Thread: Tiddy CNC.

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  1. #1
    Naming the machine seems the thing to do so Iíll call this one Tiddy after my sons favourite teddy

    Iím creating the basics of my electrical control system while aspects of the mechanicals of my machine are still in the design stage. Iíve looked at several build logs and the required wiring diagrams for my components. I would really appreciate it if some folks would help me validate my assumptions and help with a couple of questions.

    The hardware I have purchased should see a machine with a 1.5M X Axis, 1.1M Y Axis and a 0.2M Z Axis. I will be using a total of 4 Stepper Motors. My basic electrical bill of materials purchased so far is:
    1 x PS806-5 PSU (3x68V-6A, 1x5V-1A).
    1 x PS408-12 PSE (3x36V-3A, 1x12V-1A)
    4x SY60STH88 Ė Nema 23 Ė Anticipating wiring in parallel (2.73V-4.2A)
    3 x AM882
    1 x PM752 (Z Axis)
    ZPA5A-INT 5 Axis breakout board.
    Plus PLCM-E3 Mach 3 Ethernet Interface

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    Component rationale:
    Iím not an electrician and although I could see from the forum comments it was possible to build my own PSU I didnít want to and so bought the higher output unit for the X and Y Axis and then the smaller (and cheaper) PS408 for the Z axis, BOB feed and spare capacity. I did not want to stretch my budget to 4xAM882ís so settled for 3 and the PM752 for the smallest Axis. I liked the ZPA5A-INT 5 and purchased the PLCM-E3 because I wanted to run the machine from a lower power and spec PC. Iím not convinced of the PLCM-E3 yet.. So these are the choices I have made and from this basis and looking at the photos can I check these assumptions please.

    1) I am bringing mains into the panel and switching the Live through a 10A 600V toggle switch, in order to show the mains in live I have wired a Neon light with appropriate resistor in parallel with the switch. The circuit then continues on to a 10A 20mm fuse in a fuse holder.
    Assumption, have I wired the Neon correctly? Is 10A the right choice of fuse for this stage of power distribution? Is a toggle switch rated for 10A sufficient?

    2) From the panel the mains will continue to the main board via a 30A Ďchocolate blockí connector so I can remove the panel from the enclosure for maintenance/installation etc. Mains power is then sent in parallel to both PSUís.
    Assumption: Iím assuming this is ok.

    3. From the PSUís Iím using 22AWG wire to distribute the live to each stepper driver via a 6.3A fuse for each driver. Iím using Ďspadeí type connectors rather than soldering these connections.
    Assumption: Is this size of Fuse OK, the steppers should draw no more than 6A so I thought this would be a good size to choose. I believe the wire size is good for 11A 600v so Iím assuming this is OK for the HV (but not mains side) of the PSUís.

    From this point on, assuming I fix any identified issues, I plan to:
    A: Connect the HV output side of the stepper drivers to the enclosure panel sockets with my CY cable (detail below)
    B: Connect the BOB to the stepper drivers
    C: Generally tidy the wiring up.

    Iím looking at buying shrouded (but not shielded) cable for the signal connections between the BOB and Stepper derivers.. but I do have some CAT5 Ethernet cable around.

    4. Can I use CAT 5 cable within the enclosure for the signal side of the steppers to the BOB?

    So far I havenít attached a component to the board that requires an earth connection (other than the mains-in) but I have a connector block set up as my central earth point.

    5. Have I missed anything that requires connection to the Earth connector within the case so far? (based on what you can see in the photos)

    6. I am assuming that the Earth connector on my board will go back to the Earth connector on the mains-in socket?

    My panel has connectors for the steppers, limit switches and some potential expansion. My plan with these is to make up small junction boxes on each stepper so that I can unplug the motors from the cable, hopefully this will make the connections tidy and maintenance/installation easier. I have a small reel of CY cable at 4x1.5MM2 cores for the connection between the motors and the enclosure.

    7. I am assuming that I should somehow Earth the CY cable shield at the enclosure panel. I am confused how to do this, should I just connect an Earth line to the panel that houses the connector sockets (Same one the mains in and on/off switch is on)?

    Out of scope for now.. I have the ubiquitous Chinese water cooled spindle and VFD, for now Iím happy for these to remain out of scope and on their own mains lead supply.

    8. I am assuming I can do this and effectively use the VFD ĎManuallyí without any need for electrical control?

    Finally, I realise there is no E-Stop in the plan right now nor Relays used to switch the mains. I have not been able to find good material or circuit diagrams on how to wire this up. Right now I am willing to use the on/off switch I have to get the unit running and Ďupgradeí to an Estop later.

    9. If the enclosure must have an Estop and/or relay switching the inbound mains, can anyone point me towards an easy to follow circuit diagram?

    Thanks for taking the time to read and for any advice.

  2. #2
    Hi Tony

    If I were you I would implement a E-Stop circuit from the word go, when you are new to CNC which I assume you are, you will inevitably make mistakes if you have a nice BIG red e-stop button you can hit in the blink of an eye it will pay dividends in the long run.

    Do not under estimate the power of these machines your cutting tool will cut through skin and bone with ease.

    I have used a Pilz safety relay on my machine which kills everything safely these are fairly easy to wire up but not cheap!



    This would do the trick (eBay No:- 281014635581) I could give you a diagram to help fit it.

  3. #3
    Thanks Andy, I'll PM you for the diagram.

  4. #4
    I read it as 'Tidy CNC'.

  5. #5
    Tidy it aint currently, working on tidying up the wiring tonight. Not that I have confidence it wont create a fireworks display yet.

  6. #6
    OK, I've just about finished the control system version 2.0. As Andy and others said what I had may have worked in so far as it drove motors but it was not safe, had no estop chain and had other material weaknesses. Thanks to AudioAndy, Jazz, Adil and others who helped me on the Electrical. For the sake of anyone who reads the above with the same issues, I'm going to answer my own questions based on what I've learnt so far, then to the next phase, the mechanicals... :)

    1. No the neon should be in parallel with the live and neutral of the mains inbound, the way it was configured to start with the neon would only light upon a general closed circuit in the rest of the control box. The purpose of the neon is to show a live mains so in parallel to the socket pins works best for this.

    2. Didnít need to be this big, 15A will suffice. Also I discovered these in various sizes and current ratings and they helped move power and signal around the control enclosure. CamdenBoss Terminal Strip (Male+Female) 8mm 12 Way 6A3. Ditched fuses in the end and went for DIN Rail based circuit breakers on the advice of forum members, less fiddly, more robust. The wire was OK but having terminated using the spades I ended up stripping the ends and creating a neat soldered end due to several instances where wires worked loose.

    4. Didnít need to, I just used normal 22AWG wire but as the runs were so short, (4 inches) there was no need for the shroud. Also there are only actually 3 signal wires needed for each stepper driver.

    5. Did that but few components needed it.

    6. Did that, made sure I earthed the shielding from the motor power wires to it.

    6a. Used epoxy to create small junction boxes on each motor to tidy the wiring and create a robust connector to make assembly and maintenance easier.

    7. Earth configured as described. However used the pilz and safety contactor to also switch power to the VFD via the control box, added a separate mains in on the control box to facilitate this.

    8. Seems to be the case but have not go there yet.

    9. Jazz and AudioAndy stepped in a helped with a pilz relay and very detailed instructions on creating the safety circuitry as well as phone conversations to assist - thanks guys.

    Other lessons learnt so far....

    A) I wasnít happy with the 752 and AM882mix so I swapped the 752 for another AM882 so that all four motors are matched with the same drivers and for the same reason swapped the PS408 out for another PS806 so that there are now two of those. Thanks to Gary at Zapp. PS806-5 Linear power supply.

    B) Enclosure. I found them expensive and bought my first one based upon the design of the controls before the significant change to DIN rail, circuit breakers and the safety circuitry. As a result the enclosure was way too small to contain the components neatly, rather than waste the money spent on the original box I just used the lid to support the stepper drivers, BOB and smooth stepper, it actually made the wiring runs for these components small and relatively neat.

    C) Heat. Slightly concerned the enclosure may get hot so I've added some small fans, they are only 5v DC though and in use not surprisingly producing a small airflow. If I do detect heat build-up as I progress, I'll swap them out for mains powered fans.

    D) Smooth stepper. From reading various comments about the use of a smooth stepper I realise that itís not a generally popular choice. For me though it brought one large advantage in that it allows Mach3 to run on my Windows 7 64bit OS. I didnít want to install a separate 32 but partition or run something like Mach from within a virtual machine so it solved a constraint for me. In time I may see what other benefits the board (Purelogic PLCM E3) can bring.

    I'll attach some pictures of the electrical journey so far later.

  7. #7
    Quote Originally Posted by TonyD View Post
    D) Smooth stepper. From reading various comments about the use of a smooth stepper I realise that itís not a generally popular choice. For me though it brought one large advantage in that it allows Mach3 to run on my Windows 7 64bit OS. I didnít want to install a separate 32 but partition or run something like Mach from within a virtual machine so it solved a constraint for me. In time I may see what other benefits the board (Purelogic PLCM E3) can bring.
    Tony SS is mostly not popular because folks are tight arse's.!! Those that have them generally love them and see better or more stable performance.

    If yours is the USB version then power from separate 5v supply and you won't have any troubles. If you use USB power it can and will lockup at times.!

    Regards the PLCM E3 then I have one and other than ethernet then there is very little difference, it allows ever so slightly higher tuning but nothing i'd swap the USB SS for. Ence why SS still runs my main machine.!

  8. The Following User Says Thank You to JAZZCNC For This Useful Post:

  9. #8
    Different question. Into the much loved world of mechanical and forces. :)

    I'm planning on using a Y axis gantry thats made out of a 4 pieces of 15mm Ali plate, the front part has a slot as per previous discussions to allow the moving Z Axis to connect to the Y Axis screw.

    Key question on my mind right now is the length of the block which will support the gantry onto the rails relative to the center point of the spindle.
    As shown below, it feels right to me that the gantry support block should at least extend to the spindle center point, no maths to back this up but without this dimension it feels to me like the gantry would be out of balance relative to the forces acting on the spindle. Any comments? Only concern is that the block is 260mm in length right now and thats a fair amount of X Axis travel I'm eating up. Naturally the klunky design of my Z Axis, which was made with a press drill only is not very compact and thus adds to the problem. I'm comfortable with the design as is as job #1 when Im competent with the machine will be to make a new better Z Axis but thats for the future. Comments welcome. Tony.
    PS. I know there's going to be a side plate etc, I'm just looking at this one component now, happy to take feedback an anything else though.
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  10. #9
    Quote Originally Posted by TonyD View Post
    Only concern is that the block is 260mm in length right now and thats a fair amount of X Axis travel I'm eating up.
    The deflection due to the bearings on each axis is inversely proportional to the linear bearing spacing squared (which is obvious from the formulas in the Hiwin linear guide datasheet), so increasing the spacing by a relatively small amount can make a big difference. That's why it's important to space the bearings out as much as you can afford to, assuming the part they are mounted on is strong - which currently isn't the case as it's just a plate which would benefit a lot from a triangular/trapezoidal piece on the side. 260mm is not bad...probably not much point going above 300mm as other parts of the design will have a greater effect on the overall stiffness.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  11. #10
    Thanks Jonathan. I thought 260 was a lot as it was but happy to leave it there, if as I suspect this is the basic design I go for.

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