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DIY 400x400x200 printer, choice question / doubt

Posted by HugoW 
DIY 400x400x200 printer, choice question / doubt
March 08, 2017 02:32AM
Hi,

first post here, I've been lurking a while... I am building and designing-on-the-go a 3D printer with a workspace of 400x400 bed, 200mm Z axis. The bed will move up and down like with a core XY, X and Y axis on top of the machine. I am in doubt about the drive of the X and Y axis. I have found the CoreXY drive system, but I could also drive the X axis with it's own motor traveling with the Y axis. This would make the set-up easier I think. The downside would be the weight to be moved. But the weight is already considerable for a 400mm trave x-axis, adding a little motor and a lot less belt I don't think would matter much. I think I would gain a lot more from using 12mm aluminium rods for my Igus bearings instead of the heavy hardened steel ones I have now. But all this is just my thoughts, not based on any experience. Please advise from experience.

Cheers,

Hugo
Re: DIY 400x400x200 printer, choice question / doubt
March 08, 2017 03:04AM
Quote
HugoW
Hi,

first post here, I've been lurking a while... I am building and designing-on-the-go a 3D printer with a workspace of 400x400 bed, 200mm Z axis. The bed will move up and down like with a core XY, X and Y axis on top of the machine. I am in doubt about the drive of the X and Y axis. I have found the CoreXY drive system, but I could also drive the X axis with it's own motor traveling with the Y axis. This would make the set-up easier I think. The downside would be the weight to be moved. But the weight is already considerable for a 400mm trave x-axis, adding a little motor and a lot less belt I don't think would matter much. I think I would gain a lot more from using 12mm aluminium rods for my Igus bearings instead of the heavy hardened steel ones I have now. But all this is just my thoughts, not based on any experience. Please advise from experience.

Cheers,

Hugo

CoreXY is pretty nifty in many ways. For one, the tension on the belt means you don't need to use such a rigid Y axis. It's similar to adding wire tensioners to frames, but in a moving system. If the Y axis tries to move one way, the belt tension on the other side will counteract it. This means the Y axis can actually be a lot lighter then you would use for a Cartesian machine. Top it off with the fact that you don't need a 300gram motor and you're looking at big weight savings. Also consider the fact that you will not be distributing the weight evenly on the Y axis if you have a motor. Any backlash in the system will show up even more (but lopsided) if you have one side of the gantry heavier then the other. Place the motor in the centre and your rods will bow from the weight.

You'd be surprised how much difference removing weight makes. Although using Cartesian in the way you are suggesting with the bed in Z makes a lot of sense (removes some banding, less problems caused by weight of print, less likely to be kicked off bed), you don't solve the main issue which is the huge weight of the bed moving in Y. Instead you have a possibly even heavier 400mm X axis which moves in Y. If you are using Nema 17 motors, be prepared to print slow to keep the quality up.

My suggestion would be to make a CoreXY, and if the system really disagrees with you then the modifications to make it Cartesian are minimal.
Re: DIY 400x400x200 printer, choice question / doubt
March 08, 2017 02:08PM
So is a 400 x 400 heater bed available
or
do you have to cut one on a table saw?

600 mm linear rails out there cheep?

See what hardware is out there -- design around it
unless cost is no problem
then get everything custom made

confused smiley
Re: DIY 400x400x200 printer, choice question / doubt
March 08, 2017 05:04PM
One down side to the CoreXY, especially for a large printer, is the loss of belt stiffness with the really long belt lengths involved. The mass of a large carriage makes the belt stiffness even more critical. You might want to go to 12mm wide belts if using 2mm pitch, or maybe jump up to 3mm pitch belts, which are a lot stiffer. Here's a link to a Gates datasheet listing comparative belt stiffnesses (tensile modulus):

belt properties

On my 350x350mm printer, I used a modified H-bot configuration because it uses shorter belts, and I've also got a fairly low mass carriage. I used a single 6mm wide MXL belt (similar to GT2) which works OK, but I wouldn't mind it being a little stiffer.

Edited 1 time(s). Last edit at 03/08/2017 10:34PM by LoboCNC.
Re: DIY 400x400x200 printer, choice question / doubt
March 09, 2017 02:22AM
Theoretically on corexy, the longer belts make a difference but I don't see much of it in the prints. I recently switched from using steel reinforced belts to fibre reinforced on my corexy (300x200 print area) as the steel started to snap, but although the steel belts are much less elastic there is no discernible change to print quality. Going up to 9mm wide belt or 3mm pitch belt is an option but it adds quite a bit of expense and difficulty in obtaining parts (GT2 belt is now ubiquitous in 3D printing). Gt2 belt is spec'd to take a lot more punishment than most 3D printers dole out. I'd be interested to hear how you get on if you do this.

As for corexy, its a clever mechanism (as is the ultimaker style gantry [i0.wp.com]) and allows for a relatively light x and y axis. Moving the bed in Z makes sense the movements are small and slow.



I am developing the Piezo hotend z-probe [www.thingiverse.com]
DemonDeltaMicro - Micro Delta Printer [www.thingiverse.com]
Things I've made/remixed.
Re: DIY 400x400x200 printer, choice question / doubt
March 09, 2017 02:58AM
Thanks for all the replies. I answer chronological:

@Origamib; thanks, I understand what you mean.

@cozmicray; I indeed design around stuff I can get my hands on easily / cheaply. There are heated beds out there 200x200mm, four would make a 400x400 bed. But I am planning a glass bed with nichrome wire and Kapton tape heating. I have made heaters before for other purposes. It might even become a 230V~ heating, if I can get my hands on a cheap 1:1 transformer.

@LoboCNC; I have planned to use the 10mm GT2 belts. I’ll look into 3mm pitch.

@DjDemonD; I’ll let you know how the 10mm GT2 belts hold up if I go that route. Which I will probably do due to availability. I most parts from Banggood and AliEpxress.

The system will run on 24V, RAMPS with TMC2100 drivers and NEMA 17 motors. I have designed an extruder carriage Mk8 style but both carriage and extruder are made as one part. I will go with the CoreXY set-up because of the above advise.

Cheers,

Hugo
Re: DIY 400x400x200 printer, choice question / doubt
March 09, 2017 12:21PM
I guess its just priority
Heater maker or 3D printer maker???

The good Digital Dentist has convinced many -- aluminum tooling plate

Glass a good thermal insulator 400 x 400 with nichrome wire
it will look like the Alps when heated up??

Flat hot bed = good prints

Perhaps stainless tubing in ceramic bed
with super heated steam from your neighborhood reactor???
Controller would have to control steam inlet (servo valve)
Steam outlet --- cook hot dogs --- keep buns warm


confused smiley
Re: DIY 400x400x200 printer, choice question / doubt
March 09, 2017 04:21PM
You can get silicone heaters at that size for very cheap. I have a 280mm 240v heater I bought for £20 from aliexpres.
Re: DIY 400x400x200 printer, choice question / doubt
March 09, 2017 04:45PM
Don't stick a heater to a piece of glass. It doesn't work very well.

Here's a Taz printer with a glass bed and heater glued directly to it:



After the glass broke, I converted it to aluminum and put it on 3 point leveling instead of 4. Here's the same heater glued to a piece of 1/4" cast tooling plate:



Here's the whole conversion process for that printer: [www.instructables.com]

Not sure about flatness? Here's 85 wheels for nerdy derby cars printed in one go, nearly edge to edge on 1/4" cast aluminum bed plate:



Here's a 250+ mm diameter print in ABS printed a the same machine:



Still not sure about flatness?

https://vimeo.com/157222577

https://vimeo.com/157784843

Any questions?


Son of MegaMax 3D printer: [www.instructables.com]
Re: DIY 400x400x200 printer, choice question / doubt
March 10, 2017 12:30AM
Thanks for all the info. I sort-of scrapped the tooling plate because of the weight. I was calculating 1/2", not 1/4", and I was still working on a Y-axis moving bed design when I considered the tooling plate. Hauling that about would not be sensible. I never considered it again when choosing the CoreXY-like design. I guess it's back on the priority list.

Cheers,

Hugo
Re: DIY 400x400x200 printer, choice question / doubt
March 10, 2017 12:38AM
1/4 tooling plate (I use 6mm) works wonderfully and I can thoroughly endorse it. It does work best on a delta where it does not need to move at all, but it can be managed on a moving Z platform. I use a counterweight for my corexy 1.5kgs, essentially my belt driven Z axis has a fair amount of mass but is easy for a nema 17 to move and hold.



I am developing the Piezo hotend z-probe [www.thingiverse.com]
DemonDeltaMicro - Micro Delta Printer [www.thingiverse.com]
Things I've made/remixed.
Re: DIY 400x400x200 printer, choice question / doubt
March 10, 2017 01:16PM
For info, my Core XY has a build area a tad under 400 x 400 and 740 in Z. The main frame is 600 x 600 x 1,000. I can print stuff like this [www.youtube.com] and this [www.youtube.com] and there are some other things on my Youtube channel. The bed weighs in at around 7kg (10mm thick aluminium topped with 6mm thick float glass) and is lifted by 3 screws driven by a single Nema 17 via a continuous belt. As configured in the videos, the Y axis including the X axis weighed in at 1,900 gms and I regularly print at 90mm/sec. All belts are 6mm gt2 - never a problem.
Re: DIY 400x400x200 printer, choice question / doubt
March 10, 2017 02:11PM
Quote
deckingman
For info, my Core XY has a build area a tad under 400 x 400 and 740 in Z. The main frame is 600 x 600 x 1,000. I can print stuff like this [www.youtube.com] and this [www.youtube.com] and there are some other things on my Youtube channel. The bed weighs in at around 7kg (10mm thick aluminium topped with 6mm thick float glass) and is lifted by 3 screws driven by a single Nema 17 via a continuous belt. As configured in the videos, the Y axis including the X axis weighed in at 1,900 gms and I regularly print at 90mm/sec. All belts are 6mm gt2 - never a problem.

Sir!
That is impressive work!!
Re: DIY 400x400x200 printer, choice question / doubt
March 11, 2017 08:57AM
Quote
SatorCodex

Sir!
That is impressive work!!

Thanks but I didn't make the post for any sort of plaudits. Just to demonstrate that even with a 600mm x 600mm frame, with belts around 2.4metres in length and shifting 1.9kg of mass, standard (ebay's finest) 6mm GT2 belts and Nema 17 motors are perfectly capable of achieving good results. The printer has been running for about 6 months and there haven't been many days when it has been idle, so many hundreds of hours of use. Never had cause to change the belt tension (or anything else for that matter). I've recently changed the design of the XY axis so I replaced the belts at the same time but to be honest, there was absolutely nothing wrong with the old ones that I've taken off.
Re: DIY 400x400x200 printer, choice question / doubt
March 20, 2017 02:11AM
Thanks for all the input. I've just bought aluminium rods instead of the steel ones for the moving X axle, reducing weight considerably. To keep things simple, I plan to use these:



Any comments? I like it to be spring loaded as it keeps tenstion, but I wonder if it is stiff enough.

Cheers,

Hugo
Re: DIY 400x400x200 printer, choice question / doubt
March 20, 2017 02:20AM
I'd say avoid those springs, they look on the face of it to be a good idea, and they're cheap as dirt as you can get them out of clothes pegs, but they will reduce your print quality. When the motor turns the belt, especially at high jerk/acceleration the spring has to compress slightly before the belt moves, this is especially pronounced during rapid oscillating moves.

Try something like this:
re-orientated_tensioner_big_part.stl
re-orientated_tensioner_small_part.stl
[www.thingiverse.com]

There's also this type which I haven't tried but which works like the spring tensioner, but its adjustable and importantly fixed in place at a set tension.
[www.thingiverse.com]

Edited 1 time(s). Last edit at 03/20/2017 05:43AM by DjDemonD.


I am developing the Piezo hotend z-probe [www.thingiverse.com]
DemonDeltaMicro - Micro Delta Printer [www.thingiverse.com]
Things I've made/remixed.
Re: DIY 400x400x200 printer, choice question / doubt
March 20, 2017 09:30AM
Quote
HugoW
Thanks for all the input. I've just bought aluminium rods instead of the steel ones for the moving X axle, reducing weight considerably. To keep things simple, I plan to use these:



Any comments? I like it to be spring loaded as it keeps tenstion, but I wonder if it is stiff enough.

Cheers,

Hugo

As long as you don't exceed the bias force of this type of spring, it won't add any additional flex to the belt. However, ad DjDemonD points out, high jerk/acceleration moves may exceed the bias force and then cause defects in your prints.
Re: DIY 400x400x200 printer, choice question / doubt
March 20, 2017 11:12AM
What?
X Axle? X guide rod?
Aluminum rods? How long?
How will they be straight?

How are they machined, polished?

What type bearing will NOT shred them?

Really? saving weight on load bearing piece that just has momentum in Y?

confused smiley

Quote
HugoW
Thanks for all the input. I've just bought aluminium rods instead of the steel ones for the moving X axle, reducing weight considerably. To keep things simple, I plan to use these:



Any comments? I like it to be spring loaded as it keeps tenstion, but I wonder if it is stiff enough.

Cheers,

Hugo

Re: DIY 400x400x200 printer, choice question / doubt
March 20, 2017 11:53AM
Subtlety is not your strong point, is it? I use Igus sliding bearings, combined with Igus hard annodized rods. Proven combo. 2x 500mm steel rod is 886 grams, same in alloy is 307 grams. That is 579 grams less to move about when moving the X axle in Y direction. That is a saving in energy so an enhancement in accuracy for the machine. The Powered hotend and sled weigh too little to make the alloy rods bend or sagg. The Y axle rods will have more load to cope with, but since they are stationary they will be steel.

[www.igus.com]

Cheers,

Hugo
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