EEVblog Electronics Community Forum

General => General Chat => Topic started by: Simon on August 16, 2012, 10:19:48 am

Title: suggestion for a mechanical engineering forum
Post by: Simon on August 16, 2012, 10:19:48 am
As I've now started in a new job as a draughsman I wouldn't mind joining a forum for mechanical engineering where hopefully people are also familiar with CAD software. So what is the mechanical equivalent to the eevBlog forum ?
Title: Re: suggestion for a mechanical engineering forum
Post by: AlfBaz on August 16, 2012, 10:25:11 am
Time to start mevBlog!:D
Title: Re: suggestion for a mechanical engineering forum
Post by: Simon on August 16, 2012, 10:38:39 am
Yea, Dave needs a mechanical partner ;) or we could have a mechanical/cad section. I think many people on here are into mechanical stuff as well. Some electronics would be nothing without the mechanical "front end"
Title: Re: suggestion for a mechanical engineering forum
Post by: johnwa on August 16, 2012, 10:57:55 am
Have a look at http://www.cnczone.com (http://www.cnczone.com). They have sections for CAD/CAM, and various metalworking techniques. It has been a while since I have been over there, looks like they have expanded quite a bit in the meantime...
Title: Re: suggestion for a mechanical engineering forum
Post by: HLA-27b on August 16, 2012, 12:16:02 pm
Besides CNCZone there is also http://www.practicalmachinist.com/vb/ (http://www.practicalmachinist.com/vb/)
Both of these are vast places.
Title: Re: suggestion for a mechanical engineering forum
Post by: HLA-27b on August 16, 2012, 01:28:35 pm
http://www.eng-tips.com/ (http://www.eng-tips.com/)       
This is the duck's guts imo.
Check out Drafting Standards, GD&T & Tolerance Analysis section.


http://www.physicsforums.com/forumdisplay.php?f=101 (http://www.physicsforums.com/forumdisplay.php?f=101)
This is also a big repository of engineering knowledge.
Title: Re: suggestion for a mechanical engineering forum
Post by: EEVblog on August 16, 2012, 01:59:01 pm
If you don't find any suitable, then I can't see why we can have one here I think.
But I do always like using the best tool for the job, so if there is another forum that does it good already, no need to duplicate.

Dave.
Title: Re: suggestion for a mechanical engineering forum
Post by: Simon on August 17, 2012, 02:05:23 pm
If you don't find any suitable, then I can't see why we can have one here I think.
But I do always like using the best tool for the job, so if there is another forum that does it good already, no need to duplicate.

Dave.

Well you see i think on here we have a range of skills and abilities and I think you will find that people who are into electronics usually have one other significant skill too that often overlaps. For example on many a photography forum I have been on there has been talk of building custom electronics.

Obviously we talk about computers here often as they are closely related to electronics and of course politics  ;)

I think mechanics and in particular machining ect comes close with electronics with CNc equipment being home built these days and things like makerbots bring the mechanics and electronics closer. Then you have all of the software these days that is a cross between computing and mechanics.

I don't know if there are enough people on this forum to fuel a mechanical / cad section you may be surprised. Some specific forums can get a bit too political about their subject and some may prefer a more relaxed environment. look at how many have moved over from a "certain other" electronics forum because of the amount of "attitude" there was. If you do want to do it probably start small and let it grow on it's own like the existing forum has.
Title: Re: suggestion for a mechanical engineering forum
Post by: G7PSK on August 17, 2012, 05:11:13 pm
In many ways you cannot separate mechanical and electrical/electronic engineering they go hand in hand along with chemistry.
Cant even write on this forum without mechanics being directly involved,  some one had to sit down and work out the stresses on the key board so that it either is not to heavy or breaks. 
Title: Some sites
Post by: FJV on August 17, 2012, 07:45:28 pm
If you want CAD specific you wanna go to Sean Dotson's site.His site has great tutorials on Autodesk inventor and Solidworks.
http://www.mcadforums.com/forums/ (http://www.mcadforums.com/forums/)

As for mechanical engineering, I haven't come across what I would call "professional level" engineering forums.

But there are some model engineering sites with sometimes really great stuff, though not consistently what I would call "professional level".
http://www.homemodelenginemachinist.com/ (http://www.homemodelenginemachinist.com/)

Title: Re: suggestion for a mechanical engineering forum
Post by: Simon on August 17, 2012, 07:51:21 pm
well I'm using the "revolutionary" solid edge
Title: Re: suggestion for a mechanical engineering forum
Post by: Galenbo on September 24, 2012, 10:51:19 am
...or we could have a mechanical/cad section...

Same problem as with Electronics. What kind of Mech/cad? What level?
Design a lab supply? or look at the rasperberrryPi as a fanboy? Getting interested in the production process of a diode?

In the mech department, you can go to study a bearing for 10 years, or look how to repair, upgrade or modify
your Bobcat 751 skidsteer, Genie Z34 telescopic boom lift or years-70 Deckel lathe.

I find the mech to have a much higher 2nd level entrance level. In electronics you can do much under the 1000 euro level in a 3x4m room. You'll see that in mech you're way more limited, unless you stay at your desk and order everything in a cnc shop.

Compare it with electronics development without soldering iron.
You really will need the lathe, alu-welding, a huge stock of half-fabricates, a bigger space to weld, grind and paint.
And the opportunities to assemble and test your model.

.
Title: Re: suggestion for a mechanical engineering forum
Post by: bullet308 on September 24, 2012, 12:44:08 pm
I have a CAD/CNC/machine tool background, more in a gunsmithing context than anything else,  and would love to see some ME/machine tool stuff here. As my focus has shifted more towards electronics, I am particularly interested in where the two worlds overlap the most. For instance, I have been looking at DIY CNC pick-and-place stuff and have rekindled my small CNC machine tool interests that I tinkered with and abandoned a decade ago (its a lot cheaper and simpler now). This also dovetails in with the 3D printer stuff as well.

(BTW, as interesting as 3D printing is, I think that at this point, the subtractive side of the house (little CNC mills, etc) still buys you more capability for your money and is much more highly evolved).
Title: Re: suggestion for a mechanical engineering forum
Post by: G7PSK on September 24, 2012, 05:25:25 pm
You don't need to spend a lot of money on the mechanical side as you don't need CNC or machine tools for that matter. A hacksaw a few cold chisels and hammers and some files and it is possible with some skill and a bit of time to make just about anything.
Title: Re: suggestion for a mechanical engineering forum
Post by: SeanB on September 24, 2012, 05:48:29 pm
Exact tools the Afghani's use to make guns........... Who needs a 3d printer?
Title: Re: suggestion for a mechanical engineering forum
Post by: robrenz on September 24, 2012, 06:33:38 pm
You don't need to spend a lot of money on the mechanical side as you don't need CNC or machine tools for that matter. A hacksaw a few cold chisels and hammers and some files and it is possible with some skill and a bit of time to make just about anything.

As someone who has hand scrapped 18" square cast iron surface plates flat to less than .000025" with nothing but a carbide scraper and bluing and red lead I agree with your sentiment. But not very practical.  If you change that from some skill and a bit of time, to a lot of skill and a whole lot of time I would agree.  I do agree with you that people tend to think cnc imediately instead of just a manual machine and that is not always a good idea unless all you want to do is rout and drill circuit boards. If you have watched any of my videos on here and think about taking the machine tools away and doing the same thing you may change your mind.
Title: Re: suggestion for a mechanical engineering forum
Post by: Simon on September 24, 2012, 07:11:34 pm
indeed, at work we still use mills and lathes for simple tasks, only complex stuff like connectors is done n the cnc equipment
Title: Re: suggestion for a mechanical engineering forum
Post by: bullet308 on September 24, 2012, 08:04:38 pm
Yeah, but I have already GOT the manual machines. :-)

Also, its hard to do the really fine work on a 13x40 lathe (glad that beast is in my fathers garage) or my high-mileage Clausing mill. If I get something small, it might as well be CNC, given the economics of it nowadays.

Title: Re: suggestion for a mechanical engineering forum
Post by: G7PSK on September 24, 2012, 09:07:40 pm
You don't need to spend a lot of money on the mechanical side as you don't need CNC or machine tools for that matter. A hacksaw a few cold chisels and hammers and some files and it is possible with some skill and a bit of time to make just about anything.

As someone who has hand scrapped 18" square cast iron surface plates flat to less than .000025" with nothing but a carbide scraper and bluing and red lead I agree with your sentiment. But not very practical.  If you change that from some skill and a bit of time, to a lot of skill and a whole lot of time I would agree.  I do agree with you that people tend to think cnc imediately instead of just a manual machine and that is not always a good idea unless all you want to do is rout and drill circuit boards. If you have watched any of my videos on here and think about taking the machine tools away and doing the same thing you may change your mind.

I started work as a horologist's apprentice, he could cut a gear for a watch or clock out of a piece of sheet brass by hand and file the teeth on it drill it by hand with a wheel brace and fit it to a staff that he had turned up on a watchmakers lathe that used hand held tools and the finished watch or clock would keep perfect time, on some watches to a second a month or better. I am afraid that I never got that good before I left to do other things, but it was a great experience and I learn a lot of skills that were useful in other fields. 
Title: Re: suggestion for a mechanical engineering forum
Post by: Mechatrommer on September 25, 2012, 07:59:31 am
You don't need to spend a lot of money on the mechanical side as you don't need CNC or machine tools for that matter. A hacksaw a few cold chisels and hammers and some files and it is possible with some skill and a bit of time to make just about anything.
As someone who has hand scrapped 18" square cast iron surface plates flat to less than .000025" with nothing but a carbide scraper and bluing and red lead I agree with your sentiment. But not very practical.  If you change that from some skill and a bit of time, to a lot of skill and a whole lot of time I would agree.  I do agree with you that people tend to think cnc imediately instead of just a manual machine and that is not always a good idea unless all you want to do is rout and drill circuit boards. If you have watched any of my videos on here and think about taking the machine tools away and doing the same thing you may change your mind.
I started work as a horologist's apprentice, he could cut a gear for a watch or clock out of a piece of sheet brass by hand and file the teeth on it drill it by hand with a wheel brace and fit it to a staff that he had turned up on a watchmakers lathe that used hand held tools and the finished watch or clock would keep perfect time, on some watches to a second a month or better. I am afraid that I never got that good before I left to do other things, but it was a great experience and I learn a lot of skills that were useful in other fields. 
you may ask him to do it again for 36 teeth helixal gear (slanted about 30 degrees) about 3cm diameter, 3cm length of hardened steel or alloy, it has about 2.5cm diameter hole through, some bevel and chamfer for me, i'm willing to pay 1/10 of the cnc machine price. i have this broken plastic gear from my foot massager machine that i want to redo from hardened steel, its been like 8 years i'm not able to figure out how to do it at affordable price. the best i achieved is with some hardened steel plates embedded in fiberglass moulding but broken in the first application. if he's willing tell me i'll provide the CAD for him and material to use ;)
Title: Re: suggestion for a mechanical engineering forum
Post by: G7PSK on September 25, 2012, 03:11:22 pm
That would be tough, he died about 15 years ago, but it could be done by hand I am sure, all hardening is done after the gear has been hobbed any way.
It always amazes me that every one thinks of CNC first for lathes and mills, I know a company just up the road from me that still has a large collection of plug board lathes as they are far faster for producing many items than a CNC. They do have CNC's as well but for speed of operation they cannot beat the old plug boards for simple things like bushes and threaded parts even parts with holes  drilled in them and slots cut for high volume the plug board is faster.
Title: Re: suggestion for a mechanical engineering forum
Post by: Simon on September 26, 2012, 05:46:35 am
CNC is good for complicated items where more than one tool is needed and you want many, so instead of having to manually change the tools for each part you pre-load them and "forgetaboutit"
Title: Re: suggestion for a mechanical engineering forum
Post by: G7PSK on September 26, 2012, 07:45:32 am
Thats the thing about plug board lathes you load all the tools for the job on the turret and any other tool position that may be needed load the auto feed and go away and forget while attending the next machine the Company that I referred to has about 20 of these old machines and only for people looking after them two of which just spend their time removing the finished item and the swarf, the setting up is done by the other two skilled people and that is the trouble it takes more skill to be a plug board setter than a cnc machinist, I know another company who employs a cnc miller and he used to be a car salesman until he decided to become a machinist to which end he went on a weeks course at the cnc machine tool factory. The first company I refer to makes parts for company's such as Rolls Royce and British Nuclear Fuels etc the second company makes equipment for McDonalds and Tesco etc. CNC is destroying core skills and so is CAD I have seen some really atrocious drawings produced by so called CAD draftsmen due to them having left school and taken up the job of CAD trainee, the old school draftsmen would have to do the actually work during their training for a five year apprenticeship,  not day release to the local tech for a year.     
Title: Re: suggestion for a mechanical engineering forum
Post by: robrenz on September 26, 2012, 12:39:16 pm
Core skills inherently diminish as technology progresses.  :'(
Many tool and die skills are completely wiped out because of wire and sinker edm technology.
Many manual machining skills are unnecessary because of cnc even in a non production environment.
Practically all advanced drafting skills are totally unnecessary because of cad.
Additive processes (fused metal deposition) will displace many subtractive (machining) processes.

As someone with a few old school core skills I find this on one hand sad, yet I love my solidworks and cnc and what they help me to accomplish. But if I had to pick one or the other I will stick with the core skills.  If you unplug the power I still know how to design, draft and machine.
Title: Re: suggestion for a mechanical engineering forum
Post by: G7PSK on September 26, 2012, 05:38:22 pm
The problem with designers using cad and not understanding some of the core skills manifests itself when they design something that has to be manufactured largely by hand, this is something that I have come across many times such as a stanchion 6 meters long in 150mm RHS the plans called for a plate welded on the ends 8mm double sided fillet weld. A hopper for a ship loader that was not able to be made as the angles on the drawing meant that the 8 pieces of SS plate 10mm thick and 3 Meter long and 2 meter on the longest end would not produce the shape required, all laser cut, a very expensive mistake made by a junior draftsman. Many more some of which I can no longer remember clearly but every time caused by CAD, I have never had a hand drawing that was so wrong.Garbage in garbage out. 
Title: Re: suggestion for a mechanical engineering forum
Post by: Mechatrommer on September 26, 2012, 06:07:16 pm
the problem is not the CAD (its nothing but drafting with computer), the problem is skills and experience. tell me if any junior doesnt make mistake? once i was told by a seasoned engineer about his young age, he almost got fired for his mistake. as with drafting with pencil, die skil etc, those skills are no longer necessary, they deserve in archive book just in case of armaggedon. drawing exploded 3D can now be done in no time with CAD, and any angle view you want in case the draftman make mistake, not to mention uploading to cnc machine.
Title: Re: suggestion for a mechanical engineering forum
Post by: robrenz on September 26, 2012, 07:09:53 pm
"Simultaneous Engineering" is an attempt to minimize these occurrences and to spread multidisciplinary knowledge. In other words have all groups involved from the beginning instead of the throw it over the wall mentality.  If implemented well with cooperative groups everyone benefits and the learning curve for newbies is shortened.  Many entrepreneurs embody simultaneous engineering because they are all of the disciplines combined in one person.
Title: Re: suggestion for a mechanical engineering forum
Post by: HLA-27b on September 26, 2012, 07:12:44 pm
People often make the erroneous assumption that CNC means inherent accuracy. Nothing can be farther than the truth. Accuracy only happens if YOU care (and know how) to measure it! If you want to manufacture an R8 collet for example, as seen on robenz's videos you need a grinding machine and more importantly an accurate set of gages. To manufacture the gages you will be doing mostly manual work and you will be measuring the hell out of it regardless of the method of manufacture.

CNC is good if you want to churn out many parts with averagely skilled workforce. Then again if you want to churn out millions of parts CNC is no good, you get yourself a good old cam operated lathe (aka. screw machine).  If you want plumbing fittings or ammo cases by the million and dirt cheap this is your tool of choice since the beginning of the 20th century until at least the end of the 21st, not even remotely threatened by the advent of CNC machines as they require 4 times more energy and floor space and are slower.

If you need a die for some aircraft fuselage part with crazy compound curvature CNC is your friend. But then again there was no CNC during WWII yet no lack of aircraft, so I might be missing something.

To cut it short

Manual machines  - One offs, Repair work, Home shops (I'd go manual for a home shop every day of the week)
CNC Mashines - Small batches 1000 to 10.000 pcs, Complex curvatures, compound surfaces
Cam lathes, Screw machines, Thread rollers, Broaches - Million part batches

Of course all of these machines work on soft annealed metals. After machining most parts undergo heat treatment which is notorious for crooking an distorting parts to ruin any accuracy so far attained. This is why manufacturing people don't fuss all that much about accuracy up to this point. The main object is to remove the bulk of the material and to leave just enough to be machined after heat treatment. At this stage most parts are too hard to be machined conventionally. So the final and most accurate machining is done by grinding and for the ultimate in accuracy lapping and super-finishing.

For any of these you need a full set of measuring tools. If you can't measure it, it ain't accurate.
Title: Re: suggestion for a mechanical engineering forum
Post by: G7PSK on September 26, 2012, 08:35:31 pm
No the problem is not the CAD it is the fact that the operators of many computers running CAD programs have had no experience on the shop floor or know how to use the tools or materials that are required for the job,they do a course on how to use the cad software at tech and then are set loose designing the machines and equipment that others are then expected to make. Some of the CAD operators that I have run up against have no knowledge of engineering either, they have replied to a job advert for a CAD operator having got a school certificate and the numb skulls doing the hiring have hired them. I have seen bendy beams and wobbly floors and a whole host of other horrors in my life due to so called CAD designers.
Title: Re: suggestion for a mechanical engineering forum
Post by: Mechatrommer on September 27, 2012, 02:29:14 am
you dont expect a draftmen to design something and works wonderfully, thats not within their skillset by definition, but a good draftmen knows how his drawing converted into reality. thats what a team for, to support and educate each other esp the one below you. and thats also make a junior become experienced. but also a very good junior is self-taught and quick learn to become multidiciplinary, but how many person you expect to have such ability?
Title: Re: suggestion for a mechanical engineering forum
Post by: chickenHeadKnob on September 27, 2012, 04:37:26 am
This thread is drifting from simon's original question. My vote would be to go to cnczone for CAD discussions.
Title: Re: suggestion for a mechanical engineering forum
Post by: G7PSK on September 27, 2012, 07:47:17 am
All the old school draftsmen had the skills due to the requirement during their training to work on the shop floor.
That is my argument, these days they do not insist that someone should do time on the shop floor during their training, they just go to tech and learn how to use a computer program. And as they say Garbage in Garbage out with computers.