Page 1 of 2 1 2 LastLast
Results 1 to 10 of 12

Thread: basics of converting manual tools to CNC

  1. #1
    Gunco Veteran panaceabeachbum's Avatar
    Join Date
    Dec 2005
    Posts
    1,071
    Feedback Score
    7 (100%)

    Default basics of converting manual tools to CNC

    Here is the message I put on the other thread, thought i would post as a seperate thread in case others had an intrest. Richard

    It looks pretty confusing when you look at the g-codes but the software I use actualy does all the hard stuff.

    I start by making a 2d drawing in either autocad or maodelcad, just a basic line drawing thats in scale. I then take the dxf drawing into the software from www.deskcnc.com and chose the items I want to machine and thru the conversational dialoug boxes I choose the cutting tool, depth of cut per pass, total depth and finish pass that suits the material I am working with and the software generates the g-code(x-y-z cordinates) to controll the milling machine. The software is free to download if you want to give it a try, it will also generate 3d gcode files from a number of diff drawing file formats like stl, point cloud, IGS. Another good software package that will generate gcodes and also control a cnc machine (and its free) is kcam from www.kellyware.com

    As far as the machine its fairly simple to attach some servo or stepper motors to the lead screws of your milling machine. Ususaly some sort of gear or belt reduction is needed, I like the gates xl timing belts from www.mcmaster.com, they also have the cogs, ballscrews and nuts as well as about anything else you can think of. Once youre motors are mounted and attached to the lead screws with a solid system like the timing belts you will need an amplifier/drive for each of the axis you plan to drive. The amplifier just takes the low voltage step and direction output from your computer , along with the output side of a dc power supply suitable for driving your motors and sends the appropriate signal to the motors to move the exact amount the software specifies. I like the amplifiers from http://www.geckodrive.com/ , there rated up to 20 amps and 80 volts. Most of the stuff in my shop uses 24v 10 amp power supplies built with a transforrmer, capacitor and rectifier. Nothing fancy. The drives from Gecko are available for either servo or stepper motors. The gecko drives will except standard step and direction commands from any of the 2 dozen software packages out there, a bunch of which are free. I like the software and controller from deskcnc, as it does 4 axis machining, thread milling, digitizing, and has all the industry standard cycle start, repeat and pause features but if your not using it every day the software from kellyware or mach 5 is great.

    The difference in servos and steppers, stepper motors have multiple windings , each step represents some number of degrees of revolution, to move a given distance the software sends a step and direction command to the amplifier/drive and it in turn sends the proper number of high voltage/current pulses to the motor to move the specified distance. Servo motors are just big brush type DC motors but have encoders on one end of the main shaft, the encoders are usualy a plastic disk with hundreds-thousands of small lines and an optical arangement that can count the lines as they pass. The computer sends the same step and direction command to the drive, but in this case the drive applies current to the windings until the proper number of lines on the disk have passed the optical reader in the encoder. The advantage of servo motors is the motor cant skip any steps, the drive keeps applying current until the proper count is reached, the stepper drives simply send the specified number of pulses to the motor and dont have any method of ensuring the motor has moved the specified distance. This is why I prefer servo motors, steppers are usualy cheaper but not when you get into the large ones needed for full size machine tools. Alot of times good deals on servo motrs can be had on ebay, just make sure you get single phase , dc ,brush type. The 3 phase ac brushless motors can be very cheap but the drives are not so I would avoid those.

    Every thing you need to get started is fairly cheap, the belt reduction system and mounts for your machine are hard to price without knowing model. Servo motors for a machine the size of the x3 sieg can be had around $100 each, the drives are about $115 each. For a bridgeport size machine motors can be had as little as $200 each, same drives as above. A simple dc power supply can usualy be put together for $75 or so.

    Hope some of this rambling helps.

  2. #2
    Everyone NEEDS a Glock! glock's Avatar
    Join Date
    Feb 2006
    Posts
    983
    Feedback Score
    1 (100%)

    Default

    ok question... what makes the one you sell so expensive? Is it the fact you have to buy them then do the work? ps thx
    Last edited by glock; 03-28-2006 at 03:35 PM.

  3. #3
    Indian Admin Winn R's Avatar
    Join Date
    Feb 2004
    Location
    About 40 mi. north of Atlanta.
    Posts
    5,946
    Feedback Score
    18 (100%)

    Default

    Richard -- Thank you.

    Quote Originally Posted by glock
    ok question... what makes the one you sell so expensive? Is it the fact you have to buy them then do the work?
    I had to go and look. That's the cheapest cnc mill I've ever seen!!
    There is no nonsense so errant that it cannot be made the creed of the vast majority by adequate governmental action. -- Bertrand Russell


    "Never attribute to malice that which can be adequately explained by stupidity." Robert J. Hanlon

  4. #4
    Gunco Regular grasshopper's Avatar
    Join Date
    May 2005
    Posts
    433
    Feedback Score
    43 (100%)

    Default

    Hi Richard, Thanks for the Info. I have been reseaching the CNC conversion for sometime now. I am glad to know someone here is in the business. I have a HF Mini Mill and 3 clifton servo motor with encoder. But I need other parts like the driver and mounts. Do you sell them? Any help will be appricated. Thanks

  5. #5
    Master Endmill Breaker Rhino_66's Avatar
    Join Date
    Feb 2004
    Posts
    1,367
    Feedback Score
    8 (100%)

    Default

    After finding out how easy a DIY DRO kit was to assemble for the mill, I have been thinking about getting one for the lathe too. The thought of CNC conversion is really appealing. It would be nice to be able to run several identical parts, or be able to walk away from a large complex part while the machine is running (at least between tool changes).

    AK barrel profiles would be a good one for a standard pattern to keep handy on the database.


    .
    The most damning evidence is the truth.

    That which does not kill you, really really really hurts...



    Gunco Member #21

  6. #6
    Unclear Engineer ozzy the nuke's Avatar
    Join Date
    Apr 2005
    Location
    Home on the range
    Posts
    1,013
    Feedback Score
    2 (100%)

    Default

    Great idea on the separate thread. This looks like a hot topic.

    Basic question: How do you deal with backlash? TIA
    No matter what happens, somebody will find a way to take it too seriously. ~Dave Barry, Dave Barry Turns 50

  7. #7
    Gunco Veteran panaceabeachbum's Avatar
    Join Date
    Dec 2005
    Posts
    1,071
    Feedback Score
    7 (100%)

    Smile

    Quote Originally Posted by glock
    ok question... what makes the one you sell so expensive? Is it the fact you have to buy them then do the work? ps thx
    I didnt think it would take long for somebody to ask so here is a break down to put it in perspective.

    The base machine is $500, yes its $400 in the store but you have tax and the nearest HF is a 7 hour round trip so unless I am buying 5 or more its not worth picking up

    Mini mill sieg x2 $500
    desck cnc software and controller/cpu $365
    3 qty servo motors x $165 $495 These have to be new to offer warranty
    power supply $ 65
    case $ 32
    1 Geck drive for z axis $117
    3 qty sv500 drives x$65 $195
    ballscrew and nut for z axis $63
    timing belts, cogs, bearings $110
    Raw aluminum for mounts $68
    fastners $14
    wire and connectors $59
    So far we are at $2083 for just the raw materials sitting on the work bench, subtracted from my $2757 price this leaves $674 for labor which we will eat up below long before we get to any actual profit

    add to this aprox 20 hours machine time to make all the mounts, tap holes , and machine the original castings for the z axis ball screw, and an additional 10 hours to fit and adjust everything and build and wire the controller cabinet as well as wire the motors and were at 30 hours laber per machine total. I charge $45 per hour for walk in work and can stay busy at that rate for years to come, 2/3 of the industry standard $65 per hour for machine time
    30 hours divided into the remaining $674 that I charge over the actual cost of the materials used eqauls $22.47 per hour I invest in the project.We then have to subtract the $11 per hour that I spend in power, tooling , rent on the building and everything else and I am working 30 hours for $11.47 per hour which eqautes to a me selling the machines for a grand total of $344.10 above the actual set in stone, money paid out cost that it cost me to produce them.

    I only have 2 more machines that will be sold at this cost as I can stay busy on alot of other stuff at $45 per hour spindle time, which will yeild over $30 hour net. My future plans are to sell the retrofit kit and let the end user go thru all the joy of hand fitting and wiring etc.

    If you look at the machines I sell you will notice all my brackets and gaurds are machined from aluminum, fully enclosed , dual thrust and ball bearings on every axis, not just flat plates and a stack of washers like most.

    Hope this puts my pricing in perspective, it sure tells me I need to move on to something with more $ per hour invested

  8. #8
    Gunco Veteran panaceabeachbum's Avatar
    Join Date
    Dec 2005
    Posts
    1,071
    Feedback Score
    7 (100%)

    Default

    Quote Originally Posted by ozzy the nuke
    Great idea on the separate thread. This looks like a hot topic.

    Basic question: How do you deal with backlash? TIA
    On all the machines I use in my shop , including the lathes, I have fitted ball screws and ballnuts. I also use needle thrust bearings on all the screw supports so there is no(well very little) backlash at that point. Mcmaster.com has decent prices on ball screws .

    The machines I sell with acme screws do have some backlash but the software is capable of compensating by rotating the screw in the opposite direction some pre determined amount at each direction change

  9. #9
    Unclear Engineer ozzy the nuke's Avatar
    Join Date
    Apr 2005
    Location
    Home on the range
    Posts
    1,013
    Feedback Score
    2 (100%)

    Default

    I am thinking that a lot of my chatter may be coming from backlash. Do you find that you can use more length of the end mill after you install the ball screw/nut and thrust bearings? I was surprised to see how much of the end mill you were using in the photos of making a gas port. If I tried to use that much of the end mill, my table would vibrate too much.
    No matter what happens, somebody will find a way to take it too seriously. ~Dave Barry, Dave Barry Turns 50

  10. #10
    Indian Admin Winn R's Avatar
    Join Date
    Feb 2004
    Location
    About 40 mi. north of Atlanta.
    Posts
    5,946
    Feedback Score
    18 (100%)

    Default

    Okay -- now I'm really confused.

    I'm thinking in terms of replacing the lead screws for the x and y axis; but that wouldn't have anything to do with how much end mill was showing???

    McMaster has alot of listings under ball screws. I'm an idiot, what would a 55 year old Bridgeport mill use to cut back 45 thousands of backlash?
    There is no nonsense so errant that it cannot be made the creed of the vast majority by adequate governmental action. -- Bertrand Russell


    "Never attribute to malice that which can be adequately explained by stupidity." Robert J. Hanlon

Page 1 of 2 1 2 LastLast

Search tags for this page

There are currently no search engine referrals.
Click on a term to search our site for related topics.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •