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  1. #1
    Join Date
    Dec 2008
    Location
    Melbourne
    Posts
    269

    Default Homann Designs TM20LV CNC conversion

    This is the start of a journey. I've had a Taig CNC mill for over 10 years now and it is a fabulous machine. I was after a larger machine and the Grizzley G0704, BF20 or Sieg X3 seemed popular choices.

    If all turns out well I'll should be able to provide a nice controller kit for this type and size machine.

    The G0704 is not available in Australia. The X3, is as are a number of BF20 style machines. In the end, I chose a TM20VL from Titan Machinery. It looks similar to the G0704 and the BF20L but does have some differences. I could have got a BF20L for less, but I was not sure of the quality. Also I wanted an R8 spindle so I could use TTS tooling.

    I'm planning to do the conversion following the CNC Conversion DVD by Hoss. Obviously it depends on how close the machine is to the G0704.


    The TM20VL has the following Specifications:

    • Spindle taper R8
    • Spindle travel 50mm
    • Quill diameter 60mm
    • Table size 700mm x 180mm
    • Table travel (longitudinal) 550mm
    • Table travel (cross) 180mm
    • Max. dist. spindle to table 360mm
    • Max. dist. spindle to column 185mm
    • Machine depth 580mm (to front handle)
    • Machine height 930mm(head fully extended)
    • Machine height incl stand 1730mm
    • Head tilt 90º both ways
    • T-slots 3 slots, 10mm studs
    • Range of speeds 0-2500 RPM
    • Motor 800W BRUSHLESS DC, single- 240v single -phase

    Cheers,


    Peter.

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  3. #2
    Join Date
    Dec 2008
    Location
    Melbourne
    Posts
    269

    Default

    I picked up the machine from the shipping depot. I ended up using a scissor jack trolley to get it off the trailer. I raised the trolley to the height of trailer and shoved, pulled etc.

    A few pics below.

    Cheers,

    Peter

  4. #3
    Join Date
    Dec 2008
    Location
    Melbourne
    Posts
    269

    Default

    It looks like a new top plate with the bearing mount for a ballscrew will need to be made.

    I took a few photos of the X/Y ballscrews. They are 25mm diameter. The X screw nut mounts differently to the G0704 ones. You can see that in the photo. Hopefully there will be enough room

    I also took of the left endplate from the X-axis. There is no bearing race, just a hole as a bush. A bit disappointing.

    I'll make new endplates and I think I'll use this style of ballscrew supports.
    1 set Fixed Side FK12 and Floated Side FF12 Ballscrew end supports CNC DIY | eBay

    Comments always welcome

    Cheers,


    Peter.

  5. #4
    Join Date
    Dec 2008
    Location
    Melbourne
    Posts
    269

    Default

    Ok, I removed the table to see what is underneath. Below is what I've found.

    The X Nut is quite interesting. It is low profile which is not good. The screw is 25mm diameter so there is only about 35mm clearance.

    The nut has backlash adjustment. There is a 3mm ball bearing sitting in the nut. As the backlash adjustment screw is tightened the ball is forced against the screw.

    Cheers,

    Peter
    Attached Images Attached Images

  6. #5
    Join Date
    Dec 2008
    Location
    Melbourne
    Posts
    269

    Default

    Removing the saddle to look at the Y nut was next.

    You can see the nut mounted to the back edge of the saddle. You can also see the bolt that holds the nut to the saddle.

    With the saddle removed, you can see the gap through the base. Lots of room for the Y-Axis.

    The Y-nut is interesting and has the same ball bearing backlash adjuster. The hole for the screw seems off centre but preliminary measurements indicate that it is on the centreline of the mounting boss.

    Cheers,

    Peter


  7. #6
    Join Date
    Dec 2008
    Location
    Melbourne
    Posts
    269

    Default Need help on mounting the X-axis ballnut.

    So, now I need some help on how to do the X-axis ball nut.

    I plan to make new end plates for the table which will hold the ball-screw end mounts. At this stage I'm planning to use 1605 ballscrews and use the FK12 and FF12 style ball screw supports.
    FK12 16mm BALLSCREW END SUPPORT BEARING BALL SCREW CNC | eBay

    I also plan to use a FK12 on the Y-axis as well.

    The ball nut mount is more problematic. The ball nut mounts are 25mm apart so I could use them . The centreline of the lead-screw is 15 mm above the base and this is where the problem is going to be I fear.

    I have a Taig CNC mill, and the TM20VL saddle will fit if machining is necessary.

    The dimension of the Ballnut from CNCShop is attached.

    The diameter of the ballnut is 28mm excluding the mounting flange. This gives me a 1mm clearance to the 15mm centreline. I could mill a clearance slot in the saddle for the flange. I would then have to mill the top of the flange so that it does not interfere with the bottom of the table.

    I could also remove the top and bottom of the flange which is my preferred plan at this moment. The Taig mill won't be able to do this though.

    Any ideas welcome.

    Cheers,

    Peter.

  8. #7
    Join Date
    Dec 2008
    Location
    Melbourne
    Posts
    269

    Default

    When I order the screws from linearmotion2008 I'll see if they will remove the flanges as they have done these type of mods for others doing the G0704 CNC conversion.

    Cheers,

    Peter

  9. #8
    Join Date
    Dec 2008
    Location
    Melbourne
    Posts
    269

    Default

    The mill has an R8 taper and I plan to use TTS tooling.

    The drawbar for the collet is too long. What is that all about, how can the drawbar be too long.

    With it threaded all the way into an R8 collet or tooholder it is 1/2 too long. It has a 7/16-20 UNC thread so I could thread it further and shorten the bar.

    I might turn up a spacer for the top, that way it may still be usable when I use some bevel washers later for a power drawbar.

    Does anyone know where to get bevel washers locally?

    Cheers,

    Peter.

  10. #9
    Join Date
    Feb 2008
    Location
    Australia
    Posts
    988

    Default

    Quote Originally Posted by phomann View Post
    The mill has an R8 taper and I plan to use TTS tooling.

    The drawbar for the collet is too long. What is that all about, how can the drawbar be too long.

    With it threaded all the way into an R8 collet or tooholder it is 1/2 too long. It has a 7/16-20 UNC thread so I could thread it further and shorten the bar.

    I might turn up a spacer for the top, that way it may still be usable when I use some bevel washers later for a power drawbar.

    Does anyone know where to get bevel washers locally?

    Cheers,

    Peter.

    My DM45 (Titan) had the same issue with an R8 Face Mill I purchased from H&F, I just turned up a spacer, but I've lost it now so I just use a large nut as a spacer.

  11. #10
    Join Date
    Dec 2008
    Location
    Melbourne
    Posts
    269

    Default

    Hi Chris,

    Thanks for that. I wonder why they make them too long? Other than it is easier to shorten them, a bit harder to lengthen them.

    Cheers,

    Peter.

  12. #11
    Join Date
    May 2005
    Location
    Cockatoo Vic
    Posts
    996

    Default

    Quote Originally Posted by phomann View Post
    Does anyone know where to get bevel washers locally?

    They are called "Belleville Washers"

    Here is one place,

    ASI Springs - Products

    Google comes up with a few options.

    Greg

  13. #12
    Join Date
    Dec 2008
    Location
    Melbourne
    Posts
    269

    Default

    Hi Greg,

    Thanks for that.

    Cheers,

    Peter.

  14. #13
    Join Date
    Mar 2007
    Location
    Melbourne - Mexico
    Posts
    655

    Default

    Awesome news Peter, glad to hear the machine arrived and your straight into it.

    I think it may be difficult to knock the flange down on the nut (hardened), but having said that an angle grinder could get through the outer coating allowing it to be machined further. You can make the nut connector block sit at the back of the nut, but this would reduce precious travel. I dont see how it could fit over the nut as it would pose the clearance problem your trying to get around.

    I would probably venture down the path of removing some of the webbing as you have suggested. However i would try to make a shallow square pocket (clearance) for the nut to sit in, thus reducing the amount of casting you have to machine and thus retaining as much rigidity as possible. A simple bracket arrangement could then be used to attach it to the table bottom. I assume your referring to photo 1-5 in post #4.

    Is there any option to move the drive screw to another position on the machine, either behind or underneath and connect to it with some bracket. I was thinking could a slot be machined down the guts of the casting and have the table connect to the screw through the slot to a screw located below. Maybe some pedestals could provide the clearance required to run the nut.

  15. #14
    Join Date
    Dec 2008
    Location
    Melbourne
    Posts
    269

    Default

    Hi Mike,

    My first option is to see if linearmotion2008 will grind the nuts down as they have done it for others. If they do that then I can use the existing mounting holes,etc.

    Initially I plan to make the end plates and nut holders out of corian to check the fit. It will be quicker and allow me to fine tune everything before cutting it out of aluminium.

    Cheers,

    Peter

  16. #15
    Join Date
    May 2003
    Location
    Perth WA
    Posts
    3,784

    Default

    Hi Peter,
    It is a common problem trying to fit ballnuts in a compound table. Attached photo shows a conversion I did in 2007 using nook ballscrews and double nuts. Note the ballnuts do not have a flange and method of fixing is via a threaded portion of the nut. Also note in the photo the Y axis has an off centre mounting so that it can be adjusted for allignment. A mill has no give in it so allignment is very important and worth considering at design stage.
    If you are following Hoss then you will be on the right track.
    Cheers,
    Rod

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