3-axis moving gantry design CNC style 3D printer

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    Question 3-axis moving gantry design CNC style 3D printer

    Hi all,

    I joined cnczone last year and wanted to make my own CNC milling machine. After lot of research I finally gave up because of space and sound constraints in my apartment. Then a few months ago I was making an iot temperature module but none of the enclosures I bought were good fit, plus they all require a lot of manual post-processing to make the correct holes and rectangles for connectors. So this drove me towards a new project, make my own 3D printer.

    I researched a lot about 3d printers, looking at multiple designs(i3 prusa, mendel, delta, etc) but none of them use linear rails on all 3 axis. Looking at the differences and similarities between the two machines I realized that a 3D printer made using linear rails could easily be converted into a CNC machine. On top of that if I design a 3 axis moving gantry then I can have a machine with nearly 100% build volume which will take care of my space constraint.

    Now my questions are :
    1) I am considering a build volume of around 400mm(x)X400mm(y)X500mm(z). Will a moving gantry have sufficient strength in an all metal construction? What if I move down to 300mm(x)X300mm(y)X400mm(z)?
    2) Aluminium is lighter but steel is stronger. For a moving gantry which will be preferable?
    3) Based on what I have read I need 3 (ball screw + linear rail + support) for each axis. Something like this https://www.amazon.com/Happybuy-Ball...0483684&sr=8-7 . Other then this I need a base plate to put everything on, 1 support plate for y and 2 for z axis, another ball screw so that I can drive x axis from both sides and 4 motors(2x1y1z). I have not considered electronics/heatbed at all because I think I have sufficient clarity on that. Is their anything else required to complete a basic frame for 3D/CNC machine?
    4) The bed on which all this is going to be placed. Should I use aluminium or steel to provide sufficient stability? What is the minimum depth I can use for bed? How do I get a bed with pre-drilled holes? I have a black&decker hand drill. Can I drill reliable holes using that?
    5) Is their a 3 axis moving gantry design or BOM available to refer to? (Answered by similar post builds that came up)Can I just make paper drawings, buy stuff and wing it or do I need to make a CAM model before I jump in?

    I should also point out that when I move to a bigger place with a garage, I plan to add a CNC module on this machine so that I can mill aluminium. That's why the machine needs to be sufficiently sturdy and precise.

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    Default Re: 3-axis moving gantry design CNC style 3D printer

    400mm Z stroke is way too much for a typical gantry mill. This is an area where 3D printers and CNC routers differ. The spindle takes up a lot of vertical space. Your gantry would have to be gigantic.

    How are you going to make your own? Your drill is a Black & Decker? This is not a good sign! There are frame kits for 3040 and 6040 type machines on Ebay. Making your own BOM for everything that would need to be added to such a kit: that is doable.

    There are engineering compromises that make selecting the right components for a hybrid machine difficult. It's going to be either: 1) very expensive, 2) very slow as a CNC, or 3) very sloppy as a printer.

    Also, I really think that with 3D printers... people talk about frames a lot, but the important things for actually getting the damn things working are the extruder mechanism, the heated bed, and calibration (auto or otherwise).



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    Default Re: 3-axis moving gantry design CNC style 3D printer

    Quote Originally Posted by eorl1986 View Post
    1) I am considering a build volume of around 400mm(x)X400mm(y)X500mm(z). Will a moving gantry have sufficient strength in an all metal construction? What if I move down to 300mm(x)X300mm(y)X400mm(z)?
    I think that is HUGE and totally pointless. Have you ever thought about what you are going to use it for? Are you EVER going to print anything which requires that size? Are you aware of the printing times required for printing? 3D prints can easily increase MASSIVELY in time when high accuracy is needed, even with pretty small parts. Will you be willing to have your printer working over night and day or only when you are in the vicinity, or perhaps you never leave home...? Have you considered the heating necessary for such huge bed? I don't think so. Have you considered that the huge bed must be heated up even if you just print small parts, generating a lot of wasted heat? Most of all, I don't think you ever going to print anything which requires that size and if you have space constraint to start with, then a good place to start is to reduce the size. Remember that a print volume of that size will require about 1/3 extra floor (and roof) space, so you will need at least 600 x 600 X 800, so that is massively large for a 3D printer...

    Quote Originally Posted by eorl1986 View Post
    2) Aluminium is lighter but steel is stronger. For a moving gantry which will be preferable?
    Steel is heavier also, meaning you will need VERY powerful steppers. You will have HUGE problems with speed, and high speed is very valuable in every 3D printer, not only the printing speed, but also the non-printing moves are extremely important. The larger the object the more benefit you get from high speed. Acceleration is the other thing which is extremely important. 3D printing has a very high number of small movements and if you don't have good enough acceleration you will never get the machine up to the high speed (even if you would have high possible speed). With a steel gantry you will have huge problem with the high inertia, so you will NOT have a chance to get a respectable acceleration. If you absolutely MUST build this printer then go for aluminium. You will have zero benefits from using steel. Aluminium is strong enough unless you select .

    Quote Originally Posted by eorl1986 View Post
    3) Based on what I have read I need 3 (ball screw + linear rail + support) for each axis. Something like this https://www.amazon.com/Happybuy-Ball...0483684&sr=8-7 . Other then this I need a base plate to put everything on, 1 support plate for y and 2 for z axis, another ball screw so that I can drive x axis from both sides and 4 motors(2x1y1z).
    That kit is for a CNC, not for a 3D printer. I would not use ball screws on the X and Y because the noise will kill you and you add another heavy thing which you will have issues driving fast enough for satisfying results. You will also quickly wear out the X and Y ball screws because of the huge number of moves and position changes. Consider belt drive. It wins hands down over ball screws. Ball screws on Z is OK but you need two, unless you plan building a CNC style printer, but I don't think that would be a good idea. The supported round rails are OK, but they are massive overkill. You will have zero benefits from using 16mm ball screws and 20mm rails. 1204 ball screws for Z is all you ever need, and if you want to use supported round rods, try to find 12mm. Those would be more than enough.

    Quote Originally Posted by eorl1986 View Post
    I have not considered electronics/heatbed at all because I think I have sufficient clarity on that.
    Actually, I think you underestimate the importance of those parts and I honestly don't think you know what you need or must have for such a huge printer.

    Quote Originally Posted by eorl1986 View Post
    Is their anything else required to complete a basic frame for 3D/CNC machine?
    I think you have a good idea of what is needed, but I think you start something you will not be able to finish because you underestimate relevant parts. I also think it is a very bad idea to think about this as a 3D printer/CNC build. It is not a good idea to combine those two. Decide what you want to build and build THAT only. If you already now know that you have noise and space constraints than forget about CNC, build a good printer instead.

    Quote Originally Posted by eorl1986 View Post
    4) The bed on which all this is going to be placed. Should I use aluminium or steel to provide sufficient stability?
    Aluminium is all you need. No benefits in using steel. In fact, my CNC is capable of milling aluminium with good speed and quality and that is made of aluminium. Of course, for a CNC, the more robust the better, but for a 3D printer there is no benefit in steel bed.

    Quote Originally Posted by eorl1986 View Post
    What is the minimum depth I can use for bed?
    What do you mean by that? The thickness of the aluminium plate? For a CNC or for a 3D printer? A CNC must hold some heavy fixture apart from the heavy material you work on. A 3D printer does not have the same problem, the printed plastic is very light, even if you would use up a full reel for a single print, that is only 1 kg, which is nothing compared to the weight of my vise which is on the CNC table.

    Quote Originally Posted by eorl1986 View Post
    How do I get a bed with pre-drilled holes? I have a black&decker hand drill. Can I drill reliable holes using that?
    Well... yes and no. I only had a had drill (but a very high quality) when I built my first CNC. I bought this stand for this machine:

    https://www.conrad-electronic.co.uk/...B.EPS_1000.jpg

    It is very stable and made it possible to drill holes accurately. Without this I would have failed. I also bought two circular saws, which I regarded was necessary to be able to cut aluminium. The other alternative is to place an order and buy the parts readily drilled...

    Quote Originally Posted by eorl1986 View Post
    5) Is their a 3 axis moving gantry design or BOM available to refer to? (Answered by similar post builds that came up)Can I just make paper drawings, buy stuff and wing it or do I need to make a CAM model before I jump in?
    I would think that you need to make your own home work on this.

    Quote Originally Posted by eorl1986 View Post
    I should also point out that when I move to a bigger place with a garage, I plan to add a CNC module on this machine so that I can mill aluminium. That's why the machine needs to be sufficiently sturdy and precise.
    Again, I think you should forget about combining a CNC and a 3D printer. While they look similar for some people, they are different machines with different tasks.



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    Default Re: 3-axis moving gantry design CNC style 3D printer

    Thank you for your replies. Your replies have forced me to be more realistic and make something that I can use. Based on that I think I will go with a 3d printer as I can't use a CNC right now in my apartment. Maybe in the future I will have space for two machines.
    I will reduce the total volume and look at all aluminium design.
    A_Camera regarding your comment about underestimating electronics, I just feel more clear about them because I have more of an electronics and software background and I have worked with multiple stepper motor drivers. Mechanical hardware is where I have struggled for most part.

    But to more relevant matters, you talk about not using ballscrews on x & y axis. I understand the weight issue, but based on my reading ball screw has higher precision that belt mechanism. Also ball-screw will provide more stability to the structure. Are these minor differences not important in 3d-printing or is the difference small enough to be insignificant for a DIYer?



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    Default Re: 3-axis moving gantry design CNC style 3D printer

    Speed is important in a 3D printer. It is a consideration for a router too, but more so for a printer. A printer needs to be zippy and accurate as well as tight. You have to be able to pick acceptable parameters for each type of filament and object to have a good printer.
    There are plenty of bad or sub par printers and kits out there. Plenty of decent and higher quality machines available too. What you see very little of are machines that do more than just printing. Like laser engraving, probing, routing etc. This is an area that is undergoing heavy R&D by quite a few makers. It is certainly challenging.

    My suggestion is to get you a starter 3D printer kit and get going with it. A couple hundred bucks for a machine and a roll or two of filament and you are on your way. There is enough of a challenge with one of those and getting your feet wet that should hold your interest for some time. Then from there you can experiment and have a much better understanding of what is needed and wanted for either upgrades or your next machine.

    Lee


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    Default Re: 3-axis moving gantry design CNC style 3D printer

    Quote Originally Posted by eorl1986 View Post
    Thank you for your replies. Your replies have forced me to be more realistic and make something that I can use. Based on that I think I will go with a 3d printer as I can't use a CNC right now in my apartment. Maybe in the future I will have space for two machines.
    I will reduce the total volume and look at all aluminium design.
    A_Camera regarding your comment about underestimating electronics, I just feel more clear about them because I have more of an electronics and software background and I have worked with multiple stepper motor drivers. Mechanical hardware is where I have struggled for most part.

    But to more relevant matters, you talk about not using ballscrews on x & y axis. I understand the weight issue, but based on my reading ball screw has higher precision that belt mechanism. Also ball-screw will provide more stability to the structure. Are these minor differences not important in 3d-printing or is the difference small enough to be insignificant for a DIYer?
    Just to give you an idea, here are two videos. The first one is my CNC at maximum speed. The CNC is based on 1605 ball screws and 16mm fully supported round rods, similar to what you linked to. The maximum values I can get now is 10,000mm/min speed and 900mm/s/s acceleration. On my fairly small machine I found this crazy and scary fast, so I backed off a bit and set the X and Y to only 9,000mm/min, the Z to 7,000mm/min speed and all three to 700mm/s2 acceleration. Now, that is fast for a CNC, I think on a DIY machine with moving gantry you can forget about this, and should be happy with half of that speed.



    Now the second video is my plastic fantastic 3D printer after my improvements. The speed of that is 15,000mm/min on X and Y and 5,000mm/min on Z and I wish it was even faster especially the X and Y, but compare the noise of the two machines...



    Ball screws can be annoyingly noisy at high speed and with a 3D printer you will hit the speed limit of ball screws LONG before I hit the speed limit of a belt driven printer. Ball screws are not suitable in my opinion for DIY 3D printers driven by steppers, and you will not get any benefits from using ball screws. Imagine that noise with ball screws at the 9min 22 seconds marker in the video, the honeycomb fill pattern... Not only the noise, but all that shaking would rip your machine apart in no time.

    The accuracy of belts is more than enough once you have done accurate measurements and trimmed the steps per units. Of course, belts wear faster than ball screws, but they costs peanuts to replace. Also, don't have too high hopes on cheap ball screws. They do have play (backlash) which isn't an issue on Z (because of gravity) but can be an issue on X and Y, while you can easily eliminate that if you are using belts on X and Y by increasing the tension.

    My background is also in software/firmware and electronics (40 years of career), Mechanical engineering is just a hobby for me, which is why my mechanical solutions are not as sexy as others are capable of doing on this forum, but my experience is that it is too easy to underestimate the challenges even in electronics. The reason why I am saying this is that you will most probably not design and make you controller boards but buy ready made ones and they all present different problems and require attention. The advantage of having your (and mine) background is that we probably can fix electronic/electrical and programming issues, but unless you really KNOW what you are doing you may do very serious mistakes which might be expensive to fix. Like if you buy the wrong type of steppers, which I think is a very common mistake, or the wrong sort of drivers or motion controllers and so on.

    I actually also had an idea of making my CNC into a combination of CNC and 3D printer, but after some careful consideration and some advice from experts I realized that they are right, it is not a good idea. So I ended up buying a super cheap plastic 3D printer kit to use as a learning material and to give me some ideas about how to build my own. I have already a CNC which I designed and built, so I can say that I had a pretty good idea even before, but I thought it is better to have one for real and use that as an aid and also to learn about printing. So, now I am in the process of building my own.

    3-axis moving gantry design CNC style 3D printer-printer-1-jpg

    This is about as far as I am now with the mechanical parts, but my ambitions are lower than yours. Mine will have a 200x200 build plate and only 150mm Z. For my needs this is enough. I will have a moving table, driven by 9mm wide belts on X and Y and 1204 ball screws on Z. Using 2 x MGN12 on Y and Z and 2 x MGN9 on X. I like moving table because that is easier to make and definitely easier to adjust so that everything is squared. It requires a little more space than moving gantry but provides better rigidity, so I like that design.

    Anyway, whatever you decide to build, you will need more machines. Circular saw and good drilling machine is a MUST, but you will also come to a stage when you realize you need an angle grinder, sander and I don't know what not. Also, if you can only have one of each sort of machines, don't buy battery powered ones, buy better quality mains powered ones instead. In my opinion battery powered ones are for complementing mains powered ones only, not suitable for everything. You will also need measuring instruments. Perhaps you have those already, but since you are not a "mechanical guy" I thought I'll mention it.

    Whatever you do, I wish you good luck. This hobby is fun, but you have to be realistic otherwise you will fail and give it up too soon.



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    Default Re: 3-axis moving gantry design CNC style 3D printer

    Thank you Leeway and A_Camera. A_Camera you passion for the field after being 40 years in the industry is inspiring.

    I think my best best right now as you guys have suggested is to get a 3d printer DIY kit and upgrade it as I learn the complexities of the machine.

    A_Camera one of the primary reason initially not to go with kit is exactly as you stated, problem with under powered, under protected boards, power supply. Getting my apartment burned down because of some cheap board is really terrifying. I know if I buy these parts by myself(even if assembled) I will only buy the best PSU, the best solid power relay(rated many times the current I will use). Ofcourse the cost saving of buying a whole kit will probably offset the cost of replacing PSU and electronics.

    As a last favor can you suggest a 3d printer kit with solid all metal build(I plan to go dual extrusion in future).



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    Default Re: 3-axis moving gantry design CNC style 3D printer

    Consider the Prusa i3 mk3. That's what I'm about to build. There are plastic components in the X and Z assemblies, but their multi-material system works differently. You still only need one head.



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    Default Re: 3-axis moving gantry design CNC style 3D printer

    I have some really nice printers and some that are not that great. They work, but not quite as robust as the bigger ones I use.
    I have bought two kits.
    The Prusa Mendel back in 2012. It was okay, but nothing like what is available today. Since I don't do much experimenting on my production printers, I recently bought this kit.
    https://www.3dprintersonlinestore.co...yABEgJiNfD_BwE
    It's okay for what it is. You better have some nice tools or rather metric hex drivers to make assembly easier.
    It's got some screws.
    The assembly instructions are pretty good, but falls short when it comes to the dual extruder installation.
    They finally sent me the rest of the instructions. I have been having issues with the main. Now it needs a main board replacement. They are sending that out.
    The mechanicals though are worth the cost. Nice power supply. It has a fake Cymera dual extruder, which should work fine when I get the new board. The old board does not heat the second extruder nozzle. The extruder fan plug does not work and it will not send the Z axis all the way up top to hit the home switch.
    New board should fix it.
    But I do not recommend it for a beginner.
    Spend a little more and get the Prusa I3. It is a much more reliable machine and has an owner that is at the forefront of hobby class printers. Good hobby class to light production class printers.
    The biggest reason I bought the Cube was for the frame and mechanicals that I can build on.

    Lee


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    Default Re: 3-axis moving gantry design CNC style 3D printer

    I like original prusa but I want the electronics and PSU outside in a box as I want to enclose the machine for better heating.

    So in terms of popularity and price point right now, I see four options

    Vevo Tornado : https://www.gearbest.com/3d-printers...01.html?wid=21
    CR-10S : https://www.gearbest.com/3d-printers...pp_779174.html
    Tronxy X3S : https://www.gearbest.com/3d-printers...95.html?wid=21
    Cetus 3D : https://www.amazon.com/Cetus3D-Cetus...+printer&psc=1

    Which one would you suggest in terms of frame stability? I want a frame that is as strong as I can get so that I don't have to worry about that again. For example the video A_Camera posted, I don't think I can make that z axis upgrade you made as I don't have the capacity to cut or drill holes on that thick a piece of metal. Although I can change bolts screws, belts, heating mechanism, stop switches, electronics , motors, pre-sized pre-drilled metal pieces, etc if required.

    Please suggest!!!



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    Default Re: 3-axis moving gantry design CNC style 3D printer

    The first three are virtually the same printer. I don't really care for a moving table on a large printer like those. For large prints, that table will get heavy with plastic. Then the moments of direction change could easily dislodge the print from the bed and the result is a lot of wasted time and plastic. Not such a bad thing on smaller prints. I prefer that the X and Y move the extruders and the bed only raises and lowers. All of my printers are like that for that reason.
    Of those 4, I would choose the Cetus.
    It's a nice printer and built well. Easy to upgrade some later on. It has the moving bed too, but a much smaller printer.
    The extra weight on the bed of the larger moving beds will also mean that you have to slow the prints way down to succeed. That is not desirable on large prints. Faster is better.

    Lee


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    Default Re: 3-axis moving gantry design CNC style 3D printer

    Quote Originally Posted by eorl1986 View Post
    Cetus 3D : https://www.amazon.com/Cetus3D-Cetus...+printer&psc=1

    Which one would you suggest in terms of frame stability?
    That one, but no guarantee given from my side. The reason is that only that one looks quality in my eyes. That is the only one using real linear guides, the others just have plastic wheels run in the extrusion gaps, which I think is a terrible solution. In your case I'd go for the best quality and not fall for the size. Like I said, maybe if you buy a printer with large bed you will print a few large objects for fun, but then you'll most probably print smaller objects. Also, what would be the point of having a large printer which is flexing, badly balanced and printing crappy quality. One of your links have a Youtube demo video in it, and I'd be very sad if that was the best my printer would be able to do. Even though my current printer is an acrylic one, it uses dual steel rods on ALL axes with real horizontal ball bearing slides and already right out of the box, after assembly and some configuration changes I could print better quality than that demo video. Don't worry about boxing it at this time, wait until you know you'll need it. An open solution has advantages also, one is that you can easily see and access all the necessary parts and change/adjust whatever you need to.

    Regarding my video and the changes I made, you don't need to use the same solution, and perhaps today I would do it differently as well, probably would come up with a simpler solution and would not use that thick plate on the Z as I did.Anyway, 10mm aluminium is not that difficult to drill, but regardless what you are drilling, a drill stand is a good idea to buy, even if you buy one like the one I had first, this one.

    3-axis moving gantry design CNC style 3D printer-drill-stand-jpg

    That stand is not the cheapest but considering it is pretty solid and well made, it is worth the investment and is easy to store it under a table if you don't need it for a while. I still have it even though I don't use it any more, except if I need to drill somewhere else and need a transportable drill stand.



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