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Member postings for John Stevenson

Here is a list of all the postings John Stevenson has made in our forums. Click on a thread name to jump to the thread.

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Thread: true Space
21/08/2009 13:35:16
Gordon,
I couldn't see a way to get  true 2D engineering drawings from this, I may be wrong but I couldn't find an easy way.
There are quite a few of these 3D rending packages out there, mainly related to producing games renderings and animations but not aimed at 2D precision work.
 
The Alibre offering is very good, $99 gets you version 11.2 Standard package, you also get the option to buy support which 'may' allow you the upgrade to v12 when it comes out at a discount, I don't know.
 
I have bought the $99 version and it does do what they say, You can draw in it just as 2D or do the 3D model and the 2D drawings are done automatically, update the model and the drawings update.
 
All these packages have a steep learning curve but Alibre do help with free tutorials both inside the program and web based. They also have a well supported user forum which is also very helpful.
 
The free Alibre Design Xpress is good but for the extra it's well worth upgrading.
Alibre allow you to use this on 3 computers with no strings attached.
 
 
One think to watch though with these very powerful 3D packages is that it's very easy to design shapes that can't be machined either easily or even at all

John S.
Thread: Really useful?
20/08/2009 08:44:53
I think mine has to be the digital calipers.
Internal, external, depth and step measurement in 0 - 1, 0 -2, 0 - 3, 0 -4, 0 - 5, 0 - 6" and the same in metric.
 
And if you buy a cheap pair and grind the jaws up you now have precision odd leg calipers .
 

John S.

Edited By John Stevenson on 20/08/2009 08:45:29

Thread: Metric vs Imperial - Practical or Traditional?
17/08/2009 19:27:35
Posted by its-smee on 17/08/2009 09:35:49:
I assume JS that you are a founder member of the flat earth society.  If you can't make constructive comment - then don't.  Do not drag this forum into a slanging match like so many other forums.  If you wish to make negative comments then I suggest you go elsewhere
 
 
 Why would you want to divide a metric or decimal measurement by 3 ?
Base of metric and decimal is 10
 
None of my machines imperial or metric  has a scale or dial on it that can be divided by 3
 
And a 1874 quote by Rankine is hardly relevant in this day and age and again as a point of interest I left the flat earth society when I sold the Reliant, it wasn't you that bought it was it ?
17/08/2009 08:59:02
Another example of the flat earth society.
 
John S.
Thread: Flashing adverts on Forum
16/08/2009 14:46:57
Thank you David, one point I have noticed  with web designers is that the word simple is not in their vocabulary.
 
Most web designers are pyrotechnic engineers in disguise .
 
John S.
Thread: Subscribers only
16/08/2009 12:40:43
On the back issues of MEW I was doing a search on some CNC related articles and found that issue 140 is 134 duplicated and issue 143 is actually 142 duplicated.
 
Any chance of 140 and 143 being corrected.
 
Nice touch this as it certainly speeds up searching, what are the plans on how far to go back ?
 
John S.
15/08/2009 20:11:41
Posted by Dave Jones 1 on 15/08/2009 19:49:39:
i see the back issues for MEW have been put on (i only subscribe to MEW btw).  I have

Where ? navigating this site is like trying to read Ower Gerts mind, you spend hours only to get nowhere <g>

John S.

Edited By John Stevenson on 15/08/2009 20:13:25

Thread: Flashing adverts on Forum
15/08/2009 19:05:20
Same in Firefox, download an add-on called Add Block Plus and they all go away.
 
However that's not really the answer, the advertisers pay to advertise on the site and if everyone switches them off they are not getting any value at all.
 
No the onus is on the web site to make it readable instead or suffer loss of traffic.
 
One banner on the right hand side says "Support our Partners" how can i support them when it doesn't allow me time to apply a truss.
 
John S.
Thread: Sigma Jones/BCA Jig Borer
10/08/2009 13:45:30
There was a guy advertising on the home workshop ads page at:-
 
http://www/homeworkshop.org.uk
 
Who was making these in batches, not seen the advert lately but it may pay to put a wanted advert on there and see who bites.
 
It's a free advert page, very popular, gets loads of hits and even David Clark and the webmaster here use it .
 
John S.
Thread: Index to Issues of MEW ?
04/08/2009 20:30:00
Thank you for that David, However that link isn't available from the home page.
 
http://www.colinusher.info/index.htm
 
John S.
04/08/2009 09:27:00
Used to be one on Colin Ushers web page but looks like it's been removed ?
 
John S.
Thread: To Web Master
03/08/2009 00:00:04
Keith,
Can you do something about the flashing adverts on the side, either get them to merge or give them more time before they change.
They are really infuriating and degrade the site even the dog is having epileptic fits and I have to keep throwing him in the bath with the washing.
 
John s.

Edited By John Stevenson on 03/08/2009 00:00:15

Thread: Phase Converter Which Type?
02/08/2009 23:54:53
Aidan.
You are correct with your understanding of a static converter, they are a fudge.
 
The rotary once running can be left running and you start and stop the mill motor on it's normal controls. the rotary converter doesn't replace the machine controls more live it supplies your 3 phase electrical supply.
Can be noisy but they are needed for things like 2 speed motors which require a true 3 phase supply.
 
Digital Phase converter or Inverter or VFD depending on who's terminology you use take in single phase and spit out 3 phase but at 240 volts and for this you need a motor that can be rewired from star to delta. Basically the terminal box on the side of the motor needs 6 terminals.
 
3Hp or 2.2 Kw is about the maximum you can get on single phase and a quick look in a manual rates one of these at  11 amps input current.
 
One advantage of these inverters is that it's possible to get variable speed and so save changing belts as much.
 
They also have the added advantage of soft start and breaking and are a lot better for the motor, they also monitor the motor and provide overload features far better than the old thermal trips as fitted to the push button startes of old.
 
John S.
Thread: Milling Machine Low Speed Torque
01/08/2009 23:43:00
After fitting well over 300 plus inverters over the years and working closely with IMO, Telemechanique and Yaskawa technical let me explain a few truths about how these work and how the ratings are arrived at.
 
First how they work, they take AC in, turn it to DC and chop it into pieces, organise it then change it back to AC but 3 phase. Its how the chopped up bits are organised that's the magic bit .
 
Now the BS part. the all singing all dancing feature is called Vector drive, where this differs from the old type of variable frequency drive is that it monitors the load and when it drops it bungs a bit more down the line to play catch up then drops back as it does.
 
The next bit they all push is Constant Torque and we need to explain a bit more about these chopped up bits. Technically at 50 Hz [ in the UK ] 240 volt single phase in with spit 240 v out 3 phase but as you drop frequency it drops voltage so at something like 15 Hz it probably putting out 60  to 70 volts AC three phase.
 
Now they say it will produce constant torque at all speeds, what they NEVER tell you is that torque is based on output voltage so at 50 Hz you get full torque of whatever the motor is rated at.
At 15 Hz you get full torque based on 60 to 70 volts, so a 3.3 actual reduction but in theory Constant Torque .
 
Most machine tools get torque by gearing, a 2:1 reduction doubling the torque but this cannot happen electronically, only mechanically .
 
 
What happens in practice and I can prove this as I have a CNC  X3 here that has a two speed direct belt drive and inverter, no names but well know torque vector all singing all dancing. At low speed 20 Hz in the high range which equates to about 1,000 rpm when the cutter enters the work it slows as the Vector drive part kicks in and speeds the spindle up to compensate for load.
 
However the feed isn't linked to the vector drive and that slowing down doesn't take into account the feed has remained constant with the result it's chipped, rubbed the cutting edge and we are now playing with half a deck.
 
 
It can be over come but it's acase of working on available power and gear ratio's, I have even got the technical side agreeing with my findings.
 
Whilst a inverter drive is nice and to be honest I wouldn't be without them it's not the answer to a straight swap on something like the small Chinese millers with DC drives which have inherently more torque at low revs anyway .
 
 The above is a very advanced technically description of how these things work, for a more laid back description you need a Heavy Goods license.
 
John S.
 
Thread: spin indexers
30/07/2009 19:28:55
Just to point out that the Spin Indexer as sold by Arceurotrade, is to a unique design that can hold ER32 and 5C collets on the same tool with no modifications.
 
Given that the 5C series works in fixed sizes and the ER system works over a 1mm or 40 thou range per collet with no gaps this gives you two bites of the cherry depending what collet system you run.
 
Another plus is the ER series is the only work holding and tool holding system readily available so it has a spin off for the people who share collets between a mill, lathe and attachments.
 
John S.
Thread: collet thread
24/07/2009 23:17:34
http://www.webbikeworld.com/motorcycle-tools/thread-file/

John S.
<< First < Prev 248 249 250 251 252 253
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