Gina

I have a spare Mega+RAMPS

A very interesting concept but I think I shall just go with what is already half built I've decided to go with moving the extruder in the Z direction and moving the whole XY plane up and down. The Y rails can be attached to the corner uprights with wheels. The XY motors are already designed to go on the Y rails but now the pulleys will also be attached to the Y rails. The only problem I see with this new arrangement is attaching the acrylic panels that form the fume cupboard that were originally going to be attached to the outside of the frame.

That is using PLA with an unheated bed. I guess I could do that but I really want to print ASA for use outdoors in lots of UV and need UV resistant filament. PLA would last a while but I don't know how long and PLA is cheap.

WOW!!! That is da biz!! SO, another giant printer using fishing line cord I like it. But it needs a whole room to work in - that is a little difficult! Maybe a "miniature" version. Hmmm... Interesting I wonder

To date I have only seen one 3D printer using cords and drums and it was a small one with 200mm square bed. But what I will say in defense of this system is that my Titan printer works very well - both fast and accurate That was after I beefed up the cantilever Z axis system But the bed is not very heavy, being a silicone heater pad attached to 3mm borosilicate glass, framed with printed PETG and insulated on the underside with 12mm thick polyurethane foam and 6mm plywood. Although a 400mm square x 3mm borosilicate glass plate is available I doubt it would be satisfactory with a same size silicone heater.

Yes, I have considered leadscrews but the friction concerned me, particularly with a heavy weight. Actually, I've been thinking about the extreme weight and thinking it's not really practical to move this much weight. I'm thinking instead of moving the extruder in all three directions. Either that or abandoning the Giant printer yet again. My Titan is working well and pretty much does all I want ATM. I think the Giant is more for the challenge though I did think of using it to print a mini dome observatory but I've already printed most of one big enough for a single camera plus lens rig with DIY fork mount.

Having read up about the Duet it seems it's going to be much easier to mount than the Mega+RAMPS and I won't need the LCD display and control unit as it will be controlled via the web server.

Thought I'd have a quick look at where I'd go to with the Giant printer. X and Y drives are sorted out but there are some decisions to be taken on the Z drive (print bed). I was going to use two rails but I think I'll do the same as with the Mini - use the corner uprights with wheels on those. Pull-up could be the same as the Mini too with a bar at the back and pulleys at the front with all four cords winding up on the bar (or with drums to increase diameter). The print bed is a bit of a problem. I have a 400mm square mains driven heater pad, adhesive on one side to be stuck to an aluminium plate. The latter is the problem. I thought I had a 4mm thick piece but both 400mm squares I have are 2mm. 6mm seems to be advised. A thought is 500mm square by 5mm thick from Amazon @ £26.57 (otherwise it seems like at least £60 for 400mm square x 6mm thick). Wonder if this would suffice. I know the heat would drop off near the edge of the heater but I could insulate the 50mm frame round the edge. Might bow a bit with the heat but this may be covered by the auto-bed-levelling. Any thoughts?

Ah yes, I see I've been looking into adding cameras to my printers and trying to decide where to put them. Looks like yours is on the RHS near the top. I was thinking of a similar position. I've been reading about the Duet and like the improved fan control. I also like the idea of the web interface. I've almost read all the Duet information and it seems to have everything covered including mains powered print bed heaters as I shall have in my Giant printer. Certainly, the wiring up etc. seems well thought out and very logical I also like the extra g-code controls. I think it might let me print filament types that have proved difficult with my present printers. It seems very likely that I shall be using the Duet for my Giant printer (when I get back to it).

With this being a new build I think I shall use it as a test-bed for the Duet Wi-Fi control board. At least a test-bed initially but no doubt the Duet will stay. I need to design the mounting parts for the control electronics and PSU etc. so it makes sense to try the Duet and make the parts to fit that. The Arduino Mega and RAMPS etc. are "old hat" now

Are you still using a camera with your new printer setup, Dave?

I'm a Borg beating wild witch of the west

I have resisted buying Borg telescopes

Made a decision - positive attitude is one on my New Year Resolutions Ordered the Duet Wi-Fi and registered my account Decided that a processor and interface board specifically designed for the purpose is a much better bet than a number of bits cobbled together. Reducing connections improves reliability too. I can't see anything against it other than "having all your eggs in one basket". I shall just have to be super careful

Sounds brilliant I'll probably get one once I get my confidence back after the devastating pile of dead Pies I have learnt a few things about the RPi in the process so not a total loss

Hmm... Judging by the number of Raspberry Pies I've blown up I think this might be best left. I'm rather OCD about checking connections too but I still managed to fry the Pies!! Or judging by the smoke - almost burnt to a cinder!!! I take it the Duet firmware allows Core-XY?

The drive drums could be a problem, as on thinking about it I don't think my present 3D printers would be accurate enough. The Pilot printer has calibration problems (orthogonality of the X and Y axes) and the Titan printer only goes down to a 0.6mm nozzle as it uses an E3D Volcano hotend and the prints will have ridges. Actually, any 3D print will have ridges from the layers. Maybe I could try to improve my lathe.

My Pilot printer is playing up again (Titan is fine ATM). The ASC/weather station is on hold awaiting parts so I'm looking at 3D printers again. I've put my new "Mini" printer on the table to look at and think about. This will replace my Pilot printer as a small high precision 3D printer. The Pilot just won't hold orthogonality due to it's overall design whereas the "Mini" has a full V-groove extrusion framework and very solid. It also uses Core-XY, moving the extruder in the XY directions rather than the Y axis by moving the print bed. This makes for faster printing plus a much smaller footprint for the 200mm square print area. Been looking at the Duet Wi-Fi again but not so keen on the price. Is it cheaper anywhere else? Mind you, for what it does it's pretty good value - combining RPi, Arduino Mega, RAMPS, stepper drivers - and it does it very much better it would seem

I'm thinking I might put further hardware construction for this project on hold until I get more suitable parts. The price of 28BYJ-48 stepper motors has rocketed so replacements will cost a lot more - almost as much as NEMA11s! I don't think they're worth it except for projects where the load is guaranteed to be very light and space/weight is important. Found a smaller stepper motor but at twice the price :- Smallest Nema 8 Step Motor 1.8deg Bipolar 0.2A 1.6Ncm/2.3oz.in 20x20x28mm 4-wire

I have some NEMA14 stepper motors I bought for my various clocks and one of those will just fit between camera and casing. Better would be NEMA11 ones which are smaller. Trouble is suppliers seem to be still on holiday as the earliest delivery is 15th January I think I would feel happier using one of these for the lens cover too as the gears in the 28BYJ-48 are so fragile. 28BYJ-48 stride angle = 5.625° /64 = 0.087890625° NEMA11 with 1.8° and 16x microstepping = 0.1125°. 10 steps of 28BYJ-48 corresponds to about 8 steps of NEMA11 so comparable for focussing. I have ordered a couple of these :- Stepper Motor Nema 11 1.8°10oz.in 0.8A 28HD1411-02 CNC Router KIT Bipolar UK

All these photos of foreign parts with super-duper clear skies are putting me off imaging in the UK Well, almost I can't afford to go to such places so my decent site for the UK will have to do If we ever get some decent weather and I get my equipment working I'll take a photo...

These little 28BYJ-48 stepper motors are really too cheap for anything other than really light duty. After all, what can you expect for just a pound!! Yes, that's all they cost. I think the focuser problem may not be the top catching but could be its inertia. It might be alright if it was just turning the lens. I'm going to sleep on it.

Lens gear 25mm radius 25 teeth - pinion 12mm radius and 12 teeth. Total spacing = 37mm. Gear ratio 25:12. This gives a ratio of about 2:1 and for roughly double, juggling the figures gives pitch circles of 30mm and 7mm radius with 30t and 7t (ratio 4.3:1).

Brought the rig indoors to check the focussing and I've found the problem - the gearbox in the stepper motor is broken - a couple of teeth broken on one of the gears so it would move one way then stop. I guess the cone caught on the casing. The problem with these little cheapo stepper stepper motors is that the gearbox contains tiny nylon gears that won't take the torque the stepper itself is capable of producing. I shall just have to make sure nothing can jam up. I could increase the gear ratio to give more torque available to turn the lens. I think I'll change the gear ratio anyway as the focussing speed is rather fast - accurate focussing needs 10 ticks or less and with a standard rang of 10,000 this is rather small. Of course, this can be changed in the code but a higher gear ratio would mean less affect of backlash in the gearbox.

Yes, I thought of that but the GPIO lines seem to be very sensitive to even very tiny currents pulling them up. On power up the GPIO lines are floating and since the logic is CMOS it's very easily destroyed - as shown by my pile of dead RPies. A 3.3v Zener diode could be used to prevent the line going above +3.3v but it's getting complicated again. Seems the only really safe way of interfacing the GPIO lines with external circuits of higher voltage is to use opto-couplers. It says this in the book I've got on interfacing the RPi. Exploring Raspberry Pi: Interfacing to the Real World with Embedded Linux