new build (needs a name )

Im just starting to design my own CoreXY printer build , This will be my forth build (i3 , Rostock, cherry pi, hypercube evolution) but this will be my own design.

Also need a name for it.

The brief plan is,
300,300,300 build size
Linear rails for X,Y,Z
Carbon fibre x-axis
Belted for z axis
4040 aluminium for the frame
Completely enclosed except electronics, removable for printing PLA, thinking PIR panels
Duet wifi
Flex3drive
least amount of printed parts ( nearly finished a cnc router that cut aluminium)
9mm gt3 belts pullys
Thinking about trying one of the swiss micro hotends with titanium heatbreak
8mm cast heatbed, 750w 240v heater, thermal fused, 3 point leveling.
bl touch

I have put some thought into thermal expansion but i really dont think its worth worrying about exept for the heatbed (copying DD ideas there).

There is a few other ideas floating about my head, remote cooling, fum extraction/ filtering etc

The design will be done as i go along and have the parts in my hand.

i want to be able to do long print runs overnight so any ideas on safety would be welcome or any other ideas

Thanks Adam

Edited 2 time(s). Last edit at 05/28/2018 09:27AM by adambrum.

Little bit of an update but no photos yet (sorry)

got some Chinese linear rails not expecting much but after cleaning them and greasing with THK AFF grease there ok. 12mm for Y and 9mm for X

decided to go with gates 6mm 3gt belts (these are 2mm pitch just thicker) couldn't find these as open ended so got long belts, should be here soon.

Duet wifi arrived

Still waiting on the flex3drive, nearly four weeks and the only reply ive got is "it wil ship this week" 2 weeks ago ! pity nimbles out of stock

Routers finished and cutting wood, just need to practice aluminium and i should have some nice custom parts

Most important thing first, It has a name and its THOR,

Bad pronunciation and mix of words, 300mm build area corexy = three and core = THOR

Now to a technical question, Im planning on having a 15mm carbon fibre square tube across x axis, i do have a piece and its remarkably stiff but im now thinking about the heat.

Carbon fibre is fine just not sure about the resin, from a bit of reading it should be ok to 80, now the heated chamber is going to be 45-50 but the heatbed is going to be at 100+ and the carbon is about 30mm above that.

Anyone got any thoughts ?

The resin in the carbon tube will be perfectly fine. You would have to place the hot end directly on it with zero airflow for a period of time to do anything. Eventually it would soften the resin, but only in that one spot. The rest of the tube would simply hold the structure. In a printing environment even with a super heated environment, I would have zero issues with using carbon parts.

Good to know, Im at a carbon fibre research centre in a few weeks, might see if i can get some free off cuts

E3D used a carbon fibre gantry for the X axis of their tool changing CoreXY machine, see [e3d-online.com]. So you are in good company!

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Pultruded CF has a negative coefficient of thermal expansion (shrinks as it gets warmer). Aluminum is positive. You will have to provide some way to deal with that if heating the chamber.

Ive been looking at thermal expansion quite a bit and come to the conclusion that apart from the heat bed im better to ignore it.

I have a steel linear rails, aluminium frame , rubber belts and carbon fibre. I did think about going all steel for the frame but without a large milling machine it would probably be twisted.

I have seen reports on this forum and others, from people who have built coreXY mechanisms using linear guides, that everything works fine when they set the machine up, but seasonal temperature changes in their workshop, either up or down, cause the mechanism to bind and they have to reposition the linear guides. In theory, this can happen with i3 type machines if the XZ mechanism is built using linear guides. As temperature changes, the aluminum frame expands and contracts, moving the Y axis (or Z axis) linear guides closer and farther apart. Linear guides have very tight tolerances (that's what makes them so good!), and when mounted properly, don't flex much. In a machine using end supported guide rails, the rails will flex enough that expansion of the frame won't matter, but with linear guides, you have to modify the design to allow the frame to expand, especially if you are going to heat the enclosure/frame so you can print ABS. It may be enough to mount the X axis linear guide on a piece of aluminum that is bolted to the Y axis bearing blocks (I did that in SoM) or, if you're going to attach the X axis linear guide to the the Y axis blocks without an aluminum bar/tube, use a second X axis bearing block:



At the bottom of the photo, the X axis rail is bolted to the Y axis bearing block through a spacer (yellow). The opposite end of the X axis, at the top of the photo, has a second bearing block mounted on the Y axis bearing block to allow the Y axis rails to move apart when the frame heats up. As the Y axis rails move apart, the X axis linear guide follows the bottom Y axis rail and slides in the upper bearing block. I've been using this for over a year, heated and unheated, and it never binds.

If the machine won't be subjected to wide temperature swings, you probably don't need to bother with this.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I am going to get temp swings, still at the designing stage so adding an extra bearing block is no problem especially if it saves problems later.

This does pose a few questions,

If i have a steel rail on aluminium then the aluminium expands approx 0.2mm more than the rail,

If i have a steel rail on carbon fibre then the steel expands more than the carbon fibre, cant find any actual data

So the solution must be steel rail on a steel tube or angle with an extra bearing on y-axis but that increases the weight which im trying to reduce or i could machine a groove in aluminium bolt the rail tightly in the middle and nip up the rest allowing it to expand less that the aluminium.

Edited 4 time(s). Last edit at 06/17/2018 06:05PM by adambrum.

Had some spare time today to play on the router,

This is the start of the x axis carriage, first printed then cut in mdf as im still new to routing and then on to aluminium

Quote
adambrum
If i have a steel rail on aluminium then the aluminium expands approx 0.2mm more than the rail,

If i have a steel rail on carbon fibre then the steel expands more than the carbon fibre, cant find any actual data

So the solution must be steel rail on a steel tube or angle with an extra bearing on y-axis but that increases the weight which im trying to reduce or i could machine a groove in aluminium bolt the rail tightly in the middle and nip up the rest allowing it to expand less that the aluminium.

My printer, SoM, uses a linear guide mounted on an aluminum tube for the X axis and has linear guides screwed to a thick aluminum plate for the Y axis. UMMD has Y axis linear guides screwed to cast tooling plate. I don't know exactly what's going on there but maybe when the aluminum expands each screw slides/stretches a few um. You'd think that with heating and cooling cycles things would get out of alignment, but it doesn't seem to happen.

Regarding CF- the coefficient of expansion is usually not given because it depends on the directional lay of the fibers in the epoxy, and the way the layers are stacked on each other.

Linear guides screwed to aluminum seems to work fine, even with temperature changes typically found in 3D printers.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Good to know, i can make the x-axis from single piece of aluminium