The thoughts that result in this are from the thread Ideas for a BIGGER 3D Printer.  This may be referred to until I copy relevant parts from there to this blog.

Firstly, a change of plan - this printer will have the print bed fixed and move the extruder to provide the Z axis and include moving the whole XY frame.  The Y rails will move up and down the corner uprights on V-slot wheels.  More of this later, first the construction details.

I've long since abandoned my plans for a Giant 3D printer that was a metre square and 600mm high but I still hanker for a bigger printer than my "GinaRep Titan" with around 300mm cube build volume.  I guess my desire for a bigger 3D printer aligns with the "Dob Mob" desire for bigger and bigger telescopes   Also, I'd quite like to make use of the experience of building my Titan printer.

So how big is actually practical?  Of course it depends on how much space is available and ATM for me it is not much!  But I'm making progress on clearing up and will soon have my "workshop" room cleared.  One totally MAD idea I had was to clear out the smallest bedroom and build a 3D printer into it.  Accessibility would be a question of walking or crawling right inside the printer   Size of prints would be limited by what would go through the doorway

Apart from available space there is virtually no limit to the frame size depending on materials used.  V-Slot aluminium extrusion is readily available up to 1.5m long.  If you want transparent acrylic sides, 2ft square or up to 2ft x 4ft are readily obtainable and I think larger sizes can be obtained as secondary double glazing. 

In researching all this it's the print bed size that seems to be the most difficult, principally due to wanting it heated.  400mm square bed heater pads are available and borosilicate glass plate 400mm square used to be available but only 3mm thick which I think is too thin for 400mm square though it has been fine in my 300mm square Titan.   I gather that aluminium is suitable for a print bed and then it's mainly a matter of getting a piece that's sufficiently flat.  I have already ordered and received a 400mm square silicone heater pad with a self-adhesive side to attach to the bed plate.  Its mains voltage and 1200W - that should heat up a decent lump of aluminium pretty quickly

This is the bed heater  40x40CM 1200W220V Huge Cube 3D Printer Heatedbed Build Plate Silicone Heater Pad

The aluminium plate has been much more difficult and it seems that 400mm square is only available to special order, cut to size, and expensive.  I have found a source of 500mm square x 5mm thick which I think should work.  The outer 50mm of the aluminium plate could be insulated to reduce cooling and help with getting an even temperature out to the edge of the heater pad.  With the print bed fixed at the bottom of the printer, the weight is less important and there's plenty of power available to heat this much aluminium.  I might be able to could cut this plate down to 400mm square using a aluminium cutting wheel on my bench mitre saw.

I decided to make the frame from V-Slot aluminium extrusion from Ooznest and the other frame parts and V-Slot wheels from the same source.  The frame is 1m high and has 1m x 20mm x 20mm extrusion for the corner uprights.  Front and back are 570mm x 20mm x 20mm rails and the sides are 500mm x 20mm x 20mm.  These are all joined together with aluminium corner plates giving a very rigid structure.

Just been removing parts that are in the wrong places for the new Z axis arrangement.  I hope to take some photos soon.

Now looking into the XY plane components and arrangement of wheels that run on the corner upright rails.  It would seem that to retain the full coverage of the print bed, the main frame will have to be extended by around 40mm in the X direction.  First diagram shows the corner uprights in green moved out from the corners between the front, back and side members.  A little more than 2x20mm would ensure clearance between Y rails and uprights as shown in more detail and with one of the running wheels, in the second diagram.

If I reduce the length of the Y carriages by 15mm I can achieve 400mm Y range and move the frame members shown in blue inwards to form a proper corner.  This can be seen in the first diagram below.  Further "fiddling about" and I think I might be able to use the original frame dimensions with just a 1mm gap (easily achieved) in the side members as shown in the second diagram.

I've ordered some smaller pulleys :-  V625ZZ 16x5mm 5mm V Groove Sealed Guide Pulley Rail Ball Bearing 625VV  These are designed for use with fishing line, which I'm using.  The ones I have ATM are 25mm diameter and 8mm ID whereas the new ones are only 16mm OD and 5mm ID so both smaller and easier to mount.  Should let me reduce the length of the Y carriages.

I'll see what the surface of the aluminium plate is like but if it's badly scratched or the filament doesn't stick very well I could use LokBuild   Same supplier as the extrusion and wheels etc. so I'll wait before ordering to save on carriage.  Actually, LokBuild looks very interesting and I'm considering trying it on my Titan printer or maybe the new Mini as that would be cheaper.  If it works as well as they say it would be a minor miracle

Seems I'm virtually working on two printers at the same time

On looking into all the measurements, I would seem I have two choices, either replace several frame members with longer ones or sacrifice a few mm of printing space.  In fact to cover 395mm or even 390mm instead of 400mm in one direction hardly seems that important.  I'm saying to myself "is the hassle (and possible cost) of increasing the frame size by replacing extrusion members, worth it to gain a few mm of extra printing space?" and I'm thinking - probably not.

Here's a photo of the XY frame (or it could be called "Z carriage") with the current Y carriages and pulleys, except that there is only one V-slot wheel to run on the corner uprights because that's all I have ATM - it will need three more.  It will also need replacements for the XY frame members as these were previously members of the main frame.  I was at first thinking I could get away with using just the Y rails rather than a full frame but I think this would be asking for trouble - a full frame is more rigid and the extra two aluminium extrusions don't add much to the weight compared with the three stepper motors, extruder, etc.  And this will only be a fraction of the print bed weight.

I think I pretty much have the design of this printer worked out and have ordered the parts from ooznest.  I have found enough V-slot wheels and spacers etc.

1. Front & back top frame rails
2. Side rail - I already have one so only one more required
3. Right angle NEMA 17 motor mount.  2 used, have one so one more required.
4. 10mm diameter x 500mm long smooth rod for Z drive.  3 turns per 100mm so 15 turns for full Z range.  Cord is 0.48mm wide so about 7.5mm to wind onto rod.
5. 5mm ID, 16mm OD, 22mm long to try for XY drums.
6. Also ordered a print melting tool for general use with 3D prints (not just this project).

Quote

Product	Model	Quantity	Price	Total
Sub-Total:				£50.58
Parcelforce Express Next Working Day:				£6.94
VAT (20.0%):				£11.50
Total:				£69.02
V-Slot Linear Rail - 20x20mm - Cut To Size   - Colour: Silver   - Length Range: 501-600mm   - Enter Precise Length: 570   - M5 Tapping Service: None	VSLOT2020	2	£6.30	£12.60
V-Slot Linear Rail - 20x20x500mm   - Cutting Service: No	VSLOT5002020	1	£4.50	£4.50
Right Angled Stepper Motor Mount   - Size: NEMA17	RASTEPPERMOUNT	1	£4.00	£4.00
MODIFI3D Finishing Tool	T-S3-M3D	1	£22.99	£22.99
Precision Hardened Steel Smooth Rods   - Rod Diameter: 10mm   - Rod Length: 500mm	STEELRODS	1	£9.40	£9.40
Rigid Motor Shaft Coupler   - Size: 5x5mm	CPLR-R	2	£3.60	£7.20

 

Here are photos of the XY frame (Z carriage) in the main frame from above.  Second photo includes the print bed heater.

Not sure how much plastic this could print at a time - maybe I should cater for 3Kg reels of filament   Mind you, that would be a very expensive print!!  And what if it failed near the end

Hoping I'll get a delivery from ooznest tomorrow so that I can continue this project

Ooznest delivery is going to be in a day or two but I have received the pulleys from Makers Hut so I can design new Y carriages and sort out the fixings for the ones that go on the XY frame.

The smaller V groove pulleys are just the job   I have attached two on an M5 bolt with washers between bearings and between bottom bearing and V-slot extrusion of the frame with Tee Nuts in the extrusion.  This produced a very solid mounting.  I think these and the non-stretch fishing line cord will produce a very accurate XY drive, this has certainly proved to be the case with my Titan printer which has smaller V groove pulleys.  (I compared the cord and pulley drive with timing belt and pulleys, on my Pilot printer and the cord was noticeably better.  The cord has less stretch than timing belt.)

The aluminium plate has arrived.  It's flat to nearer than 0.1mm in one direction, with a very slight bow of possibly 0.2mm in 500mm in the other.  That would work even without nine point auto-bed-levelling so that's fine.  As for scratches, both sides are protected by plastic sheet so none   It may well bow when heated from one side but we'll see.  The other point is that this plate is bigger than needed.  I do have an aluminium cutting disc for my bench electric mitre saw but don't know how well it would cope with 5mm aluminium sheet.  Anyway, there's plenty to do before I need to decide.

Working on the design of the XY frame component layout, in particular whether to have the motors at the front or the back.  Another idea was CoreXYZ but I think that may be too complicated.  My Mini printer has the motors at the front as conventional but then the XY plane is fixed and the bed moves for the Z axis.  CoreXYZ has the advantage that the XY motors are fixed so the Z carriage (XY frame) is lighter but with using non-stretch cord rated at 80lbs and three or four cords taking the weight I don't think the extra weight of two NEMA 17 motors and their brackets will be too much.  It will still be a lot less than the print bed with its thick aluminium plate, heater and all the other bits and pieces.

The reason for motors at the front in the more usual CoreXY arrangement is that it leaves the extruder and hot end clear from the front.  With a moving XY frame the front frame member obscures the extruder anyway.  I don't think I can do without the front frame member.  With the XY motors mounted on the frame, their power cables will loop downwards  so it's a case of either motors and cables at the front or crossed cords.  The cords could be enclosed in a lightweight 3D printed cover but the front piece would be thicker than with the motors at the front.  I'll have a play about I think - there may be other things that influence the choice that I haven't thought of.  This is my first XYZ nozzle motion printer.

It may be worth increasing the main frame size though I could always do that later.  Probably best to get something working before worrying about getting the best out of it even it that means going for a slightly reduced printing area   I have various ides for different hot ends and extruders.  eg. two colour or two type filament printing and also maybe making use of my 3mm filament stocks.  I may want to use bigger X carriages to take two extruders etc.

This is a lot trickier than I thought!!   It's not so easy rearranging things so that they all fit into a moving frame.  With the fixed XY plane, the motors and pulleys could be outside the XY movement system.

I think I have the answer

Y carriage.  First attempt...

Second attempt