3d Printer Linear Rod Design Semi Corexy

3d Printer Linear Rod Design Semi Corexy



Smooth rods dimensions for coreXY 300x300mm?



I am planning to build a machine based on coreXY that has a printable area of virtually 300x300mm with 1 extruder. I would like to be able to switch between directly feed and Bowden with one extruder, every bit well as to mount more than one extruder (upwards to 4, with a Bowden setup of class) and withal become at least 200x200mm as a printable area. I am still writing a tentative 3D model of the printer, but I estimate the smooth rods of the X and Y axes volition exist near 500mm.
I don’t know the weight of a typical direct feed extruder: given that 4 hotends should not weigh more than 400g, or alternatively a nema17 motor should not counterbalance more than than 400g, I guess that the central wagon begetting the hotend(s) should weigh not more than than 1kg including the nema motor with i extruder, or the iv hotends.

So what would be the right diameter for the Ten smoothen rods?

I tried to do some deflection calculations (for example
here
and
here) to get some worst case numbers, although many variables cannot be taken into account (for example rods are stock-still, but the frame is not perfectly rigid, etc). Still, with a wagon weight of 1kg and 2
steel
smooth rods with free ends, the deflection should be:

  • 0.15mm for rods with diameter 10mm
  • 0.07mm for rods with diameter 12mm
  • 0.04mm for rods with diameter 14mm

Given that this is really the worst case scenario for deflection (rods are not gratis only fixed, the deflection should be calculated over the length of the printable area and averaged considering of the length of the carriage that is non null, etc.) my judge is that 12mm diameter should be more than enough.

On the other hand, the Y axis (the outer i) should back up a heavier load because of the 10 smooth rods and their respective supports. I don’t know exactly how heavy they may exist considering I cannot notice weight information for all the parts I am planning to apply, but I guess it may reach 3 kg (the 2 Ten smoothen rods would weigh i kg on their own, plus the key carriage that may attain ane kg, plus the other supports). In this case the deflection should be:

  • 0.12mm for rods with diameter 14mm
  • 0.07mm for rods with diameter 16mm
  • 0.04mm for rods with bore 18mm

So, with a diameter of 16mm for (unsupported) smooth rods, there would be a theoretical total (X + Y) vertical deflection of 0.14mm in the center with respect to the borders (worst instance), which should be still adequate for the get-go layer if the bed is flat enough, the rods are directly (for instance
50 microns / 300mm, although I would like to know how to compute the correct value for 500mm), and bearings quality is decent. Alternatively, I may use supported rails.

What is your experience?

Edited i fourth dimension(s). Final edit at 08/23/2015 07:12PM by cristian.

Hi,

IMHO, smooth rods are not the adept choice for large printers,
considering the deflection is besides of import and that bearings have some play as well.
A CoreXY is meant to run fast, especialy with a large build surface area.
So you will need the all-time possible accuracy to get perfect prints at high speed.

I call back you’d rather ready a single linear rail on an aluminium profile for Ten,
and 2 linear rails on the overall structure for the Y axis.
Some Hiwin linear kits for Kossel mini printers can be great.

++JM

I have searched a piffling and the problems with linear guides are that they are generally expensive and often I cannot discover data about their accuracy, in item for used ones. I likewise wonder what happens to their straightness when they are fixed to aluminium profiles that are not perfectly straight.

I agree with J-max.

I accept made ii CoreXY. One with smooth rods and 1 with my own type of linear runway.

The fashion I encounter it, the trouble with the linear rods is non deflection (I use 12mm) but rather the play in the linear bearings. The play in these is only and so big that at high speed I take strong vibration and instability as a result. The internet says you tin can buy the more expensive bronze bushings instead of linear bearings and that volition solve that – But then you lot are out of the “cheap” solutions anyway so I recall you should just go for the Hiwin or similar.

The Hiwin (or homemade) is simply a simpler and neater solution in my opinion. Less parts and more than flexible for the future.

As you can see I still apply linear rods for my table because the load is constant and the motion slower.

Edited 1 time(south). Final edit at 08/24/2015 03:25PM past LarsK.

It is difficult to compare the 2 coreXY builds in the motion picture considering of many, many differences. Too this, bearings
are not all
the same, and a linear guide may also have some play if information technology is depression quality. In both cases (linear guide or shafts) I would like some indication about the precision rating of what I buy, that I find quite hard to obtain for all the parts. Information technology is relatively like shooting fish in a barrel for shafts to find hardness, straightness and dimensional data, less easy for bearings, and nearly impossible for affordable linear guides (secondhand ones in item). I must also acknowledge that I am not still able to interpret the technical specifications of brand new quality linear guides (although their price needs no estimation).

Edit:
here
is some farther basic explanation of shafts and bearings fits that I can sympathise equally a newbie.

Edited ane time(s). Last edit at 08/24/2015 04:57PM by cristian.

The links you but gave are for ball bearings (not linear bearings), for holes (non shafts) and the last i for hole and shaft fits – As in when you want to put a coupling on a shaft or a push button fit into a roller bearing.

I personally cannot answer your question. I have a master degree in mechanical engineering and I have four years work feel.

That is considering the information you are looking for is very much feel based and empirical and kept within the firms that has it. If you go buy a second hand NSK linear system you will go proficient quality. You might not exist able to summate what it will be, merely it will work.

What I can say is this; The approach with computing the deflection is way besides simplistic when information technology comes to avoiding vibration when going high speed. Further, the deflections you calculated are on the conservative sides and more, in the range where, as yous indicate out yourself, negligible. Yep, if yous determine to print a full 300×300 part you might get a 0.1 difference from center to edge because of this, merely that is completely negligible when considering all the other sources of fault.

My suggestion for y’all is then this;

Instead of spending then much fourth dimension on the theoretical side, try to see what options y’all actually have. What kind of parts can yous actually get for the money you want to spend, what is the experience of other people.

My input to you is then: I tried the Chinese linear bearings and the play in them is property me from going high speed. I found it harder to blueprint with linear rods because using rail allowed me to easier put parts together and I constitute that going with linear rods needed more parts.

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Other people here on the forum have said the same. Some people take said that going with statuary bushings (or linear evidently bearings) instead of linear ball bearings gave good results. Many people are happy with the Hiwin slides (I have not tried those).

I am not saying I am 100% right. Simply I am sure you are ameliorate off googling for opinions like mine above then trying to google yourself to a depth of understanding that I tin can with much certainty say yous volition not discover out in that location.

Edited 2 time(southward). Final edit at 08/24/2015 06:04PM past LarsK.

The problem is that in that location are infinitely many options, equally many as the sellers online times the experiences of other users. But the experience of other users may aid me as well as lead me to bad choices. For case you have a lot of experience in mechanical engineering science, that I guess helped you to build your own type of linear track. If I try to build my own, maybe I will fail completely for some stupid error in the pattern or associates of the function since I have no experience.

Moreover, in that location are thousands of users opinions online but many of them are newbie like me, and there is no guarantee that they understood all the mistakes they made nor that I would make their very same mistakes. Most people here purchase inexpensive Chinese bearings (and low quality rods) without regard for their technical specifications (remarkably, some sellers specify information about fit tolerances and even vibration, although I don’t know how reliable they are), and so in that location is no surprise when they say that systems based on smooth rods perform poorly. Even so, if somebody tried supposedly good quality/well coupled rods+bearings and yet found that they perform poorly,
then this information would be very valuable.

Besides that, I do believe what you are saying almost the fact that expert linear guides are easier to install, more compact, silent and probably even more precise than most of the designs based on smooth rods (for sure meliorate than the designs that
I may realize
with my poor DIY capabilities and feel), however I have no idea of what is a “good” linear guide for the printer I want to build. Hiwin website is non helping me in that respect (the descriptions of their products is a re-create-and-paste everywhere, and I need more fourth dimension to play and win “spot the differences”), near of Ebay stuff is affordable only in the US (I live in Europe) or has dead links to non existent technical specifications (that I would non be able to understand anyway), Aliexpress has a lot of products that may exist equally skilful as Hiwin stuff or equally bad as cheap Chinese bearings. Even without understanding technical specifications, I should read hundreds of users posts to understand what I may buy at a reasonable quality/price ratio, since prices change unfortunately from country to state and “quality” has different meaning from user to user (quality for me may be crap for somebody else and vice versa).

1 manner or another, my head will blow before I build this printer. Even in that instance, thanks all for reporting your feel!

Edited i time(s). Last edit at 08/24/2015 07:55PM by cristian.

Hi,

I mostly concord with LarsK.

You can dig deeply into technical specifications of each component.
If you do and so, exist aware engineering a new printer will probably takes yous years.
Through, yous will never be shure to get the best design and the best possible component.
Information technology’s only experimentation. That means, errors, adjustements, money…

My advices are :
Don’t be cheap or gear up to spend more on necessary upgrades.
Don’t dig to much into technique, because y’all won’t reinvent the bike anyways.
If you can stick to a working existing pattern, information technology’due south time and coin savings.

Nigh smoothen rods/linear rails.

The diameter needs to be large to become enough stiffness, exponentialy for large print volume.
Quality bearings are effectually $15 each, polymers /bronze bushings are around 5€ each.

Larger means more weight. Yous need to be lightweight for a good acceleration.
Because you will demand ii smoothen rods and at last 3 bearings,
the price will be not then far to a unmarried good Hiwin rails and wagon.
Hiwin kit for kossel

Technical data @ hiwin.com

You can also choose any aluminium profile V-guide organization
like Openbuilds or Makerslide. Which works properly too for a 3D printer.
Information technology’s a less expensive solution, nevertheless lightweight.
A Spanish supplier.

Aluminium profiles in europe.

++JM

Edited i time(s). Last edit at 08/25/2015 07:03AM past J-Max.

Yes, I approximate I have no other choice than builiding by trial and fault unfortunately…

If I ever manage to build the printer, I volition post some reviews of the linear guides I buy.

Thanks for your advices.

Quote

cristian

Yes, I guess I accept no other choice than builiding past trial and error unfortunately…

If I ever manage to build the printer, I will mail service some reviews of the linear guides I buy.

Thanks for your advices.

I congenital the SmartCore Printer with a 300×300 bed .. with no problems .. exercise a search on it.. in that location is a OpenJcad that all you lot practise is input the dimensions and information technology will give you the Box, belt and rod sizes..

Thanks mike3, I am actually a happy possessor of a smartrap (the original model) and I wanted a second printer a fleck more than solid even if not in the aforementioned budget. So I am considering a printer that, even if information technology is non fully in the reprap spirit, has a metal structure and no cantilever.

Hello,

To me, a wooden box may be stiffer than a module20 aluminium structure,
and you already take an enclosure. But it’s maybe a question of await.

Through, the SmartRapCore have 6mm rods, which is a likewise small diameter IMHO,
even for the 220×220 regular print area. Some users upgraded to 8mm.
I can’t imagine a 300×300 impress expanse may work well with 6mm rods.

Through, maybe the output expectations are low.

With the 10mm MDF frame, which is noisy, the last problem with the SmartRapCore
is the genuine Z axis which is not strong enough.

Some users upgraded to
the andreasL’southward improoved Z axis.

I’ve tested information technology and information technology works pretty well.

Just two things virtually it, the maximum Z resolution on a full step is 0.2mm,
so yous demand a 0.9° motor to hope achieve precisely 0.1mm or 0.05mm layers.
Or, you can add a reduction, geared or belt.

I’thousand curently building some other coreXY printer inside a 19mm wooden box chassis.

Seriously, it’south not expensive, very strong, and stands well vibrations.
It’s ways quieter than 18-carat SmartRapCore,

and better than other inexpensive aluminium profile printers.
To give y’all any comparison, it’south closer as a module40 construction, maybe better.
I believe information technology can hands stand a 300×300 print area.

Anyways, the most of import part should be the guides.
Did you made any choices ? I volition probably employ Hiwin MGN or possibly Igus W guides.

++JM

I have been reading a little near linear guides (
a NSK tutorial

for example, or a
funny HIWIN video, whatsoever suggestion for farther reading is very welcome) to understand better their pros and cons, the bachelor types, etc. I am really becoming a large fan of them (except for their price), thanks to the suggestions in this thread. I haven’t made a choice yet, I am trying to sympathise if I would be able to mount them properly: they demand a perfectly flat support, which is not that easy to get without proper machining (that I cannot practise past myself or at the makerspace nearby).

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Nonetheless, given the price and the difficulties of building a big printer, I am now considering a smaller printer but very precise (I will write more on this on the other thread I opened in this forum section).

Most wood vs metal structure, I don’t really know how well wood behaves at i-0.1 mm scales, in item over time (even if MDF should not undergo dramatic deformations), I feel more than confident about metal.

How-do-you-do again,

Well precision does not comes from your building material

but from your guides alignment and the lower play they permit.
If you’re more than confident with aluminium, and own the tools to work it properly, it’s ok.

To get a flat support, you tin can buy
total aluminum apartment contour, but at last 10mm thick.

It’s better than aluminium extrusions module20 alike, even if information technology’south a fleck heavyer.
Those you can utilise them for chassis only.

For the guides, the load will always exist lower than what the rail’southward static rated moment allows.
Even the Hiwin MGN seven allows ii.84 Nm.
Then don’t waste your fourth dimension to try to make a difference between them.
The 2 things important are the weight and the play.
No matter with the play if you buy a genuine rail system for a serious brand.
It will be definitely ways better than chinese smooth rods ones, and will last longer.
Throught, keep in mind these are consumables.

The Hiwin MGN 12 looks like a good option, because the carriages

are large enough to mount our stuff on information technology.
Otherhand, the
Igus W series
are larger and lighter,
the play can be adjusted, and they cost less to change.
Both will need a good support anyways.

Last, a rail selection depends of your budget too.
To me, it’due south more than important to invest more into your rail,
than to spend 100€ or more than for whatever expensive hotend.

++JM

Quote

J-Max

Howdy,

To me, a wooden box may exist stiffer than a module20 aluminium construction,
and you already have an enclosure. But it’south maybe a question of look.

Through, the SmartRapCore have 6mm rods, which is a too small-scale bore IMHO,
even for the 220×220 regular print area. Some users upgraded to 8mm.
I can’t imagine a 300×300 print area may work well with 6mm rods.

Through, maybe the output expectations are depression.

With the 10mm MDF frame, which is noisy, the concluding trouble with the SmartRapCore
is the genuine Z axis which is not potent enough.

Some users upgraded to
the andreasL’s improoved Z centrality.

I’ve tested it and it works pretty well.

Just two things nearly it, the maximum Z resolution on a full step is 0.2mm,
and then you need a 0.9° motor to promise reach precisely 0.1mm or 0.05mm layers.
Or, you can add a reduction, geared or belt.

I’m curently building some other coreXY printer inside a 19mm wooden box chassis.

Seriously, information technology’s not expensive, very potent, and stands well vibrations.
It’southward ways quieter than genuine SmartRapCore,

and amend than other cheap aluminium profile printers.
To give you any comparison, it’s closer as a module40 construction, peradventure meliorate.
I believe it tin easily stand a 300×300 impress expanse.

Anyways, the about important role should be the guides.
Did y’all made any choices ? I will probably use Hiwin MGN or possibly Igus Due west guides.

++JM

Built my Smartcore from 18mm cabinet class plywood.. cutting the centers out of the sides and back to reduce the noise .. very quite .. went with 8mm rods all around..300×300 impress surface area .upgraded to the andreasL’due south improved Z axis.. all in in all the price was around 165.00 usd .. after debugging and calibrating perfect prints every time..

Edited 1 time(s). Last edit at 08/31/2015 09:21AM by mike3.

Practiced
winking smiley

++JM

Quote

J-Max

Well precision does not comes from your building textile

but from your guides alignment and the lower play they allow.

The building fabric is very important to maintain precision over external stresses and fourth dimension. Wood can warp over time because of prolonged deformations, humidity, … MDF is less prone to that, only its stiffness is negligible with respect to metal, which is important in particular in the areas of contact of 2 surfaces. This does non mean of class that wood or MDF cannot be used to build a 3D printer (it has been done many times, I did it to reinforce my smartrap also) but one has to exist aware of the possible drawbacks and design the printer to minimize these bug.

Quote

J-Max

To get a flat back up, you lot can buy
full aluminum flat profile, but at last 10mm thick.

It’south improve than aluminium extrusions module20 akin, fifty-fifty if it’south a scrap heavyer.
Those you can utilise them for chassis only.

Thanks for the link. Perhaps because of automatic translation, I have been unable to find data most the precision of the pieces.
Motedis
makes them besides although not big enough. They specify also the thickness tolerance (most 0.3 mm). I take no idea of the needed precision to mount linear guides, anyway.

Quote

J-Max

For the guides, the load will always be lower than what the rail’s static rated moment allows.
Even the Hiwin MGN 7 allows 2.84 Nm.
So don’t waste product your time to endeavor to make a difference between them.
The two things important are the weight and the play.
No thing with the play if yous buy a 18-carat rail system for a serious brand.
It volition exist definitely ways better than chinese smooth rods ones, and will terminal longer.
Throught, keep in mind these are consumables.

I agree virtually the load, in that location are however things that are very important to know about play, for instance if rails have to be used in pairs or non. The gamble with expert linear guides is that they don’t slide if they are not properly mounted. Besides that, I concord that even the “worse” linear guide from a serius brand should be amend than cheap linear begetting + smooth rods.

Quote

J-Max

The Hiwin MGN 12 looks like a good choice, because the carriages

are big enough to mount our stuff on it.
Otherhand, the
Igus W series
are larger and lighter,
the play can be adjusted, and they cost less to change.
Both will need a skillful support anyways.

I haven’t read near igus products yet, it is on the TODO list.

Quote

J-Max

Final, a runway selection depends of your upkeep as well.
To me, it’s more of import to invest more into your runway,
than to spend 100€ or more than for any expensive hotend.
++JM

Well, I found the hotend that suits my needs for most twoscore€, I will stick to that.
smiling smiley

The rest will go in the linear guides!

Howdy,

Misumi is a serious brand too.
Actualy, information technology’s more expensive than Hiwin for the same quality.
Look at Hiwin documentation on their website,
you’ll become the aforementioned kind of informations.

Talking almost the build cloth, don’t think aluminium cannot expand too.
Pannelwood is not similar solid wood. It may non change as much as you retrieve.
If y’all utilise some finishing, information technology volition be sealed and won’t motion anymore.

Your arguments apply to solid wood versus heavy metal structure.

A 3D printer is a CNC, merely it’s closer to a laser CNC than to a CNC manufactory.
On a 3D printer external and internal stresses are no large deal.
If you utilize good guides, the more than the structure will stand is light vibrations.

I don’t desire you lot to trust me blindly, but appreciate some material accept its own properties,
and metallic does not overwhelm other materials someday.
We’re talking here about 20×20 profiles.

Just by resting my mitt on a 300mm piece, it will curve apace about 0.3mm,
while a 19mm MDF pannel won’t bend half of that.
If you own precise measuring tools, effort this.
Through, MDF will bring other interesting properties,
like dumping vibrations on the construction and maintain heat improve.

That’south why I far adopt a 19mm structure than a 20x20mm profile structure.

If you programme to use 40x40mm or greater profiles, I will reconsider.

Otherhand, a 20x20mm aluminium structure looks ameliorate than any MDF one
winking smiley

++JM

Edited four fourth dimension(s). Last edit at 09/01/2015 04:08AM by J-Max.

Quote

J-Max

Misumi is a serious brand as well.
Actualy, it’southward more expensive than Hiwin for the same quality.
Wait at Hiwin documentation on their website,
you’ll go the same kind of informations.

Misumi website provides online configuration and direct sell, manifestly. I am non aware of Hiwin resellers, I constitute products online here and at that place but it is difficult to find the exact product I want.

Quote

J-Max

We’re talking hither about 20×20 profiles.

Just past resting my hand on a 300mm piece, it volition curve quickly most 0.3mm,
while a 19mm MDF pannel won’t bend half of that.

I think you would be surprised. I don’t have a 20×20 contour here nor a 19mm MDF panel, but I can do some rough calculations just for the example you lot made. The formula can exist found online (for example
here), and approximate Young’s modulus for MDF and aluminium is
here. The moment of inertia for 20×20 profile is for example
here, while that of MDF tin can be hands calculated by the formulas
hither.

According to those approximate formulas, in order to bend by 0.3mm a 300mm long 20×20 profile you lot need to use about 28kg. A 300x300x19mm MDF console will curve a chip less nether the same weight: 0.22mm. However 20×20 profiles should be used in pairs for the structure, so that two parallel 20×20 profiles will bend just 0.15mm. Metal wins!
winking smiley

Conversely, a 300x300x19mm panel can probably withstand shear stresses much better than a 20×20 contour foursquare construction of the aforementioned size without diagonal supports. But it will also weigh much more.

Edit: I forgot to write that for MDF the weight should be evenly spread in the centre along one direction, so the comparing cannot be actually fair.

I would utilize 20×40 or 30×30 profiles for the construction, in whatever case.

Quote

J-Max

If you lot own precise measuring tools, try this.

I am waiting for the delivery of a dial test indicator with precision +-20µm, I will do some tests as soon as I get information technology.

Edited 1 time(due south). Last edit at 09/01/2015 06:18AM by cristian.

Hi over again.

Forget theory a minute, get that small aluminium extrusion in manus, feel it, measure by yourself.
Theory is a perfect world where metallic could win everything
especialy if you compares the wrong parts. Delight read me again.
I did not compare that extrusion to a 20x20x300mm MDF piece, only to a 19mm

pannel

.

I mounted a foursquare 300mm module20 extrusion structure by the past,
thinking this will be the ultimate structure I can get for my machine.

Merely holding my hand on the top of that aluminium frame and the dial indicator jumps !
The type of jointing you lot volition use tin make things even worse, like universal blocks and little squares.
The interest of that kind of frame falls if y’all demand to put 3 large aluminium triangles at each corner.
That profile’s wall are just too thin i’m affraid, and that’s also light too.
I replaced that expensive aluminium frame past a inexpensive 19mm MDF pannel structure
with better results at any points. Stiffer, heavyer, vibrations dump, so on.
I just share my experience, I don’t need to convince you lot.

Aluminium extrusion still accept advantages, it’s straight, it’south easily cuttable, information technology take t-nut rails,

which makes structures like shooting fish in a barrel to be mounted with costly hardware,
you can hide cables or belts within, and information technology looks less DIY akin.
Employ module20 aluminium frame if you lot like. Information technology’s not so bad.
It’s surely better than any acrylic frame or whatsoever 6mm plywood ane.
Choose what y’all like for your second machine, y’all need to enjoy it.

It volition be probably functionnal and beautifull anyways.
winking smiley

++JM

Quote

J-Max

Forget theory a infinitesimal, get that pocket-sized aluminium extrusion in hand, experience it, measure out by yourself.

I don’t own any 20×20 profile (or any other size, yet), nor a precise measuring device (notwithstanding) so I cannot do that now. I will measure deflections by myself as presently every bit I get everything I need, I am looking forrad to that.

If you lot ain a precise measuring device, information technology would be bang-up if you may share some of your deflection measurements too. I volition do the same as soon every bit I can. Nosotros are off topic all the same, information technology should be washed in a new thread for readability.

Quote

J-Max

Theory is a perfect earth where metallic could win everything

I was joking almost metallic “winning”
smiling smiley
, it simply has dissimilar properties from wood, equally you already pointed out, stiffness beingness one of them.

Quote

J-Max

especialy if y’all compares the wrong parts. Please read me again.
I did not compare that extrusion to a 20x20x300mm MDF slice, but to a 19mm

pannel

.

I compared a foursquare MDF panel of width/length 300x300mm and thickness 19mm (I assumed 300mm for the dimension you had not previously specified) with a 20×20 aluminium profile of the length of 300mm, so please read me again.

Quote

J-Max

I just share my feel, I don’t need to convince you lot.

I appreciate that you share your experience. On the other hand I share my thoughts as information technology is usually done in discussions, this is non supposed to be a challenge.

Afterward finding the
formulas
for the tolerances and those to summate the order of magnitude of the life of linear guides (for case
these), I experience no longer and then “lost” and I call back this is really the right manner to go. I can’t actually remember why I wanted to apply polish rods in the first identify.
winking smiley

Many thanks J-Max and LarsK for your suggestions, they accept been illuminating.

Hey there. I actually like the design on you bots. Any chance younwant to share the STL’s for the plastic parts??

All-time regards Thomas




3d Printer Linear Rod Design Semi Corexy

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