Prams and teddies again

[John Stevenson 1Participant @johnstevenson1]

Damn it, give me the extra and I’ll go round and brick the windows of anyone that complains – can’t be fairer than that can I ?

 

John S.

[Richard ParsonsParticipant @richardparsons61721]

The problems of coldness in the workshop. Over here from mid-September to early March it gets COLD. Often as low as -30°C or lower. We have the answers which are

· 3 (no more) layers of clothing, which can include ‘Long Johns’ or Swambo’s tights is she is not looking.

Good insulation and an inner door which was a curtain made of ‘Bubble wrap’ (Cheap).

· A ‘Kandelo’, My previous workshop was a 10’ by 8’ wooden shed and I built a portable ‘Kandelo’ (it was moved outside in summer)

What is a Kandelo? It is a wood/rubbish/coal (if you can get it)/dirty oil/etc burning storage heater. Mine was made in part of a 40 Gallon oil drum and had 8 ‘circulations’ on 2 levels. When I had built my new ‘workroom’ I sold the shed and Kandelo to some wood workers, who used it as an office/warming room. Whilst the owner and his helpers were at lunch, the next door mob tried to unfreeze their Propane/butane bottles. The shed, the Kandelo and the ‘next door mob’ are no longer with us!

If the editor wants I will write up how to do it and throw in the oil burner for good measure.

[Richard ParsonsParticipant @richardparsons61721]

As to CNC articles I have no objections to them. I do not use CNC kit myself because I have no CAD package that works. I have tried the ‘free’ version of Alibre but it is always arguing with ‘silver-light’, I have ditched it. Apart from that I think I got hold of a Hungarian-ised version – EEK!

Does anyone know of a diagrammatic representation of the ‘G’ code instructions to act as a ‘halfway house’ between the drawing and the ‘G’ code instructions? Are there any ‘G’ code subroutine libraries in the public domain? Are there any ‘G’ code library management software available?

Ps if you are using MS Word do not use bullet points

Dick

[David Clark 13Participant @davidclark13]

Hi Steve Garnett

Who said we would be doing a special CNC exclusive to Smiths.

I sid we might do an A5 magazine.

If we did it would be free with the current MEW.

Nothing about it being a special was mentioned.

regards david

Edited By Diane Carney on 06/06/2011 00:43:25

[Chris TriceParticipant @christrice43267]

I think you misunderstood David. Steve is saying he agrees that a CNC special WON’T happen and why by suggesting the conversation that would take place if you did pitch it to Smiths.

[Steve GarnettParticipant @stevegarnett62550]

Posted by David Clark 1 on 05/06/2011 09:18:59:

Who said we would be doing a special CNC exclusive to Smiths.

Only me, postulating the possibility in the above post, as Chris has pointed out. Read the bit before the dialogue carefully… I was just hoping that this was better than throwing teddies out of prams!

Edited By Steve Garnett on 05/06/2011 11:22:54

[Anonymous]

Paaah, it’s much more fun throwing teddies! Mind you this is all WI stuff compared to the tantrums, hissy fits and teddy throwing that I’ve seen on the flying field, particularly in competitions.

 

If nothing else the ‘controversial’ threads seem to attract a lot more posts than the more technical ones; that might say something?

 

Regards,

 

Andrew

[John Stevenson 1Participant @johnstevenson1]

Posted by Richard Parsons on 05/06/2011 08:52:26:

Does anyone know of a diagrammatic representation of the ‘G’ code instructions to act as a ‘halfway house’ between the drawing and the ‘G’ code instructions? Are there any ‘G’ code subroutine libraries in the public domain? Are there any ‘G’ code library management software available?

 

Dick

 

 

I think there are a lot of misconceptions out there as regards G code, many seem to think it’s another language and the lack of G Code speak will not let you use CNC which could not be further from the truth.

 

Let me take you thru something I do on a regular basis but although it’s regular they are never the same, so basically many one off’s which others tell us that CNC is no good for.

 

I do a lot of electric motor repairs for three different companies not the rewind bit, that’s their bowl of rice but repairing shafts , bearing housings ripped off splines etc. One oft repeated job is brush rings for largish DC motors, usually fork truck motors which can cost up to £7,000 to replace so they will repair them.

 

The brush ring comes in with all the brush boxes hanging off and what is left of the insulated ring is burnt away. Repair consists of making a new ring out of Tufnol, putting all the holes and slots in and fitting the old brush boxes back on, old way takes about two to two and a half hours.

 

First off make a sketch as good as possible then grab a sheet of Tufnol and band saw a circle out. Hold in chuck and trepan centre out if circular or if square with rounded corners onto the rotary table on the mill and work out arcs and straight lines.

Mill out curved slots and curved counterbores, layout hole positions and drill.

Cut outer diameter or shape to suit and then fasten brush boxes back on.

 

As I say for a simple one all circular and all holes could be just under two hours. Funny shaped ones with lugs and curved slots possibly up to three hours, that’s the old way.

 

New way is make the same sketch as before but now draw this in CAD, export as a DXF and into a simple CAM system, something like Cut2D, look to see what is the smallest hole and choose a cutter smaller than this or equal to, I tend to use cheap 3mm single flute router cutters from Silverline at £1 each, very cost effective.

Tell cut 2D to profile the holes, you don’t drill if the hole is larger than the cutter, then do the curved slots and counterbores.

 

Then do the inside shape but leave 4 tabs on 0.5mm thick by 3mm long to hold the inner so it doesn’t flip up and break the cutter, same on the outside.

Tell Cut2D to generate the code and save to a memory sick.

 

Now grab a sheet of Tufnol literally nail it to the MDF sacrificial bed on the router, guess where the centre is, touch the cutter on the top surface and zero all axis, raise the cutter and press GO

 

Average brush ring at 8″ diameter and 10mm thick will take about 10 minutes to cut, snap out from the tabs and clean up and reassemble the boxes as before.

 

From sketch to finish is now under one hour. I have not even seen the GCode at any point nor do I need to.

For these brush rings there are so many different shapes and many are very close to another that it’s easy to get mixed up so other than a couple that are regular repeats I delete the files afterwards because it’s quicker to draw a new one than cut, copy, paste, scale and make mistakes.

 

Years ago we had to write code or alter it but things have moved on and programs are so much better today.

 

Andrew Johnson in the thread “How would you make this part” spent 40 odd hours programming his bevel gear, OK a lot of that was his learning curve but using a modern program, which wasn’t out when Andrew was doing this, I ‘drew’ the gear and got all the information from the screen and the code in 10 minutes.

This when entered into the CNC told me it wanted 1 hour and 58 minutes to cut and again I had never seen the G Code.

 

So you can use them for one off’s and not repetition and contrary to popular belief you don’t need to know GCode.

 

John S.

Edited By John Stevenson on 05/06/2011 12:05:39

[NJHParticipant @njh]

Hi John

 

I’m not teasing you about CNC here I can see that you have a very good reason for using it in your quoted tasks. What sort of price is a set up to do those sort of things?

 

Regards

 

Norman

[John Stevenson 1Participant @johnstevenson1]

Norman,

Prior to CNC they were willing to pay 2 – 2 1/2 hours labour plus a bit of materials,

the fact I can now cut this down to an hour only off sets the extra cost of machinery.

 

Why rock the boat

 

I’m often asked to code a job for others with no CAM packages, usually simple job but probably involve a lot of arc’s etc, one job that springs to mind is exhaust flange plates that bolt to cylinder heads for the guys making their own headers.

 

From being given say a gasket I can draw and code this within an hour so I charge one hours labour

John S.

[NJHParticipant @njh]

Sorry John

 

I wasn’t wishing to pry in to your commercial dealings.

What I was getting at was I assume you must have a comprehensive CNC set up and I was wondering just what sort of investment in equipment is needed to go down that route.

(Again please don’t tell me what yours cost but what lathe , mill, computer, software packages etc. you think necessary ) I know there are various mods for conventional lathes but I’m thinking here purpose built stuff – not the esoteric kit F1 workshops use of course but the sort the dedicated amateur / small jobbing pro might find useful.

This is only my curiosity really so please don’t take too much time ( I think I’ve used up all the spare room in my workshop and emptied my “playtime” account even if I did get interested in the process )

 

Regards

 

Norman

[David Clark 13Participant @davidclark13]

Hi John

Using Q parameters on Heidenhein you can write a program that you only need to input the the two hole centres and the two radii and it can calculate the whole thing as it runs.

I also did the same with hexagons.

Just needed cutter radius and AF and it did the lot, any size within the machine capacity that you want..

regards David

[John Stevenson 1Participant @johnstevenson1]

David,

Don’t muddy the water, we are trying to convince some people how simple it is

 

Norman,

Now these are just my views on it and remember there are many ways to do the same job and there will also be many views on you question of what is necessary.

 

I’ll deal with milling machine first as mill and lathe are two totally different animals, a lot of people think that a lathe is just a two axis mill but nothing is further from the truth.

 

First off you need a mill be it a converted X2, X3 type and by this I mean to take in all makes from the various people, You can buy older redundant Denfords and Boxfords ex education, for not a lot of money if you can get in on the ground floor.

Top of the range are the turnkey machines like the KX1, KX3 and the Tormach. So the price here is very flexible and can’t really be defined.

We then need a dedicated computer to run it, an older desktop that still has a parallel port will do fine, these can be had for anything from free to £90, not worth paying more and a modern computer probably won’t have a parallel port anyway.

 

We are now into the realms of software, the controller program to run on the computer I use, Mach3 costs about £100 to license it. There is a free controller that runs on Linux called EMC which is free.

 

The last two bits of software are CAD for drawing your part and CAM for turning the drawing into code that the controller can read.

 

CAD can cost from free to £5,000 depending on what you want to do.

Draftsight from Solid Works is free and is a very powerful program not unlike Autocad, they give it away to get you to move on to full 3D at £5K but if you are happy with Draftsight it’s a marvellous deal.

 

Again CAM can cost from free to £50,000 [ no misprint ] again depending on what you want to do.

 

CNC Code maker, Cambam, Lazycam and the wizards inside Mach are all free.

Paid programs around £100 to £150 cover Cambam Pro, Cut2D, and Sheetcam and possibly the level 1 hobby version of Dolphin.

 

So for a milling machine, leaving out the flexible cost of the machine you can actually get started for free if you go the Linux / EMC / Draftsight / Cambam route.

 

I’ll do lathes later.

 

John S.

[Martin WParticipant @martinw]

John

 

It is a pity that this information hasn’t, as far as I am aware, been presented in MEW in this type of format. Rather than showing screen shots of computer screens with code etc. a simple explanation of what is required and the relative costs would encourage some to take the plunge into the CNC way of producing widgets etc. While I can’t justify the expense of going down the CNC route, nor do I have the room, I would certainly be interested in reading an article along these lines.

 

Not so much about what is produced but the setting up the component parts and how they interact plus relevant/typical costs for a small workshop environment.

 

In one of my earlier post I classed myself as a CNC Luddite, not because I can’t see the advantage of CNC but more because what I produce doesn’t warrant CNC and while I am still learning I get great pleasure in hand mangling bits of metal.

 

Cheers

 

Martin

[NJHParticipant @njh]

Thanks John

 

This just what I was hoping for – I await the lathes post with interest.

I think my position and attitude mirrors Martins and I endorse all that he has said. How about an article in this vein for MEW – I’m sure those readers with ” traditional interests” ( sounds better than Luddites!) would find this acceptable. It might earn you a few bob too!

 

Cheers

 

Norman

[blowlampParticipant @blowlamp]

Posted by Martin W on 06/06/2011 00:00:06:

John

 

It is a pity that this information hasn’t, as far as I am aware, been presented in MEW in this type of format. Rather than showing screen shots of computer screens with code etc. a simple explanation of what is required and the relative costs would encourage some to take the plunge into the CNC way of producing widgets etc. While I can’t justify the expense of going down the CNC route, nor do I have the room, I would certainly be interested in reading an article along these lines.

 

Not so much about what is produced but the setting up the component parts and how they interact plus relevant/typical costs for a small workshop environment.

 

In one of my earlier post I classed myself as a CNC Luddite, not because I can’t see the advantage of CNC but more because what I produce doesn’t warrant CNC and while I am still learning I get great pleasure in hand mangling bits of metal.

 

Cheers

 

Martin

 

I have supplied an article along these lines to David at MEW, but I don’t know if or when it might be published.

 

In it, I’ve tried to show how a part can be draw quite simply in an (affordable) CAD program and transfered to an (affordable) CAM program, to produce the instructions (G-code) for the CNC milling machine/router to run.

As John S. points out, there’s virtually no need to look at, let alone fiddle with the code once the CAM has produced it. The whole point of a CAM program, is to relieve you of the tedium of figuring out the right numbers and appropriate instructions and allow you to concentrate on other, more important things.

 

Martin.

[Donald MitchellParticipant @donaldmitchell68891]

Hi, as a self confessed CNC Luddite, I have been totally bored to death by the number of articles about G-Code etc. However, the last two posts to this list, by J.S. and Blowlamp, have made me pick my ears up considerably and I would very much like to read a “simple” introduction to setting up and running a CNC system in my workshop.

Who knows, I might even become a covert !!!

Donald Mitchell

Bonnie Scotland

[Martin WParticipant @martinw]

Hi Martin

 

It’s a shame that your article or something similar hasn’t been published in MEW earlier as it would have demystified much of the CNC process. I think that many readers, me included, thought that there was a need to get into some form of programming to get the system to operate. This as far as I am concerned was not something I wanted to be involved with as I have had a career in electronics/computing and had taken up small scale mechanical engineering after retirement as a change and to fulfill a long term passion to make things out of metal that whirred, revolved and that looked good. To date I have managed to make extra bits and pieces for my machines plus a range of bits for friends and family.

 

DC how about an article or series on an introduction to CNC or CNC demystified? I am sure that a page every now and then, even monthly, wouldn’t create too much of a storm especially if it was made clear at the outset that this was exactly what it says “An Introduction To CNC”

 

Martin I look forward to reading your article in a future edition of MEW.

 

Regards

 

T’other Martin

 

PS

 

It looks like there is interest already!!!

Edited By Martin W on 06/06/2011 11:48:47

[VersabossParticipant @versaboss]

Posted by John Stevenson on 05/06/2011 22:49:52:

…..

I’ll deal with milling machine first as mill and lathe are two totally different animals, a lot of people think that a lathe is just a two axis mill but nothing is further from the truth.

 

…….

I’ll do lathes later.

 

John S.

Hi John,

That’s the kind of article I am waiting for, too. Gathering dust under the bench in my workshop is all the stuff for converting a lathe (to be exact: a spare cross/topslide) to CNC.

Linux comp with EMC, steppers, ARC stepper drives are ready, but other commitments have brought all to a standstill.

However, what provoked my posting here: I never grasped the notion that mill and lathe are fundamentally different, except that the coordinate letters are different. So I would be most interested to learn why it is so.

To give an example: can you explain the difference between milling a tapered front side on a rectangular bar, and turning the same taper on a shaft in the lathe. Is really more in it than the mill moving in y and y, and the lathe in z and x?

Greetings, Hansrudolf

[David Clark 13Participant @davidclark13]

Hi There

Will be published soon.

regards david

 

[John Stevenson 1Participant @johnstevenson1]

Lathes, as in CNC lathes and again this is just my take on it, other may vary.

 

Lathes are just two axis machines whereas mills are 3.

In a mill bed side to side is X, front to back is Y and up and down is Z

 

In a lathe bed movement is called Z and cross slide is X so basically a lot simpler, where lathe gets complex is in threading where the spindle has to be synchronised to the Z axis just like a gear train.

Most small CNC lathes use a simple index pulse of one count per rev to keep this in sync, Industry use a minimum of 1024 per rev times 4 to give 4096 counts per rev.

 

Home shop CNC can’t use these at the moment [ or rather can but with some expensive add on cards ] because the affordable controllers like Mach3 can’t handle these.

 

So there are issues at the moment with threading, EMC under Linux can thread but it’s not a program for a beginner who has little Linux experience.

 

Biggest drawback to a CNC lathe is setting up for a run of parts. This isn’t down to CNC but real world experiences when doing batch work.

 

You take a bar say 30mm and need to turn down to say 12mm for 30mm long.

Manually you will keep taking cuts and measuring and gradually creep up until you finish up on the 12mm diameter.

 

The last few cuts may be shaving cuts to get to size.

Now when you do the next one if you just take the readings on the dials or DRO and take reasonable cuts to size then chances are you will be under size because of the spring in the bar and you need to adjust the last cut to get on size.

 

Same thing happens with CNC, you take a scratch pass, measure so you can set that in as a diameter and cut the part, them measure the finished article, then adjust the tool offset to compensate for the operation.

It may take two or even three passes to get everything dialled in to size.

 

Now if you want to only make two then you have wasted these.

Even when set up correctly any changes like swapping from steel to aluminium can cause a change in size, same if you go from a finished size of say 20mm down to a new size of 10mm.

 

This isn’t a CNC fault or machine fault, it’s just real world experience and something you have to live with. If you are doing 200 parts a bit of sacrificial bar to get sizes set is a small exercise when the time savings on the 200 parts far outweighs it.

 

Personally, and this is my take and I know it’s also shared by others, is that unless you have room for a manual lathe AND a full CNC lathe then fine, if not do not buy a full CNC lathe it will restrict you and more importantly it will slow you down.

 

Tony Jeffree had the right idea when he converted his ML7 to CNC. He arranged it so that it can still be used manually but with the option of bring the CNC in to play for repetition and threading although previous errors as mentioned still apply.

 

With this he has the best of both worlds, the ability to make to odd 1 or 2 manually and the ability to make the odd 10 or 20 via CNC.

 

I personally think for the home workshop if you want to go the CNC route you are better off with a hybrid than a full CNC lathe especially in the UK where we struggle for workshop space.

 

Doesn’t apply in the USA where they just partition off 2 acres of the North 40 and throw a dozen tractors and a back hoe in for good measure

 

John S.

[Chris TriceParticipant @christrice43267]

I’ve been seriously considering modifying my Super 7 to CNC as per the articles that have been appearing. It appeals because it doesn’t commit the lathe solely to CNC so reading your comments only encourages me further. Thanks for taking the time to post. That’s the sort of information and opinion that worth its weight in gold.

[Author]

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