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  1. #1
    Join Date
    Dec 2007
    Location
    Adelaide
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    381

    Default Arboga Manual to CNC Conversion

    I've completed the first stage of my manual to CNC Arboga mill conversion, I decided to use a ball screw hung off the side, a 700N gas spring is mounted on the other side to balance/reduce the weight, IF - and that is a big if - this works OK I can lock the quill in place for CNCing and still have the use of the quill if I need to. The other option was utilise the existing rack and pinion, this would have relied somewhat on gravity to eliminate any backlash - a ballscrew seems to be a more positive system and any backlash would be from the ballscrew and nut plus any flex in mounting system/drive belt.


    I initially mounted just the gas spring on it's own and found that it more than balanced the weight and had a slight positive affect on the system - once the stepper and ballscrew (which are not light) were fitted I estimate the overall weight of the Z axis system that the stepper has to lift is around 5-10 Kg plus any friction, the gas spring unfortunately does not reduce the mass so the stepper still has to contend inertia plus the weight + friction.


    The ballscrew is 25mm x 5mm pitch the drive belt is 18mm wide 5mm pitch with a 2.5:1 ratio - the stepper is closed loop Nema34 12Nm 1.8deg per step, these are not a full closed loop system but a sort of hybrid system in that the stepper provides feedback to the stepper driver so the driver can try to regain lost steps should these occur, if the lost steps can not be made up the driver can alert/signal the motion controller - how the motion controller handles this depends on the motion control software and is a bit of an unknown for me at present. The 2.5:1 ratio multiplies the motor torque - it can easily be changed with different pulley sets and possibly removed altogether if I mount the motor directly above the ballscrew for direct drive.


    The ballscrew nut mount is a section of 70mm square tube that was left over from a long ago carport build, the ballscrew top bearing and motor mounts are made up of 100mm wide Al plate, 15mm thick for the bearing mount and 10mm thick for the rest.


    With everything bolted up tight and a DTI placed under the quill I could not detect any backlash when I rocked the drive pulley back and forth by hand, next step for me is to temporarily wire up the motion controller, bumble my way through the setup procedure and do some tests on backlash and possibly speed tests as well.




    This all new to me, while I think I'm headed in the right direction with what I'm doing, I may well not be - I did vow at one time that I would never venture into 3D printing or the CNC world - I've had my 3D printer for over a year and now this.

    20210727_135439.jpg 20210727_135553.jpg 20210727_135630.jpg 20210727_135635.jpg

  2. #2
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    55
    Posts
    1,836

    Default

    Good progress!
    I think youíve said previously but I canít recall the answer - what controller/software are you going to be using?

    Steve

  3. #3
    Join Date
    Jul 2016
    Location
    Melbourne
    Age
    33
    Posts
    1,366

    Default

    How will you deal with the column locks? I have a very similar modig drill and its not much of a mill but its a great drill.

    Sent from my SM-G973F using Tapatalk

  4. #4
    Join Date
    Dec 2007
    Location
    Adelaide
    Posts
    381

    Default

    Controller is DDCS Expert stand alone(offline) 3/4/5 axis I think it is the same as a FOINC 350 - reading posts from various forums most use the Fanuc post processor, there is an active Facebook group with what looks like a lot of users but not a lot else so if I have issues to solve I'll be pretty much on my own - I did a lot of looking around and did not really find any 'turnkey' solutions for manual to CNC conversion unless you go the route of buying a fully built and working CNC mill - my budget does not extend that far.


    The column locks - I have been using it for quite a while without locking the column, took a while to get the column gibs just right - a good cutter sharp cutter and easy does it, I have never driven the mill hard - locking the column helps if using a single point cutter like a boring head or a flycutter, I can't see myself using them in a CNC situation. As I said it is all new to me - using the column for the Z axis may turn out to be a bad idea, if so I can always do what many people have done and use the quill - a stepper on the fine downfeed, I've purchased a small stepper for the 4th axis I have planned and can always use it on the quill, another thing that I could possibly try is a solenoid on the column lock, the controller has 24 outputs for driving such things as coolant pumps, air lines etc it may be possible to operate a solenoid from one of the outputs.

    Screenshot 2021-07-27 223518.jpg Screenshot 2021-07-27 222814.jpg Screenshot 2021-07-27 222435.jpg

  5. #5
    Join Date
    Oct 2011
    Location
    Norwood-ish, Adelaide
    Age
    56
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    5,977

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    Quote Originally Posted by familyguy View Post
    ...using the column for the Z axis may turn out to be a bad idea, if so I can always do what many people have done and use the quill - a stepper on the fine downfeed...
    As a general rule, keeping the quill as short as possible while milling reduces wear and tear on the mill. Driving the table up and down will give you a more rigid set up.

    Quote Originally Posted by familyguy View Post
    The column locks - I have been using it for quite a while without locking the column, took a while to get the column gibs just right - a good cutter sharp cutter and easy does it... another thing that I could possibly try is a solenoid on the column lock, the controller has 24 outputs for driving such things as coolant pumps, air lines etc it may be possible to operate a solenoid from one of the outputs.
    That is something that is worth looking at, as once again it will increase rigidity & improve surface finish.

    Michael

  6. #6
    Join Date
    Dec 2007
    Location
    Adelaide
    Posts
    381

    Default

    I cobbled together some components and in the first instance powered up just the motion controller to set up the Z axis parameters. The large square transformer is 245v to 215v - this powers the 2 small 24Vdc power supplies - 1 for the motion controller system power and the other for the IO power that provides voltage for control signals to the stepper drivers and anything else that may be connected to either the input or output ie coolant pump relay, limit/proximity switches etc. In theory I shouldn't need this type of drop down transformer - but the 24Vdc power supplies are 220Vac input and my mains voltage hovers around 240V to 247V so rather than take chances I'll be using this transformer in the final build.


    The toroid transformer is one I had earmarked for a power amp project I intend to build in the future - it has 2x50V windings so for the test I'll be using 1 winding for 50VAC into the stepper controller - the stepper controller can take either AC up to 80V or DC up to 100V.
    After double checking connections and voltages etc I power it up and there was panic for a few seconds when the screen did not come on instantly but once the loading system message appeared I was able to start breathing again, the screen is colourful, has a lot of pages/screens of information and I can see that for some time I'll be going around in circles wondering how to get back to a particular menu or screen, I eventually found my way to the axis setup screen but didn't get very far, I found I couldn't change any parameters unless I was signed in as a supervisor - time to go back and read the user manual.

    20210728_150022.jpg 20210728_150409.jpg 20210728_150716.jpg

  7. #7
    Join Date
    Dec 2007
    Location
    Adelaide
    Posts
    381

    Default

    After sorting out the password, there are 3 levels of access (bottom level is 666666 - double devils number, is this an omen?) I still could not get any movement from the Z axis, - it dawned on me eventually that the stepper driver dip switches may not be set and sure enough they were set for maximum micro-step, with this reset for no micro-stepping I had up and down jogging. The motion controller user manual is not bad and does not read like a google translation from Chinese to English - but even so I could not find where to jog a set number of steps so I could do some preliminary checking of backlash so I turned to the MPG controller. Plugging this in gave me nothing, checking and changing some of the parameters for this device still gave nothing, not knowing if it had some sort of fault like loose wires or bad solder joints or if there were some other settings deeper in the motion controller that I hadn't found I decided to open up the MPG controller and have a look, while the build quality is ok I saw a few wires that had been extended, not great but what do you do when the wire has been cut off too short to reach the solder joint, I did find one bad joint, the wire had come away completely, after fixing this didn't change a thing, the motion controller has a screen that shows the status of all of IO ports - MPG port is one of these, I could see the rotary encoder was working but there was no other activity - something is not connecting with the IO power supply, then it hit me I could see I had not connected the 24Vdc supply at all, great work I thought. With power to the IO ports, the MPG (manual pulse generator) worked seemingly as it should, I was able to do a preliminary test for back lash - DTI under the chuck and zeroed, move Z axis up one full turn of the rotary encoder up and then back down one full turn, the DTI returned to zero, so far so good but I feel there must be more to it as far as checking for back lash, I'll need to do some more youtubing.

  8. #8
    Join Date
    Dec 2007
    Location
    Adelaide
    Posts
    381

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    I've been making slow progress with my CNC conversion - even though I vowed to do no more electronics repairs, I guess I'm just too soft and found my self with an amp, 3 speakers and 4 output transformers to wind, I did though manage to farm out the table and get it machined to allow clearance for the X axis ballscrew nut - the Z motor mounts were done and tested a while back - the X and Y motor mounts are finished and I am at the stage where I could reassemble everything and only have the electronics in the control cabinet to mount and wire up. But with the XY table on the bench now would be the time to add some lubrication grooves and external oil points to the dovetails and also the ballscrews, the mill had no lubrication grooves at all. I did a trial assembly of the Y axis and connected it up to my jury rigged controller setup, not surprisingly there is no backlash I uploaded 3 small videos to you tube, Z axis trial, Y axis trial and using the MPG controller to elongate a mounting hole on a Chinese XY table.


    While the XY table has been out of action I purchased one of the el cheapo Chinese XY tables from the 'bay', it can be seen in the video sitting on the floor - I mounted it on the mill base so I still had a functional mill that I could use in making the X and Y motor mounts - also my ballscrews did not come with keyway slots which I need for the 'flexible' couplings between the motor and ballscrew, while they are not really flexible they do tolerate a small misalignment that might creep in.


    The Chinese XY table is not great but adequate for what was asked of it, I found I had to adjust the gibs constantly for the first few hours of use and it seemed to get better the more I used it. It is obviously made as quickly and cheaply as possible and from viewing youtube videos the build quality of them is very variable, mine does not seem too bad - I did notice that not one edge had been broken so I ran over every corner with a file before the inevitable happened. If the MPG controller turns out to be PIA for manual milling then I may use the Chinese XY table bolted to the main mill table for used as a manual mill for quick jobs like cleaning up a saw cut.


    The aviation style connectors I ordered finally arrived and I realised that I did not take a great deal of notice of the size, the 6 pin connectors are ok for the stepper feedback cables but not for the main wiring that powers the motors, pins are small and I was not keen to have 6-8 amps going through them - I located some ex military connectors in Lithuania, seller was very helpful, they arrived quickly and look to be up to the task.

    20211101_211227.jpg s-l1600.jpg s-l1600 (1).jpg


    https://www.youtube.com/watch?v=QpD7WQyAAQs
    https://www.youtube.com/watch?v=p1nUxvbOujo
    https://www.youtube.com/watch?v=bDaxn1OnPUQ

  9. #9
    Join Date
    Dec 2007
    Location
    Adelaide
    Posts
    381

    Default

    I'm getting closer to finishing the XY ballscrew and stepper mounts, I decided to go with a simple gravity feed oil system for the slides and ballscrew - the slides and ball screws are fed via a small bore (4mm OD) copper pipe which leads back to an oil cup mounted on the rear ballscrew cover - one for each axis. I tested this with the XY table assembled on the workbench using ordinary 30/40 motor oil from my workshop oil can, takes about 3-4 hours for the oil cup (5ml when full) to empty, I notice that the motor oil does create some drag so when it is finally finished I'll investigate the use of something less viscous. I know it is not ideal to have the ball screw on the same feed as the slides but looking at other diy conversions on youtube I see many don't bother with oil feed to the ball screws and I figure that any lubrication is better then none, being for hobby use I can't see the ballscrews wearing out in a hurry, in addition if they wear out they are readily available - not like the original lead screws - acme thread, 0.2inch pitch, 0.875 inch diam, I'm expecting to add 2-3ml oil every few months.


    The X axis ball screw is covered by the table but the Y axis ball screw is partially exposed so I made front and rear covers/shields for it, the covers are wide and deep enough to cover the sides as well, these were made from 2mm thick steel plate, my folder had no hope of bending 2mm steel plate so I cut out the individual bits and tried stick welding, the first cover warped badly and while I was able get it sort of straight it looked crap so had to be thrown out, for the next try I used the oxy and fusion welded it together - by the time I was nearing the end of the 2nd cover I was getting pretty good to the point where I didn't need to file/cleanup the welding and the best part is not even a hint of warp. The motor mounts are fabricated from heavy angle iron and 6mm plate, every thing slid together nicely with almost no issues, but - the X axis had a bad shudder in one direction only when the ballscrew was turned by hand, I eventually traced this down to the ball screw being a fraction too long and rubbing on the underside rear of the table, just touching it, I'll cut a few mm off the end.


    The clearance machined for the Xaxis ballscrew mount broke through to the top of the table so I had to make up an cover, held in place with 4x3mm screws, once it is up and running I'll seal this with a bit of silicon - just in case I use flood coolant at any stage.


    I still have a way to go - I've wound 2 transformers so I can use linear power supplies, a single transformer for the Z axis and a larger toroid with 2 secondary windings for X and Y axis, I was going to run straight AC to the stepper drivers but am now leaning towards a bridge rectifier and reservoir capacitors.
    20211117_112949.jpg 20211117_115543.jpg 20211117_194828.jpg

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