Tech Spam thread - because 1/4" BSP gets 5 hand spans to the jiggawatt

[Nominal]

7 hours ago, Bling said:

What type of bolts would you use on critical car parts? High tensile 8.8 suitable? Any particular coating to avoid / go for? One example is steering connection to rack, thread has seen much better days.

Rack connection will just be a pinch bolt I would have thought, not a place where 8.8 is necessary?

If you are interested, this book is a good read

 

[Bling]

Yeah pinch with the bolt sitting in a slot. Probably not much price difference but just wanted to make sure I was on right track and that the bolt wouldn't be something even stronger given location. Not worried about overkill on bits like that. 

[UTERUS]

The price difference it's so little that I use 8.8 everywhere, unless I've decided to use 12.9 cap screws.

[RUNAMUCK]

^^^^exactly what sparky said. 

Up until a few months ago, I didn't even know Blacks sold cheese bolts. (Low tensile) 

Just go to blacks, and when you're paying tell them [my place of work] cash sale please @Bling. You'll get a pretty decent  deal. I havent been asked for my staff ID for years when doing that. But if they ask say ah fuck it's in the truck at work.

[Bling]

We use Konnect at work so getting bolts isn't an issue, thanks for the offer though @RUNAMUCK. I'll probably find a bunch I need first and throw them in with a work order. Failing that i'll just grab a Champion bolt pack while out and about, cheap enough.

[RUNAMUCK]

My query for tech spam is,

From.which point is the length of PK belts measured? Ie, from the trough of the Vee ribs, the top of the ribs, or the flat back of the belt?

I need to buy a belt, and I have a very limited range of adjustment. I have all the cbf's to go back to the shop 25 times to get the right thing.

[Mof]

Hey now I've learnt something too

"The effective length is a measurement of the entire length of the Micro-V but it is measured at the cord line versus the outside circumference of the belt"

http://www.mechanexpert.com/how-to-read-a-micro-v-belt-pk-number-a-technical-tip-from-gates/

[RUNAMUCK]

So the cord line must be the centre of the belt then? 

Or the inside circumference, plus the outside circumference divided by two.  

Maybe not quite. But yeah.

[h4nd]

Anyone else have that problem where a windows 10 laptop goes back to sleep too fast even when the power settings are changed (happens when using external USB keyboard)?

I've found a solution if anyone needs it.

[fletch]

6 hours ago, RUNAMUCK said:

So the cord line must be the centre of the belt then? 

Or the inside circumference, plus the outside circumference divided by two.  

Maybe not quite. But yeah.

Get one that's too long next time you go to nick a part, or an old one from somewhere and cut it. 

Wrap it round the pulleys and trim it to the perfect length and take it to supercheap and hold it up to all the ones they have to find a match

[governorsam]

9 minutes ago, fletch said:

Get one that's too long next time you go to nick a part, or an old one from somewhere and cut it. 

Wrap it round the pulleys and trim it to the perfect length and take it to supercheap and hold it up to all the ones they have to find a match

cut it to length and measure it.

thats the belt number/length  you need.

saw it on skid factory somewhere.

[peteretep]

Hey guys I have a work related question, I am designing a machine that applies hot glue to cardboard. The cardboard is moving pretty fast so I need fast acting guns & associated equipment. We have an automatic glue gun that we often use with a solenoid that claims to be able to cycle 8000 times/minute, or 133 times/second, or once every 7.5milliseconds, with a minimum bead deposition time of 2milliseconds. How does the 2ms relate to the 7.5ms? It takes (7.5-2)/2=2.75ms to open, 2ms minimum open time, then 2.75ms to close?

 

An alternative product can cycle 120 times per second, or once every 8.3ms, with a minimum open time of 5ms, so does that mean it takes (8.3-5)/2=1.65ms to open, stays open for 5ms, then takes 1.65ms to close? So its faster to operate between positions, but must stay open for longer once open?

 

The outputs from the PLC are high speed, 0.5ms on, 1ms off

 

timeline for gun 1

0 - tell PLC to operate solenoid

0.5ms, signal received at solenoid, starts to open

3.25ms, solenoid open

11ms, solenoid has been open for 7.75ms, it will take 1ms to send signal to close, so send signal from PLC to high speed output

12ms, solenoid starts to close 

14.75ms, solenoid closed

 

timeline for gun 2

0 - tell PLC to operate solenoid

0.5ms, signal received at solenoid, starts to open

2.15ms, solenoid open

9.9ms, solenoid has been open for 7.75ms, it will take 1ms to send signal to close, so send signal from PLC to high speed output

10.9ms, solenoid starts to close 

12.55ms, solenoid closed

 

so if I never need to operate less than 5ms, then gun 2 is arguably the better choice? Or have I mixed up how this works?

[kyteler]

To my mind the 7.5 cycle time is between close and open and would remain static irrespective of whether the open time ran 2.0 or greater. You could include the signal transmission time in that 7.5 but I would think it safer to have that as a factor non inclusive. 

If that makes sense. 

Keep in mind that I'm an idiot. 

[Testament]

physically what are the glue guns, how do they work? are they piston things with variable stroke, is there a pressurised supply of glue behind them, or mystery under the blanket operation?

until measured with a high speed recorder or something I would probably question the accuracy of most of those timings anyway - so may just have to take a stab at it and adjust from observed production result anyway

[locost_bryan]

On 08/11/2019 at 06:58, Nominal said:

Rack connection will just be a pinch bolt I would have thought, not a place where 8.8 is necessary?

If you are interested, this book is a good read

 

Commonly used Whitworth or B.S.F to SAE / A.F (inches across flats) sizes and conversions to metric and decimal inch dimensions.

http://www.baconsdozen.co.uk/tools/conversion charts.htm

[peteretep]

1 hour ago, Testament said:

physically what are the glue guns, how do they work? are they piston things with variable stroke, is there a pressurised supply of glue behind them, or mystery under the blanket operation?

until measured with a high speed recorder or something I would probably question the accuracy of most of those timings anyway - so may just have to take a stab at it and adjust from observed production result anyway

there is pressurised glue in line feeding the guns, the times relate to the pneumatically operated solenoids which open the valves for the pressurised glue lines. We can measure everything pretty accurately as the cardboard is moving via servo with encoder feedback. Problem with that is we need to buy a machine to test it, costing $25k

[mjrstar]

Open vs close times may differ on a pneumatic solenoid operation due to the volume of the shuttle (unless balanced shuttle). Even then they wouldn't be exaaaacccttly the sane. 

 

It wouldn't surprise me if the times listed are plus minimum open deposit time. More like a design duty of the solenoid rather than something useful to start your calculations fron.

 

That sort of rate may also beat the daylights out of the needle seal and piston.

Also does a change in viscosity effect the actual cycle rate say a thin cold glue could be effectively be easier to apply quickly than a thickish hot glue. 

We use nordson glue gear (at a much slower rate) they seem reasonable, with the odd failure. 

 

[NickJ]

Anyone know a supplier for brake liner adhesive in NZ?

[Mof]

Brake linings?

Try Diggers Brake and Cable 

He might be able to sort you out 

[peteretep]

16 hours ago, mjrstar said:

Open vs close times may differ on a pneumatic solenoid operation due to the volume of the shuttle (unless balanced shuttle). Even then they wouldn't be exaaaacccttly the sane. 

 

It wouldn't surprise me if the times listed are plus minimum open deposit time. More like a design duty of the solenoid rather than something useful to start your calculations fron.

 

That sort of rate may also beat the daylights out of the needle seal and piston.

Also does a change in viscosity effect the actual cycle rate say a thin cold glue could be effectively be easier to apply quickly than a thickish hot glue. 

We use nordson glue gear (at a much slower rate) they seem reasonable, with the odd failure. 

 

Nordson is the most common in NZ, mostly as they have the best service really, just screw you over on pricing, plus everything is imperial

 

and yeah, does change depending on viscosity, but I dont have that info and I trust that whoever helps us set up the machine will set it for best results.