I give up …

This topic contains 10 replies, has 5 voices, and was last updated by  Dui, ni shuo de dui 3 weeks, 3 days ago.

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  • #118691

    Turbinbjorn
    Participant

    I give up … trying to print the parts for my MPCNC.

    I found it damn impossible to square the gantry, so I ended up with reprinting all the gantry parts. Having adjusted the printer and gotten comfortable with some nice PET-G, I figured a more precise print would make difference.

    It did not. It’s 1 degree out of square – and I assume that this is too much to break in. I roughed out the bolt holes, I’ve tightened and loosened all I can, I I’ve tried all sugguestion I’ve come across here.

    20191020_185021

    I’ve also had issued with the rollers. The tube opening seems to narrow! I don’t understand how that can be. The feet are somehow fitting well enough, even though there’s a slight gap between the parts. I also broke some of the feet bolt holes snugging it too hard.

    20191020_185034

    Well – all these issues combined – have taken quite a toll on my patience and motavation! I thought that my printer was square enough – but I’ve realized that a veeery sliiiiightly skewed axis results in a huge out of square-ness when it’s enlarged in the MPCNC. Especially the gantry, since the construction “doubles” the skewedness when combining the x and y axis. I tried rotating one print of the xy burly 180 degrees, so that a potential skewing would be countered. But it didn’t help.

    Sooo – to conclude: I don’t want to give up on this thing – even though it sometimes keep me awake in the night. I really like the project and this great community. I’m not blaming Ryan for anything, I only blame myself and the lousy cheap second hand printer I got.

    My solution to this predicament is that I’ll get the parts, either from Germany (licensed) or from Ryan… so that’ll be the third time ordering items for my MPCNC! (nr 1 lesson learned: don’t buy stuff from China without knowing what you do, and don’t take lightly on printing precise parts…)

    A small questi0n for Ryan at the end of this rant: I’ve seen on Instagram that you are tinkering on a new version for the z carriage. Can you give us a hint on when this may be ready? I don’t want to order the parts if a new revision is around the corner.

    #118700

    Ryan
    Keymaster

    Lets start with one big question, What are you making that you are worried about a little inaccuracy? Did you know you can and should square your axis before every cut and exactly why The Dual endstops got months worth of work put into them. Even without them you can square by hand Like we all used to or use hardstops when you power on.

    comfortable with some nice PET-G, I figured a more precise print would make difference.

    Super flexible and not nearly as rigid as PLA, and why I do not recommend it. On top of that there are plenty of reasons that can be skewed but over the internet and with pictures I can only offer suggestions. Frame square? How far off is your printer with a 100mm test in all directions including diagonals, what are the dims of your rails? Exactly what tension bolts do you have loose and which ones are tight?

    I’ve also had issued with the rollers. The tube opening seems to narrow! I don’t understand how that can be. The feet are somehow fitting well enough, even though there’s a slight gap between the parts. I also broke some of the feet bolt holes snugging it too hard.

    The gap is supposed to be there all clamping surfaces have at least 2mm gap, or it can not clamp. It should be stated in the instructions.

     

    Sooo – to conclude: I don’t want to give up on this thing

    Just use it for a while. 99% of the time accuracy has zero effect on the final project (signs, carvings, even a small PCB would be so slightly out of square you would not notice). For most it builds fine, for some there are issues. I understand the frustration but have you cut a square yet to see if it is out of square, or how bad. Jamie showed me all sorts of math and how a skewed axis is still running true.

     

    My solution to this predicament is that I’ll get the parts, either from Germany (licensed) or from Ryan…

    Nope, just use it. You have to learn CAM and endmill selection anyway. Beat up this build and be ready to build another when and if you need to.

     

    A small questi0n for Ryan at the end of this rant: I’ve seen on Instagram that you are tinkering on a new version for the z carriage. Can you give us a hint on when this may be ready? I don’t want to order the parts if a new revision is around the corner.

    I should not post pictures like that. Lesson learned. What I am working on could be weeks or months or not work at all. I have designed a few dozen machines but only release things that work and are significantly better, or significantly different (zen).

     

    Again. Just make some stuff and have fun. If there is something that needs 0.1mm accuracy we can help you do that with the machine you have already built. I have people getting mad that there things are a few tenths of a mm off and some that have never even bothered to measure anything.

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    #118701

    Ryan
    Keymaster

    If you keep all your threads together I could look back and see what you have and have not tried.

    If everything is perfect to the best of your knowledge, make sure the 1.75″ bolts are loose, and the 5″ is a bit snug. That closes the angle like you need, but the 2.5″ bolts also have an effect. Tighter on a tension bolt move the rail away at an angle based on the previous pivot point and loosening them moves it towards it.

    1 user thanked author for this post.
    #118703

    Turbinbjorn
    Participant

    Thanks alot Ryan, I really appreciate that you take your time and respond so thoroughly! You’ve said it so many times already – and every time I realize that you are right: just try it out!! I guess I’m a little too nitpicky and nervous about getting things right. I have no clue about engineering and mechanics, having mostly been doing woodworking as a hobby. In the end, in a far future, I have a dream of  constructing a small plastic water wheel (yeah – you are allowed to laugh!!) to run an electrical turbine. I tried constructing it with wood, and got very obvious to me that every single detail has to be quite precise, to prevent wobbling and uneven rolling. That was the reason for why I started looking for a CNC, to cut shapes in plastic sheets. But honestly, I have come up with a thousand neat things to do with it since then, and if the day comes that I’ll be making this water wheel, I might end up with a LR2 🙂

    #118705

    Ryan
    Keymaster

    I know how it is, yours looks way out and you have been trying to get it perfect for so long. But I bet it is not nearly as far out as you think, and a little tweak before each job probably make it “perfect”. In the early versions some builds were sooo much further out. I am okay with this type of frustration but just make sure you don’t get frustrated cutting plywood or some old bard wood and complain it is 0.001mm out…..hahahaah.

    On top of all that I don’t think most people realize how far out things are that we cut by hand, it is just a higher expectation with CNC. Think how many times you use a tape measure to mark one side, cut it with a hand held skill saw. never thinking to measure it after you cut it let alone check diagonals to compound the error.

    We can get you there, but just get it dirty already…..Maybe I will have something else to print when you need it (But I can tell you now printer accuracy will be a much larger factor!)

    #118720

    Jeffeb3
    Participant

    As a spftware engineer, I frequently expect things to be bit for bit perfect. Like the part needs to have the md5sum as the design. But that’s not how it works in the real world.

    Nope, just use it. You have to learn CAM and endmill selection anyway. Beat up this build and be ready to build another when and if you need to.

    This is great advice. You will learn so much more about what’s important and what actually makes you enjoy it. Maybe you’d rather spend time on changes to parts or faster speeds, or desiging thing to work better than accuracy. It’s also possible your build it totally fine.

    #118723

    Kevin Russell
    Participant

    Mine’s a bit out of square as well.  I have the outer rails perfectly square and uses those to square up the gantry.  I’ve since moved to end stops and use them to square things up.  It’s way easier this way.

    The jigs and parts I’ve been cutting with the mpcnc are way more accurate than anything I’ve ever been able to make by hand.  Especially things that require precise spacing of holes.

    #118727

    Dui, ni shuo de dui
    Participant

    One degree is quite a bit off to be honest. It does have an impact, especially when doing large parts that needs to fit together. But as Ryan said, in your case you should focus on the important stuff, get the machine dirty and learn the CAM. You can come back at squareness later.

    I have the same issue on my machine and it does get annoying sometimes. I cannot square it by hand because it would end up binding when pushing the side of the axis on this direction. I can however push it in the other direction and get it even way more out of square easily. Which doesn’t really help me.

    I’m not sure if the reason is my table being out of square, or something weird in the motor carriages. It is not the gantry itself because even with the gantry removed entirely the problem remains. It is actually quite hard to check for squareness on the tubes and I can’t manage to find a reliable consistent spot for measuring between the corners because the motor carriages or gantry system is always in the way.

    #118753

    Ryan
    Keymaster

    or something weird in the motor carriages.

    Did you pair a mirrored roller with a non mirrored to cancel any printing deficiencies?

    #118764

    Turbinbjorn
    Participant

    Thanks again all, I really appreciate this community! As Ryan often suggests – I’ll hook it up and get it running. I’m somehow a little comforted by @forcerouge who says one degree is quite a lot. That’s how I’m feeling! But then again, let’s get it dirty and see how it goes.

    #118830

    Dui, ni shuo de dui
    Participant

    or something weird in the motor carriages.

    Did you pair a mirrored roller with a non mirrored to cancel any printing deficiencies?

    Don’t forget my machine is entirely different, I’m using linear bearings so the motor carriages are a totally different design. But now that you mention it, I’m not sure I mirrored the thing while designing it.  I’ll check, thanks!

    I should have mentionned it in my previous post, the OP cannot guess that, sorry my intention was not to criticise the design of course, it was just to say that one degree actually matters. But indeed, it doesn’t need to matter just now, it can be fixed later.

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