work with what you got build


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  1. #1
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    Default work with what you got build

    Here is a photo of my franken build. i got a good deal on 15' of 4" .25 square tube and this happened. i had 3 2' lengths and didn't want to cut them so I just gave my self plenty of Z. The I beam with it's sporty orange paint was $15 bucks and sitting on the 4/5/6 blocks it is within .1mm almost by accident. I'm a bit concerned about how easy the I beam twists. I'd like to weld the ends closed but I'm concerned it will move a lot. I am also considering padding it out from the steel with some aluminum to provide some dampening. The Y gantry beam is 2.5" x .25" squre aluminum. I actually tried to mill in the steel but it bowed about 3/32 due to the stress freed in the cut. I likely could have kept it straight by just skimming the very outer surface but I tried to have a registration shelf for the HG20 rail. The Y plate and Z slide was designed before I had the 4" square tube. I have a 400mm ball screw that I may swap the 300mm ball screw out for to give a bit more total spindle movement. I want to be able easily accommodate a vice.


    work with what you got build-20180821_213446-jpg


    Need to figure out what to do for the X table. I has been an adventure so far.

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    Attached Thumbnails Attached Thumbnails work with what you got build-20180821_213446-jpg  


  2. #2
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    Default Re: work with what you got build

    I can see that you are a tinkerer and builder for building sake, like me.

    If I am wrong, please explain your purpose for building and your expected finished product and usage.

    Don



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    Default Re: work with what you got build

    I hope it will be able to do aluminum accurately (no clue how fast), PCB milling, and wood. No clue what it will look like when it is done but I have all 3 axis moving now and need to adjust the Z height down a few inches. I have it square to about .1mm. X is ~600mm travel, Y is ~ 900, Z is only ~ 200 right now. The close I get the work to the Y fixed gantry the more rigid it should be.

    I'm thinking about some bracing to shore up the I beam in a trapezoid configuration that uses the bottom 4" tube to counter twisting. I'm going to get the electronicals hooked up after I lower the X axis.

    My motor is a small 500w brushless ER16 spindle and I need a better mount for it. Anyone have suggestions for good threads on spindle mounts that be easily trammed?



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    Default Re: work with what you got build

    I was able to get the X working. I have a temporary bed which is .25" steel plate and fairly flat.

    how do you rotate images in this forum?

    work with what you got build-20180822_203252-jpg

    Attached Thumbnails Attached Thumbnails work with what you got build-20180822_203252-jpg  


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    Default Re: work with what you got build

    Rotate the images in your computer before you send them to cnczone.

    Don



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    Default Re: work with what you got build



    crappy motor mount but all axis are ready for electronicals.



  7. #7

    Default Re: work with what you got build

    Awesome! Will follow your build thread for sure.



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    Default Re: work with what you got build

    Looks pretty heavy , are your motors strong enough ?



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    Default Re: work with what you got build

    it is working at around 75mm/s/s (right units for grbl?) accel and 2500mm/m. X can go a lot faster but the X is much lighter than the Y/Z carriage which is about 40-50lbs. I'm running DRV8825's at around 2A. Motors can do 4A and I have some TB6600 clones I plan to test out. First cuts were square with axis and a bit not square on diagonals. I tried to use an indicator to calibrate the steps per rotation and got a decent amount of variance. Could be the indicator it is new and I have not used it much. Need to check with a dial test indicator. No visible steps on edges and no chatter from the spindle yet. I"m doubling the speed and doing another run to see how far I can push a little 4mm straight flute cutter in MDF making some drawer sides.



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    Default Re: work with what you got build

    Well I learned that it takes about 2 minutes to run DRV8825's without cooling > 2A before they hit thermal shutdown!

    The machine easily cut 1750mm/m with 2.5mm DOC with 4mm 2 flute (straight) in 9-11 ply .7" plywood. cuts came out very clean.

    Drawers are ready for assembly and I may make a few more so I plan to keep pushing the little spindle on the next batch.





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    Default Re: work with what you got build

    I like what and how you are doing it.
    To avoid overheating, turn down the amps (if you can) or switch to the TB6600 drivers.



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    Default Re: work with what you got build

    i had a wire stuck in my fan. I have a little 12v squirrel cage fan running on +5v and running silent (which is why i didn't notice it was stuck). Keeps the drivers under 35C mostly.


    I made a part for my manual milling machine today. Some success and some failure. I'll post a video. I think my spindle bearings may be crapping out or I may need a bigger spindle for this machine.



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    Default Re: work with what you got build

    Lots of failures to enjoy here!


    I did end up with a working part. Please comment if you have any questions.





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    Default Re: work with what you got build

    The gantry looks pretty wimpy compared to the rest of the build. Also, does it only have a single profile rail? Those are rated for some torque on them, but not much, really should double up (if there isn't another hiding somewhere.)
    Also the bed could probably use some bracing, but you mentioned that's temporary anyway.
    That type of spindle is pretty light duty. I've seen some of that general type that are just a motor with an ER collet holder pressed on one shaft and a fan on the other. No precision/preloaded bearings, tons of runout and a spindly little shaft. Looks like the one you've got is a step or 2 up from those, but still lots of room for improvement there.



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    Default Re: work with what you got build

    Quote Originally Posted by skrubol View Post
    The gantry looks pretty wimpy compared to the rest of the build. Also, does it only have a single profile rail?
    .
    it is surprisingly stiff but I have more of the 4" steel stock to replace it with if things keep improving. I can do some testing if anyone wants to know the practical stiffness of the current 2.5" x .25" aluminum square tube setup. This is much more stiff than c-beam.

    Quote Originally Posted by skrubol View Post
    Those are rated for some torque on them, but not much, really should double up (if there isn't another hiding somewhere.)
    good eye. Yup it only has one rail. I have a SBR16 mounted on the back however I couldn't see how a single SBR rail would help in the position it is in. I just left it unattached and it does provide some support to the gantry beam. I may install the 2nd 1000mm rail where the SBR16 is on the back, but I may just wait till I get the larger 4" x .25" installed. It is getting quite heavy though and if it falls over it may never get back up. If it falls over on me I may never get back up.
    Quote Originally Posted by skrubol View Post

    Also the bed could probably use some bracing, but you mentioned that's temporary anyway.
    .25" steel should be pretty stiff no? The aluminum beds I've seen seem much less robust unless I am milling something about the strength of extrusion.

    I can drop the bed about 7 more inches. I'd like to have my vice semi-permanantly installed and be able to plop something on top for larger flast stock like MDF/plywood. The problem with that is that I believe the lower I drop my spindle the less rigid my setup is with the Z rails in motion. The really ideal setup is to have the vice as close to the Y gantry as I can get it.

    Quote Originally Posted by skrubol View Post

    That type of spindle is pretty light duty. I've seen some of that general type that are just a motor with an ER collet holder pressed on one shaft and a fan on the other. No precision/preloaded bearings, tons of runout and a spindly little shaft. Looks like the one you've got is a step or 2 up from those, but still lots of room for improvement there.
    Yup, I have a thread going in the spindle section and I am now looking to get something with angular contact bearings. The spindle is pretty good at running adaptive cuts but it does not like slot cutting at all and 2d contours need to be limited to .2mm doc or less. The runout is as bad as .044mm



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    Default Re: work with what you got build

    If you can fit a rail on top without getting in the way of your screw, that is a fairly common way to mount a second rail, it's often better than 2 rails on the front, but harder to align.

    You definitely don't want more room between the bed and the gantry than you need. You're right that longer Z extension is bad (not only does it add more opportunity for flex in the Z, it will want to twist the gantry more.) Stiffness is the square of thickness (all else equal,) so .25" steel isn't super stiff compared to something with a frame, but it's mostly a lack of stiffness in the Z axis, where it's probably least likely to show. Also if your vise is bridging most of the space between the rails that will stiffen things up as well. Aluminum extrusions can be quite stiff, but most of the machines made out of the thinner stuff are pretty wimpy.

    I'll take a look at your spindle thread as well.

    Machine certainly performs better than it looks!



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    Default Re: work with what you got build

    Quote Originally Posted by skrubol View Post
    If you can fit a rail on top without getting in the way of your screw, that is a fairly common way to mount a second rail, it's often better than 2 rails on the front, but harder to align.

    You definitely don't want more room between the bed and the gantry than you need. You're right that longer Z extension is bad (not only does it add more opportunity for flex in the Z, it will want to twist the gantry more.) Stiffness is the square of thickness (all else equal,) so .25" steel isn't super stiff compared to something with a frame, but it's mostly a lack of stiffness in the Z axis, where it's probably least likely to show. Also if your vise is bridging most of the space between the rails that will stiffen things up as well. Aluminum extrusions can be quite stiff, but most of the machines made out of the thinner stuff are pretty wimpy.

    I'll take a look at your spindle thread as well.

    Machine certainly performs better than it looks!
    I ended up buying a .8kw motor with 2 pairs of 7002 bearings and a HY 1.5kw vfd. That should add about 3 lbs to my y/Z setup which is already very heavy.

    I have ~700 mm of X rail but only around 400 of actual travel ( I can space my X rail block closer to improve this a bit if I want.). Effective Y travel is ~790mm. I have some lengths of .125" square tube I could weld a frame with however my welding skills took a 20 year break and did not come out the other end with much left.

    For the bed what inexpensive options do I have that I can fabricate? If you could direct me to threads with good beds that would be helpful.



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    Default Re: work with what you got build

    I wouldn't worry too much about 3lbs on the Z, cutting forces are likely much higher, and static forces are easier to deal with than dynamic forces. May need to put some a tension spring or something to help the Z axis stepper if it starts stalling.

    Even bolting a couple square or rect tubes to the plate between the carriages can help a bit. I'm not sure on 'next step' beds that won't blow the budget. I'm in a similar (though bigger) situation, I've got the bones of a router (PCB drilling machine actually,) that has a very light duty frame for a table that I'm going to throw some aluminum tooling plate on to get it up and running, but I'm probably going to end up eventually getting a VMC table off ebay and having to spend more on freight than on the table. It'll probably be the most expensive single part of the build.



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    Default Re: work with what you got build

    My new spindle was supposed to arrive today. They UPS hit me with a weather disruption delay....

    Made a pcb this evening with flatcam.

    watching this is really thrilling stuff.




    if anyone is interested in flatcam and easyeda I'm happy to provide details.



  20. #20
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    Default Re: work with what you got build

    Mounting plate for new spindle. I'm planning on using a clamping method and I was wondering what folks think about that vs just bolting through the flanges on the spindle mount?



    work with what you got build-20180923_132616-jpg

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