2017 DIY Controls for a CNC Plasma Cutting Table

Transcription

1 2017 DIY Controls for a CNC Plasma Cutting Table Plug and play controls for a CNC plasma cutting table have greatly increased in cost over the past few years due to Microsoft no longer supporting Windows XP and computers no longer having a parallel port. Since new parallel port computers are no longer available, CNC controls manufacturers have switched to a USB or Ethernet connection between the computer and controller. The cost has now jumped to between $2500 and $3000. DIY individuals have been able to source and build controls at a much lower cost, but there are so many choices out there that may people do not know where to begin and not all components work as well as their ratings. This article will suggest components available today that have been proven to work well for CNC plasma cutting for the lowest cost. If you can connect wires, you can build a CNC control system. First, the most important component in CNC controls is the motor driver. Geckodrive is a company that manufactures stepper motor drivers in the USA and it the best choice for your control package. The G250 is a 3.5 amp 50 volt motor driver. Geckodrive sells 4 of these drives with a motherboard and case and calls it the Geckodrive G540. This is the best choice when building a CNC controller. Do not get fooled and purchase Chinese controls from Ebay with the same ratings. They are junk and need to be avoided. However, Ebay is a good source to buy the G540 at a cost lower than the list price of $299. Today, it could be purchased for $269 + $6.95 shipping for a total of $ The manual and configuration file can be downloaded from the geckodrive.com website. Next, you will need a power supply to power the controller. Ebay is also a good source to purchase a 400 watt 48 volt switching power supply. Today s cost is $21.62 with free shipping from California.

2 The optimal motors for controller will have a rating of 3.5 amps and an inductance of 3 or greater. I choose to lower the voltage of the power supply by turning the potentiometer near the terminals to set the voltage to 44V. 44V to 48V will work. I also use 3.3K current set resistors on the motor plugs to limit the maximum current to the motors to 3.3 amps. Per the Geckodrive manual, the maximum voltage should be 32 times the square root of the motor inductance and the power supply requires 60% of the total motor current. A 400 watt 48 volt power supply has 8.3 amps. The current required is 4 x 3.3 = 13.2 x 60% = 7.92 amps. You will want an enclosure to mount the Geckodrive and power supply. An aluminum enclosure made for the G540 can be purchased for $65 on ebay or $79.95 from Automation Technology Inc. Quantity (4) 623 in-oz motors can be purchased from ebay for $199 with free shipping. These motors are 3.5 amp and have 3/8 output shafts. You will need 4 conductor 18 gage shielded or non shielded wire to connect the motors to the controller.

3 In order to guarantee that the G540 stays cool, homanndesigns.com sells a G540 chiller for $37. Geckodrive has done testing and blowing air on the back of the G540 is recommended. The model number is GC-01 V2 Gecko 540 chiller. This can be powered from the 48V power supply and has the added benefit of 200ma 12 volt power if it is needed to power other parts of the system. Another item required is a relay to trigger the plasma torch. A 48V coil relay with 30 amp contacts can be purchased from jameco.com for $5.09. One will be required or two if you want to control an addition accessory. Above is a list of the basic components required to build a CNC control package. Next, you will need to choose your operating system and how to connect the computer to the G Windows XP with Mach 3 and a parallel port connection to the controller. 2. Linux CNC (operating system and controller software) with a parallel port connection to the controller. 3. Windows 7 with Mach 3 and a USB connection to the controller. 4. Windows 10 with Mach 4 and a USB connection to the controller.

4 In order to have a USB connection between the computer and controller, a product called the UC100 is required. The UC100 can be purchased on Ebay for $45 and you will need a M/M DB25 adapter for another $5. Software licenses from lowcostcncretrofits.com Sheetcam license $149 (when running Linux CNC) Mach 3 / Sheetcam combo $285 (when running Windows XP or Windows 7) Mach 4 / Sheetcam combo $339 (when running Windows 10) For drawing, QCAD and Inkscape can be downloaded from the web for free. Torch height control: The most popular option is the Proma compact 150 for $286, but the Price CNC THC for $335 has a better enclosure and antidive feature. Another unit called the MiniTHC can be purchased for $290 on ebay. Another newer model by Soft Circuits is equivalent to the Proma unit and costs $200 shipped. All units read the arc voltage and output an UP or Down signal.

5 What is it all going to cost? Least expensive method: Linux CNC with a parallel port connection to the computer: G540 $276 Power supply $22 Chiller $37 Relays $10 Enclosure $75 Parallel cable $ motors $200 Sheetcam $150 Soft CircuitsTHC $200 Total $980 Most expensive method: Windows 10 with a USB connection to the computer: G540 $276 Power supply $22 Chiller $37 Relays $10 Enclosure $ motors $200 Mach 4 / Sheetcam licenses $339 Price THC $335 UC100 USB adapter $50 Total $1344

6 Notes: The G540 has 5 inputs and 2 outputs. This is exactly what is needed for a CNC plasma table. Inputs: 1. X home, Y home, Z home (wire in parallel Normally Open and home one axis at a time) 2. Arc OK from plasma cutter 3. Torch up from THC 4. Torch down from THC 5. E-stop (additional e-stop or limits wired in series Normally Closed) Additional info: CPC port for Hypertherm Components to build interface cable: A99521-ND PINS A1358-ND PLUG A32516-ND CABLE CLAMP