Why these machines in particular come back in good shape
The TPS 4000 and TPS 5000 were built around a power module cooled by forced air, with a separate feeder and an interconnecting lead. That layout carries heat and vibration away from the electronics, so the boards age more slowly than in compact machines. After ten years of single shift work most of the power train is usually still sound.
What does wear out are the moving parts and the ones the wire or the coolant passes through. Below are the subassemblies in the order in which they come in for repair at our service centre.
What wears out and how you will know
Power module
The power module fails rarely, but when it does, it is the most expensive item on the estimate. The symptoms can be misleading: the machine starts, holds current at 150 A, and at 300 A loses voltage or throws an overheating error after a minute of arc. The common cause is often not the module itself but a layer of welding dust on the heat sinks, which works like a blanket.
The second typical scenario is a short circuit after metal filings have been drawn inside. A machine standing next to a grinder picks that up within a year. That is why on intake we always take the cover off and look at the module, the connectors and the tracks before we connect the power at all.
Fans and clear air paths
Fans are a wearing part. After a few thousand hours the bearing starts to whine, the speed drops and the machine loses duty cycle even though it still works. The symptom is simple: at full current, after 2 to 4 minutes, a temperature error appears that was not there before.
Replacement is cheap, roughly 150 to 400 zloty net each plus labour. Neglecting a fan costs you the power module, so it is the best invested part in the whole machine.
Wire feeder
The VR feeder runs for the whole arc time and collects dust off the wire. The rollers, the inlet guides, the pressure arm and, less often, the motor with its encoder wear out. The symptoms: the wire runs unevenly, the current jumps by a dozen or so amps, and the weld face shows cyclic narrowing.
We check that by measuring the feed speed over a length, not by eye. We set 8 m/min, measure the wire fed out in 30 seconds and compare. A deviation of more than 5 percent, or instability between runs, means replacing the rollers, and sometimes the motor.
Cooler and coolant circuit
The cooler is the second cause of falling performance after the fans. The pump loses output, the heat exchanger silts up inside, and after years the coolant turns to sludge. The symptom: the torch heats up at 250 A although it is rated for 400 A, or the machine reports a flow error on a longer weld.
We measure the flow on the return line and the coolant temperature after 10 minutes of work under load. If the flow is below the maker's requirement, we change the coolant, flush the circuit, and only then judge the pump. The coolant itself costs a few dozen zloty, the heat exchanger and pump roughly 600 to 1 500 zloty net.
Interconnecting lead
The interconnecting lead between the power source and the feeder carries current, gas, coolant and control signals. It is the most exposed item in the whole set, because it lies on the floor, gets run over by a trolley and is bent every time the machine is moved. The damage is usually internal and cannot be seen from outside.
The symptoms: the arc breaking up when the lead is in a particular position, a coolant leak after a few minutes of work, communication errors with the feeder. A new 4 m lead is roughly 2 000 to 4 500 zloty net, so when valuing a machine we check it separately and describe it in the product listing.
Control panel
The membrane keypad and the knobs do not like spatter and solvents. After years a key stops responding and the encoder jumps values both ways on a single turn. The machine still welds, but setting a parameter takes three times as long.
Replacing the membrane or the encoder is roughly 500 to 1 500 zloty net. It is worth doing before a sale, because the panel is the first thing the next user judges.
What is added on CMT machines
In CMT the wire is retracted and fed at high frequency, which adds a drive in the torch and a wire buffer between the feeder and the torch. Those are two subassemblies an ordinary TPS does not have, and they are the ones that most often need attention.
The drive in the torch has its own rollers and its own bearings, working in a reciprocating motion. A worn drive shows up as a loss of short circuit repeatability: the process stops being quiet and spatter appears where CMT should not produce any. The wire buffer in turn has to move freely, and a dirty one introduces resistance that upsets the synchronisation.
When taking in a CMT machine we run a test on 1 mm sheet and judge the process by sound and by the weld face. If the process is loud and throws spatter, the cause lies in the drive, the buffer or the lead, not in the settings.
Four things to check yourself
Before you call in the service centre, sift out the faults you can clear on the spot in a quarter of an hour. In practice every third report ends with one of the items below.
- Take the covers off and blow out the heat sinks with compressed air at reduced pressure, from the side, not straight at the board. Dust alone can cut the duty cycle by somewhere over ten percent.
- Check the level and the colour of the coolant. Dark coolant with sludge is a signal to change it, not to top it up.
- Change the contact tip and blow through the torch liner. Most current fluctuations come from there, not from the power module.
- Measure the supply voltage under load, at the socket, not at the distribution board. A drop below 380 V across the three phases explains a loss of current with no fault in the machine at all.
If the symptom does not go away after those four steps, the cause lies deeper and then diagnostics with measurement makes sense.
The load test, step by step
None of the faults above shows up in five seconds of arc. That is why we load every machine for real, on material, for longer than the cooling cycle. Without that, any assessment is guesswork.
| Stage | What we do | What we read from it |
|---|---|---|
| 1. Internal inspection | covers off, assessment of dust, connectors, signs of shorts and leaks | the decision whether to connect the power at all |
| 2. Cold start | start up, going through the menu, testing every key and knob | the state of the panel and of the settings memory |
| 3. Feeder | feed speed measured at 3 set values | the deviation in percent, stability between runs |
| 4. Short arc | a weld on 3 mm sheet, 120 to 180 A | striking stability, the amount of spatter |
| 5. Long load | 10 to 15 minutes of work at a current close to the maximum | whether the machine holds current and stays out of a temperature error |
| 6. Cooling | flow on the return line and coolant temperature after the test | the state of the pump, the exchanger and the clearance of the circuit |
| 7. Lead and torch | moving the lead under load, checking for leaks | breaks in the arc, leaks, communication errors |
What you will find in the machine description
We do not judge a machine by the date on the rating plate, only by what the test showed. In the product listing we give the result of each of the seven stages, the list of replaced parts, the contents of the set and anything missing. You get an inspection report with the extended service package. On that basis the machine is given condition A, B or C.
Condition A means full working order and cosmetics beyond reproach. Condition B means full working order and visible signs of work: scratches, worn printing, grinder marks on the casing. Condition C is a machine in working order but with clear wear to the casing or an incomplete set, which we always state plainly.
On top of that comes the first year of the basic service package in the price of the machine. You buy further years separately, and then repairs come out cheaper and we provide a replacement machine for the duration of a repair.
When a repair stops paying
A simple rule: if the estimate exceeds half the market value of a sound unit, the repair is an investment rather than maintenance. On a TPS 4000 that is usually the point at which the power module and the interconnecting lead have to be replaced at the same time.
| Repair | Indicative net cost | Decision |
|---|---|---|
| Fans, coolant, rollers, panel membrane | 800 to 2 500 zloty | always worth it |
| Cooler pump and heat exchanger | 600 to 1 500 zloty | worth it |
| Interconnecting lead, 4 m | 2 000 to 4 500 zloty | worth it if the rest is sound |
| Complete feeder | 4 000 to 9 000 zloty | needs working out, sometimes a separate feeder is cheaper |
| Power module | 6 000 to 12 000 zloty | only if the rest is in good shape |
| Power module plus lead plus feeder | above 15 000 zloty | better to replace the machine |
In that last case it makes more sense to hand the machine over in part exchange. We will value it as part exchange, faulty units included, and deduct it from your next purchase. For the changeover period you can take a machine on rental, so that the job does not stop.
Bring the machine in for a test
We do diagnostics with a load test in Krotoszyn, usually within one working day. Call before you come so that we can prepare the bench and the coolant, or have a look at the used MIG/MAG category, where every machine is checked in our service centre and carries a condition of A, B or C.