipment are bronze. I don't know how that compares to brass but it seems to be the thing to use.
Maybe it is time to look at ball bearings and an offset shaft like Ian Adkins' design.
The first drive shaft got retired because the bearing lands were off centre. At the end of its life the bearings and lands were still in good condition.
I ran it from 10/07 to 01/08 but up to that point all I had made was lots of HDPE test shapes.
I replaced it with a plain steel shaft that I bought from BitFromBytes. That had the big advantage of being solder-able.
It worked well for a long time but eventually the bottom land on the shaft wore down so much that the pump halves closed together when using undersized filament (2.7mm).
The bottom land has worn down from 3mm to 2mm. The bearings show a little wear but still have some life left in them. This is after running 5lbs of ABS through the extruder.
In the last few weeks I replaced the shaft with a new zinc steel one and switched to brass bearings in an ABS extruder with HDPE filament guide. That worked well until I noticed the pump halves closed together again. When I opened it up I found that the brass bearings had rotated in the ABS, but they had also worn down a lot, considering the short time I had used them.
The drive shaft lands are still fine though.
So it would appear that the best combination is stainless steel bearings and a stainless steel shaft, but I would have to find another way of attaching the nut.
Most metal bearings I have recovered from old equipment are bronze. I don't know how that compares to brass but it seems to be the thing to use.
Maybe it is time to look at ball bearings and an offset shaft like Ian Adkins' design.
Subscribe to:
Posts (Atom)
