Build Thread DIY CNC machine on the cheap! - Page 4


Page 4 of 7 FirstFirst 1234567 LastLast
Results 61 to 80 of 128

Thread: DIY CNC machine on the cheap!

  1. #61
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by davida1234 View Post
    Roughen up the inside and pour sand concrete into them! Let it cure for at least 30 days. I really mean it.
    That's actually the only idea that came to mind before, but the problem is concrete shrinks slightly when cured. I might end up with a tiny gap between the concrete and the inside of the pipe that could lead to a whole host of problems. I was also afraid that 1" (x2) diameter concrete might not be able to hold up under the bending stress of a 30 - 40kg (estimate) gantry, causing it to crack and disintegrate from vibration (might take a while but it's plausible). The other issue with this idea is it would take considerable time to get the the reinforced pipe redone in case I needed to replace it. I did a little research and found that it's tricky to reinforce steel using concrete, it's usually easier if it's the other way around, with the steel on the inside.

    Finally, I haven't' any idea of how I'd even start roughening up the inside of the pipe. I know it's possible, but most ways I can think of involve some kind of specialized or power tools.

    Thanks for the input.



  2. #62
    Member davida1234's Avatar
    Join Date
    Oct 2009
    Location
    United States
    Posts
    733
    Downloads
    0
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    I am not trying to insist on that idea but see that as the most viable option for strengthening a thin wall pipe.

    You would have to keep the uncured concrete moist for one week to avoid shrinkage. Bump stops in garages are built that way.

    DIY CNC machine on the cheap!-unknown-jpg

    You could roll up sandpaper and push it through the pipe. Concrete "sticks" to metal. Not much roughening needed. More like cleaning the metal inside,

    If you want further strengthening, you could also put some wires inside the tube before putting concrete in.



  3. #63
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by reg.miller View Post
    Hi, those tubes will bend like hell. You need some solid support. I have a project I call my junkyard CNC which has some aims in common with what you are doing. I use solid round bar rather than tube, even that needs solid support. If you have access to extruded aluminium sections as used in window and door frames you may find something that acts as a support. Look at the gantry on this video. I got my steel beams and extruded ali from the scrap yard. It took some time to find really heavy walled extrusions but it is a very strong solution. The ground bar and balls screws are new chinese "junk".
    Hello Miller,

    Great machine you've built! Looks real solid but I was shocked at how heavy your gantry turned out to be! It's good to know so I'm not surprised by mine later.

    I was disappointed with the steel square tubing and went out to look for anything I could find with a uniform surface. I found that round tubes are uniform in diameter (probably because they run them through dies while they don't for the square ones) and bought a few to experiment with, but until now, I hadn't came up with an arrangement that could work as a linear rail for the bearings. The idea I came up with (more like "I decided to use") is very similar to yours!!! I didn't have time to draw it in sketch up, so I just scribbled something on paper I hope you guys can understand.

    It's a small town I live in and I haven't come across any hardware shops that carry aluminum extrusion . It's only commonly purchased items that hardware shops stock and if you need anything specialized, you have to place an order and fork out good money for it! There's lots of challenges I'm facing with this machine that wouldn't exist with access to little well processed aluminum, so if it was within reach, I'd definitely use it. One of my goals for this build is that every component I use should be available locally for ease of maintenance (Now that'd be an accomplishment!). I like your idea of using SBR20 mounted round bar with the skate bearings. You must be getting some really sooth rolling from those.

    Quote Originally Posted by reg.miller View Post
    Avoid use of any tube if you can. It will not be solid enough, you will not be able tighten bolts tight enough of tubing to hold things solidly. The tube will crush.
    I don't really have a choice here. I'll probably start with these and upgrade to your design later. I won't be machining any metal with it, just wood with low feed rates.


    Quote Originally Posted by reg.miller View Post
    I have modified the bearing blocks to make them stronger and easier to make since this was taken. I can post a pic if you are interested. On the top I use opposing standard bearings, as can bee seen, underside I've used a single U-groove , double row ball bearing. ie two bearing blocks above to support the gantry ( approx 50kg ! ) and the U-groove to nip up in the middle underneath. The U bearings are chinese junk and you need to order at least twice as many as you need. Seems the Chinese have trouble getting the holes in the middle and this causes tight spots when the bearings are clamped tightly. I have not found a EU or US equivalent product.
    I get the idea and I'm very interested in seeing a few more photos. Please do post some more. I'd like to see in greater detail how you did your X-axis bearing blocks. You weren't clear as to whether the Chinese get difficulties getting the holes on the mounted round bar or on the U groove bearings. I had similar problems with skate bearings from china, they kept binding up and they made weird noises. I'm done with sourcing components from eBay for the time being.

    Quote Originally Posted by reg.miller View Post
    drive from both sides to ensure no twisting between X and Y
    I'll just let my bearing blocks eat up a little more of my X-axis length to avoid racking so i can use a single drive down the middle.


    Quote Originally Posted by reg.miller View Post
    Hope that is helpful.
    I was. thanks.

    Isaac.



  4. #64
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by reg.miller View Post
    this was made using only hand tools ( patient filing and tapping ) and an electric drill on a drill stand seen in the background.




  5. #65
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by davida1234 View Post
    I am not trying to insist on that idea but see that as the most viable option for strengthening a thin wall pipe.

    You would have to keep the uncured concrete moist for one week to avoid shrinkage. Bump stops in garages are built that way.

    You could roll up sandpaper and push it through the pipe. Concrete "sticks" to metal. Not much roughening needed. More like cleaning the metal inside,

    If you want further strengthening, you could also put some wires inside the tube before putting concrete in.
    You're right. The set up would be much more rigid with concrete reinforcement, problem is, I'm not that good at composite materials or building them for that matter, which is why I shied away from it.

    Quote Originally Posted by davida1234 View Post
    If you want further strengthening, you could also put some wires inside the tube before putting concrete in.
    Even better, If I added a couple of reinforcing bars on the inside.

    The concrete would definitely work if done well, but through all my experimentation, I have bought A LOT of steel which I must find a way of using on the machine (otherwise it would go to waste). So, with that in mind, I came up with this...

    Attached Thumbnails Attached Thumbnails DIY CNC machine on the cheap!-exploded-jpg   DIY CNC machine on the cheap!-section-jpg  


  6. #66
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Hello routalot!! How have you been?

    Quote Originally Posted by routalot View Post
    Its good to see some progress with the machine,have you learned enough yet to generate a toolpath?
    Not even close! Been preoccupied with the whole linear bearings dilemma. I watched a few videos on how to get from sketchup to machining a while back, just to get an idea but nothing beyond that. I'll probably start with the software once I'm confident I have reliable linear bearings. It was a little difficult getting myself to learn the software aspect of "CNC'ing" when I couldn't produce a good set of linear bearings.

    Thanks for the reminder.



  7. #67
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by cyclestart View Post
    Is black pipe commonly available in your area ? It's used for things like sprinkler systems and natural gas.
    It's much stiffer than curtain rod and has no coating to flake.
    Hello cyclestart,

    Nope! We don't have black pipe here. The only natural gas you can get around here is in gas cylinders sold at fuel stations. There's no public gas line. Galvanized steel water pipes were about as close as I could get to black pipe when I looked. Nice and straight, good wall thickness but a rough finish on the outside.

    The curtain pipes are the best option for now.

    Thanks,
    Isaac



  8. #68
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by reg.miller View Post
    Hi routalot, if that qu was aimed at me, no, I have not bothered with toolpaths yet since that is more a case of using a CADCAM package. I need to concentrate on finishing the h/w , without which the rest is a bit academic .

    For OP, here is the new format guideblocks. This should be easy enough to make and is way more rigid than messing with bolts and pipes. I does require being able to tap an M10 thread in an ali block. The 45 deg face was cut with a hacksaw and a couple of hours of careful work with a file and an set square, once the holes were drilled and tapped. Conforming to OP's do it by hand objectives.

    http://piments.com/cnc/new-guide-block-pair.jpeg

    mounted on machine:
    http://piments.com/cnc/guideblocks-detail.jpeg

    Note scrapyard origin of the ali blocks. They were previously used by someone to mold lead fishing weights, explaining the odd cut-out on the inside faces ! LOL.

    I originally started with 80mm I-beams but as the weight of the gantry and z-axis assy crept up to 50kg, I found they flexed too much ( a couple of thou ). Always worth digging out the formulae from somewhere like engineering toolbox before building a rig ( or at least putting a dial gauge on and leaning on it ).
    I'm loving your machine!! It's got so much in common with the ideas I've been playing around with although you are way ahead of me. Please link me to the build thread if there's one. Correct me if I'm wrong, but isn't a couple of thou equal to 0.05mm? If I'm right, then I personally wouldn't might that degree of deflection on my machine! I'd be lucky to have that as it stands.



  9. #69
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    DIY CNC machine on the cheap!-exploded-jpg
    I'll drill matching holes at the top and bottom of the 6040 steel tube and secure the curtain pipe on top using self tapping screws on the inside of the 6040. I can only do this for one of the pipes, so the other unsecured pipe will merely provide counter pressure for when I snug up the bearing block.

    DIY CNC machine on the cheap!-section-jpg
    There's a section sketch of the bearing block.I'll try this out tomorrow before I can do a major overhaul of the original design. I'll be really glad if I get smooth motion! For extra support of the rail, I could screw 2" flat bar onto either side of the 6040.

    You guys are all great and very helpful, thank you.

    Goodnight,
    Isaac.

    Attached Thumbnails Attached Thumbnails DIY CNC machine on the cheap!-section-jpg   DIY CNC machine on the cheap!-exploded-jpg  


  10. #70
    Member
    Join Date
    Jun 2012
    Location
    SA
    Posts
    153
    Downloads
    0
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    OK, if you feel constrained to use tube you need to fill it. I share your doubts about cement / mortar filling. IMO it will crush to power rather than sustaining force.

    You could try banging in solid MDF or aluminium blocks in the ends. This would still crush to a point but at least allow you to put a useful torque on your bolts.

    I guess you don't have the same market of ali windows / doors where you are. I pick up all my stuff from the scrapyard. I would not be able to go to a commercial supplier and buy the same thing in 1m or 2m lengths but I can ( occasionally ) get some really sturdy extruded beams for the weight of the metal at the local scrapyard. My solutions are adapted to the local ecosystem and probably will not correspond to your situation. Adapt and survive !



    Even better, If I added a couple of reinforcing bars on the inside.
    Be careful. Steel bar ( torbar ) only adds strength if it is fully enrobed by at least and inch of concrete. One of the major defects in construction is when this is not respected and steel is too near to the surface. At this point is becomes a weakness not a reinforcement. If you have 2" tube there is NO point in adding steel inside. IMHO, forget cement/concrete filling.

    I like your idea of using SBR20 mounted round bar with the skate bearings. You must be getting some really sooth rolling from those.
    I use standard industrial bearings, not "skate bearings". They are cheap enough in those sizes. In fact the original ones also came from the scrapyard and were from patio doors. I think were originally good quality durable bearings, and even after years of service most were still good bearings.

    The guide rail assembly is pretty solid and accurate enough to allow be clamp down pretty hard on the bearings to minimise play. I have two issues that limit that. One is the U-groove bearings which are chinese and they apparently have trouble getting the holes in the middle !! The second in my choice of industrial I-beams as the base. They are pretty good but obviously not engineering precision. They do require careful selection when buying and a little patient file work to true them up afterwards.

    I thought of getting a local machine shop to grind them flat but here in the south of France we are closer to sub-saharan Africa mentality then German or Swiss precision. Also the cost of someone with a machine capable of grinding >1.5m in one hit is probable more than the cost buying a precision ground part.


    I would seriously recommend driving from both sides. If I unlock one side of my set-up and push firmly by hand, I can easily induce about 1cm of movement in the unconstrained side. I have about 70cm between the x guide rails. That gives you an idea of the play you will have if you just drive from the centre line. There is a trick with a crossover wire as used to ensure perpendicular movement in the slider of a draftman's table. That is quite effective, with a few pulleys and a tensioned stainless steel cable. Check that out if you really do not want two X motors.

    I had no problem with the guide blocks. My beef with the chinese bearings was only on the U-groove bearings, where eccentricity seems to be a problem. The SBR20 rail was pretty good. I have no issues with that. I initially cut the bearing axis holes at 45 deg. , that worked out OK, but was making life hard for myself. The later version was much more rigid and easier to manufacture. Cut the holes in a rectangular block and cut the 45 into the block later.

    If you want some more detailed shots, please say what you want to see. I will see what I have.



  11. #71
    Member
    Join Date
    Jun 2012
    Location
    SA
    Posts
    153
    Downloads
    0
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    You must be getting some really sooth rolling from those.
    The results are pretty good, though a little short of what I hoped to achieve. It is nice and smooth but play and flexibility add up quickly when you look at all the sources of error. But yes, it's pretty smooth even when nipped up really tight.

    Yes, I had about 4 "centiemes" of flex in the I-beams, which I reported as 2 thou. I did not want to remake all I had done with larger section beams so I added some flat bar to the centre section of the beams. That improved it a bit.

    If I heave along the x axis, I can induce about 6 centiemes of movement. My initial design aim was to do 1 thou accuracy machining. That may have been rather optimistic with a bearing based construction. Though I am not wildly off the mark, so far.

    I "hoped" to be able to machine mild steel, though I knew this was questionable. I will find out when the the mill bites metal whether it starts to resonate and shatters the tool or not !! I still hold hope for small diameter end mills, correct feed speeds and proper lubrification.

    Once I have all the axes trued up , I should have no trouble achieving accuracy on aliminium.



  12. #72
    Member
    Join Date
    Jun 2012
    Location
    SA
    Posts
    153
    Downloads
    0
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    There's a section sketch of the bearing block.
    You can use angle iron but it will flex under pressure. This may be adequate for the light work you are intending this machine to do, or you will need to spot weld it at regular intervals.

    I was using angle iron welded on top of the I-Beam before I went to the ground SBR20 bars. I did a spot weld each side about every 30cm. Again requires some careful work but the result was quite good in terms of accuracy. However the mild steel started to wear quickly when I put pressure on the bearings. I then looked at using square stainless steel tube but despite being a ***** to work with it is not that much harder as a material. I was quite surprised when I looked up the material hardness. I decided that it was not worth all the effort if it was going to wear quickly. Since you will be putting less pressure on the bearings, this may be suitable for what you want.

    So for your design choices you could use angle iron where I have used SBR20 and use my 45 degree bearing blocks or also use angle iron to hold the bearing axes as in your sketch. I think angle iron is a better solution than round mild steel tube, which will be hard to align and fix.

    You mentioned problems getting all bearings to have firm contact. This is alignment problems, it's like trying to cut the legs on a chair so that they all touch the ground ! First solution is to use two bearings one side and one on the other : with a three-legged stool they will always touch. Four legs gets more tricky I use one U-bearing underneath and two blocks on top for this reason.

    With my bearing blocks I have two pairs on top of the round bar, so that's four points of contact. This did require some careful alignment and some shim-sheet to account for slight inaccuracies in making the blocks. Also when linking the two sides with the gantry, you may find bearings start to lift. More adjusting and shimming is needed to get things spot on.

    In your context you can cut open various drink and food containers for shims. They provide good uniform sheet, though the range of thicknesses is a bit limited. 25 and 32 thou' seem quite common in steel containers. Ali drink cans can be thinner.

    I've gone through several iterations to get the solid guides I have now. Hopefully I can save you some time by pointing out the limitations I came up against.



  13. #73
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Oh Yesss!! My linear bearing problems are history!
    I got some time to spare today and tried what I had sketched. Got smooth motion, no binding, no play, even when i hadn't aligned the "block" (noticeable in the photos). I just bolted everything up, tightened the appropriate screws and VIOLA!!! It worked. I'm sure that I'd get even smoother motion if I took the time to straighten things up.

    Attached Thumbnails Attached Thumbnails DIY CNC machine on the cheap!-20190319_184101-jpg   DIY CNC machine on the cheap!-20190319_184044-jpg   DIY CNC machine on the cheap!-20190319_184052-jpg   DIY CNC machine on the cheap!-20190319_184035-jpg  

    DIY CNC machine on the cheap!-20190319_184112-jpg   DIY CNC machine on the cheap!-20190319_184219-jpg   DIY CNC machine on the cheap!-20190319_184232-jpg   DIY CNC machine on the cheap!-20190319_184244-jpg  



  14. #74
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Forgot to mention that I did not have bolts long enough to hold the two angle irons with the bearings together, so I joined 4 pairs of threaded rod using three nuts to get around this. Also the pipes are only held onto the 6040 at either end using rubber bands.

    I had to cut a couple of nuts in half to gain clearance otherwise they'd scrape on the pipe.

    Attached Thumbnails Attached Thumbnails DIY CNC machine on the cheap!-20190319_184412-jpg   DIY CNC machine on the cheap!-20190319_184427-jpg  
    Last edited by imbaine13; 03-19-2019 at 12:58 PM. Reason: adding info


  15. #75
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by reg.miller View Post
    I use standard industrial bearings, not "skate bearings". They are cheap enough in those sizes.
    I have since switched to small machine radial bearings as well.

    Quote Originally Posted by reg.miller View Post
    I would seriously recommend driving from both sides. If I unlock one side of my set-up and push firmly by hand, I can easily induce about 1cm of movement in the unconstrained side. I have about 70cm between the x guide rails. That gives you an idea of the play you will have if you just drive from the centre line. There is a trick with a crossover wire as used to ensure perpendicular movement in the slider of a draftman's table. That is quite effective, with a few pulleys and a tensioned stainless steel cable. Check that out if you really do not want two X motors.
    I think if the bearing in the individual blocks are far enough apart from each other, I could get away with using a single drive. I have seen a few designs implement this. There's a disadvantage of requiring a significant portion of the X-axis travel, but it kind makes up for it by only using a single drive. I'm trying to aim for as much simplicity as possible.

    Quote Originally Posted by reg.miller View Post
    If you want some more detailed shots, please say what you want to see. I will see what I have.
    I'd love to have a more detailed look at your X-axis bearings blocks.

    Thanks



  16. #76
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by reg.miller View Post
    The results are pretty good, though a little short of what I hoped to achieve. It is nice and smooth but play and flexibility add up quickly when you look at all the sources of error. But yes, it's pretty smooth even when nipped up really tight.
    Just wondering exactly how tight you get your bearings. If I get mine too tight, friction goes up wildly, so I get them to a point where I'm able to stop them rolling, but just barely, and only with sufficient force. Seems to me like you get yours wicked tight, judging by the worry you expressed about the pressure crushing my pipes! Aren't you having problems with rolling friction? I know you have them all set up to the gantry, but could you get your bearings blocks to roll down the rails by gravity alone without the gantry?

    Quote Originally Posted by reg.miller View Post
    Yes, I had about 4 "centiemes" of flex in the I-beams, which I reported as 2 thou. I did not want to remake all I had done with larger section beams so I added some flat bar to the centre section of the beams. That improved it a bit.
    A little confused here, is that 4 centimeters?





    How much longer before your machine is ready? By the looks of things, you can't be that far off.



  17. #77
    Member
    Join Date
    Jun 2012
    Location
    SA
    Posts
    153
    Downloads
    0
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    4 centimeters ( french ) hundreds of a mm

    I clamp down the bearings more than you would in a more normal bearing application. But since they will not be turning fast and not doing many miles that is acceptable. I tighten them so it will run on when pushed but not that far. ie there is quite a bit of rolling friction. You can see that here:
    http://solaire-chauffe-eau.info/cnc/slide.mp4

    This does require pretty evenly separated guides. I had to work on one of the I-beams which was a few thou' higher at one end.

    Also if you have cheap chinese bearings where they cannot get the holes in the middle it tightens up on every turn. Just got a new batch today and had 1 good one out of three , at least that got me running.

    The main reason I do this is to clamp down the double row U-groove bearings to remove axial play which would allow the vertical members to the gantry to move side to side. As you say you can control the other direction by widening the bearing separation. That is one thing I improved from earlier version which lacked the rigidity I wanted under load. Once I have it set up correctly there is pretty much the same pressure on all four of the smaller bearings. None slips more readily that the others.

    I think this is important since if you have one near to lifting off you will find that you have little rigidity in that sense. This is how I found out I needed to attend to getting them spot on.



    I think if the bearing in the individual blocks are far enough apart from each other, I could get away with using a single drive.
    The problem is not really from the bearing spacing once that is wide enough. It is from twisting of the vertical supports. The gantry acts as a long lever and whatever your verticals are made of they will twist.
    I used 16mm of steel plate about 15cm wide and even that gave me 1cm at the other end when only one was fixed.

    If you want to got for centre only, at least add the cross-over cable. That helps a lot and is probably good enough for your project.

    I'll see what photos I can find of the blocks.

    Last edited by reg.miller; 03-19-2019 at 02:10 PM.


  18. #78
    Member
    Join Date
    Jun 2012
    Location
    SA
    Posts
    153
    Downloads
    0
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    I thought I had posted these but I can't see them looking back. Sorry if it's a dupe.

    http://piments.com/cnc/guideblocks-detail.jpeg
    http://piments.com/cnc/new-guide-block-pair.jpeg
    http://piments.com/cnc/new-guide-block-zoom.jpeg

    I that what you wanted?



  19. #79
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by reg.miller View Post
    You can use angle iron but it will flex under pressure. This may be adequate for the light work you are intending this machine to do, or you will need to spot weld it at regular intervals.
    The only angle metal available here is hot rolled steel and the rough flaky surface doesn't help the case. I have also become rather untrustworthy of the straightness of the steel I can get around here. I'll stick to the round curtain pipe for now, after all, I'll only use the machine for wood and plactics.

    Quote Originally Posted by reg.miller View Post
    However the mild steel started to wear quickly when I put pressure on the bearings.
    You must have a tonne of pressure on those rails from the bearings!!! At the tightness I'm comfortable with, I run the bearing block back and forth a few times and couldn't see any marks created by the bearings on the pipes!!!

    Quote Originally Posted by reg.miller View Post
    You mentioned problems getting all bearings to have firm contact. This is alignment problems, it's like trying to cut the legs on a chair so that they all touch the ground ! First solution is to use two bearings one side and one on the other : with a three-legged stool they will always touch. Four legs gets more tricky I use one U-bearing underneath and two blocks on top for this reason.
    This actually caused me a lot of frustration! I also tried the three legged chair method with the bearings but it only slightly improved things. I eventually set out with a system capable of a large degree of self alignment, hence this set up, which I'm happy with so far. I might replace the curtain pipe with a thicker walled regular steel pipe if the bearings start crushing this one.They've only turned out a little bulkier than I expected, but it doesn't really bother me as long as it gets the job done.


    Quote Originally Posted by reg.miller View Post
    In your context you can cut open various drink and food containers for shims. They provide good uniform sheet, though the range of thicknesses is a bit limited. 25 and 32 thou' seem quite common in steel containers. Ali drink cans can be thinner.

    Great idea. I'm sure this will come in handy sometime in the future! Better start stocking the fridge ASAP lol.


    Quote Originally Posted by reg.miller View Post
    I've gone through several iterations to get the solid guides I have now. Hopefully I can save you some time by pointing out the limitations I came up against.
    Since you mentioned it, did the bearings create a flat track along the SBR20 rods enough for them (the bearings) to warrant retightening?

    BTW, what's your machine's work area?

    Grateful for the help.



  20. #80
    Member
    Join Date
    Feb 2017
    Location
    Uganda
    Posts
    90
    Downloads
    4
    Uploads
    0

    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by reg.miller View Post
    4 centimeters ( french ) hundreds of a mm
    WOAH!! Is that how much your X-axis I-beams were deflecting downward? That is crazy!!! Waiting to see what mine will be like, good thing I've got an idea of a solution in case mine deflects unacceptably.

    Quote Originally Posted by reg.miller View Post
    I clamp down the bearings more than you would in a more normal bearing application. But since they will not be turning fast and not doing many miles that is acceptable. I tighten them so it will run on when pushed but not that far. ie there is quite a bit of rolling friction. You can see that here:
    http://solaire-chauffe-eau.info/cnc/slide.mp4
    Are you able to stop them rolling by hand? By that I mean, can you push the bearing block and hold a bearing with you fingers, tight enough to stop it rolling?

    Quote Originally Posted by reg.miller View Post
    The problem is not really from the bearing spacing once that is wide enough. It is from twisting of the vertical supports. The gantry acts as a long lever and whatever your verticals are made of they will twist.
    I used 16mm of steel plate about 15cm wide and even that gave me 1cm at the other end when only one was fixed.

    If you want to got for centre only, at least add the cross-over cable. That helps a lot and is probably good enough for your project.
    I see. I guess I'll get to that when the gantry is done, although mine will only be about 600mm wide at most.

    Thanks again.



Page 4 of 7 FirstFirst 1234567 LastLast

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

DIY CNC machine on the cheap!

DIY CNC machine on the cheap!