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Thread: DIY aluminum vertical mill build

  1. #13
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    Miscellaneous stuff:

    The spindle has a 15 tooth pulley and the motor has a 45 tooth pulley with an L timing belt, all from sdp-si. Both were bored on the lathe to fit. As the motor RPM is from 340-1700 RPM at the spindle is 1000-5000. I wish the bottom end was a bit lower in case I do some steel but I want that high end. I can always get a 25 tooth pulley for the motor later on and switch it out for the situation without much fuss.

    Performance. I didn't get much time with the mill until that POS vise gave out on me. Material removal rate with the Sherline CNC was .025" DOC at 10IPM in 6061. With the new mill it was at .050" DOC at 20IPM in 6061 and the finish was mirror smooth both on facing and profiling. I'm sure the feed could be pushed up faster, I'm going to try 25IPM right away when the Glacern is mounted.

    Tooling. I'm using the Sherline end mill holders. Run out is excellent with these: anywhere from .0003" to .0006" at the tool when screwed on to the spindle. The X2 head had .0008" in the spindle bore alone, after tolerance stacking I bet it would be pushing a thou and a half at the tool. Plus these tool holders are nice and cheap at $30US per. I also have a single insert face mill, 3 drill chucks and a boring head, all Sherline.

    Weight: The two main blocks are 70 pounds each, totaling 140. Head assembly with motor is about 23 pounds. The rest of the aluminum (head parts not included) is 43.5 pounds. Steppers are about 2.5 pounds each for another 7.5 pounds. Linear rails, and ballscrews I would guesstimate at another 12 pounds total. Counter weight is 15 pounds. So total machine weight = 240 pounds.

    Well, that's it for a bit guys. Thanks for reading.

    Serge

    Last edited by sergizmo; 01-02-2010 at 06:49 AM. Reason: added stuff


  2. #14
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    Quote Originally Posted by MRM RCModels View Post
    Design looks good. Are you looking to get more travel than your present cnc mill with the same performance? I'd also advise making some denim bellows for the linear slides. Really helped mine with the swarf. Did you ever look at a 1.5kw Chinese spindle with VFD option. For what you're doing might be worth the investment.

    You sanded both surfaces perpendicular by hand ? You have a bigger pair than I do.
    Thanks.

    The performance is much better. It is waaaaaaay more rigid than the Sherline, the frame being 6" by 5" solid aluminum for both base and column. No backlash (.0001" on all axis, measured with a .0001" test indicator) and much, much faster. Jogging at 120IPM no sweat. I turned it down to 100IPM because much faster than that was kind of scary.

    The perpendicularity was mainly achieved by gluing shims to the end of the block of the right thickness in the right places and testing this with the block stood up on the surface plate with a square. Then the JB weld was used. After that I did some checking and a little draw filing to get it square within .0015" over 5". Most of the sanding was done to get stuff flat.

    I don't like the look of those Chinese spindles for several reasons. First, they are a bazillion RPM, min RPM is too fast. Second, it is a cartridge type spindle and would require a precisely bored hole in a mounting block, something I can't do at home. Third, ER nose. I can't preset my tools in a multiple tool program. And fourth, it's Chinese made. The Sherline spindle is of much better quality.



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    Any questions, comments, suggestions, ideas, criticisms, etc... ?



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    Quote Originally Posted by sergizmo View Post
    Any questions, comments, suggestions, ideas, criticisms, etc... ?
    Nice project.

    One thought:

    If you had it to do over again, make the base wider. If you look at commercial CNC's versus those intended for the home, I always notice the saddle is very wide on the commercial units. You want the support of the table linear rails tied to the base as far apart as possible I think. This would be particularly easy to do on your machine.

    If you want even more rigidity, you could fill the base and column with epoxy granite. It made at least a 15-20% difference on my IH mill to do that.

    Cheers,

    BW

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    Thanks Bob.

    The base and column are solid (no cavity) 6" by 5" aluminum blocks. So there is nothing to fill. They clock in at 70 pounds each (6" x 5" x 24" x .098"lb/in^3). The spindle will fail before these monsters bend.

    It would have been nice to make the base wider, reducing saddle overhang. From what I had available at the time, these two pieces were the best option. Unfourtunately I didn't know about the local Metal Supermarkets at the time, they have some pieces that could have been used for the base. One was 8" wide by 3 1/2" thick, that would have done nicely.

    Serge



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    ^^^^^^^

    To add to the above. The rail blocks on the base protrude about .2" off of each side. So there is 6.4" in the center of the saddle that is fully supported.



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    Hi,
    Very impressive build indeed! It shows what can be done with limted tools, dedication, some careful thought and "a bit" of elbow grease. Can't say I completely understood the "shimming/bondo process" of getting the important surfaces flat and perpendicular but that says more about me than you and/or the process ;-)

    Would love to see a video of it action once you get the Glacern vise mounted!

    Again, excellent work, thanks for showing us!

    /Henrik.



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    Hi Henrik,

    Thank you very much!

    I'll try to explain getting the ends perpendicular a bit better.

    1) I stand the block up on the granite surface plate, with the down side being the end I want to square up.

    2) I "test fit" shims of various thicknesses under the end that is down and check perpendicularity with a square off the granite plate. I keep moving the shims around, and using different thicknesses and checking with the square both off the main flat surface and my reference side surface. After the end is square I note the positions of the shims with a marker.

    3) The shims are super-glued in the spots noted down with a marker.

    4) The granite plate is covered by saran wrap, stretched tight and the ends taped down to the sides of the plate with masking tape. I keep stretching the saran wrap over the plate by pulling and re-applying the tape until the top is a smooth surface.

    5) The saran wrapped surface plate is sprayed down liberally with non-petroleum based silicone spray.

    6) JB Weld is mixed up and applied to the end being squared up (The one with the shims).

    7) The granite plate is then placed on top of this end. The weight of the plate squeezes the JB weld down to the shims. The silicone covered saran wrap allows me to remove the plate later.

    8) After about 6-8 hours, the plate is peeled off and the excess JB weld that squeezed out over the sides of the block is trimmed off with an exacto knife. The saran wrap is removed from the plate.

    9) I wait another 24 hours.

    10) The end is checked for perpendicularity on the granite surface plate (JB weld side down) with a square and feeler gauge on both the flat sanded top surface and reference side.

    11) Any filing that needs to be done to get it to where I want it is done. This was pretty minimal, the process itself does most of the work.

    I hope this clarifies things a bit.

    Serge



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    sergizmo, that squaring process is also used in the professional world, though usually with moglice or something similar rather than JBWeld!

    The other difference is that rather than build it relative to the surface plate, they would square the column on the machine itself and then inject the material between the two pieces with a dam to hold it inside.

    It works very well.

    Cheers,

    BW

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    Thanks for the info Bob.

    I wanted to do it separately so the column could be removed later. The machine will have to be torn down to be moved sooner or later.

    The JB is in the mild steel range for strength and hardness which is fine. Plus it does not shrink. It's just being used to create a surface, there is no movement or anything. I wouldn't think of using it on a moving surface or the like.

    http://jbweld.net/products/jbweld.php

    I'm having problems with the electronics again... Missing steps on the X and I had a freeze where it seemed to be stuck between steps. It's a really simple program, a domino top surface and profile. It machined the first one OK except for a couple missed steps on the X (a ridge on one layer of the roughing pass), second started missing more steps and the third out and out froze. I also could jog in .001" increments on the X but not .0001". This is getting really frustrating. I'll shoot out another email (hopefully he responds this time...), call if there is no response and try some things like Sherline mode to see if that fixes it. This is Gecko 250 based and I heard about that problem (needed Sherline mode) with some of them.

    If that doesn't work and things aren't resolved via email or phone I'll start to look at another electronics package... Probotix, Keeling, etc...

    Serge



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    Hi Serge,
    Thank you for the explaination!

    As for your electronics - if possible, try swapping the X- and Y-axis drives and see if the problem follows the drive or if it stays on the X-axis. If it follows the drive, well then it's the drive. If it stays on the X-axis it could be a wiring problem (although not likely) or a heat problem as you seem to have indicated already.

    The manual for the G250/251 calls for a minimum pulse width of 1uS, Mach3 will put out at least that, normally ~3uS even without increasing the pulsewidth setting. If Sherlinemode is needed you may have a problematic LPT-cable, I've seen that be the case. Obviosuly I don't know what the OEM may have put in between the LPT-port and the G251/251 which may be causing the problem as well.

    If you don't get the suport you need from where you bought it, and you suspect the problem is with the actual G250/251, you can always try contacting Geckodrive directly.

    /Henrik.



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    Henrik,

    I sent the control back, and assume something was done to check/fix that drive. I was very clear in the emails about what was going wrong.

    The computer was bought brand new. It may have an "under powered" parallel port, I've heard of this. Newer motherboards can have them.

    The first thing I'm going to try is Sherline mode. It seems there are many, many people who have had to do this with the 250/251. If that doesn't work I'll look at the cable, thank you for the suggestion.

    Serge



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