Advice needed: Large printer, whats worth the price? and other things.

Hello,
I am new here and want to build my first 3D printer for making 1:1 scale prototypes for work and to just have fun. I have been reading around for months and dreaming of having my own 3d printer .

My criteria is:
1. Not cost the earth,
2. Can print 400mm x 400mm x 450mm objects,
3. Has a small footprint, space is at a premium including when running,
4. Is fast, I loved richrap's prusa hotend video [www.youtube.com]
5. Prints nicely though i can survive sanding and trimming stray strands,
6. Prints PLA, Nylon and Polycarbonate,
7. runs quietly.


I was initially thinking of making a large rostock a makerbot replicater but with the extruder away from the hotend as the extruder in the replicator makes it have to have a much larger frame.

What model should i base my printer on and what problems will i encounter?
What are those models strengths and weaknesses?

Is it all right to make the frame and or rods out of cast iron? I heard that a flexing frame reduces print quality and cast iron dousnt flex though I would be unhappy if it shattered.
Should I use spectra wire or rubber belts? I heard the elastic nature of the material makes the print head overshoot when it moves fast.
Anyone tried using toothed bars or bicycle chains and sprockets in place of the belts?

Do I really need chromed steel rods which have an insane price tag?
In fact what is worth the money on quality parts and what isnt?

What parts of a 3d printer is noisy and how can I dampen it?
I'm thinking of putting an enclosure around the printer to keep dust out. What air flow is required? exhaust fan at top, middle or bottem?

I look forward to your answers

stonefisher

Lots of requirements. The build size is probably the primary filter.
Checkout the Rapidbot Mega - only one I know with huge build area - like 29"x10" - about $1250
I personally am currently waiting for the Morgan SCARA bot to be completed - nice build area and easily expandable.
For the footprint, basically count on 3-6" bigger than the build area size. For the 8x8", typically 12-14" square.
A friend has made a Rostock, but continues to have bed leveling issues.
The idea with the chromed steel rods is smoothness.
X-motion bed belt is often loudest - it moves the most frequently
Enclosure is good for heat management. ABS has heat requirements and Fans are wonderful on the extruder and the electronics. Heat management can become an issue.

The larger you go, the sturdier frame you need, and it can make a huge difference in your requirements, depending on the need for accuracy. Cast iron may be a bit much, due to the fact that, for one thing, it has to be cast. I am doing a large printer, it gets complicated as the size goes up, and I am doing a heavy steel frame. (see my thread). Parts such as motors and rods tend to get more expensive as the quality goes up. Electronics and bearings are available from such a broad range of sources that you can save a few bucks there. As to bicycle chain, it is too heavy and has backlash. Use the belts. You want all the weight in the fixed parts, and the dynamic parts should weigh as little as possible. The bigger you go, the truer this gets.

I was a prototype technician I built this for one to one real prototypes larger printer definitely needs a fantastically strong frame to get good results and having a remote extruder causes all sorts of problems so moving a good strong reliable extruder is a lot of mass to be accelerating and decelerating never mind if you decide to move the table again a lot of mass to accelerate and decelerate here is a couple pictures of the one I designed and built

Edited 1 time(s). Last edit at 06/19/2013 12:34PM by cnc dick.

That's one hell of a machine you got there. What kind of speeds does it get given that everything is lead screw driven?

@purteesteve Yep print area is the deal breaker. None including the models you listed have the print area I need to make a 1:1 scale model. This is why i'm going to need to make a giant version of one of them.I really like the delta rostock design as it requires less parts to make and it seems really fast. It also has a good horizontal footprint which is key for me. I understand that the print area is so large on a rostock if you are really silly you could print an item large enough with a large enough bed that you would not be able to remove the printed object from the printer without cutting it up. You say your friend built a rostock but is having leveling issues. What are those issues? Is it a one off problem or a recurring plroblem?

@maxx mayhem This is another reason why I am interested in the rostock design. You cant get surdir than a triangle. I was thinking of using 20x40mm or 40x40mm extruded aluminium frame. They cost about the same and I have found a reasonably priced supplier in the UK. I was thinking of doing it similer to the rostock max design except all aluminum frame as this cuts down on the price om those insanely expensive rods and it definately keeps the weight off the print head carriage.

@cnc dick. That is one nice big 3d printer. I see it is partly using 20x60mm aluminium frame in its construction and comparing the print bed to your chair roughly a 40x40x30mm print area? Whats with the electronics? you managed to make it fill two bix boxes.

As with thermals as I understand it you need a fan on the extruder depending on model of print head. I was thinking of getting the hot end from e3d which needs a fan al the time. You need a fan on the pinted object for certain plastics like pla and not abs and you need a fan on the stepper drivers to ensure they dont skip steps.

What I would like to know is how to install a duct fan on a rostock printer and does the print head frame have to have a balenced centre of gravity?

Has anyone tried putting a rotary tool on a 3d printer and use it as an engraving tool? That would be usefull to me as well.

Print speeds from 50 mm a second to150 mm a second print area is 17" x 14" x 14" if I remember right rapids are 300 mm/s because of its size and mass could not use reprap electronics I am using Mach 3 which is a mill based CNC software to run machine like I said everything has to be massive the heated bed is actually a large electric griddle 110 V under quarter inch aluminum plate topped with glass and tape in my opinion the big problem with reprap was unreliable extruder and hot end so I designed mine first very heavy but very reliable this is my goal because it was going to have to print 24 hours a day sometimes maybe up to seven days to get the full large prints never got to build the enclosure which I would have needed to get large parts like that largest ABS print I did was probably 10" x 6" x 3" but no whopping or lifting from bed before I got laid off and dismantled it and moved it home if you Google large scale repstrap you should find a little more on machine

Edited 2 time(s). Last edit at 06/20/2013 11:29AM by cnc dick.

The size of the print area, lenght of the rostock arms and the overall size of the machine are all related, but NOW do you work out the required arms lenght and the resulting bed or work area. !!!!


I am thinking of using 300mm or 350mm arm leghts, but now do I related this to the required bed/machine size. Can any help


thanks


Paul

@paul2d3d. The kossel is the newer version of the rostock but using 15x15mm extruded aluminium for the frame. At this page at the bottem [reprap.org] is a spreadsheet that will tell you what lengths of extrusion gives you what print area and what length you need to make the arms. Also you will want to install the auto leveler that Johann has made.[www.youtube.com]

I am thinking of making a kossel 1m wide and 2m high when I get the money. Just have to beef up the joints as I will be using 30x30mm aluminium extrusions for the frame.

Edited 1 time(s). Last edit at 06/24/2013 05:24AM by stonefisher.

Thanks for your help , usefully data


Paul