Question, I am looking for info on making/extending a 3d printer working area. So I’d like to be able to print (as a wish, not cast iron) 200x600 and maybe 500 high. So I am looking for the problems I will face ie engineering challenges and previous solutions. As an example say increasing the 8mm rods to 10mm or 12mm in order to get more bed travel and keep rigidity. I dont know if I can get as big as the above but I’d like to get a wanhao3i at its stock 200x200x180 to a practical / cost effective size limit. ie I cant see the point in spending a huge amount of $s but bang for the $ and over time as i can afford to do it.
Moving the platform on large machines is not very space-efficient, and it makes machine rigidity more difficult to control. Have a look at the Herculien and Eustathios machines: https://plus.google.com/communities/108524206628971601859?utm_source=chrome_ntp_icon&utm_medium=chrome_app&utm_campaign=chrome
If you’re going 500mm you need 12mm rods. For the 600 you need 12mm at least!
For rods seeing variable side-load (such as Ultimaker gantry cross or i3 Z stage) diameter should be around 1/35-1/40 of the span for Bowden or 1/25-1/30 for direct drive. Rough ballpark for initial design. Diameter needs to be nearly proportional to length! That puts you into downright stupid rod sizes for big spans. DO NOT USE ROUND RODS OVER 400mm SPAN. Switch to v-wheels on extrusion or linear rails bolted to extrusion.
@Ryan_Carlyle Thanks, I sort of thought Id have to move to a different rail type. What I really wondered on was the relative mass of the bed v the head, ie it becomes better at some point to more the head as its lighter?
@Steven_Mething yes, my personal opinion is that i3 style Y beds stop making sense over about 200mm usable X or Y dimension. Aside from the moving mass, the flex wiring for heatbed power starts to get more and more unsafe at higher bed powers. Reasonable people can differ though. It just makes less and less sense as you scale up.
@Mark_Rehorst Yes I already have, both the round ones with the extrusion underneath the entire length and the flat “D” shape like ones. I Suppose really I am keen with my limited funds not to redo the mistakes of earlier experimenters but to 'stand on the shoulders of giants" So 600x200 would be a bit of a luxury, 400x200 would probably be enough.
Speaking as an owner of a 300mm x 275mm x 320mm printer; I can say that prints using substantial amounts of your build envelope will be slow unless you use huge nozzles and layers. Just something to keep in mind.
Yes I am aware of that but printing the item in several parts and then cleaning it up, glueing it and cleaning it up again will also take time. if each big part takes overnight or 24hours but I can walk away I think that will be a win for me.
That was my thinking too. Though I underestimated how long it would take, I think.
I switched over to using special plastic bearings instead of the usual metal ball or roller bearings. Less cost, less maintenance, less noise, same speed and accuracy.
Depending on sizes and prices , when it comes to metal bearings and the like, I tend to like THK and SKF. They often pop up on ebay for a good discount, but still they’re a bit pricier than I would prefer.
I have been trying to get “decent” bearings here in NZ. From a NZ shop each bearing from say THK is $15NZ+ each and I need 5+. Goos idea though I might have a go on ebay if I can be convinced I’m getting genuine SKF and not a chinese clone “re-badged” or otherwise i might as well pay $10 for the 5 striaght from china. Assuming of course sellers will ship to NZ, many will not. Plastic bearings I have been quoted over $30each and the wanhao user group has warned me off them.
Be careful with overnight prints… There’s a good chance one will fail and envelop your hot end in a giant angry ball of molten plastic, or worse.
Ive asked in the wanhao 3i google group and the comments are avoid plastic bearings.
3d printers are fickle machines. The bigger and faster you want them to run, the harder it gets. And budget printers make it harder.
My thoughts are that running a moving bed that big will be heavy, you’ll have to slow everything down to compensate. So a print twice the length might take much more than twice as long.
Next you have to worry about print adherence, all FDM plastics shrink a little on cooling, and the bigger the print, the more annoying it becomes. ABS is particularly bad.
My third thought is that 3d printing is a hobby full of very enthusiastic people, but there’s not yet a lot of science behind the development, it’s still a young fringe hobby. The advice other users give is often contradictory, or doesn’t apply to your situation. So ignore everything I just said. 
I agree on mass/inertia. Also not just the bed, as I print a big item its mass and C of G will become an issue also, hence I think the bed has to move only vertically where its a small and slow amount anyway. This means the head has to move in 2D I suspect.
@David_McGuigan As a fellow David I second everything you said. 3D printing outside of industrial applications came from tinkerers. Some of the “do this, not that” out there may be well intentioned but based on mistakes or improperly spec’ed versions of parts. I am hoping we can keep getting many more engineers (I’m one) and scientists into it to remove some of the voodoo and anecdotal evidence and such.
Thankfully multiple axis CNC motion systems are well understood, we make them all the time. We just need to make them cheaper than many current CNC motion systems are, since printer loads are a bit lower than CNC milling loads.
@Steven_Mething It may be worth looking into this, a bit. From what I see so far there’s some valuable thoughts there.
Oh, I was late with the SoM link. Oh well. Good link, though.
@David_Simmons lol, “Voodoo and anecdotes” is precisely the phase I’ve used in reference to 3d printer advice you frequently receive online.