plasma table idea

[CwazyWabbit]

You must be impressed with it if it persuaded you to splash out on the Hypertherm

What's the next project to be cut on it? And will there be more video?

[simonr]

I'm building a (hopefully) less scary Segway using BLDC Hub Motors and there are a couple of brackets & bits that need cutting. The big job I intend to use the Hypertherm for is to gut all the mounting brackets for my next Electric Vehicle. On the Freelander they were all laser cut out of 6,10 & 12mm plate - at some expense! Hopefully I'll be able to run these on it.

I'll post some more video of anything that looks cool!

Si

[CwazyWabbit]

Sounds like a good project to have a CNC plasma for, will look forward to the videos

[Lewis]

Can I buy one yet?

[simonr]

Can I buy one yet?

Soon!

I need to create a full bill of materials and make a forward mods to the design to make it easier to assemble. Once that's done, write some assembly instructions.

Si

[landroversforever]

Soon!

I need to create a full bill of materials and make a forward mods to the design to make it easier to assemble. Once that's done, write some assembly instructions.

Si

What sort of money are they likely to end up at (without a plasma)?

[robertspark]

Looks very nice Si. Last hurdles on mine. Don't think you'll be disappointed with the hypertherm it's just the capital cost shock

[simonr]

What sort of money are they likely to end up at (without a plasma)?

I reckon about £250 for the laser cut & folded bits. Then you need to source the box section (because you can make it any size you want), belts, pulleys, V rollers, motors etc yourself. I think you could source them (eBay / China) for less than £350. Mine ended up costing a little more because there was some experimentation with bits that didn't turn out to work very well! You also need an old PC + screen.

I've used a wireless keyboard with a trackpad (£19.99 from PC World) which doubles as a remote control for Mach3.

I think you could bring the whole thing in (excluding the Plasma Cutter) for under £600 if you were careful which bits you bought and where from. I intend to list the sources for everything in the Bill of Materials.

There are still a couple of bits I want to change in the design - mainly to make it easier to assemble. I did quite a lot of building & taking apart because I'd not (for example) left enough space to get a spanner in to a nut.

Once I'd figured it out, it took 7 hours to go from a pile of bits to something I could start wiring up. With the changes, I think I could reduce this to about 4 hours.

Si

[simonr]

Looks very nice Si. Last hurdles on mine. Don't think you'll be disappointed with the hypertherm it's just the capital cost shock

eBay was my friend!

Si

[robertspark]

Si / Barry, how have you wired your emergency stop?

Do you just wire it back to the breakout board port, or do you break the power supply (output) to the drives? (+ plasma torch)

I've got a few mushroom stop buttons (2), and they are basically serial wired, and normally closed.

I'm concerned about the smooth stepper because it can store a few seconds of process, I was wondering if I need a hard wired estop via say three 5v or 12v relays (I have 2 power supplies) + a torch

thanks for any advice

Rob

[simonr]

Don't worry about the smoothstepper. If it gets an EStop signal, it cancels everything in the queue.

I have the EStop output on the BOB connected to the enable lines on the stepper drivers. When Mach3 is in EStop mode, the drives are disabled -so they stop immediately.

The EStop button just connects to the EStop line on the BOB.

The BOB has a 'charge pump' which receives regular pulses from mach3. If the PC crashes, the pulses stop and the EStop output disables the steppers.

It seems to work pretty reliably. My Mill uses the same setup with SmoothStepper and similarly works fine.

Si

[discomikey]

Simon, i may need some brackets cutting for my dissertation, care to try it out on some 3-4mm steel? really impressed!

[Blanco]

(Quote function not working for me)..... Mikey that must be one hell of a dissertation, most people get away with a couple of ring-binders

[discomikey]

(Quote function not working for me)..... Mikey that must be one hell of a dissertation, most people get away with a couple of ring-binders

put it this way, I get to play with diggers and electronics!

[robertspark]

Just do a cad drawing and it's easy to import into sheetcam

Rob

[robertspark]

well, I've hit a snag ..... smoke signal from a drive, and despite carefully setting it up and bench testing it ( at some length ) when I went to run it this weekend, I cooked one of the drives.

under closer inspection of the circuit board for the TB6600 drives I bought, it seems that they have some interesting diodes in them that are rated at 3A, and the diode arrangement used is not as per the datasheet (hoping to have a closer look at the drive schematic to see i I have a bigger problem [i have an alternative TB6600 drive on order]. The drives are rated at 5A, and I had them set to run at 4.2A (which aligns with my steppers). the travel speed on the bench was impressive.

Not sure about running fuses on the drive inputs, logic would say yes, although the IC's were suppose to be protected from over-current, and the maximum rating of the drives is 5A, running 4A fuses / circuit breakers did not seem a good idea (at the time + still not convinced) given the trip / time to blow time the surge current could or would be above 5A.

se la vie

[robertspark]

Now I'm absolutely baffled!!!

replaced the damaged drive, but this time checked absolutely everything wiring wise:

found one error, basically the B+ was swapped with the B- (not convinced if this would have caused the issue as from from a search of the net the stepper would have just run in reverse given it was wired as a parallel wiring configuration).

However, my caution meant that I wired up the multimeter as an ammeter onto the electrical supply to the drive, so that I did not over set the current on the drive, but set it correctly to the 4.2A as listed in the datasheet.

My problem is the ammeter was only reading 0.8 Amp, and as soon as it was increased to about 1 Amp the drive went into fault (suspect over temp as the heatsink got warm). Consider that I was not driving the stepper at this time, just in standby mode.

The supply voltage was 42V

The drives use TB6600 chips which have a voltage rating of 8 to 42V (50v max), 4.5A (5A max), and a power rating of 40W.

Would you not expect the drives to be set to draw 4.2A regardless of the voltage? (although I must admit 4.2A @ 42V supply voltage is 176W, and the chip is only rated at 40W, but then I don't think there is a ~200W rated drive on the market unless I build one with some mosfets)

Any suggestions from electronics guru's out there?

Just ran them again and turned the voltage down to 36V, and the drive seems fine but running at about 0.86A (~31W) [measured on the drive supply input]

How are you getting on Si with your table?

Have a good christmas and great new year.

Rob

[simonr]

Sorry to hear you're having problems Robert. Personally I'd check that there is not a short in the stepper motor wiring. Swapping B+ & B- will make no difference. Check the resistance between A+ and A- and make sure it's similar to B. If not, either your wiring is wrong or the motor is duff!

Mikey - I'd be happy to cut them, but you'll need to wait a few weeks. I've been too busy lately to power it up even though I've just bought a new plasma cutter!

Si

[Cynic-al]

Is the current not linked to load on the motor?

On the reprap I was told to set the drive by motor temperature rather than current but I'm not 100% sure of the logic?

[simonr]

Any luck Robert?

While the Chinese stepper motors may say they are rated for 50v, I personally would not use them anywhere close to that. 42v is probably too close!

Higher voltages make the cost of the components higher - so is likely the first thing they will cut back on if they were trying to save a few pence.

Today for the first time I connected it all up with the Hypertherm cutter - and it works nicely! The Hypertherm according to the spec ought to have been able to run on 230v single phase. However, when connected as per the manual it just showed an under-voltage error. It seems that the cutters were made in two versions. One is 108 to 600v single or three phase and the other is 415 to 1000v single or three phase. You can tell by the rating plate. If it says Max Voltage 1000v, it's like mine and if it says 600v it will work on mains.

I connected it up to my Inverter, originally bought to run my mill, since converted to single phase. It's rated at 7.5Hp and runs it happily up to 40A.

The results are pretty good! It has a Pilot Arc so will cut rusty, dirty steel just as happily as clean. The kerf is about 1mm compared to 1.5 for my old plasma which only makes a difference cutting very small features. I need to experiment with speeds & current - but overall I'm pleased with the cut quality.

I'll stick my old plasma in the For Sale section in the next few days once I've taken some photos!

A good conclusion to a good project!

[robertspark]

Yes, I've had some luck.... sort of, I've got some new replacement drives from another manufacturer, the wiring was all fine but corrected the B+ / B- swap (multimetered everything).

No one seems to rate these TB6600's other than their smoke output is impressive.

ahh well, I have a plan (but it'll take another month) [i'll keep you posted]

I've got the new drives working fine for the moment, just a little slower with 36V (I actually killed 3 drives that were all fed off the 42V supply so I suspect it may have been the back EMF that did it given I was running them at a fair speed, the one (z-axis that I had on a 24v supply by chance is fine [42v power supply does not provide enough current to run all 4 drives, or so I thought])

I'm just trying to sort the welding out on my table now (I was not going to put legs / a frame on it and just stand it on the deck but had a thought.... given I've got a rolling chassis in the garage at present that I'd put some short legs on it and a frame that can be assembled with an angle iron bed, and run above the chassis.... I've also found a set of (ex-trolley) wheels for it, nope I did not commandeer the trolley!

still want it easy to assemble and disassemble which I think it will be.

Also doing the end of year / once a year garage + outside office clearup at present

Good to hear the hypertherm is proving to be a good choice, which one did you go with? Powermax 1000? 65?

I saw a 1000 go for good money on ebay a short while ago, but thought that it was 3-phase hence not to my available power supply comparability, but I think there is a 230v one available just not for the european market I don't think. I think you can also get "fine cut" consumables for them too, although I think they limit your cut depth.

Suggest have a search for "Jim Colt" + "hypertherm" on one of the other cnc / practical machinist forums, he does a number of good posts, and also responds to specific questions and advice, seems to know his stuff, there is also a bit on youtube about his own setup.

Rob

[simonr]

That's a bit more positive!

I think to store mine, I'm going to attach 4 pulleys to the roof joists and hoist it into the roof void. I can then lower it on to a folding frame when it's needed. It only weighs 15 to 20 kg so doesn't need more than nylon cord to hold it.

The TB6600's are OK, just not at the max voltage! They are exactly what I'm using at 24v - and they deliver sufficient speed (for me at least). The difference I suspect is my table is light weight, so it doesn't need much torque to accelerate any axis.

Personally, I wouldn't run any of the Chinese drivers at more than 36v, regardless of what they claim! If you want higher voltage, use something like a Gecko Drive These are what I've used in my Lathe. It's rated to 80v and will run full current at 80v all day long. However, they are comparatively expensive!

Si

[robertspark]

Been looking at the leadshine AM882 (or AM882H) or their replacement the EM806 (bit pricey though for the new ones at double the AM882, and the AM882's are 4x the TB6600's...), hopefully I won't kill another one.

(more things to fiddle with those leadshine drives than a megasquirt .... almost anyway)

The new TB6600, seems to follow the Toshiba datasheet much more closely:

Old drive (highly not recommended! [especially with 3Amp diodes and I was asking for 4.2A from the drive settings...])

http://www.soonwell.com/ebay_file/new_pic/HY-DIV268N-5A-6.jpg

http://www.ebay.com/itm/CNC-Single-Axis-TB6600-5A-2-Phase-Hybrid-Stepper-Motor-Driver-Board-Controller-/251224738311

(don't be tempted to buy them at that price, link just for a full set of pictures + description!!! [again don't recommend at all!!!])

New drive (not sure about recommendation yet):

http://www.haoyuelectronics.com/Attachment/TB6600_module/HY-TB6600-Module-1.jpg

http://www.hotmcu.com/tb6600-1-axis-stepper-motor-2phase-driver-board-for-cnc-router-p-56.html

But the new ones will hopefully be happier at 36V, although I've decided to stop fiddling with them until the rest of the table is welded up....then have a go at cutting some plate and see what happens.

Rob

[simonr]

I just ordered one of these:

http://www.ebay.co.uk/itm/5mW-Red-Cross-hair-Pattern-Laser-Module-12mm-3V-Operation-/151458324425?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item23439e9fc9

A laser cross-hair projector. It was only 5.50GBP delivered - so worth an experiment.

Obviously, the plasma torch is in the way of it projecting at the cutting point - but I figure that if I angle the laser and mount it next to the torch, such that when the torch is lifted say to 40mm, the cross hair will be spot on.

It runs off 3V - but I only have 5v & 24v in the controller. If I connect it in series with a 1k2 Resistor it should be about right on the 5v feed.

Si

[CwazyWabbit]

Well it does say it'll handle 5v max .... although I guess that might shorten it's life a bit

PS your pc power supply should have 3.3v available