Messages

221

General Mach Discussion / Re: Physical buttons for plasma

« on: January 27, 2016, 08:12:51 AM »

Hi Hood - Hopefully I've worded this carefully enough to avoid a good kicking from Terry   - but here goes...

I kinda left it vague because it depends on what you want to do and what your THC can do. We can wax lyrical about speeds but ultimately you'll probably end up slowing Z down to match the capabilities of any (including mine) "budget" THC. Spend a few grand on one and the game changes entirely (so I'm told).

To give some perspective though, here's what the tables I've built in the past did (with my THC). I'm sure there are better (and worse) tables out there so I'm not saying this is good or bad - just what they were.

My THC samples at 1KHz. If it's set to do 1 step pulse per sample (which it is) then it can obviously drive the Z at 1000 pps. The Z was rack n pinion with a steps per of 42.44131816 steps/mm.

so Z moved at 1000 / 42.44131816 * 60 / 1000 m/min i.e. 1.4m/min.

Lets say then that it's cutting at 6m/min. It can therefore handle a slope of 6/1.4 = approx 13 degrees. I've yet to find this to be inadequate. Of course it means it couldn't cut corrugated - but it wasn't designed to - it was simply designed to cope with "typical" warpage.

With the Z I see no problems in setting an extremely high accel with the setup I propose as there will be little mass to it and the servo should  be more than capable of handling it even direct drive.

Remember with THC the Z accel is not used so it's irrelevant.

222

General Mach Discussion / Re: Physical buttons for plasma

« on: January 27, 2016, 05:36:20 AM »

Acceleration in THC controlled Z is not missing by fault, it's missing by design. Trying to put it back is missing the point.

The reason THCs have no acceleration is twofold. Firstly, if you have need or time or room to accelerate then you're already hopelessly out of position anyway so the game's already over. Secondly if you accelerate you also have to decelerate. THC MUST be able to CHANGE direction as quickly as is possible. The only way you can do that is to have NO deceleration ramp. If you have no deceleration then you CAN'T have acceleration.

Re: Speed design of Z: Let's assume your Z can move WITHOUT accel as fast as the fastest feedrate in the XY plane you'll ever need. In that case your system can follow a 45 degree slope in Z (maximum).

First question is: Do you need to be able to do this? - adjust accordingly.
Second question: Is your THC response fast enough to do this? - adjust accordingly.

223

Tangent Corner / Re: Electro-Punch design

« on: January 26, 2016, 11:42:38 AM »

No worries. Whatever you do though - we're gonna need a video when it's finished 

224

Tangent Corner / Re: Electro-Punch design

« on: January 26, 2016, 10:05:29 AM »

Hey Russ - take a look at this...

<a href="http://www.youtube.com/v/yKAq-zS77hg?hl=en_US&amp;amp;version=3" target="_blank" rel="noopener noreferrer" class="bbc_link bbc_flash_disabled new_win">http://www.youtube.com/v/yKAq-zS77hg?hl=en_US&amp;amp;version=3</a>

if you look at the 1:50 mark, they're PULLING the wire through the straightener a length at a time and then chopping it whilst its stationary.

Ian

225

General Mach Discussion / Re: Physical buttons for plasma

« on: January 26, 2016, 08:26:48 AM »

NOW why Modbus Ascii ?? I do not have a clue only a guess.  Ascii uses a CRC check of teh code to insue it is what it is. I GUESS they wanted that type of secure mode to talk to a high end machine and it just trickled down in technology. IT DOES make it a PAIN to work with for low end stuf.

Hi Terry - we've discussed this before - I guess you've forgotten - check our email conversations.

Modbus ASCII actually uses an LRC whereas Modbus RTU uses a CRC. Moreover the LRC is only 8 bit whereas the CRC is 16 bit. The end result is that as far as error detection is concerned RTU is the WAY more robust than ASCII.

[Differences Between the Two Concatenation Operators]

226

VB and the development of wizards / Re: Doing something wrong

« on: January 26, 2016, 05:06:41 AM »

Ah the stupid overloading of the + op in VB and the like.

Here's the official word from MS

Differences Between the Two Concatenation Operators

The + Operator (Visual Basic) has the primary purpose of adding two numbers. However, it can also concatenate numeric operands with string operands. The + operator has a complex set of rules that determine whether to add, concatenate, signal a compiler error, or throw a run-time InvalidCastException exception.

The & Operator (Visual Basic) is defined only for String operands, and it always widens its operands to String, regardless of the setting of Option Strict. The & operator is recommended for string concatenation because it is defined exclusively for strings and reduces your chances of generating an unintended conversion.

Here's what that actually means:

Look - we screwed up - ok?. We made TWO concat operators because we're dumb. Worse we made one that works always and one that sometimes doesn't. Just use the & ok.

227

Tangent Corner / Re: Electro-Punch design

« on: January 26, 2016, 04:50:51 AM »

I reckon you're on the right track there Russ - looking good.

Still tryin to draw like Ian .... some day. 

Those are great drawings. Is that Rhino you're using?

228

Tangent Corner / Re: Electro-Punch design

« on: January 25, 2016, 12:32:39 PM »

Cheers Brett

<sarcastic-mock-teenage-voice>
  Yeah Terry - it's like a scheme suggestion not a design.
</sarcastic-mock-teenage-voice>

 

229

Tangent Corner / Re: Electro-Punch design

« on: January 25, 2016, 11:06:38 AM »

Hey Russ - how about something like this?

230

General Mach Discussion / Re: Physical buttons for plasma

« on: January 23, 2016, 06:28:40 AM »

No worries. Although a divider etc. interface is dead easy to make, I just decided I didn't want to go near the H&S/legal nightmare of selling them.