EG/Steel lathe/mill/grinder - basic design proposal


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Thread: EG/Steel lathe/mill/grinder - basic design proposal

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    Default EG/Steel lathe/mill/grinder - basic design proposal

    Hi all

    Lurker for some time but my first post here. I have designed many CNC machines in SolidWorks, but only ever built a 3D printer (yes I am one of THOSE people but ya gotta start somewhere). I have hit upon what I think is a good design for me, therefore posting here to get your thoughts. The design is not complete but as I have little experience actually building a CNC machine I though it worth sharing.

    This will be a hobby machine, benchtop size, with a modest work envelope of roughly 150mm cubed. I will use it to make parts for rockets (e.g. de laval nozzles), IC engines, PCB milling and other projectlets. I will be machining mostly ally, and turning some free cutting steel (for the rocket nozzles).

    Posting in EG because I think my questions below are related to the EG design - happy to post somewhere else.

    I have a gas MIG welder, a Boxford/SouthBend 5" lathe, and a small Hobbymat/Prazimat benchtop mill (BFE65). I need it to be less than 80kg, so that two people can move it comfortably.

    I plan to weld the frame using stress reduction strategies during welding (for the steel, not for me). And then... stick it in Mrs Me's ceramic kiln to get it up to 680C to properly stress relieve it. After that, MUCH cleaning of carbscale and then milling of the rail mounts, and filling with EG. I know there other threads active on the "EG in steel" design, not looking to hijack that thread but that is the approach I am proposing here. Where tubes are enclosed, I will bore 30mm ports for the EG.

    Because of the size of the kiln, the welded frame is strictly limited to 615mm long, and 350mm high & wide. I can (and plan to) bolt stuff on above these limits. The steel tube is 50x50x5mm, the end plates are 1/4 inch. Although I have not yet put top & side plates in yet, the spaces between the vertical plates will be filled with EG, with the exception of the large hole at the tailstock end which will have a tube welded into it - I have included this feature for weight reduction and future upgrades. 0.02mm accuracy over the 150mm work envelope would be awesome.

    There will be a milling table bolted to the steel tubes at the bottom of the frame.

    Motion control hardware: HG15 rail, 12mm ballscrews, NEMA23 steppers, stepper or servo for the 4th axis (a seperate motor to the spindle motor itself).

    Although I may be dreaming as there are some obstacles to overcome (more on that later), this design will give me a small mill, grinder and lathe in one. I like this design because after so many years procrastinating over whether I need a lathe more than a mill, this design appears to give me both. Bonus feature: 4th axis is built in.

    Problems & questions:

    1/ how the heck does one keep the lathe spindle aligned to the rail axis?
    I am very nervous about spending so much time and effort on something that will not be adjustable after initial alignment. I really don't want to cast in the lathe spindle in EG. Therefore I have designed an overly complicated adjustable spindle, that pivots around the centre of the spindle housing (you can see the matching external radius in the pic below). While its great fun designing such things, I can't help thinking that there must be a better way - is there another way around this problem? Adjustable rail mounts? (I think I understand how to get it aligned initially, it's adjustment that concerns me)

    2/ lathe "Y-axis" - an axis too far for a hobby machine?
    In the pic below there is a dummy lathe autotool changer on the tool platform (a later project for sure!). I plan to put a milling spindle there. To make this device a 3-axis mill, I need to add another axis - that moves perpendicular to the ways that are attached to the frame. That's three axis stacked together. I have ideas for how this might work, but I know that this is akin to a lathe "Y-axis" which is only available on VERY expensive kit. Is this achievable for me, with my hobby-level aspirations for work envelope and accuracy?

    The other option is to just mount the milling table on sliding ways, but then I will lose my "4th axis milling" badge. I would consider upgrading the X-axis (that bolts to the frame) to HG20 or even 25 if it helps.

    EG/Steel lathe/mill/grinder - basic design proposal-screen-shot-06-25-18-06-48-a

    Similar Threads:
    Last edited by bazmonaut; 06-25-2018 at 04:26 PM.


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EG/Steel lathe/mill/grinder - basic design proposal

EG/Steel lathe/mill/grinder - basic design proposal