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  1. #231
    Hi Rob. I had the same thought initially. A water level. Although old fashioned, for long distances, I do not know a better method today.
    But still, the question remains, what do to first. Rails or bearings?

  2. #232
    An easy way to check the coplanarity of the two rails is by stretching two diagonal strings and check if they touch in the middle. With thin fishing line and eventually compensating the thickness of the line for the one above you could get very good accuracy. When you have the ends coplanar then you can straighten the rails with a straight reference (the hardest part).

    For the perpendicularity of the gantry to the x axis, draw with the cnc the corners of a rectangle, and measure the diagonals which should be equal. The larger the rectangle, higher the measured accuracy.

  3. #233
    One more great ideea. Thank you paulus.v

  4. #234
    Quote Originally Posted by Radu_Andrei View Post
    Hi Rob. I had the same thought initially. A water level. Although old fashioned, for long distances, I do not know a better method today.
    But still, the question remains, what do to first. Rails or bearings?
    Work from bottom to top i.e Frame, X rails, Gantry, Y rails, Spindle, then you are not so likely to be re-iterative with your adjustments.
    Albert Einstein may have been a genius, but his brother Frank, was a monster

    Having just moved to Windows 10 (which is crap) My stress levels are through the roof !!!

  5. #235
    Ok. Thank you.

  6. #236
    Quote Originally Posted by Radu_Andrei View Post

    Regarding your post, ˇˇThe difficult part is bolting down the first rail absolutely straight.ˇˇ, before doing that, is it not necessary to set the y axis linear bearings/rails absolutely perpendicular to the x axis rails?

    Actually, getting the gantry square to the other rails is one of the easiest adjustments, and it was almost the last thing I did. I am assuming that you are able to adjust the gantry - in my case, I can loosen the bolts between the gantry and the plates which carry the bearings so that if I turn one ballscrew, I adjust the "squareness" of the gantry. So, get it as close to square as you can - I used a carpenter's square - and then cut a test piece. As someone has suggested, drill four holes on the corners of a square and measure the diagonals. I used the shanks of drills as pegs in a piece of MDF, having used the same size drill to make the holes. With a little bit of schoolboy trigonometry, you can then work out how much you need to turn just one of the ballscrews driving the gantry to bring it into square. Tighten bolts and check again. I wrote a short piece of gcode to drill the holes so that I could ensure that I always approached the holes from the same direction to remove backlash from the process.

    My very final adjustment was to use the machine itself to skim the strips of wood I use as bed supports so the the bed was reasonably flat once I screwed down a sheet of plywood. Not good enough for precision metalwork, but this is a woodworking machine. I machine a smaller spoil board if I want more depth accuracy for a particular job.

    Good luck!
    Last edited by Neale; 10-12-2018 at 10:54 AM.

  7. #237
    Hi. Happy new year! I know it's february, but after holidays and furniture orders, I just managed to get back to the cnc project last week. Hope you are all well.

    So I took the whole thing apart, removed the wooden frame it had underneath, bought some steel tubing and made a new support for the cnc.

    I managed to get the rails coplanar, with the two strings method, and a cheap usb microscope.
    I have used a straigh edge to do one rail on each axis, then by moving the gantry, got paralel the second. It took a while but it worked.
    Today I got the y and x square with the 4 holes method. All methods, mentioned in this thread, so thank you everyone.
    I only have left the ballscrews allignement.

    Reassembling the cnc, I noticed there were some screws loose. It might be that I did not tighten them in the first place, or they came loose while the cnc functioned. Anyway, I used only bolts and plain washers, and it might be not good enough, so I intend to upgrade this with something else, before I get the cnc working again.

    Doing a bit of reasearch, I found a few option, the best one being crazy expensive. Some nord lock washers. But still there are a few which might work. Tab washers, safety wire, and locktite (I do not like this idea, as I am not sure if I can unscrew the thing). It might not be a must to upgrade all the bolts, but some for sure, like the ballnut bracket ones.

    What do you use in order to prevent screws from coming loose due to vibration? And is it a must to use any special type of bolts, or the cheap silver one will do?

  8. #238
    Quote Originally Posted by Radu_Andrei View Post
    Hi. Happy new year! I know it's february, but after holidays and furniture orders, I just managed to get back to the cnc project last week. Hope you are all well.

    So I took the whole thing apart, removed the wooden frame it had underneath, bought some steel tubing and made a new support for the cnc.

    I managed to get the rails coplanar, with the two strings method, and a cheap usb microscope.
    I have used a straigh edge to do one rail on each axis, then by moving the gantry, got paralel the second. It took a while but it worked.
    Today I got the y and x square with the 4 holes method. All methods, mentioned in this thread, so thank you everyone.
    I only have left the ballscrews allignement.

    Reassembling the cnc, I noticed there were some screws loose. It might be that I did not tighten them in the first place, or they came loose while the cnc functioned. Anyway, I used only bolts and plain washers, and it might be not good enough, so I intend to upgrade this with something else, before I get the cnc working again.

    Doing a bit of reasearch, I found a few option, the best one being crazy expensive. Some nord lock washers. But still there are a few which might work. Tab washers, safety wire, and locktite (I do not like this idea, as I am not sure if I can unscrew the thing). It might not be a must to upgrade all the bolts, but some for sure, like the ballnut bracket ones.

    What do you use in order to prevent screws from coming loose due to vibration? And is it a must to use any special type of bolts, or the cheap silver one will do?
    I use tensile bolts with either spring or serrated washers. Where I need nut & bolt I use nyloc nuts.
    No bolts have came loose.
    Examples:

    https://www.ebay.co.uk/itm/SHAKEPROO...qgg:rk:10:pf:0
    https://www.ebay.co.uk/itm/M2-M2-5-M...OicKyTw5sf01Co
    https://www.ebay.co.uk/itm/M4-M5-M6-...ID805KSc9mzpls
    https://www.ebay.co.uk/itm/A4-STAINL...nSZw:rk:3:pf:1
    Last edited by dazp1976; 14-02-2019 at 12:27 AM.

  9. #239
    Hi dazp1976. Thanks for the reply. In the end I did use plain and spring washers, as they were easily available. Not the cheap silver springs, as they go flat. I used tensible bolts for bearing cases and nut cases, but not for rails, as they are quite expensive. Will upgrade in the future if necessary. So problem solved for now. The cnc is working fine and did quite a few medium sized carving with it.

    I ran the machine 5 hours straight at most until now, but there is a job that is on my mind, a 4x2.5 feet carving, which will be a table top with some glass over it. Anyway, the job will take apx 11 hours to carve, and
    I have no clue for how long can this cnc machines function without a break. For a 5 hour cut, the x motor which does most of the work, gets quite hot, like you can hold your hand on it for 5 seconds max, but I did read in some previous posts that it is quite normal. It is nema 34 1200 oz.

    What do you think? Should I break the job in two parts or do it in one go? Did anyone used the cnc for such a time or longer?

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