Ultra reliable large print area concept advice - (inc 3D model images)

[Sams]

Hi all, my first time posting on here.

I am fairly new to 3D printers but I have been learning fairly fast. I do have existing mechanical knowledge and some decent equipment though.



What I want:

In terms of size I am looking to make is something that is capable of printing a box around the 600X x 350Y x 400Z mm mark (24 x 14 x 16") with the greatest reliability to the lowest maintenance possible.

Due to the long time it's going to take for the larger prints I want to be able to leave it unattended for as long as needed. If this means 24 hours a day for a whole week then that's what it has to be be able to do, if possible and without ever having an issue. I also don't want to ever have to recalibrate it or do any sort of tweaks. I wish to use it for my auto business so this means I just want it to work and in the shortest amount of time possible. If this means going to much more trouble and cost initially making it then so be it.

I do have the means to line things up nice and level and square in general. For example I will use my mill to cut each section down to length and square off the ends. Done at the same time and with the same cutter this will make everything be damn near identical in length. The joys of a digital read out.

With all these demands luckily I only need to use PLA so no heated bed and I can use a fairly course resolution print, these don't need to look pretty.



Current planned concept:

- No round linear rails or support rails, rather all square type linear guides for all 3 axis. Very likely all 15mm in width.

- No belts either, they stretch, wear out and have elastic issues so it's not an option unless it's 16mm wide and no more than 200 to 300mm long in total. Instead I wish to use ball-screws assemblies for the X and Y-axis and twin acme screws for the Z-axis. In my limited research it seemed to indicate that stepper motors can have RPM/missed step issues with normal ball screws, so instead I plan on using only ones with a 10mm pitch. This means for 80mm per second they will be doing 480 RPM which should be completely reliable.

- Main rectangular frame made out of 40 x 40 extrusion channel with flat aluminium gussets for all the outside corners

- A lifting table for the Z-axis made from maybe 30x30 channel, still thinking about this one. I may bolt down an aluminium plate, face it off flat and then put a piece of glass on it. I will also probably have the guides on the four outer corners with one cariage each.

I already have purchased an NSK 360mm travel lead screw assembly for my Y-axis, despite being used I can feel no slop at all with any amount of force, it's amazing.

- Single Nema 23 frame steppers for the X and Y-axis, probably a 17-frame for either of the lengthways ends of the table and the same with a reduction box for the extruder.

- Print nozzle on the large size- possibly 0.5mm? Also with a temperature stabilised tip, lucky for me I don't need to do any of this part.


Now the top cross-bridge is harder to describe but that's what's in the 3D images. So here's the basics:

- A vertical and horizontal 30 x 60 extrusions joined together

- Guide rail on top and bottom of the vertical section, with a joiner between them that holds the print head assembly

- 30 x 30 sections bolted to twin linear carriages for each end

- Light weight brackets and supports to keep the inertial weight down.


Pictured:

In my 3D model I have the cross boom with the 2 of 30 x 60 sections across, 30 x 30 ends, my existing lead screw shaft, ball screw nut, nut to Y-axis carriage bracket, top and bottom linear guides and a single carriage for each.

I don't however have the bracket between the top and bottom linear carriages yet and hence why my ball screw nut bracket is just floating there.


3d-printer-A-3.jpg3d-printer-A-1.jpg3d-printer-A-2.jpg


Estimated cost:

That's the basics, as a rough guess I am estimating it will cost me $1500 to $2000 all up ready to go. But if I have a budget blow out then it will go ahead regardless, even if I don't have much cash this is something I really need.



So with that wall of text if anyone read all or part of it then I would appreciate any suggestions as I have a lot to learn still. Tell me that I am fooling myself if need be, just be specific as to how and why.

[curious aardvark]

so you basically want to build a smaller version of this:

Having met the 3dp people I reckon if you contacted them, they'd definitely help you build your own small version.
The company makes and sells the bits, and just made the printer because they had the bits already :-)

Just don't believe them when they tell you what they use to make prints stick ;-)

[richardphat]

Then you certainly wont print in ABS. Stay away from ABS if you're going to print gigantic object.
Look for .7mm nozzle, saves an amount of time you'll love it.
You will need to search if you need a big heat bed or a giant heat chamber to get reliable result.

You will still have much maintenance to do. 3D printing and maintenance free never gets along together.

[Sams]

I didn't get notifications for these replies, I shall need to double check my settings for this board.

Curious Aardvark: Thanks for the video, this model printer is one I looked at previously. I went away from this type of design because of packaging reasons. Many of it's design features have merit though, for example I like the linear system they came up with, it would provide good support even when used with only single carriages. However in my potentially ignorant point of view their anti-backlash system that "they came up with" is just a simple spring loaded nut over a multi-start thread. I think this is just a simple way of making a drive system. While I have no doubts at all that it works great the ball screws I have in mind don't have backlash and won't wear out like those plastic nuts doing. But hey I could be wrong. Otherwise the print area is excellent and I quite like the truss shaped reinforcement for the sides. Also to be able to have a print resolution like that they must be doing a whole lot right.

Richardphat: I indeed don't want to touch ABS, I don't want to mess around with heated beds and climate controlled cabinets. PLA seems to have good dimensional stability and is easy to work with so it seems to be the logical choice. A 0.7mm nozzle sounds good too.

So what sort of things can you think of that might need maintenance? I am sure I have a overly simplistic and optimistic view of things right now. Apart for the reapplication of the bonding tape.

[richardphat]

• Typical nuts and screw that becomes loose due to vibration on small infill shape. The nozzle might even get loosed and you will have leakage.Those are real killers even on slow/normal speed (30mm/s 50mm/s)

• Clogged nozzle (partial or full) if temperature control is failing (PID) value can be a pain in the butt to adjust. You may want to buy several nozzle so you can increase the machine productivity in case it happens.
• Jammed hotend (well, not the clogged nozzle); i.e, sometime the heat goes up through the peek and clogged in the tubing.
• Heating element such as heating resistance are cheap but are thrash after few weeks of use. You might buy heating cartridge for better performance, and might want to buy several in spares when they are less effective.
• Depending on how you will fix your glass/acrylic bed, ex. Ultimaker using the edge, paper clamp on circular bed from Rostock, you will end up having an important curvature of your glass. Which is enough to completely mess with the first layers.

Pretty much what I had in my mind, at 1:23AM, might remember something later. You may want to put extra time for an autobed leveling device to save the time.

[Sams]

This is the exact sort of advice I am looking for thanks. Should you happen to think of any more then I would very much like to hear it.

As for your points-

- Fasteners: I didn't think of this one but it makes a lot of sense. Even if I will try and make the gantry as light as possible I might have some harsh acceleration rates and which will make it will cop a bit. For the frame I think it's a non issue, once you see what I have in mind you may agree. Now that I know this potential issue I will use Nylock type nuts and Loctite for the rest. I will be careful with which grade I use, this machine is going to have heaps of fasteners with the basic construction and lots more in the reinforcing ribs. This means if this is a problem then it will be a big one.

Thinking about it I was going to join the top two 30 x 60 sections with bolts through the top face of one and T-nuts into the other with 40mm long bolts. But I can drill right through both pieces and use a bolt that has a length that's 90mm minus the T-slot depths. This way I can have a lot more bolt tension and with nylock nuts. I will need to check if I can fit this in the channel and still slide a T-nut over the top or else I am limited as to what I can add later without having to take it apart. I might be able to use button heads on one side though.

- Print head: I didn't elaborate on this much in my initial post. The print head this one guy I know developed has a nice fully enclosed heatsink with a 40mm fan in the side. In it, at the end I presume is a temperature probe which is used in a closed loop system to regulate the temperature at the ideal point all the time. I would think this and the good design in general would help avoid clogging overall.

- heating element: I shall look up what this heater cartridge is. Having a heating element stuff up a few days into my print would be pretty frustrating. I will have the best option I can get my hands on along with minimum of a one spare just in case. Same goes for the tips but I am pretty sure I can just drill out the blocked ones on my lathe using a mini chuck to hold the right size drill bit.

- Bed: This is can guarantee will be good. If I use glass it would be thick and have a nice flat base under it. Chances are though that I will just have an aluminium plate that's a decent thickness like 12mm that's clamped using blind threaded holes from the bottom up into it. Pending how good it is initially it would be faced off to be dead flat, I am unsure if I can do that job in my mill due to the lack of sufficient Y axis travel, but with my 100mm cutter I may have enough

I do plan on having self calibration built into it to pick up the position.



Here are two more images, this time something I have designed for me to make myself completely:

cross slide nut to carriage-2-1.jpg cross slide nut to carriage-2-2.jpg

The ball screw nut bolts to the front flat face as shown on the left hand pic and the other side will bolt through the top part of the print head carriage and into the top linear guide carriage.

Due to being part of the moving assembly I wanted it to be rigid but also light. Sure I could of designed something fancy and ultra light but I don't want to spend too long machining this up. Despite how it looks it shouldn't take too long to make as most of it is machined using simple cuts. It's massively stronger than what I need and the program tells me it should end up at just over 100 grams. While I am sure if I really wanted to I could halve that again but the machining time would be about 4x fold.

I will post more images as I have them. I shall start the main part of the frame soon I think.