Need some guidance on building slightly modified printer

Hey everyone,

I've been lurking around here for a while but am now trying to stop procrastinating and start building.

First I need to know what I'm building

I have a lot of experience with 3d printing on a BfB3000 at work. I've even done a few mods like re-making the bed holder out of MDF and building an aluminum heated bed. I also moved the plastic spools above the frame and routed them directly into the extruder heads, etc... Nothing too fancy.

I am building this 3d printer for a specific purpose and as such I have some specific requirements for it. Mainly, my issues are with bed size. I need approximately 280mm in either X or Y. The other lateral dimension and Z can each be approximately 150mm. I have seen some designs that are much bigger than this, and some that are almost big enough but not quite. Ideally, I would be able to upgrade this machine to print nylon in the future which would mean replacing most of the plastic parts with MDF, metal, or something else, but for the time being, I just need to get up and running as soon as possible.

I'm trying to find the path of least resistance from an existing design to what I am looking for, but my mind is kind of blown by the sheer number of possible paths out there. Trying to understand all of the possible combinations I could try and their pros and cons is dizzying. Hence, I need a bit of guidance to help me sort through all of this.

From what I can tell, I need to choose all of the following in a compatible way:

-Frame design
-Axes design
-Bearings
-Bed material
-Bed heating method
-Bed heating electronics
-Stepper motors
-Brains

Is anyone willing to guide me through this process? I feel like once I build one, I will be able to modify the heck out of it and design new ones autonomously, I just need to be shown the ropes the first time.

Thanks!

Another person on the forum (sorry, I'd like to properly attribute, but I don't recall who it was or which thread I read it in) suggested a very clever method for increasing one dimension (actually you get Z-Axis increase as well)

Increase the length of the threaded rod for the verticals triangular end sections of the frame. This will increase the Y-Axis dimension, as well as the z-axis dimension.

You'll need to modify the length of the three pieces of threaded rod that make up each end section, as well as increase the length of the two threaded rods used for the z-axis. You'll also need to order a longer section of drive belt for the y-axis to compensate for the increased travel.

enjoy

I would seriously advise against simply increasing the lengths of threaded rod to "up-size" a Prusa, etc. The M8 structural members are too flexible at those lengths. You could increase the rods to M10 - it has been done - but the costs increase significantly. For the size you are contemplating I would say to look into one of the extruded aluminum machines as they will proved the stiffness you require at a much lower price point than threaded rod. And they are much more reliably expandable than threaded rod machines.

Also, at that size you may need to increase the diameter of the X and Y axis rods to 10mm. A costly proposition, but it you must have 280x280 I would highly recommend that you consider it.

As far as the various sub-systems are concerned they should be fairly interchangeable.

The Frame/Axis/Bearings you will use will depend entirely on the type of machine and the printed parts.

The other options are independent, so any combination will work together. That is not to say that there are no constraints, rather there may be some dependencies. Specifically, when you increase the bed size to 280x280 you are now dealing with a significantly different heated bed than the standard PCB heated bed. You'll probably wind up making one from aluminum and power resistors - which is significantly different in weight - and which will require you to build a Y-axis that is as lightweight as possible.

But there are many ways to skin a cat - and none of them is wrong (so long as you get the skin off). So while the members of the forum can provide guidance and advice I would say that you will have to solve some of these issues yourself (unless you buy a kit). But novel solutions to the problems encountered in building these machines is part of the evolutionary process we are engaged in with reprap.

So welcome to the club! Just remember - there are no stupid questions here - someone else is wondering the same exact thing.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Thanks for all the replies. I'll ponder over them and post some more later when I reach some conclusions.

For now, I'll just clarify that I only need 280mm in ONE axis. The other two axes can be as small as 150mm each...

And, I ,too, was leaning towards aluminum extrusions...

I am of the opposite view than has been expressed. 280 x 280 isn't that much larger than a standard prusa. If you are only modifying it in one direction the changes wouldn't be that significant. You could get the printer up and running and then have a look at the stiffness if thats an issue. There are some very simple mods you can do easily to bring the stiffness back to what it was.

1) Put M10 tubes over the M8 rods and tension them with nuts at either end.
2) Add some MDF plates high up on the rods. I have one at the back which I mount my electrics. It stiffens the frame quite a bit.
3) Run the printer slower! This way the head inertia won't have such an effect or use a bowden extruder.

Of course there is always the Mendel 90 which could easily be modified to increase the Y axis to 280mm

I would agree that the Mendel90 is probably this stiffest and cheapest option. The issue is that not everyone has the tools/space/ability to make one. I suppose you could have the parts cut for you and assemble it, but where's the fun in that?

The one reason I would still suggest that extruded aluminum is the way to go is that it is only marginally more expensive than threaded rod, implying that fewer modifications would be needed and it should work 'out of the box' rather than trying to stiffen a standard design - I don't see too many 300x300 build area threaded rod machines out there, while this is a common sight with extruded AL machines. I just re-tuned my Prusa and the prints got marginally better, but still don't look anywhere near as nice as the prints coming off my Prism.

And yes, slowing down help a lot. I'm a bit of a turtle anymore - 50mm/s is fast for me.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]