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Thread: Denford Orac

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  1. #1
    Join Date
    Apr 2007
    Posts
    28

    Cool Denford Orac

    Should get my hands on an old Denford Orac CNC lathe but will need to convert from Tape Drive to PC control.

    Has anyone done this before, if so I really need help on this as I have no idea where to start.

    This post will be also on the Denford Forum soonish.
    Attached Thumbnails Attached Thumbnails Denfordorac2.jpg  

  2. #2
    Join Date
    Jul 2007
    Posts
    67
    Hi, Good easy decision. Rip the whole lot out and replace with Gecko drives and good breakout board. Also a VFD for the spindle with a Digispeed board to use with Mach3's PWM spindle control which is perfect for thread cutting.

    Keep the steppers and spindle index and get a power supply for 75V DC.

    Mine's setup this way and I'm cutting 316 stainless all day long. A good strong lathe although a little underpowered on the spindle. If I got the chance I'd try to fit a bigger motor and drive.

  3. #3
    Join Date
    Apr 2007
    Posts
    28
    Thanks, that's a start.
    Any ideas as to how much this would cost?

  4. #4
    Join Date
    Jul 2007
    Posts
    67
    Hi, Well gecko's are about £60 each, Go to CNC4PC website for breakout board. VFD'S come up on ebay for about £25. Google for Digispeed for the price. I'm guessing by the time youv'e got it all sorted around £300-400. But then you will have an accurate machine that will last a long time.

  5. #5
    Join Date
    Apr 2007
    Posts
    28
    Thanks you've been a great help, looks like I may well do that.

    Merry Christmas.

  6. #6
    Join Date
    Dec 2005
    Posts
    22

    Orac Lathe

    Hi
    I recently bought a same lathe ,as you did I was wondering how you made out. Did you had a chance to convert over and what software your using to drive it.
    regards
    Moe

  7. #7
    Join Date
    Apr 2007
    Posts
    28
    Not had a chance to convert it yet it's in the workshop with a cover over it, waiting for my bosses to release some funds to do the conversion.

  8. #8
    Join Date
    Dec 2010
    Posts
    0

    Up! Orac

    Any updates on this old project.

    I have my orac stripped to bare bone and waiting for rebuild



    Cheers!

    Julius

  9. #9
    Join Date
    Apr 2007
    Posts
    28
    Hi Moe

    Not been able to do anything to this lathe as bosses are not bothered whether it works or not.

  10. #10
    Join Date
    May 2004
    Posts
    402
    I converted one about five years ago. I kept the original steppers, stripped out the entire electronics and started afresh with Gecko 201's. There is just space to fit a Compac EN small footpring PC in the plinth. I made a new front panel with waterproof keyboard attached and had a monitor on a rear mounted arm.

    I agree with the previous comment regarding underpowered spindle. Sold it about three years ago before I moved, and now have an Eagland CNC lathe sitting waiting to be fitted with a new controller. Rather bigger being based on the Colchester Chipmaster castings
    Andrew Mawson
    East Sussex, UK

  11. #11
    Join Date
    Dec 2010
    Posts
    0

    Orac build starts

    Hi

    I got permission from the original poster to use this thread to post my Orac build.

    Here is a picture of my Orac before it was stripped



    I had the one with tool changer. If it had not had the changer I propably wouldn´t have bought it.



    Unlike Andrew I did not want to keep the original electronics box since it weighed very much. I decided to cut the upper part of the box to be used as chiptray.



    As everyone can notice, all the original electronics have been removed. If anyone needs original Orac electronics components please feel free to contact me. The Orac electronics were working perfectly. The CRT display has already found a new home.

    Painted the chiptray black with Hammerite and will keep the stickers on chipguard to remind of the origins of this lathe.



    Here are the Orac X and Z ballscrews. I have cleaned them thouroughly with lamp oil. Does anyone have recommendations about oiling of the ballscrews. Should they be oiled ? And with which kind of oil ?



    Cheers!

    Julius

  12. #12
    Join Date
    Dec 2010
    Posts
    0

    Orac carriage

    Orac assembly starts

    Before reinstalling the carriage it is a good idea to check that lower surfaces of the bed are smooth. Usually the carriage moves in limited area near chuck and that area gets polished and other areas may accumulate dirt. I polished bed underside with oil and very fine steel wool.



    This is how underside of the Orac Carriage looks like. It has been thoroughly cleaned and is ready to be installed.



    Plates which lock the carriage to the bed from underside are very accurate. No shimming plates are used, fit is very accurate. If you detach the carriage as I did please handle the carriage carefully and maintain the original position of the plates.



    At the picture below the carriage and the ballscrew.



    Orac X-ballscrew has double ballnuts and backlash is removed by rotating one of the ballnuts against spring loading washers. Metal piece between the ballnuts connects the ballscrew to the carriage. I decided to oil the ballscrews with synthetic vaseline.



    Thick mounting plate is placed between ballscrew assembly and carriage. Mounting plate adjusts the hight of the ballscrew to be correct for ballscrew end supports . Again no shimming plates, very nice build quality from Denford.





    I let the ballscrew be slightly loose becouse I will have to mount end supports first before tightening the ballscrew assembly to the carriage.



    To be continued...

    Cheers!

    Julius

  13. #13
    Join Date
    Dec 2005
    Posts
    22
    Hi Julius;
    see your going all the way out with the retrofit good idea. I see it has a turret, was wondering if I could get some measurment whenever you have a chance. I think it`s make it a complete machine with the turret
    thanks for the picture very interesting
    Maurice

  14. #14
    Join Date
    Dec 2010
    Posts
    0
    Hi!

    Maurice, just tell me which measurements you require and I will see what I can do,

    Build continues....

    Orac has nice side plates for the carriage. Side plates have cups to hold ballscrew covers.



    Ballscrew supports are machined steel pieces which hold ballscrew bearings.



    During disassembly I removed old bearings. I got new ones for rebuild, two side loading ball bearings SKF 7201 BECBP and one normal ball bearing SKF 6200-2RSH for top end of the ballscrew.



    At the picture below I test fitted the side loading bearinds to ballscrew. Notice that these bearins should be installed right way round. Outer part of the bearings will be sitting in support and any free play is removed by tightening the center parts towards each other as shown with arrows. I think that the bearings are wrong way round at the picture.



    Top end ballscrew bearing just sits in its holder. Originally this bearing was 62001RSH, but I got 2RSH, which means double protective cover on the bearing. I oiled the open bearings with syntetic vaseline.



    To ease bearing installment I put bearings in freezer and bearing holder to cooking plate. Thus expanding the holder and contracting the bearing.



    This way bearings slid very easily to holders. One should not ever hit the center of the bearing when installing it into the holder. At the picture below cylindrical part is end holder for ballscrew spiral cover.



    Left spiral cover is first slid into its place and then ballscrew support is fixed to its place. Ballscrew should slide nicely through the holder.



    Locking plate slides to ballscrew and any free play is removed with nut. End nut has to be tightened just the right amount to allow bearings to rotate effortlessy with no backlash.



    When tightness is good the nut is locked.



    Left side finished



    Right side is more simple. Only difficulty is to keep the cover from expanding. I do not know whether it is possible to get these spiral covers working again if you let them expand to their full length. I did not want to risk it and kept the spiral covers compressed all the time.



    X-ballscrew finally installed with holders and covers. Last step is to tighten the screws that connect the ballnuts to the carriage.



    Until next time...

    Cheers!

    Julius

  15. #15
    Join Date
    Dec 2004
    Posts
    1865
    Nice work so far.

    Mike
    Warning: DIY CNC may cause extreme hair loss due to you pulling your hair out.

  16. #16
    Join Date
    Dec 2005
    Posts
    22
    Hi
    I thaught since you retrofiting the lathe by taking everything apart , where thinking of doing the same with the turret , if so a few picture and center distance so it would give a few size to start from
    Thanks
    Maurice

  17. #17
    Join Date
    Dec 2010
    Posts
    0

    Disaster day

    Hi!

    Thank you for positive comments

    Maurice, I will get to the turret eventually.

    Disaster strikes today. Since my last post I got worried that I had installed the X-ballscrew bearings the wrong way round. Lathe sits in my workplace and there I could confirm that indeed I had made this mistake. Even though I thought that I knew what I was doing I got it wrong.

    So I had to detach my new shiny bearings from the holder. I could not use lethal force as with old bearings, otherwise it would mean a trip to the bearings shop. I placed bearing holder to cooking plate and heated it up while spraying one of the bearings with freeze-spray. I was then able to gently tap the bearing loose. I repeated the procedure to the other bearing. Luckily I got my new bearings detached with no damage. Detached bearings at the picture below. Bearings shown as they should be installed to the holder.



    I took a picture of the old bearings where you can see taper. I can not understand how I initially got the bearings installed wrong way round. Arrows at the picture try to demonstrate how any slop is removed by tightening the bearing centers towards each other. This is done with the ballscrew end nut as seen at my previous post. Propably this is clear for everyone - and it was clear for me but I still got it wrong. Bearings have now been reinstalled the correct way.



    On with the build. I connected motor plate at the frame and was able to tilt the lathe and have a look at the carriage underside. Tilting your lathe this way is not recommended, lathe should always sit on even surface. Even though the Orac is a small lathe it is still quite heavy to lift and care should be taken when moving the lathe this way.



    I was not very happy to see what I saw under the carriage. Ballscrew is exposed and unprotected at the carriage. Small chips and metal dust will find its way to ballscrew. My Orac had very much dirt and metal dust on its ballscrew. Part of the dirt has come through spiral covers which expand and contract constantly, and bigger particles have direct access to ballscrew at the underside of the carriage. If you have an old Denford Orac lathe it is most propable that X-ballscrew is already full of dirt.



    Closeup of the exposed ballscrew. This means more work. I will have to take everything apart and come up with some sort of protective covers.



    This day was a disaster,

    Until next time...

    Cheers!

    Julius

  18. #18
    Join Date
    Dec 2010
    Posts
    0

    Covers

    We meet again and project continues....

    This is where we left off the last time. I decided that ballscrew can not be left exposed beneath the carriage.



    I had to take everything apart. I removed ballscrew end holders, spiral covers and carriage side plates to expose the problem part.



    I figured that very precise cylindrical covers would protect the ballscrew very nicely. So I made a scetch what I would need.



    And now it was time to do some old fashioned manual lathe work. We have an old Emco Maximat V10 at work, nice little old lathe.



    I had some teflon bar lying around and decided that teflon is the perfect material for covers. It is very stiff and will not break or age. Relatively easy to tool with well sharpened cutting tools. Will flex slightly to give very tight fit when slipped over ballnuts. Firstly I cut two pieces with some extra length.



    Next I make a bore of 19mm to each piece....



    ... and widen the other end with boring bar. This end will connect to the ballnut.



    Here are the finished pieces. I made many test fittings to get them to fit perfectly. I made a small slot to each piece, those are for ball channels on the ballnuts.



    The last picture shows my protective teflon covers and carriage side plates installed. I used small amount of silicone between side plates and covers. Ballnut end of the cover is only press-fit tightly.



    It´s good advice to any CNC lathe owner/builder to use every means possible to protect the ballscrews against metal dust and chips.

    English is not my native language, please feel free to correct me if I am using wrong terminology.

    Until next time...

    Cheers!

    Julius

  19. #19
    Join Date
    Apr 2007
    Posts
    28
    Looking good there and you post has rekindled my interest in our Orac, I may try to get some cash out of the boss.

  20. #20
    Join Date
    Dec 2010
    Posts
    0

    Cash

    Hi!

    Orac conversion should be relatively simple. You don´t have to do overkill and dismantle everything like I did. Just clean the ballscrews and make sure that spindle bearings have fresh lubricant in them and you are good to go mechanically.

    For conversion it would be nice to have one complete kit. For example Marchant Dice sells starter kit for £168. It contains everything you need. Home/Light Industrial Controller Kit

    I do not know the quality of this kit. Maybe someone has tested it here?
    Documentation is slightly poor so you will need some sort of electronics skills in order to complete the conversion. If you go this way, keep the original Orac electronics to start the spindle motor.

    If you are going to use the Orac for light production then Geckos and better breakout boards..... of course this means more £££$$$

    Cheers!

    Julius

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