Tig...DC versus AC/DC prices

[Seano]

If you guy's don't mind I would like to throw this forward as a point of discussion as something that for the life of me I just cannot understand.

After polling quite a few machine suppliers here in the South West regarding why an AC/DC tig should cost So much more than a straight DC tig, everyone just keeps coming back to the stock answer which is Ah well AC/DC requires more production and special parts to produce than DC, ok so you have your cleaning, up / down slope, frequency, pulse, cycles to incorporate, but surely these additions don't take that much more financially to produce ?, and I am not going to get involved in company / supplier profit margins, this last part is in no way meant to be a sidway's dig at either Matt, or Steve (Weldequip) or any other supplier we may have here.

Is it just me looking at things in only two colour's or is it only just Profit I must admit that even in my own line of work (Disability / Mobility) it just seems that anything a little special / out of the norm is a license to print money, just a quick eg, a client needed a headrest extension for their chair, this amounted to a piece of 12mm square solid about 350mm long with a short dogleg then a straight and chromed... the cost £170.00 +vat.

So, anybody got any thoughts either professionals or hobbyists I am open to it all, if it helps me to understand why there is such a difference in price when at the end of the day they are not so hugely different...now I may get hung for that last line.. but so be it, over to you gentlemen.....

Sean.

 

[GrahamGKD]

I don't know the detail of the circuitry these machines use but I'm guessing the AC circuitry is a kind of add-on to the DC which is already there for the DC machine. After all, the inverter machines would not seem to use the mains frequency for the basis of the AC output otherwise you wouldn’t have control over the frequency, waveform shape and AC balance? Since there is 'extra' circuitry and it is high power stuff then it seems reasonable that it is expensive to produce. If it was a price fixing thing as I think you are suggesting then sooner or later someone would break cover wouldn’t they?

 

[piman]

Hello Graham,

I think you are right, it will need an inverter stage after the D.C. rectifier section. Plus all the wave form modulation etc. Just look at the cost of motor drive inverters of any power?

Alec

 

[Seano]

You may be right gentlemen, as I only ever think and deal with things in a totally steel, engineered, rotating, reciprocating, suck,squeeze,blow, way and no very little about electrics / electronics maybe I do not see, realize or know how or why these things cost so much to produce / build.

 

[matt1978]

I am talking purely from my own view point and not from the company, but I also, am not electrically minded, but even I can see there is a lot more inside a ACDC tig compared to a DC only.

Maybe these extra componants don't account for all of the extra cost, some of it will undoubtedly be down to market price, but I am sure some of the extra cost will also be there cover R & D time for future advancements.

If no one had of put time and money into R & D on these items then, everyone would still of been welding with a 50Hz Transformer type in Square Wave and AC Balance, Frequency, Cap Shaping, Wave Adjustment, Modulated (Mixed) ACDC etc etc would not exist today.

 

[Luke]

I don't work with welders, but I do work with Drives, both AC and DC. An AC drive converts incoming AC to DC, then back to AC - it is doing twice as much as a DC drive. Then, as already mentioned, more processing power is required to chop the DC up in to the correct AC waveform, component costs will increase, as well as R&D contributions etc. A lot of the modern AC functionality is implemented in software, so there aren't huge direct component costs, but there will be reasonable development costs.

 

[PTvor]

For standard parts you can set up to make them and churn them out in huge runs, so the set up cost is spread over a large number of units. The people making them haven't got to switch to a new process with possible scrap as they get up to speed. There'll be lots of companies making them anyway so there'll be competition. With a small volume special, it's different.

Making short runs of specials isn't necessarily a licence to print money. You could easily find it was more trouble than it was worth, but you have to do it to keep the customers quiet.

With an DC/AC tig there's extra circuitry, with heatsinks and fans to be paid for. it's more complicated to assemble, set up and test, so it's no surprise they are dearer. It's a smaller market anyway, and TIG tends to be professional, so the people using the equipment and specifying it won't be spending their own money.

That said, with a lot of things, hi-fi amplifiers, inverters, cars, computers, the basic model is the same. The extra performance models have a few upgraded parts with a relatively low extra cost to the maker, which they can charge handsomely for. They do have a thorough knowledge of the product on their side and the ability to scrap a few casualties.

If you buy the basic model and upgrade it, having to buy the upgraded parts on a one by one basis, having already paid for the basic bits, you'd probably find you were better off to buy the top model to begin with.

With a lot of things, the maker sells you a guaranteed spec as with computer chips with two, three and four cores. If you buy the four core it will have four active cores, guaranteed. The three core chip is the same, and it might be that the chip was deactivated to sell it as a three core chip for marketing reasons, it might be it was tested in the factory and played up over a certain temperature, so they could sell it as a three core chip and avoid scrapping it. If you activate the core the maker switched off in the factory, it might well work, but you are taking a risk.

 

[GrahamGKD]

With a lot of things, the maker sells you a guaranteed spec as with computer chips with two, three and four cores. If you buy the four core it will have four active cores, guaranteed. The three core chip is the same, and it might be that the chip was deactivated to sell it as a three core chip for marketing reasons, it might be it was tested in the factory and played up over a certain temperature, so they could sell it as a three core chip and avoid scrapping it. If you activate the core the maker switched off in the factory, it might well work, but you are taking a risk.

I always thought it was the latter of your suggestions - they fabricate four 'core' (or whatever) chips and then test and sort them according to how much is working and how well it is working and subsequently market the various levels of success from there? I'm a bit out of touch now but I believe they get up to similar tricks with memory (and, no doubt, lots of other things).

 

[PTvor]

It depends on the product and where you are in the production life.

With things like CPU and memory chips you can charge a premium for the latest and greatest and you need to to cover the R&D and tooling costs. Almost always a fairly low proportion meets the top spec at first, full speed, all cores working, but the rest can still be sold profitably as a low cost version, two core, three core, lesser clock speed.

As the production process matures almost all the production qualifies as top spec. That's when they start labelling top flight product as lesser spec and disabling the cores etc.

Then there's the difference between factory testing, which is quite severe, and ordinary use.

There's nothing new in this. Before the war, Marconi sold U12 rectfiers guaranteed for 250V and U14 rectifiers guaranteed for 500V. They looked like exactly the same valve. They might all have tested to 500V or more and just been labeled differently. U12s might have been U14 dropouts. Would you want to take the risk of not paying the extra for a guaranteed U14 if it was needed?

 

[Big Pete]

anything thats a one off costs a fortune, in part because the setup costs are all on one part. The bent bracket that cost £170+vat, would probably only have cost £200+vat for 10 or 20 off, because most of the money will have been in the setup of the saw and the bender, although polishing time prior to chroming won't have helped.