2019-10-15

Dissolvable PVA support

The TAZ Pro has two extruders which allows me to try and use dissolvable PVA support. Support is simple enough but hard to remove from the print cleanly, so using PVA allows extra options - just dissolve it!

I have had to play with the Simpify3D settings a bit as the settings for the TAZ 6 did not quite work. I am not sure if the bed is different, the nozzle, or what but my prints were almost welded to the bed. I have tweak the settings for nice clean prints with nGen now. The next challenge was settings for PVA supports.

I ordered some from RS (yes, the price was not silly, strangely), part 174-0082. Well, actually I ordered from someone else, and realised wrong diameter, after opening it, D'Oh, but now I have the right stuff I googled a bit to find temperature.

It is funny stuff, and I ended up printing at 205C which is apparently on the high side. I could also see from simply feeding the filament that it came out thick and slow (around 1mm).

The key setting needed to stop it just curling up was speed - it needs to be very slow. In the end I ran with 2x multiplier, 1mm wide, 20% print speed, and that actually worked. Well, mostly (the eyes went a tad wonky, but worked).


For a start, the PVA comes away from the model really easily, so that is a good start.


Then, put in warm water for a while to remove the last bits, and yay, it worked.


Now to try something more complex with enclosed parts that simply could not have been printed before.

2019-10-10

LulzBot TAZ Pro (dual extruder)

I have been 3D printing for a long time - and even coded a slicer once.

I have tried many printers. My current favourite for cost and performance is the LulzBot TAZ. We have a TAZ 6 at the office and (even though not on the A&A web site) we do 3D printing if you want.

It is a nice heated bed, which works well, especially with my filament of choice ColorFabb nGen.

I have been using to make cases for various electronics / R&D.

Sadly I slightly fried my TAZ 6 units. I have a new controller board on the way, but decided to check what they have now, and saw the TAZ Pro. So I ordered one and to my surprise it arrived in a couple of days (in spite of warnings of back orders and long lead times). Nice.

It is nice...


But is it worth the price (around £5k)?

Well, possible. It has some nice features and works very well. I have only been playing with it for a day now, but I can make some comments. The bed levelling is faster and seems more consistent. The Z axis is belt driven meaning it can easily use Z moves when moving from one part to another (far too slow when Z axis is screw). The big thing is the dual extruder.

Cura?

LulzBot recommend Cura, a good, free, 3D slicer. It works well, and makes some impressive prints, but...

  • It seems way slower than I am used to (I used Simplify 3D before)
  • The prints, whilst nice, and precise, seems brittle. I expect minor tweaks to settings would help.
  • It expects nGen to be glue sticked to the bed - and I know it can be printed without, but needs hotter bed for first layer. I tried that and it worked.
  • Somehow the prints were distorted. I am not sure if cooling is right. I am sure it could be tweaked.
However, it did work, as I say. And the reason I tried it is that Simplify3D, which I was using, had no profile for the new printer.

But, Simplify3D support emailed me one, within a few hours of asking. It works!

Simplify3D

Whilst I do not usually end up recommending paid-for software, this is good. It works well. It is way faster. It is not perfect, but nothing it, but it is nice to use. So I recommend it.

Dual Extruder

This is the first time I have used a dual extruder. But the TAZ Pro does it really well. The heads are motorised to retract completely out of the way. The full bed size is still available to both extruders. It really works well.

There are several reasons to use a dual extruder.
  • Two colour prints - obviously. To be honest this is a pretty minor use case. But it works well.
  • Mixed materials - combine fixed brittle material and flexible rubber to make complex designs - not tried it yet, but fun possibility.
  • Using dissolvable supports - this is likely to be the main use.
The dissolvable supports will be subject of another blog when the PVA reel arrives. Basically, 3D printing like this cannot always print what you want as some things are "in mid air". Using support material works, but has to be cut/broken off, and is impossible to do "inside" some designs. Using dissolvable supports allows the impossible to be printed, and then put in warm water for a while. I look forward to it.

The dual head working is impressive...


In the mean time - two colour test print...



Any downsides

The only one so far is the heads are covered by a safety guard with warning about being hot - which means you cannot see what is printed as it prints.  Ironically it means you cannot see the print head, and can end up burning your finger when trying to adjust something because you cannot see where your finger is. Elf 'n' safety gone mad, IMHO. If it always "just works" then I guess it is not a problem. TBH they should have designed with angled plastic to make a guard that allowed viewing of the actual print head. This may seem trivial but I do feel is more important than they realise. Even ignoring the practical aspects of knowing a print is not working right ASAP, seeing what is being printed it important for selling the whole idea of 3D printing...

USB-C not so easy

Using a USB-C connector for power only is, sadly, not as simple as I thought.

Yes, the pins are tiny, butt the end pins are double pins on the connector and just about solderable (0.6mm wide for two pins together).


However, whilst this works when you use a legacy cable from a USB-A, giving 5V, this will not work to a true USB-C power supply or device.

Why?


Well, resistance is not futile, it seems. There are two connectors (CC1 and CC2) on the USB-C which need resistors to GND to tell the other end you want power.

Whilst the end power connections are two pins at a time (0.6mm), the CC1/2 pins are not, and are 0.3mm wide at 0.5mm spacing. That is pretty much impossible to mill, as the milled track is anything from 0.3mm to 0.6mm wide. The picture above shows around 0.5mm milled track, which is deliberately spaced to allow soldering to the pin 6th from the right. So double pin on right (GND), next double pin in (VBUS) and then another pin we don't care for and then the CC pin. Same on the other side of the connector, except the CC pin is next to the VBUS on that side.

Yes, it is possible to solder!


Then to add the 5.1kΩ resistors to GND.


The end result is power from USB-C...

P.S. Thanks to John for pointing this out to me.
P.P.S. John also pointed out that you do need the two resistors - and cannot simply common up CC1/CC2 with one resistor (as RasPi4 did, by mistake).

2019-10-08

Powering widgets

Making widgets for the alarm system means that power is quite simple - the alarm wiring has 12V DC, and a simple regulator means I can connect to that - typically with screw terminals.

However, making other widgets with an ESP32, like the environmental monitor, or the Brexit clock, means finding a way to power them. I am not yet playing with battery powered stuff (will do, eventually), so need a power lead.

So what to use?

Initially I tried a micro-USB. Leads for this are very common, and USB-A sockets providing 5V are so common they are fitted to standard power sockets even, so seems ideal.

The issue is the connectors. I have struggled to find what I need. I did see some from China (which have not yet arrived) which have only the power tabs on them making soldering easier, and have clips to hold to the PCB. Whilst waiting for those, I tried some simple surface mount connectors.

The problem is they are not very robust, even superglued to the board, they can become detached very quickly.

I have actually made a set of tools under OpenSCAD two make tight fitting 3D cases to help hold the connector in place, which has helped, but that is still a challenge, and I am not happy about it.


The other catch is the tiny tiny surface mount connectors... Thankfully I only need the ones at the ends. For reference, the three pins at the bottom are 0.1" spaced.

So, I wanted to find a solution, and turned to USB-C. These are a nightmare, not only tiny tiny tiny surface mount tabs, but tabs under the connector so you cannot get to them with a soldering iron. Finally I found a part that will do, and from a UK supplier.

It did mean some fine milling, and even finer soldering, but again, only needing the double connectors at the ends, so just about possible. Those pads are 0.5mm spaced!


The result is a nice solid, soldered to the board, connector.


2019-10-02

IoT

I have not done much on the IoT for over a week, but being rather ill for a few days has not helped 🤮🤮🤮🤮🤮.

The Brexit clock is getting scary!

My grandson wants to do something with LEDs some time!

The environmental sensors are working well, and I have nice graphs from it... This will probably lead to some fans in the office now.



I am thinking the next IoT thing to look at may be Bluetooth. Any suggestions for how that could be fun?

But yeh, the LEDs for my grandson are going to be a thing soon. Here he is abusing his first LEDs.