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Question #: 838

Question: What resolution and level of repeatability can one usually expect from a kit-built cnc?

Current Solution

Repeatability is very good for these machines and can be as low as .001" depending on the way you control the machine. If you use the spindle, you can be moderately aggressive, but you will want to use a finishing pass to make sure the edges are exactly what you would expect. since this is a kit, there will be varying levels of repeatibility depending on how well the kit is assembled and maintained. Calibration, as with all machines, is a critical aspect of keeping repeatibility over time.

Timing belts and chain are about the same when it comes to precision as long as the chain wraps most of the drive sprocket. There are differences to each of these systems as Kevlar with steel cables impregnated within the Kevlar and the steel used in roller chain have different coefficients of linear expansion (the expansion and contraction over temperature change), and roller chain may stretch over time, so it is important to maintain the machine by tensioning the chain and timing belt, and calibrating the machine over time and when the temperature changes significantly.

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Other Possible Solutions to this Question

  • What resolution and level of repeatability can one usually expect from a kit-built cnc, and is there a significant difference between timing belt and chain drive systems?

    Repeatability is very good for these machines and can be as low as .001" depending on the way you control the machine. If you use the spindle, you can be moderately aggressive, but you will want to use a finishing pass to make sure the edges are exactly what you would expect. since this is a kit, there will be varying levels of repeatibility depending on how well the kit is assembled and maintained. Calibration, as with all machines, is a critical aspect of keeping repeatibility over time.

    Timing belts and chain are about the same when it comes to precision as long as the chain wraps most of the drive sprocket. There are differences to each of these systems as Kevlar with steel cables impregnated within the Kevlar and the steel used in roller chain have different coefficients of linear expansion (the expansion and contraction over temperature change), and roller chain may stretch over time, so it is important to maintain the machine by tensioning the chain and timing belt, and calibrating the machine over time and when the temperature changes significantly.

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    What resolution and level of repeatability can one usually expect from a kit-built cnc, and is there a significant difference between timing belt and chain drive systems?

  • What tolerance can I expect from your largest cnc machine and the laser cutter? Also, what depth can I get on the z axis?

    The largest CNC machine we make at this time (12/04/2015) is the GreenBull 6'x12' model. This model has 2 options for Z-axis travel.

    The short-z option has a total Z travel of 5.75 inches. From that you would subtract the length of the end mill used and the thickness of the spoil board to determine the maximum material thickness. (Example: If the end mill extends 1.25" from the collet and the spoil board is .75", then the material could be up to 5.75 - 1.25 - 0.75 = 3.75 inches in thickness). This is good for most sheet-type materials.

    The long-z option, used mainly for large 3D carvings, requires a custom frame and allows for up to 36" of travel.

    The tolerance of our machines, like any machine, depends on several variables. The major variables include the manufacturing tolerance, the type of machine control used, the precision of assembly, the thoroughness of maintenance, and the initial and ongoing calibration of the machine. Because we sell kits only most of these variables are outside our control. Therefore, we are hesitant to guarantee a certain level of tolerance for an end user. However, in our experience, tolerances of .001" are readily achievable with our machines.

    Click the link to respond:
    What tolerance can I expect from your largest cnc machine and the laser cutter? Also, what depth can I get on the z axis?

  • If I wanted to use the blueChick for isolation routing, what accuracy could I expect from v3.0 and v4.2?

    The blueChick v4.2, is accurate at 1000's of an inch, with the roller chain, the v3.0 with the timing belt will increase the accuracy by 5%-10%, but to the expense of structural integrity.

    Additional Information:

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    If I wanted to use the blueChick for isolation routing, what accuracy could I expect from v3.0 and v4.2?

  • What is the dot resolution (size) of the BlackTooth laser?

    The dot resolution of the blackTooth is a combination of two specifications of the machine:

    - The steps/inch (or steps/mm) which is the resolution but not the dot size
    - The size of the actual dot, which is not specifically related to the resolution.

    The steps per or resolution can actually be a range, since the driver microstepping can be modified.

    A simple formula can be used to determine the resolution:

    step per inch = (motor steps * microstepping) / (travel at one turn of the motor in inches)

    if microstepping is set at 16 (1/16 on the driver) and you are using a pulley that has a pitch of .08 inches and 20 teeth on the drive sprocket

    = (200 steps * 16 microsteps) / (20 teeth * .08 inches)
    = 3200 steps / 1.6 inches
    = 2000 steps per inch

    To increase the resolution, just increase the microsteps on the driver.

    The actual dot size will depend on the lens you are using, the material being lased, the time period that the laser energy is applied to the material, and the focal height of the lens to the work surface material. The energy from the laser will converge to a point and create a dot on the surface (which is different than the kerf of the laser cut into the material).

    The dot will appear in different sizes depending on the material because, say wood, will burn causing a dot that burns the fibers of the wood and spreads a bit. The dot lased on the surface of a plastic, say Plexiglas, the dot will be smaller because the energy is absorbed only at that point, but since Plexiglas is a thermoplastic, a bit of the energy will melt the dot edges depending on the time frame (period) that the energy is applied to the surface.

    The focus of the laser energy from the lens looks like a cone converging to a point, then diverges outward after that point. Depending on the distance from the lens to the surface of the material, the dot will be bigger or smaller. You want to find focal point (where the energy is focused into a point). You can use the technique where you lay a material on a slope and lase that material along the slope to find the sweet spot (dot) and that will be your smallest dot, or kerf location. Remember that the kerf will widen or narrow within the material thickness depending on the focal length lens specification (the cone will be shorter or longer depending on the lens focal length).

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    What is the dot resolution (size) of the BlackTooth laser?

  • I just wanted to know what I can expect to pay to build the blackFoot 4'x8' CNC machine, excluding computer, software and router? Is the kit complete or do I have to purchase additional items to finish?

    You will need to build the table unit for your machine. There are instructions on how to do this at the bottom of the product page here, https://www.buildyourcnc.com/Item/cnc-machine-blackFoot-v4
    There is no estimate on how much this will cost though, since there are too many variables involved to do this.

    - PC with parallel port and USB port
    - 20awg stranded wires for the motors - http://www.buildyourcnc.com/electronicscombo.aspx
    - 18awg stranded wires for power supply to drivers
    - 24awg stranded wires for breakout board to drivers
    (location and spacing of components varies from one person to another, so we do not provide cables/wires)
    - General purpose extension cord (cut the female end off) to provide power to power supply
    - USB cable to power breakout board
    - Parallel cable to communicate to breakout board
    - Router
    - (optional - instead of router) Spindle with power inverter http://www.buildyourcnc.com/SpindlesAndAccessories.aspx
    - (if purchasing spindle with inverter) General purpose extension cord (240v) (cut the female end off) to provide power to power inverter
    - End Mill(s) http://www.buildyourcnc.com/ProductsEndMills.aspx
    - CAD, and/or CAD-CAM software (to produce geometry, machine operations, and g-code) http://www.buildyourcnc.com/CNCsoftware.aspx
    - CNC control software (to read g-code and control machine) http://www.buildyourcnc.com/CNCsoftware.aspx

    This answer is applicable to most of our machines with the exception of the greenLean and the blueChick since those machines are equipped with a table structure.

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    I just wanted to know what I can expect to pay to build the blackFoot 4'x8' CNC machine, excluding computer, software and router? Is the kit complete or do I have to purchase additional items to finish?

  • I ordered an 80w tune on Amazon for a good deal, it took over a month to arrive and was broken on arrival. Get what you pay for I guess :( of I order a tune from you can I expect it to be better packed and arrive quicker?

    We double box our tubes. The inside box contains the tube that is surrounded by foam. This inner box is wrapped with bubble wrap and then boxed again.

    Carriers are not very careful with packages, but it is not typically from personnel handling, but the machines and conveyors that maneuver the boxes at their distribution centers.

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    I ordered an 80w tune on Amazon for a good deal, it took over a month to arrive and was broken on arrival. Get what you pay for I guess :( of I order a tune from you can I expect it to be better packed and arrive quicker?

  • in one of your posts you mentioned working on ethernet connection for boards. any estimate on resolution of that?

    USB Mach3 boards will be available on the website now. Ethernet is still something for the near future.

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    in one of your posts you mentioned working on ethernet connection for boards. any estimate on resolution of that?

  • I'm looking for a CNC which will mill 4x8 MDF/OSB and birch, as well as other 3/4" species. Previously I used a Shopbot and Partworks - can we expect the same performance from this?

    The greenBull 4x8 is designed specifically for heavy usage with a larger gantry and 3 large NEMA 34 651oz-in motors on each axis. You can expect superior performance from the greenBull since it is specifically designed for every day production of 4x8 sheets of material.

    Additional Information:


    Additional Information:
    The greenBull response was not an answer to my question. I'd still like to hear from users. There must be some suggestions comments from those that have built the machine?

    Additional Information:
    Strange that you got the response matching the greenBull answer. That was probably our automated "closest match". I would re-state the question and select the "no, the answer is not related" and let it hang out on the customer service page for a while to see if you get any bites.

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    I'm looking for a CNC which will mill 4x8 MDF/OSB and birch, as well as other 3/4" species. Previously I used a Shopbot and Partworks - can we expect the same performance from this?

  • WHAT IS THE FORMULA TO DETERMINE STEPS PER INCH OR RESOLUTION FOR EACH AXIS?

    The formula and calculation is a starting point to get into the area of steps per inch. You will then need to use the mach3 calibration utility to get the exact steps per inch.

    Formula:
    step per inch = (motor steps * microstepping) / (travel at one turn of the motor in inches)
    if microstepping is set at 16 (1/16 on the driver) then and you are using a sprocket and chain with a pitch of .25 inches and 12 teeth on the drive sprocket
    = (200 * 16) / (12 * .25)
    = 3200 / 3
    = 1066.666 steps per inch

    For lead screw that has a travel of .5 inches at one turn like the 5 start 1/2 inch lead screw and using 4 microsteps per step (1/4):
    = (200 * 4) / (.5)
    = 800 / .5
    = 1600 steps per inch

    Remember to use the mach3 calibration wizard and double check the driver microstep setting.

    Additional Information:

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    WHAT IS THE FORMULA TO DETERMINE STEPS PER INCH OR RESOLUTION FOR EACH AXIS?

  • Hi Patrick What is the name of that organization for CNC enthusiast in Houston and Katy TX and phone number please. Thanks

    The CNC group is a splinter group of the Woodworker's Club of Houston" and can be found at this website: http://wwch.org

    You can contact them via their contact us page here: http://wwch.org/ClubBus/ContactUs.htm

    They have regular meetings at the location specified on their homepage. You can also go there and talk to some of the CNC group's members.

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    Hi Patrick What is the name of that organization for CNC enthusiast in Houston and Katy TX and phone number please. Thanks

  • I have purchased the Mach3 licence from you, How soon can I expect the email with the licence?

    As long as Mach3 orders are received during business hours they are generally emailed that same day.

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    I have purchased the Mach3 licence from you, How soon can I expect the email with the licence?

  • What is the difference between a NEMA 23 and NEMA 24 motor? can I use either one on a machine?

    The frame size difference of the NEMA 23 and 24 is very slight and, depending on the motor mount both will most likely fit. The bigger difference between these stepping motors is the torque. Make sure that the motor that you purchase has the appropriate torque for the axis that it will move.

    Is is safe to go with the higher torque? Or if the torque is too high for what i need is that bad?

    You can use a motor with higher torque. Just make sure to select the correct driver for that motor.

    Additional Information:
    The frame size has nothing to do with torque. Nema 23 means a 2.3" frame. Nema 24 means a 2.4" frame. That's all. Either could have more or less torque depending on speed and power.

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    What is the difference between a NEMA 23 and NEMA 24 motor? can I use either one on a machine?

  • What is the difference between a NEMA 23 and NEMA 24 motor? can I use either one on a machine?

    The frame size difference of the NEMA 23 and 24 is very slight and, depending on the motor mount both will most likely fit. The bigger difference between these stepping motors is the torque. Make sure that the motor that you purchase has the appropriate torque for the axis that it will move.

    Is is safe to go with the higher torque? Or if the torque is too high for what i need is that bad?

    You can use a motor with higher torque. Just make sure to select the correct driver for that motor.

    Additional Information:
    The frame size has nothing to do with torque. Nema 23 means a 2.3" frame. Nema 24 means a 2.4" frame. That's all. Either could have more or less torque depending on speed and power.

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    What is the difference between a NEMA 23 and NEMA 24 motor? can I use either one on a machine?

  • one of my motors from the blackfoot kit goes back and forth rather than turning, the wiring hasnt changed since i bought it, what could be wrong?

    The motor shaft does not turn, but slides back and forth in an axial motion? Please submit additional information on this page.

    Additional Information:
    it goes one step then the next step in the other direction so it seems to just vibrate

    Additional Information:
    It sounds like this could be a bad driver? You can determine if this is the cause by connecting another motor to this driver to see if it still happens to the new motor plugged into that driver. This will either rule out the motor causing this, or if it is the driver.

    You can also possibly rule out the driver as well if you change the step and direction wires from another driver to the problem driver.

    Make sure you do these steps one at a time. It's best to consider a single variable at a time.

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    one of my motors from the blackfoot kit goes back and forth rather than turning, the wiring hasnt changed since i bought it, what could be wrong?

  • What is each axis' resolution for the blueChick in mm or µm?

    The resolution for any of our machines is based on the driver microsetting setting and the machanical parts used for each axis.

    For example:
    The blueChick uses 9 tooth drive sprockets for the x and y axes.
    To determine resolution use this formula:
    Resolution = steps / inch or the travel in steps for one revolution of the drive sprocket
    Steps = (motor steps) * (driver microsteps) or natural motor steps * microstepping setting on the driver
    Inches = t(ooth coun)t *( tooth pitch) or the number of teeth for the drive sprocket

    Resolution = ((motor steps) * (microsteps)) / (teeth * pitch)
    In this example, the microsteps is 16 and the pitch is .25 inches
    = (200 * 16) / (9 * .25")
    = 3200 / 2.25"
    = 1422.222 steps per inch

    For the z axis of the blueChick, the resolution is typically based on 4 micro steps and the travel for one turn of the motor is 1/2". Therefore:
    Resolution = (200 * 4) / .5"
    = 800 / .5"
    = 1600 steps per inch

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    What is each axis' resolution for the blueChick in mm or µm?

  • accuracy and repeatability

    Repeatability is very good for these machines and can be as low as .001" depending on the way you control the machine. If you use the spindle, you can be moderately aggressive, but you will want to use a finishing pass to make sure the edges are exactly what you would expect. since this is a kit, there will be varying levels of repeatibility depending on how well the kit is assembled and maintained. Calibration, as with all machines, is a critical aspect of keeping repeatibility over time.

    Timing belts and chain are about the same when it comes to precision as long as the chain wraps most of the drive sprocket. There are differences to each of these systems as Kevlar with steel cables impregnated within the Kevlar and the steel used in roller chain have different coefficients of linear expansion (the expansion and contraction over temperature change), and roller chain may stretch over time, so it is important to maintain the machine by tensioning the chain and timing belt, and calibrating the machine over time and when the temperature changes significantly.

    Click the link to respond:
    accuracy and repeatability

  • What are the noise levels of the 1.5 Kw and 2.2Kw spindles?

    The noise level of the 1.5 kW and the 2.2 kW are very similar. The noise level is considerably quieter than typical routers. I am going to add sound db levels to this FAQ a bit later.

    Additional Information:
    The db (decibels) reading for the spindle is 70 and an 890 Porter Cable router (a lower powered tool than the spindle) measured 90 db. Both measurements were taken in the same environment and measured at the same distance from the tool.

    Additional Information:
    Practically silent. The inverter makes more noise!

    Additional Information:
    Practically silent. The inverter makes more noise!

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    What are the noise levels of the 1.5 Kw and 2.2Kw spindles?

  • im from mexico, and i want to know if you could send something here, and what is the type of currency?

    Yes, we can send to international countries. Our currency is in USD (US Dollars). In the cart, you will find the shipping carriers and methods possible to ship to your country when you click on the "Calculate Shipping" button.

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    im from mexico, and i want to know if you could send something here, and what is the type of currency?

  • I need technical support for your Bluechick CNC and I can't get a reponse on the phone.

    You may have called outside of our business hours. Give this "Customer Service Live" mechanism a try and ask away. If you would still rather call us, please call between 9:00am and 5:00 pm Central Time.

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    I need technical support for your Bluechick CNC and I can't get a reponse on the phone.