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Messages - AdrianH

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31
I did have trouble with the controllers, I could blow then very easily, that was sorted by making my own filter network on the motor cables using back to back diodes, MOV's and caps.  Also removing some earth loops I had placed on the system by trying to earth anything I could.

Not blown a chip since.

Not the same board as you link to there, but probably similar.

fuzzy picture here it sits in an extruded aluminium box.


Adrian

I have extraction, used for welding.

32
Just found the information the Z stepper is NEMA 17 Stepper Motor JK42HS 1.8° 42x42mm [JK42HS40-1704]

Adrian

33
If you wish to see the project of building it then:

http://www.mig-welding.co.uk/forum/threads/cnc-plasma-cutter-start-of-bits-buying.52149/

The controllers are TB6560AHQ based the steppers on X and Y are 23HS9430B
X axis is 20 steps per  mm, and Y, which is my problem is 100 steps per mm as I am driving a 4mm lead ball screw directly at 1/2 stepping, it was more reliable and faster than 50 steps per mm with full steps.

Yes my Z axis is threaded rod rather then try and get a ball screw which was 5 inch long.

Adrian


34
Your feedrates are very (TOO) low.... plasma is all about acceleration too.... becuase the cutting current is constant and you need to change direction, you need to be able to have you machine accelerate and decelerate its axis as fast as possible. or you will end up with rounded corners and lots of dross.

How are you driving this plasma table?

What ampage stepper motors are you using?

What stepper drives are you using?

I started off with a load of ..... well not very good stuff and you end up buying twice to replace out the poor stuff to get the cut qulity where you want it.

Kind of like the old addage.... "measure twice, cut once"....... "design once, buy quality, never look back".

The 900mm per min is typically my G1 cut speed.

I just can not get a lot faster so it is not possible with my set-up size 23 steppers on X and y and type 17 on Z.  Currents around 3 Amps X and Y and just under for Z, all from 24Volts supply and control max rating is 24Volts.  Again Chinese set up cira £60 purchase.

I am aware it is cheap but it will have to do.

Table size is 760 by 460 ish mm.  All home made and very, very budget.

I will have a read through the information you have provided, yes I have the manual for mine rated voltage is 100 Volts in the user guide.

The input is 4.7KVA at rated output of 40 Amps, so really wants a 22Amp supply but duty cycle is 60% at that those figures.

I need to run the machine under 25 Amps if I can reasoning is it is on a 13 amp socket.

220 Volts x 13Amps = 2860 KVA * 0.85% efficiency I have 2431 KVA available, 100 Volts rated so around 24 amps cutting current.

I can push a bit higher but the garage supply which is really only rated at 20 Amps has to power PC, lights and a compressor.

Thanks for the rest of the information I will read through the posts you have listed, thanks for that.

Adrian

p.s. even your modest feed rates are to fast for me, it is a case of do what I can for fun.


35
Hello Robert, thanks for your input.

The figures you were quoting was something I have failed to find, so I can base my dead band initially from that.

I use a drag tip at the moment and these are really only cheep things so not made to any great spec,  I will be using my lathe to modify these to remove the castelations and give more of a point to the nozzle to allow me to get a variation in height.

But first will run as standard with a few normal tips and measure arc volts if I can to see where it runs now, then try to set up with THC to get back around that same level.

Knowing the 1 volt per 0.5mm will help a lot.

I guess it will also depend on nozzle diameter, speed and width of cut/thickness of metal.  Could you point me to the doc if possible.

At the end it may be a complete failure with my set-up and approach, but I am still having fun on the journey.

Adrian

36
Hi beefy;

I guess I like to play electronics, time is cheaper than money and I seem to learn a lot in the process.  None of my stuff is for profit, just to help me make more things.

If at some point in the future I had a commercial thing to do it would be a different matter.  I have a simple way to change my dead band, my travel speed is slow circa 900mm per min at the moment possibly up to 1200 or 1500 if I get this to work, still very slow in comparison to commercial equipment.

I enjoy the challenge also semi retirement helps.

If I get it to work I will try to do a video.


Adrian

37
I can pierce off the metal, only by a mm, two at most, so I tend to do that then drop after delay to in theory be 2mm under the top of the metal!

That way if the metal drops by up to 2mm it is still in contact, if the metal rises more then the torch floats up with it, but as I say at a cost.

thanks for your input it us appreciated.

Adrian

38
Hi again Dave;

I have figured a way to change the dead band on what I am trying, quite easy when I stopped trying to think to hard.

I will explain what I am trying to do in very simplistic terms and please do not laugh as my set-up is purely as a hobby, keeping the grey cells active and a bit of fun.

I picked up one of the Chinese Cut40 plasma cutters, It is still at the limit of the mains supply in my garage and as my hobby is general metalwork I could not really justify a lot of hard earned.

After a few months I built a CNC frame for it, got a straight torch head for around £30 and started to have fun, the whole lot including plasma cutter probably cost me less than £500 and a far bit of time.

But I use it as a drag head across the metal, the Z axis has a floating section and the weight of the head keeps the drag tip on the work, but this slows every thing down, acceleration and top speed etc.  It also means it will show any slop or flex in movement, my circles are not perfect circles etc.

So I have started to think how to improve it and the only way I could think of was to lift the tip off the work piece and for that I need THC, so ultra cheap THC control using a 4 input Voltage comparator project has started.

It would be ludicrous to go out and buy a £200 plus THC controller to work with a £180 Plasma cutter!

Adrian

39
Thanks Dave for the feedback, yes should be Z I talk about not X was getting late.

Also thanks for the 2 to 4 volts dead band, that was an uncertainty for me.  I guess it could be adjustable on some.

Adrian

40
Sorry the Topic should read
Question on Plasma THC control to users of this facility

I must have left it to long since posting and can not edit it now.

Adrian

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