Several of the import tool sellers have for years purchased products built to their specification in places like Taiwan, China and Malaysia. That has worked well for machines like drill presses ,handsaws, and other wood and metal working tools. I have a shop full f Grizzly , Jet and Shop Fox power tools. So its no surprise that several of the vendors have started sourcing CNC machines the same way. Like a lot of Chinese products, they are typically pretty well built mechanically Their Controls and Software leave a lot to be desired. This is a blog from a Metal Working Club in Arizona that has several plasma tables . No one liked using the Laguna table UNTILl....
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Welcome to the blog about a cost effective retofit of a Laguna Plasma table that had the basic Chinese "Starfire" CNC control (G-code reader and the separate THC . The mission was to make the software easier to use and have better , faster torch height control . This table belongs to a Metal Working Club in Arizona that has several plasma tables that are used a lot. Like the other China Syndrome blog, we are going to take you through the process and how it was done. We have pictures and a coulée of spreadsheets to share and LOTs of our comments .
The CandCNC prodcut selected is our MP3700 - DTHC5 system that includes :
New qaud processor Mini PC with 32G SSD and 8G memory.
Preloaded Linux OS (special compile
Preloaded CAD/Drawing programs
Preloaded, fully licensed Advanced CAM program (SheetCAM )
Preloaded CommandCNC(tm) control software.
A High Speed Direct Ethernet I/O card with 16 opto isolated inputs. 6 Axis of Step & Dir signals and built-in Dual AC switched outlets
The Ultra high speed DTHC5 module. With its own processor and memory for parallel operation
External PWMII remote Digital pickup for plasma signals
External remote driver interface card Buffered and filtered for noise free interface to drivers up to 15ft away.
In addition they purhcsed a single MIC-03 connection cable for the Hypertherm 65 .
Everything they need to get a modern highly automated cutting machine with a Commercail level interface.
Using CommandCNC and the high speed hardware, the torch height becomes part of the total motion control , not some orphan process
The first step in any retofit is to first profile the machine and understand how its constructed and wired.
Almost all CNC machines have the following:
Electronics that read a software "file" (often G-Code) and accurately move the axis at a controlled rate and distance
Some form of UI (User Interface) most often Graphical using icons , input boxes and buttons on a monitor screen
A Software Program that translates from the file to develop motion signals. Since 95% of modern controls are digital it takes the form of discreet pulses (Step and Direction or Pulse and CW/CCW ).
Motors and motor drivers that convert pulses to rotary motion. Mechanical components that convert rotary motion (torque) to linear motion.
Linear motion components: mechanical or electro-mechanical devices to move one or more "axis" An AXIS is a plane of movement
An I/O section that reads inputs (typically as ON/OFF or HIGH/LOW )
Outputs that are typically ON or OFF and can be l;logic level or buffered (amplified) and drive Relays (mechanical or Solid State)
The complexity comes in the way each of these are implemented and then how the system is integrated together to form a working machine. Some design put everything in one design and its more or less a "black box" where it totally propriety and sealed. A lot of older systems designed before 2000 are 100% closed . There were not a lot of individual component manufacturers and the market place was dramatically different. The Machines were large, heavy and expensive. A lot of different technologies were used: everything form "eye tracer" plate cutters to complex analog server controllers. Its tempting to buy a old model CNC plasma or router table that looks like a really good deal.....its NOT! Virtually noting on the machine is reusable with modern controls and it becomes a money pit . Even the mechanical components most likely will have to be changed. Old motors are weak compared to current types of th same size and mountings and transmissions won't match so just swappign motors is not usually the answe
There are plenty of more modern machines that use off-the-shelf components (motors, motor drivers,digital controls , etc A lot of these are either sitting not being used or have problems that can be purchased at a reasonable price and with some planning be turned into accurate and reliable machines. These type machines break down into two main classifications: 1. A good physical tram work with a good solid table base and good mechanical components (linear rails, gantry and cutting area.Thsi typically needs a full control packing with motors , (possibly new Z axis) and new control power and software . 2. Systems that are good mechanically and have good motors and good motor drivers and a user console . In this case its often that the Electronics are either a poor design and/or not user friendly. Often he software is marginal and often "simple to use" means a lack of features or support.
Its number 2 where a lot of the import tables fall with good mechanical and motion parts but bad User Interface and confusing software and terms .
In this blog we are looking at an import table that was running and cutting but not liked by its users a sat idle.
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Typical Starfire Chinese Control module and separate THC
Laguna 5X 10 Plasma table
So the first round of discovery shows that the Controls are Chinese and the THC is a separate control panel . A look into the cabinet reveals that its a tree drive (?) steppe system and a 4th motor on the Z controlled by the THC . the THC has its own Stepper driver built in. Since that unit is going away we need to add in a 4th stepper driver.
The signals are label d on the back of the THC box which makes tracing and identifying wires a lot easier.
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From the model number tag on the driver its a 2DM860 2 Phase stepper driver cablable of driving motors up to a little over 8 amsp and up to 60VDC. A quick searcjh pops up dozens of hits and even a place to buy them on Amazon.
In looking at the cabinet mad taking stock of the drivers and the signal lales we see that the original control used a coule of switching power supply to provide power for the front panel control (24VDC ) and for the inputs (also 24V). neither of those will be needed since the MP3700 has it own bias power supplies built in and runs off 120VAC . It also supplies the input power for inputs .
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At first glance its somewhat of a mess but the builders did take time to label wires and uses colours. The two smaller BIAs supplies need to go and they are removed to make riiom for a 4th Motor driver to take over the Z motion. Where as the Z motor was controlled entirely by the THC , the MP3700 and CommandCNC(tm) uses a special "Arbitrator" that switches between the Z being a normal console or G-code controlled Z and a closed loop high speed torch lifter under DTHC control. So a fully functional Z is needed and is a full axis to the software.
Best advise is to take lots of detailed pictures and make up a chart (spreadsheet) that shows the essential wires and their colors and where they go.
This is one of the more boring tasks in any rebuild but its highly essential Probably the biggest challenge is to figure out all of the signals, their names and their functions. This is where the translation of languages and different cultures tend to clash. So terminology loke "Location Success" would probably be "Touch off" . A name like "Cycle start" is probably "Code running " . This where wire tags and colours can help along with either an ohmmeter or continuity tester. A wire tracer (signal injector) that lets you "sniff " whole bundle of wires and find the conductor with the signal is handy. Most inputs are going to consist of either a mechanical switch or some for of electronics sensor that basically acts like an electronics switch. The inputs are not measuring intensity or voltage , they are ON or OFF (binary) . The terms OPEN is usually the same as HIGH and the term CLOSED is LOW. High is usually associated with logic 1 and low with 0. Here's where it gets sticky. In most systems the inputs are pulled HIGH to a power level and considered by the software to be OFF. Then if the switch is activated it ppulls that input LOW and the software sees that as ON......confused? don't feel bad. It gets worse. You can trigger any input on a high or low as being ON . Often ESTOP circtuits are setup to have to be pulled low to be OFF. That allows a signal strand of Normally Closed (switches that when not tripped are closed ) , to be strung un series and it takes ALL of themto be un-tripped to be closed and the whole string to be closed. If an ONE switch is tripped an it OPENS the whole string goes OPEN and the input they are tied to h\goes high and by setting the input polarity to be opposite and trip on a high , it trips ETOP,....whew! time for a break! we will step back next and look at the things that need to be sensed and how the existing setup on the Laguan table can be used.