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Member postings for Mark C

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

Thread: New PC.
01/01/2017 21:50:45

I needed a decent spec laptop a while back and got one from "Workstation Specialist" **LINK** on the recommendation of my software vendor. They will build to order and support is second to none. They built my laptop to suit the software and and my area of practice and it has been faultless in all respects.


01/01/2017 17:16:50

Solidedge should provide some advice on build spec for specific applications. When I get new machines I always check compatibility with Solidworks on the tech support portal to ensure I am getting a suitable machine rather than just getting a machine with lots of bells and whistles...


Thread: Then reality goes and spoils it...
31/12/2016 17:42:57

I think I will wait 'till next year and buy a laser sintering printer from China, they should be selling them off cheap by then if Trump gets really protectionist! A nice 12 micron machine with a few free buckets of different media thrown in would be good...


Thread: Waterjet Cutter Slices Through an SLR...
28/12/2016 20:57:44

The last time I had any involvement with cutting optical glass, the medium used in the water jet was garnet. It is introduced into the jet and the abrasive action does the rest.


Thread: Odd Problem with Lofted Solids
27/12/2016 19:23:13

Yes, I really should wear my glasses ALL the time on the PC...

I did in fact mean Martin, sorry guys!


27/12/2016 19:09:11

Jason, that is an interesting workflow. It is almost the same as mine with some extra stuff added in - I assume, dictated by the software. If I can work out how to make video clips I will re-do the model in SWorks for comparison. I notice you did not add dimensions, I did not add them either as I did not know them and it would have added little to the picture I posted. Would the model be parametric if you had added dimensions?


27/12/2016 16:31:30

Neil, probably not much help other than interesting from a workflow perspective, I managed that solid (I think it is the same as yours bar the dimensions) in 4 moves - check the part tree on the left...

neil part.jpg


Thread: Quill bearing temperature
27/12/2016 16:12:56

John, Instead of being childish, could we not manage a sensible discussion just for once? You are keen to inform everyone about your wide and varied work experience in R&D.


27/12/2016 15:53:22

Ah well, so much for sensible debate. If only I had been born with the ability to insert a digit into the end of a machine spindle and be able to sense not only the operating temperature of the bearings, but more importantly understand the thermal behaviour of the entire assembly.... and all without making any assumptions at all!

As a mere mortal, I have to make do with measurements of prototypes and thermal numeric modeling (which I would contract out as it is way past my basic skill level).


Thread: Take a look?
27/12/2016 12:38:11

One HUGE can of worms....

Take a look at the UK.GOV page - at the very basic level, it just means that the product conforms with all relevant requirements. Other than that, it is just a major PIA and a good excuse to add cost



PS. if you are involved in manufacturing and don't want to have a new year locked up in a padded cell foaming at the mouth, don't follow that link!

Thread: Quill bearing temperature
27/12/2016 12:14:16

John H,

I would agree with all you have mentioned.

I might add to that by suggesting a possible modification you might be able to try; As long as the drive pulley (splined spindle driver) is supported on it's own bearings, you might be able to apply the spindle pre-load through cone springs. This would provide a more linear loading with respect to temperature change (as long as the top inner race is a sliding fit on the shaft). I would look at the side loading before committing but it does look unlikely given it is a light machine.

The spindle design (although similar to a Boxford of which I have two) is really a poor design for a machine tool. As with "all" modern spindles, the base bearing should be a double arrangement to alleviate the problems with thermal expansion with the tail of the spindle being supported by a sliding radial bearing allowing free expansion of the spindle without detriment to pre-load or cutter position.

This is an interesting subject if you are interested in machine tool design and well worth reading about if you have some spare time! It has also been "discussed" on here at least once before with the same unhelpful "assumptions" made by John W regarding thermal behaviour. In the case of this type of design, the pre-load will be the result of finding a "one size fits all" compromise for the type of service the machine designer expected it to see. This would most easily be "standardised" by setting a torque loading for the spindle with the variables removed (drive pulley or belts etc.) It would be interesting to know if the machine service instructions give a torque value for the spindle?


Thread: Odd Problem with Lofted Solids
27/12/2016 00:16:40

"Hmm, so is an arc made up of lines of infinitesimal length?" Certainly small lines especially if it is a cheap system!!!


26/12/2016 21:14:47

I like the idea, a bit like straight lines being arc of infinite radius... and anyway, we have surfaces of zero thickness so why can't you expand the idea with some lateral thought? Apart from all that, apparently we live in a world of 3D printing = solids made up of sequential surfaces with some thickness, although they are trying to get them closer to zero!


Thread: Cheap 3 in 1 tig welder - any one used one?
23/12/2016 01:23:36

Not exactly cheap, but I bought one of these from R-Tech two years ago **LINK**. It was the biggest machine I could get at the time on 240V single phase. When Bodge mentioned the machines have come down in price, I would add that they have also come a long way technology wise also. The machine I have is only capable of DC (you need AC to work aluminium) but the computer controlled welding functions make it almost impossible to make really poor welds with it for most day to day repair/fabrication work. They refuse to let you stick the electrode to the work in MMA mode, MIG is a doddle and TIG is nice and smooth (although lift tig takes some practice). I have welded all sorts of machines together with it, they say 35% duty but that must be at 250A and you are going to be welding supertankers together at that power.... Most of the stuff I do is about 130A max and it will go all day (and often a fair bit of the night) at that. I was very surprised at the performance of this type of machine - and you can even pick it up and carry it to the job if necessary.


Thread: Xmas in the workshop/shed
22/12/2016 18:43:31

If I ever get done with work projects , I have all my material lined up for a bass drum pedal I want to build! Should only take a day or so but there is the small matter of freeing up machine space from other jobs to be dealt with first...


Thread: Cheap 3 in 1 tig welder - any one used one?
22/12/2016 11:19:26

For the enlightenment of anyone reading this; two gauges does not equal two stage.... it just means you can read the bottle pressure and outlet pressure. Two stage regulators have a high pressure regulator on the bottle side and a second low pressure regulator fed off it for more accuracy. The flow regulators are simply a needle valve with flow measurement on the outlet side. This is most often a bob in a tapered tube which indicates the gas flow rate rather than the gas pressure. The flow rate (volume per unit of time) is important for welding methods relying on shield gas (MIG & TIG) as it becomes very important to control when you get into "proper" welding rather than DIY "sticking together".

I think there may be some qualified/experienced welders on here that may provide more detail rather than the normal bull that gets spouted if people ask?


Thread: VAT criticisms?
14/12/2016 23:48:23

I hope you are wearing a shirt of sack cloth to sit in that new chair.

I started out as a sole trader but very quickly found out that most clients dislike this arrangement (they expect consultants to be Ltd for some reason).

I don't think there is that much in it regarding TAX advantage between the two models (sole trader or ltd.) for small companies, you get to paying your tax whatever way you go. You are correct about the admin work required as there are more formalities to be dealt with for a ltd company and as you mention, it all has to be done on time so you get the pleasure of putting several hours in as unpaid overtime!


14/12/2016 23:35:42

"disinformation or character assassination" I really fail to see how we get to this statement from my initial comments?


14/12/2016 23:02:01

Mmmmm, so the argument isn't going my way so pack up my bat and ball and off I go. Oh well.


14/12/2016 22:57:51

Michael, you might find this HMRC page interesting (direct from the horses mouth rather than via wickedpedia) **LINK**

And by the way, you do not need to be clever or wealthy to own and run your own business, you just need to be sufficiently motivated and prepared to work considerably harder than most employed jobs... I am certain JS would agree that running a business leaves little time for the sofa!


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