Emco F3 mill conversion


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Thread: Emco F3 mill conversion

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    Default Emco F3 mill conversion

    I have an Emco F3 mill which I am planning to convert to CNS.

    Does anybody have any links or experience in how hard this will be to do. I am a CNC newbie, although learning fast, and have OK hobbiest machining skills.

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    Default Re: Emco F3 mill conversion

    I've just seen another thread, which looks like a similar project.

    My first job is to replace the Y axis leadscrew with a ballscrew and stepper, and control this via a jogger switch and driver.

    To progress this, I've removed all the bolted on panels etc on the gearbox, and removed the quill assembly and motor.

    My next job will be to remove the gearbox from the machine to access the Y axis handwheel assembly so I can remove the Y axis leadscrew/handwheel pinion.

    To attach the ballscrew to the chassis I will need to fabricate a bracket that attaches the thrust end of the ballscrew to where the current leadscrew/pinion is located, and then drive the ballscrew from the other end. So, I can't disassemble too much at this stage as I need the mill working to fabricate these brackets



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    Default Re: Emco F3 mill conversion

    I've been out to the workshop again and measured the offsets between the existing leadscrew centre, and the 4 bolt holes in the gearhead assembly. This is where the leadscrew nut attached and gives the layout for the new ballnut bracket that will need to be fabricated.

    The existing acme leadscrew, which is 20mm diam, rotates and is located with a thrust bearing set into the mill chassis. This is retained with a threaded collar with 4 small holes - I unthreaded this with a punch (although a pin spanner would be more appropriate). The bearing is 42mm diam x 26mm deep. Internal diam matches the shaft of the leadscrew.

    Attached Thumbnails Attached Thumbnails Emco F3 mill conversion-imag1730-2-jpg  
    Last edited by fastbike; 08-24-2018 at 11:12 PM. Reason: Figured out how to remove the existing leadscrew.


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    Default Re: Emco F3 mill conversion

    A bit more progress today. I can source a 20mm x 4mm ground ballscrew from ebay. I have found an really useful spreadsheet to help on motor sizing so that is the next task: figure out motor, belt drive and stepper driver.

    Then I can fabricate brackets to mount all of this. I have two mounting plans I working around with:
    - the first uses the existing bearing housing in the chassis to mount the fixed end of the ballscrew, with the ball nut attached to the gearhead assembly. The disadvantage is that the ballscrew will need to be driven from the other (supported) end which is outboard of the chassis so a substantial bracket will be required to support the motor / resists torque etc
    - the second idea is to mount the ball nut to the chassis and the screw fixed end support to the gearhead. This will require a bit of rework on the chassis although provides easier / closer mounting of the motor.
    Time for some sketches / pictures tomorrow.



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    Default Re: Emco F3 mill conversion

    Progress. I've figured out the performance and loads the motor will see and have ordered 4.5NM Nema34 closed loop stepper motor and driver today from StepperOnline.

    I'm still investigating the various ways of mounting. I've come up with a third method which is to use the existing machined bearing housing in the chassis to mount the fixed end of the ballscrew, the other end being unsupported.. The ballnut will be attached to the sliding gearhead with an alloy bracket. I will need to fabricate and attach an extension shaft to the fixed end of the ballscrew and drive the ballscrew via the extension.



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    Default Re: Emco F3 mill conversion

    Quote Originally Posted by fastbike View Post
    Progress. I've figured out the performance and loads the motor will see and have ordered 4.5NM Nema34 closed loop stepper motor and driver today from StepperOnline.

    I'm still investigating the various ways of mounting. I've come up with a third method which is to use the existing machined bearing housing in the chassis to mount the fixed end of the ballscrew, the other end being unsupported.. The ballnut will be attached to the sliding gearhead with an alloy bracket. I will need to fabricate and attach an extension shaft to the fixed end of the ballscrew and drive the ballscrew via the extension.
    Unfortunately this method is not available as there is insufficient clearance for the shaft pulley inside the chassis.

    An alternative would be to use a mitre gear on the end of the ballscrew shaft. This would need to be sized and positioned to engage with the mitre gear on the existing hand-wheel axle. Obviously the hand-wheel will be removed
    So more investigation is required - in particular finding the correct size of the mitre gear and ensuring any backlash is acceptable. (NB mitre gear is a specialised form of as bevel gear with a 1:1 ratio)

    Last edited by fastbike; 09-04-2018 at 08:55 PM. Reason: Clarified gear type as mitre gear


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    Default Re: Emco F3 mill conversion

    I've pulled the existing handwheel / leadscrew combination apart. It uses two helical/screw gears crossing at 90 degrees to transmit the handwheel rotation to the leadscrew.
    The gears are metric, mod 3 with 11 teeth, giving a pitch diameter of 33mm. The teeth are 16mm long. The leadscrew gear is keyed to the shaft and secured with a washer/lock nut. The handwheel gear is pinned through a hub to its shaft.



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    Default Re: Emco F3 mill conversion

    Quote Originally Posted by fastbike View Post
    I've pulled the existing handwheel / leadscrew combination apart. It uses two helical/screw gears crossing at 90 degrees to transmit the handwheel rotation to the leadscrew.
    The gears are metric, mod 3 with 11 teeth, giving a pitch diameter of 33mm. The teeth are 16mm long. The leadscrew gear is keyed to the shaft and secured with a washer/lock nut. The handwheel gear is pinned through a hub to its shaft.
    There won't be very many that have converted your machine F3 Mill, getting the machine parts done will be the hardest part, the electronics should be quite straight forward

    Any type of gears will have backlash, if you can change them for PowerGrip GT2 or PowerGrip GT3 Pulleys 5mm pitch you would be a lot better off

    Mactec54


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    Default Re: Emco F3 mill conversion

    Quote Originally Posted by mactec54 View Post
    There won't be very many that have converted your machine F3 Mill, getting the machine parts done will be the hardest part, the electronics should be quite straight forward

    Any type of gears will have backlash, if you can change them for PowerGrip GT2 or PowerGrip GT3 Pulleys 5mm pitch you would be a lot better off
    Thanks for the help. I was coming to that conclusion when researching more info on gears and how to remove the backlash - not an easy task or one that I think I could achieve.

    So back to an earlier plan to mount the fixed end in a pair of back to back bearings in the existing housing in the mill chassis, and drive the screw from the supported end via a belt/pulley arrangement.



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    Default Re: Emco F3 mill conversion

    I got to spend a few hours over the weekend and turned down the supported end of the ballscrew (THK BIF 2004 ground ballscrew travel 257mm) as it was 30mm too long. I first attached the ballnut with tape to ensure it would not move and no chips/dust could get in, and then used the bench grinder to remove the hardened layer so I could turn it with a carbide insert. Luckily the screw had originally been turned between centres so it was an easy job to get it centred in the lathe and relatively straight forward to turn a 15mm diameter for mounting the ball bearing.

    Last edited by fastbike; 09-10-2018 at 08:06 PM. Reason: typo


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    Default Re: Emco F3 mill conversion

    So there are a few mechanical parts to make to connect the ballscrew to the sliding head, and to support the far end of the ballscrew/motor.

    The connection between the nut and the sliding head, looks like this in CAD
    Emco F3 mill conversion-screenshot-2018-09-11-07-18-34-a

    and after a bit of work at the mill like this (cut out of 12mm CRS,faced with a fly cutter on the side that contacts the ballnut flange an
    Emco F3 mill conversion-imag1758-jpg

    Last edited by fastbike; 09-10-2018 at 03:38 PM. Reason: Added materials


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    Default Re: Emco F3 mill conversion

    So a little bit of downtime as I have other commitments that need to be fulfilled. In the interim I am starting prelim work on the power supply design. The machine is powered by a 3 phase 400V AC supply. I need something in the range of 60-70V DC for the motors and a lower voltage supply for the electronics.
    I'm currently investigating a design using a 3 phase step down transformer along with a 3 phase bridge rectifier to supply the required power rails.



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    Default Re: Emco F3 mill conversion

    Quote Originally Posted by fastbike View Post
    So a little bit of downtime as I have other commitments that need to be fulfilled. In the interim I am starting prelim work on the power supply design. The machine is powered by a 3 phase 400V AC supply. I need something in the range of 60-70V DC for the motors and a lower voltage supply for the electronics.
    I'm currently investigating a design using a 3 phase step down transformer along with a 3 phase bridge rectifier to supply the required power rails.
    You could take ( 1 ) leg and neutral and Ground and use a single phase Transformer to get your 70V DC a much easier way to do it

    Have a look at this company for a 70v DC supply you may have something similar in NZ AnTek Products Corp

    Mactec54


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    Default Re: Emco F3 mill conversion

    Quote Originally Posted by mactec54 View Post
    You could take ( 1 ) leg and neutral and Ground and use a single phase Transformer to get your 70V DC a much easier way to do it

    Have a look at this company for a 70v DC supply you may have something similar in NZ AnTek Products Corp
    Thanks for the link. I'm still just at the research stage for this part of the project.

    The 3 phase power is supplied via a 3wire plus earth cable - no neutral is available in the machine so the easy way of tapping one line and neutral is not available.

    I did find this prebuilt power supply though on the local Farnell/Element14 site. - will deliver 48V which might do in a pinch.
    https://nz.element14.com/xp-power/dn...48v/dp/1634807

    In the interim I will see if I can get a 3 phase step down transformer locally - and compare costs.



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    Default Re: Emco F3 mill conversion

    Quote Originally Posted by fastbike View Post
    Thanks for the link. I'm still just at the research stage for this part of the project.

    The 3 phase power is supplied via a 3wire plus earth cable - no neutral is available in the machine so the easy way of tapping one line and neutral is not available.

    I did find this prebuilt power supply though on the local Farnell/Element14 site. - will deliver 48V which might do in a pinch.
    https://nz.element14.com/xp-power/dn...48v/dp/1634807

    In the interim I will see if I can get a 3 phase step down transformer locally - and compare costs.
    Add a neutral wire that is the normal way to do something like this

    Mactec54


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    Default Re: Emco F3 mill conversion

    More chip making today

    I designed a backplate which will attach the ballscrew support frame to the back of the mill.

    From this on the computer
    Emco F3 mill conversion-screenshot-2018-09-15-19-20-27-a

    To this (fabricated from 12mm CRS)
    Emco F3 mill conversion-imag1767-2-jpg



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    Default Re: Emco F3 mill conversion

    I found some more time this weekend to progress with making the mechanical components required.

    First off I remade the backplate as the hole for the shaft was misaligned by 1mm and I also decreased the clearance between the sliding head and the plate, to increase the mount of material left.
    I also made a small 10mm thick spacer plate to fit between the sliding head and the ballnut bracket.

    Next job was finishing the design of the ballscrew endplate and the motor mounting plate.

    The endplate holds the support bearing for the ballscrew and looks like this in QCAD ...

    Emco F3 mill conversion-screenshot-2018-09-23-20-30-59-a

    The motor mounting plate will be mounted approx 20mm behind the end plate and the space between contains the drive pulleys and belt, and is attached to the end plate with spacers and M8 bolts. In QCAD it looks like this ...
    Emco F3 mill conversion-screenshot-2018-09-23-20-35-57-a



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    Default Re: Emco F3 mill conversion

    These two parts are made from 12mm CRS. First step is to cut to rough size on the saw and then mill to 10mm thickness, before milling the edges to the final size and then drilling / boring the required holes (Would be a bit faster on a CNC mill - oh the irony

    The end plate and motor plates now looks like this ...
    Emco F3 mill conversion-imag1776-2-jpg

    (Spot the mistake on the end plate)



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    Default Re: Emco F3 mill conversion

    At this point we are finally ready for a trial fit on the machine.
    Emco F3 mill conversion-imag1781-2-1-jpg

    Emco F3 mill conversion-imag1782-2-jpg

    This also allowed measurement, cutting and test fitting of the 40x40x3 equal angle steel that will connect the backplate and the endplate together.
    Emco F3 mill conversion-imag1779-jpg

    I've run out of time this weekend. Looking forward, my next task is to remove all the parts, grind off any scale and rust and then reassemble and clamp in place so it can be TIG tacked before removing again for welding.

    The motor pulley arrives this week, so upcoming tasks will be to mount the pulleys to the motor and ballscrew shafts, cut the frame spacers, paint the frame and then a final assemble before tackling the electronics.

    Last edited by fastbike; 09-23-2018 at 02:26 PM.


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    Default Re: Emco F3 mill conversion

    Got the frame welded, and aligned, tonight. There are no photos but the ballscrew with the sliding head attached moves freely all the way along its travel (which is now 225mm compared to 200 on the original Y axis).

    Hopefully I can get more work done at the end of the week - with the next job being to attach the pulleys to the shafts.
    The motor pulley is 25T with a 12 mm bore which will need boring out to 14mm and a keyway cut to fit the motor shaft.
    The ballscrew pulley is 50T with a 12mm bore. Either I need to turn the end of the ballscrew shaft down to fit or bore the pulley to fit the 15mm shaft. Either way I'm still figuring out whether to use the two grub screws, or whether to cut a keyway in the shaft and pulley to attach and transmit the torque.



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