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Thread: (Another) LMS SX2 Mini Mill CNC Conversion

  1. #133
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    Default Re: (Another) LMS SX2 Mini Mill CNC Conversion

    Nice build. Did you mean to post here, or were you trying to start a new thread? To start a new thread, go up one level to Benchtop Machines and click on Post New Thread. If that isn't visible, click on the Title/Thread Starter on the border to get the dropdown for starting new threads. --md



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    Default Re: (Another) LMS SX2 Mini Mill CNC Conversion

    Subscribed

    Thank You,
    Paul G

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    Default X+Y Axis CNC Conversion Drawings

    There has been some interest in plans for my LMS conversion, so I'm posting some of the requested drawings for the X and Y axes parts. These drawings should be very close to what has been presented in this build thread, but no guarantees.

    Status on the speed controller and spindle light projects: Both are moving forward at a snail's pace, hope to make some progress that is worth reporting before Thanksgiving. --md

    Attached Files Attached Files


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    Default Re: X+Y Axis CNC Conversion Drawings

    Thanks for posting those! Working on my refit of my currently CNC'd X2 and I like your design.

    Eric



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    Default Re: X+Y Axis CNC Conversion Drawings

    Quote Originally Posted by Brass_Machine View Post
    Thanks for posting those! Working on my refit of my currently CNC'd X2 and I like your design.

    Eric
    You're welcome. A couple notes on some things I noticed in the drawings: 1) The 10mm ID x 12mm OD spacers used on either side of the bearing can be made, but I bought those off the shelf from a skateboard shop (Daddies Board Shop, Landyachtz Aluminum Wheels Spacers 10mm x 8mm Set of 4), and 2) the optional bearing seal is incorrectly sized in one of the drawings, it should be 22mm x 12mm, and 3) the Y-axis bearing block drawings is missing the distance from bearing center to the lower mounting bolt center, which is .798" down. This dimension is shown on the lid drawing but omitted on the bearing block.
    When I get some time I'll add the Z-axis bearing block/drive and update the drawings. --md



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    Default Project Re-Boot: Manual Jog Controller Build

    After a long pause I'm starting back to work on the mill. In the interim I've used the machine to make some small parts for a few projects and even for some wood working where I needed some accurate holes drilled repetitively on multiple pieces of material. I've made no progress on the spindle controller, though it is still on the list of things to finish. During this time I've also discovered that one of the frustrating things about converting the mill to CNC has been the loss of the ability to just walk up to the machine and use it for basic milling/drilling without the need to connect and boot a computer. I don't want to leave my Mach3 laptop computer in the garage, so the setup time has kept me from using the mill as much as I could have. Some people have left the hand wheels installed on their CNC machine axes for this purpose, but with my enclosure it wouldn't be practical. I hate to start a new project with others waiting to be finished, but I see this as a fundamental capability that will help to make the machine more usable. So, the solution I'm planning is to build up a standalone, 3-axis Manual Jog Controller (MJC) (see attached rough CAD models) that will provide "manual" mill operations on X, Y, and Z via the stepper motor interfaces without the need for Mach3; rather it will interface directly to the parallel port BOB, with the stepper motor movements controlled by step and direction inputs generated by the controller. It's basically a narrow box with 3 hand wheels, a display, and an assortment of switches and buttons for the various controls and a microcomputer to pull it all together. This controller will attach to the front of the mill stand, convenient for reaching the work for setups and touching off cutters. This is going to take a while to build, and I plan to cover this in some detail, so it will be broken into small segments. The next posts will cover the overall features, plans, and design for the controller, followed by build progress.

    Attached Thumbnails Attached Thumbnails (Another) LMS SX2 Mini Mill CNC Conversion-mpg_controller1-jpg   (Another) LMS SX2 Mini Mill CNC Conversion-mpg_controller2-jpg   (Another) LMS SX2 Mini Mill CNC Conversion-mpg_controller3-jpg  


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    Default Manual Jog Controller (MJC) Description (Part 1)

    A while back I evaluated a friend's < $100 pendant controller and found it to be nice but with a few shortcomings. Some of the other pendants from VistaCNC, at almost $300 are very nice (from reviews, never tried one myself), but I started thinking that maybe for that cost I could make something that would work better for the way I want to control and use the mill.
    What I want is a controller that gives me a manual operations interface, i.e. two hand operations for milling (X,Y table movement), with a third Z control. With the stepper motors in the control loop, very precise positioning control, as well as auto feed would also be possible. DRO displays for each axis are mandatory, and some other programmed functions would also be nice but can be added over time. I still want to have access to CNC operations too. Here's the feature list so far:

    Hand wheel jog controls for X, Y, Z axes, with individual calibrations, step scaling (.001, .010, .100, etc.), backlash compensation, individual axis on/off controls (simulates locking an axis, and also to prevent inadvertent movement from bumping a hand wheel).
    DRO displays for X, Y and Z positions, with ability to set zero on each
    Auto feed on any single axis using a cruise control style interface to set/resume/cancel the feed established using the hand wheel. Feed could be set via display interface too. The Resume function would use the direction set by moving hand wheel and pressing Resume button.
    Support for functions such as peck drilling cycles and bolt circle/patterns, maybe circular and rectangular pockets, etc., again to support rudimentary operations.
    MPG inputs for Mach3 when operating as a CNC machine. I'll need to add more inputs to support the 3-axis MPG, though I probably have enough inputs to support a single MPG input.
    Spindle speed control (via display interface/controls; this is future implementation once spindle controller is finished)

    There will also be a USB interface for re-programming software and maybe assisting in setups that are too complicated for the onboard micro to handle through the built-in display, such as calibrations and backlash determinations (remember I generally don't want to hook up a computer for most operations).



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    Default Manual Jog Controller (MJC) Description (Part 2)

    This post is an overview of the electronics and mechanical workings of the controller. Each hand wheel is connected via a shaft to a rotary encoder inside the box. I picked 24 step encoders with detents at each step. To keep costs down, these are mechanical encoders, but they have 100k revolution life rating so they should be ok for longevity, and are cheap (< $5 each). The shaft is supported by a small ball bearings so that the encoder is not subjected to any radial or axial loads; only rotation torque. The encoder shaft slips into the end of the hand wheel shaft and is secured with a set screw. The encoder end of the shaft is threaded on the OD so the hand wheel can be pulled tight against the support bearing using a nut and spacer. The encoders are panel mount types, so a U shaped bracket supports the encoder body over the end of the shaft. The encoders each produce two square wave outputs that are offset by 90 degrees (in quadrature). These signals go into a microcontroller for scaling and can also be used for speed and direction determination, or ignored if the enable switch for that axis is turned off. The encoders can also be routed out as MPG signals for use with Mach3 in CNC support mode. The top of the box is angled at 45 degrees and has a rather large 4x40 LCD character display, which is also interfaced to the microcontroller. To the left of the display are three buttons that will be used to zero the X, Y, Z DROs and maybe support other functions such as axis calibration. Further left is the auto feed "cruise control" buttons: Set, Resume , Cancel. On the right side of the display are either 2 or maybe 3 buttons for menu navigation/selection. To the far right is an eight position rotary switch to select the jog mode and other functions, such as changing to Mach3 support mode. So far I have spent about $65 for parts including shipping. The electronics came from Digikey and SparkFun, and bearings from VXB. I already had a microcontroller board (also from Digikey), so adding another $20 for that, I'm at $85. There will be another $20 or so for wiring and other stuff before it's over. The enclosure is going to be 1/2" birch ply and 1/4" sanded ply panels, all scrap from other projects. Fasteners and incidentals will add a bit more, so the final estimated cost should be $125 or so. The controller will mount to the front of the mill stand using some kind of sturdy but removable bracket TBD. The hand wheel arrangement is: far left is Y axis, far right is X axis, and center is Z. Distance between X, Y hand wheels is about 10 inches. The interface to the BOB will be a standard 25 pin printer cable, exiting the bottom of the box. When operating as a Mach3 MPG, there will be another smaller connector, probably one of the round metal connectors, forget what they are called, with 8 to 10 pins. Attached some pics of the electronics. Note the red button switches, those are momentary normally open type. Digikey had the little rubber caps that will make those waterproof. The three silver buttons have green LED lamps and are latching type switches. Those are the enable buttons for each axis and will light green when the axis is enabled. The three silver parts wiht flat shafts are the encoders, and the rotary switch has the long handle and an aluminum anodized knob. The large LCD display is 4x40 characters with a nice white backlight. It should have enough space to allow displays of X, Y, Z DRO, plus spindle speed, and support a menu area for function select. I decided against a keypad, at least for now. I started making some parts, so the build posts are next.

    Attached Thumbnails Attached Thumbnails (Another) LMS SX2 Mini Mill CNC Conversion-img_7411s-jpg   (Another) LMS SX2 Mini Mill CNC Conversion-img_7412s-jpg   (Another) LMS SX2 Mini Mill CNC Conversion-img_7413s-jpg   (Another) LMS SX2 Mini Mill CNC Conversion-img_7414s-jpg  

    (Another) LMS SX2 Mini Mill CNC Conversion-img_7415s-jpg  


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    Default Manual Jog Controller Build (1)

    I decided to tackle making the hand wheels first. My model drawings show these as single piece wheel/shaft, but it's much easier to make the wheels and shafts separately, especially on the mini-lathe. The scale of this controller constrains how large the hand wheels could be, and I looked at the pendants, and also the radio control car controllers for reference, and decided on 2.5" as a good size. Larger might be better, but this size will allow good gripping of the wheel for precise movements, and the handles will allow for rapids. I had access to some cutoff pieces of 2.5" round 7075 aluminum that served as the stock. I found a .75" long and 2" long piece. On the mini-lathe, the outside jaws on the 3 jaw chuck were used. The .75" piece was faced and turned enough to make it smooth and round, then turned around in the chuck to face the other side to final thickness (0.6"), and then center drilled with #7 drill for 1/4-20 tapping. I waited to tap until after the center was hollowed out to save on tapping depth. Using a boring bar, a pocket of about 1" was cut into the face to a depth of .3" (half thickness of the wheel). With the compound set at 45 degrees, the boring bar was also set to 45 degrees and then the edge of the pocket was worked back until the taper reached the bottom of the pocket. The edges were chamfered, and then the center hole tapped to finish the part. The 2" piece was faced, turned, then turned around to face the other side, and the diameter turned for a distance of about .7". Then I moved to the bandsaw to part off the two pieces about .7" thick. Returned to the lathe to face the cuts to finish thickness (.6") and repeated the center drilling, boring, tapping, chamfering to complete the other two wheels. See attached photos of the finished hand wheels. Each wheel took a little under 2 hours to complete, not fast but the finish turned out nice. I used brazed carbide bits for roughing and boring, and HSS for finish facing/turning. One comment/tip that I've heard about and used here was to keep a set of diamond files handly for touching up the brazed carbide tools. I touched those up after finishing each wheel and it really worked to keep them cutting well. Next up I will get started making the wheel handles and shafts. I have not decided on a handle material yet, chromed steel would be ideal if I could find some pre-made ones at a good price. Delrin might be good also.

    Attached Thumbnails Attached Thumbnails (Another) LMS SX2 Mini Mill CNC Conversion-img_7417s-jpg  


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    Default Re: (Another) LMS SX2 Mini Mill CNC Conversion

    Glad to see you are back at it!. Will be following along.

    Eric



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    Default Re: (Another) LMS SX2 Mini Mill CNC Conversion

    Quote Originally Posted by Brass_Machine View Post
    Glad to see you are back at it!. Will be following along.

    Eric
    Thanks. Did you make the mods to your machine? --md



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    Default Re: (Another) LMS SX2 Mini Mill CNC Conversion

    Not yet.. Been too busy with other projects, unfortunately. I have been gathering the parts though. I plan to do something close to your build. I have an older HF mill with the tilting column, but have purchased from LMS the X2s base and solid mount column. Trying to find a machine shop that can recut the dovetails to 60* so I can use thicker brass gibs. And I have to finish modding the Lathe so I can cut my ballscrews with more precision.

    I like the idea of a stand alone control box so I can use it manually without powering up the shop PC.

    Eric



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