Peter Wallers Robot Ramblings

[peterwaller]

I have been doing a little more experimenting with the Alloy 910 Nylon.
The dying seems to work much better at near boiling temperature but this can alter the shape of the printed items.
Thick parts are OK as are smaller ones as seen below.

But larger thin parts are very prone to curling as below and would probably be better dyed before printing although I haven't tried that yet.

Although the Polycarb probably isn't as resilient as the nylon it does print really nicely but is dificult to remove from the build plate.

[peterwaller]

I finally decided I had to bite the bullet and see which of these materials stood up to a spinner best.
So I designed a small holder that was bolted to the base plate and took 4 samples at a time.
The samples were 12 x 46 x 2 mm locally thickened to 4 mm at the mounting end.

Because the target cant move away from the robot it is probably more stringent than real battle but it was the same for all samples.
The samples were HI ABS, PLA 850, PC-Max, Alloy 910 and a piece of polycarb sheet although this was just 1.6 mm thk.

All were surprisingly similar non broke or shattered the recently sharpened blade on Anticyclone cut through them equally.
The PC Max also had layer separation which is probable due to be printed at too low a temperature.
It should be 250 -270 C but the firmware in the Prusa has a limit of 260 and if I try and go above 250 it triggers and stops printing.
The only real conclusion I can come to is that the blade on Anticyclone works really well.
I need to have a bit of a rethink of the test method, any suggestions always welcome.

[joey_picus]

Aside from using a less effective blade (!) all I can think of is using a more standardised, almost scientific approach - an example I've seen before is what Dale Heatherington did in the States (about halfway down) with a gravity fed test rig and a static spinner rather than a robot. Since the impact depends almost as much on driving and relative position as it does on blade and material it would make the results more consistent, if nothing else, although they're pretty consistent (and worrying) already...

[peterwaller]

I didn't really want to design a rig so I decided the obvious thing was to run the spinner against and actual robot chassis.
I had a reject nylon anticyclone chassis and the older design fully surrounding nylon armour so I put those in the arena with anticyclone and ran it for some time with the chassis jammed against the arena wall.
The results were quite promising just a bit of erosion along the bottom of the armour but virtually no penetration of the 2mm nylon armour see below.

[peterwaller]

Although the nylon is probably the best for actual armour I still wanted to see if I could stop the polycarb filament from de-laminating.
A quick walk down to my corner shop and a chat with Trevor and he said he could build me a version of the printer firmware with an elevated maximum head temp although he pointed out that as you approach 270 c there is a danger of melting the PTFE tube in the head.
He emailed me the file and I have now downloaded it into the printer.
My first attempt was printing the spinner test sample at 255C with the recommended bed temp of 80 C.
This was an obvious failure as it left part of the first layer on the heated bed and could be easily de-laminated but I noticed that the thicker part further from the build plate was OK.
It seemed that the bed plate was cooling down the plastic too much causing the poor inter-layer bonding.
So I upped the bed temperature to 95 C and the results showed no sign of de-laminating.
I repeated the print at 260 C and 95 C but the results didn't show much if any improvement.
I ran both the 255,95 and 260,95 samples against Anticyclone both were easily cut but neither showed signs of de-laminating so it looks as the the polycarb is going to be usable after all.

[Shakey]

If you wanted a test print doing on a hotter printer my one has a hot end that'll hit 350 degrees.

[Roboteernat]

Peter, you really need to get a new hot end for your printer.
A nice all metal one will be great, as you know, the PTFE tube will melt and cause major issues. Mine 'melted' at 260 causing me to strip it and re ream the hole.
Btw is it an i3 you have?

[peterwaller]

Yes it is an Prusa i3 and an all metal head is on my to do list any suggestions / recommendations always gratefully received.

[Shakey]

You can never go wrong with an E3Dv6 and titan extruder. It's the setup I put on mine and it prints brilliantly. It does make some filaments a little more prone to jams though as the increased metal portion of the hotend increases friction.

[Roboteernat]

I would agree on the E3D hotend, I have 4 of the things on my other printers and all great - well, 2 are official E3D and 2 are Chinese copies.
All still are great, but finish quality of the chinese is as you expect!