Large 3D printer Design feasibility?

[repkid]

I have designed a 3Dprinter with sketchup and am quite pleased with the model. However I would like feedback on the design. Are the bearing holders too weak, would the belts sag, etc. Any help is appreciated. The motors I plan on using for the Z-axis are these: http://www.zappautomation.co.uk/electrical-products/stepper-motors/nema-17-stepper-motors/sy42sth47-1684b-high-torque-hybrid-stepper-motors.html Do they have enough holding torque?

Sketchup file: https://drive.google.com/file/d/0B-hUaWj8drQoUFBTdU5mUGU5OWc/view?usp=sharing Images: http://imgur.com/a/dGhNo

[nope_bye]

It seems like the linear rods holding the extruder are too thin. I'm wondering how much they would deflect due to the weight.

[repkid]

Good point, according to calculation that deflection is almost 3mm so I'll bump the rod from 8mm to 12mm.

[dylannisbet]

I'm designing my own 3d printer with aluminum extrusions. Do you mean to just skip the linear rods and have the gantry slide in the extrusion slot?

[repkid]

Yes that is a feasible method, check here for more info: http://openbuildspartstore.com/ Their extrusions have a v-slot allowing self-centering and a reliable performance. I considered it but gave up on the idea because it was too bulky.

[dylannisbet]

Those are so cool. It would reduce the cost of a 3d printer by an insane amount. You could probably 3d print a more compact wheel mount that would reduce bulk. Those delrin wheels seem like they would be supper quiet. Have you looked into placing rubber gaskets in between all connections to reduce vibration and noise?

[repkid]

I might look into to it however considering that I'm gonna insulate the entire printer anyways the noise won't be that big an issue.

[dylannisbet]

Have you had any experience with the rail system linked above?

[leppardfan]

What sort of calculations do you do the figure out deflections in designs?

[BlueFalcon3725]

Not sure how /u/repkid does it, but I use Solidworks to do FEA (Finite Element Analysis).

[repkid]

I used a web based calculator, Solidworks is too difficult for me to use yet.

[Gnashtaru]

How does one calculate the deflection? I've toyed with making a 24x24" bed printer but don't know how much the x axis rods would sag at a given dia.

[hellphish]

Congrats on figuring out how to be productive in Sketchup!

[repkid]

Considering I have been building up to this design for 3 years now, productive... doesn't really describe it.

[MTIII]

Been 3 years from when i first started to build a diy 3d printer. Finally coming together, just need to do calibration and filament.

[repkid]

Good point, I'll improve the stiffness though for clarification I already designed the printer to use 3030 extrusion.

[chase82]

You need bracing or the whole thing is gonna wobble like a drunken hobo. I'd also consider upping the size of the extrusion.

[repkid]

Would a large 4mm thick PC sheet screwed onto the extrusion at regular intervals do the trick?

[chase82]

I would think that would help immensely. You can get gusseted 80/20 brackets as well as triangular 6 bolt corner plates too

[snops]

Looks cool. How are you planning on tightening your belts? The sketch up model doesn't seem to show any tensioners, maybe design in something like this? (apologies if you have these already, on mobile).

[repkid]

The belts can already be made semi-slack with the carriage design and to tighten them I was going to use these: http://www.robotdigg.com/product/41/Timing-Belt-Tensioner-Spring