|Tony Jeffree||28/09/2012 10:10:10|
395 forum posts
Isn't the whole discussion of whether or not John M's jointing technique is new or old rather missing the point?
The important point (to me, at least) is that he is using techniques that I haven't seen described in MEW before, and seeing what he has done is already causing ideas to spark in my brain.
Laser cutting is getting more and more accessible to the model engineer - either as a bought-in service or if you want to go the whole hog, the entry price for a small laser cutter is comparable to that of a small CNC mill. Admittedly, you would pay more to buy a laser cutter capable of cutting sheet steel, but as demonstrated with the wooden CNC mill a couple of issues ago, there's a lot that can be done with other materials (wood, perspex...) as the starting point, and even a small laser cutter will handle those materials to a reasonable thickness. Combining the accuracy of laser cutting with the kind of easy-to-assemble jointing systems John M is using is very interesting. With free software available for CAD, the idea of shipping a set of drawings to your local friendly laser cutting house & getting back a kit of parts for your machine is very appealing indeed, and as John M indicates, the premium over the cost of material isn't outrageous either.
|Chris Courtney||28/09/2012 11:31:44|
|28 forum posts|
I agree with you Tony, I only replied to John M about the joint because he specifically said he'd like to see other examples of that type of joint. The idea of providing dxf sets ready for laser cutting by your local laser cutting company has been gathering momentum in the Reprap community and the US Maker movement. It is great to see a solid looking design appearing in the model engineering community. As you say low power lasers capable of cutting acrylic, MDF and Plywood etc. are becoming much more affordable. Once you have a laser cutting system it is amazing the number of applications you find for it.
|David Clark 1||28/09/2012 11:53:15|
3357 forum posts
I get a lor of people saying how they like your series.
You did get TiN wrong, it saysTiCN on the original which is why I altered it but I got it wrong as well.
I just searched for the right colour and it showed somewhere on the internet that TiAIN was gold.
|mike mcdermid||28/09/2012 15:54:56|
|97 forum posts||
Sorry it might be my post that came across as not a new trick in the book,
not really ,my intention was to point out that a certain jet engine company are using the same jointing and construction method to make mich lighter jigs and fixtures , not made out of solid billets etc and are cheaper in the traditional toolmaking sense materials wise, these things are holding micron repeatability ,they have invested considerable amounts of money in proving this works and its used in production, its a very effective method
the sticky for me was when the development guy at RR was saying patent this that and blah blah and the two guys next to me pointed out this wasn't new and that several companies had done this before
those reprap or is it makerbot? also use this principle but this is the way things are headed lots of big companies do light tools (light on material costs or use, not lightweight materials)
I read an article once on a division master for thread cutting by the time I had thought it through a stepper ,driver and pc would do the same ,the PC is what im used to but i would do the division master experiment to learn something new
I suppose if you come from a world of CNC its nice to just use your brain and hand co-ordination on a manual machine ,if your coming at it as manual guy your also learning something new Folks not used to seeing a machine cut threads are often mouth agape when (tongue in cheak statement) they realise the machine does it all for you....
|John Stevenson||29/09/2012 11:35:43|
5068 forum posts
Playing devils advocate here.
I like John's idea, it stirs the grey cells up to allow you to think out the box, is it new ? No, similar has been done for years but is it new to the forum readers ? that's what matters.
In a conversation on the phone the other day with Tony we discussed a lot of this and the negative side of the conversation I have is cost. John has quoted material cost and material cost X 2 for labour.
Now working from the layout drawings that John put up and taking the stepper motor as a size 23 for scale I did a quick work out and that first full sheet alone would cost me about £240 and I have very good laser cutting contacts.
Now material costs would be about £30 for this sheet at bulk rates and so total cost based on Johns figures should be £90. There is a big discrepancy somewhere.
Laser cutting works on a material cost and cost per inch or millimetre the machine has to travel, they know these costs to a fine art. That's why when you send a job in for cutting they always program it up before they get the order so they know the price.
If you then price up the common extruded alloy that a lot of routers use this method becomes expensive, at least in the UK on our prices.
However now for the positive bit, anyone of a squeamish disposition as regards CNC need read no further, thank you for your time.
On the market in the UK are cheap plasma cutters that can be bought for around £200. They use single phase and compressed air, no expensive gases or rental bottles.
Do a search on Ebay in Industrial tools for Cut40, if you search by lowest first you will get some 2 pin plugs followed by the consumables, tips etc which are very, very cheap.
Now if you get your CNC, bolt a length of box section to the bed sticking our with the torch on the end, pack the sheet you want to cut so it's just touching and clear of the bed movement if follows that any moves the bed makes will be transmitted to the torch.
Remember those 2 pin plugs [ incidentally Maplins are cheaper ] if you wire a push button switch to a length of wire and plug into the plasma cutter.
Now put the switch onto the spindle so any programmed Z move makes contact.
Is the light coming on ?
So you program your part, allow for the cut width just as you would with a milling cutter.
Z comes down, hits the bed [ best to put a sheet over the tee slots or fasten a sheet to the top of the box section ] plasma fires up and it goes round and cuts your shape.
Quick, easy, low cost and an extra manufacturing technique at your finger tips.
Incorporate John's captive bolt system and tenons and you have yet another skill.
|John Stevenson||29/09/2012 11:42:05|
5068 forum posts
One other quick point.
On the designs I have seen the fastener design is reversed to Johns.
He has a hex head set screw fitted in the slot and a nut on the top. The ones I have seen have a deeper slot and the nut is held in the slot close to the bottom of the slot and a screw fitted from the top.
This makes more sense to me as it gives a choice of screws to be used, pan, posi, allen etc and neater at the top.
Plus hex headed set screws are not as easy to source as say allen or pan head and plain nuts.
Does the same job and if you want a locking design you can always use nyloc nuts in the slot.
|John McNamara||29/09/2012 16:13:16|
1313 forum posts
Hi ALL.... Hi John S
A pretty good day at the exhibition, the doors opened at 9:AM and it was very busy by 9:15 By 5:PM I was all talked out having had no break apart from a coffee and a sanga on the go.
I have attached an image of the cutline and a rough nesting as drawn the area is about 1.5 x 1.1metres. There is also a small number of 2.5mm steel sheet parts about a quarter of a square metre. The laser cutter may re-nest the parts for a better yield. and no we did not ask for the off cuts.
I avoid providing material to laser cutters unless it is special alloy, if there is any trouble with warping it is the laser cutters responsibility if they use their sheet. (Subject to their terms, conditions and tolerances sheet). Anyway it was an excellent job well within spec.
The actual price paid was $450 Australian dollars for materials and labour. Hence my rough stab at some sort of back of the envelope pricing model. Material Plus material x 2 = labour. For light steel.... Because this thread is read from many countries, I guess actual pricing comparison is rather error prone. Hence my avoidance of actual pricing in the first instance.
Laser cutters charge in several ways... a setup charge nominally around 50 dollars if you give them a perfect file that does not need reworking, (we did provide a good file). Otherwise there is a hefty hourly rate for redrawing. On top of this is the cutting length, and in particular the number of holes pierced; the machine has to run slower. (on this job rather a lot). Yes they make a profit on the materials, they need it to pay for large increases in power and gas expenses and machines that cost more than the median house.
For more specialised work there are different gases, at somewhat extra cost. Nitrogen for instance if you want a bright edge, without the fine blue scale left by oxygen, Different gasses also can improve the quality of the edge. Worth discussing if you have a critical application. We just asked for "run of the mill".
Anyway another big day tomorrow........
A added a couple of rough photos, Better ones tomorrow.
Edited By John McNamara on 29/09/2012 16:16:33
|Michael Gilligan||29/09/2012 16:58:21|
17073 forum posts
Well done John, it looks good
[and, nice to see someone found a Beer]
You mention permanent Loctite; so let me offer one suggestion ... something we used very effectively on vibration test fixtures:
Use 638 or similar Loctite on the Mortice & Tenon joints, [don't waste it on the nuts & bolts] and you should achieve a "permanent" structure without needing to tighten the nuts & bolts too aggressively.
Although it's not stricly an adhesive; the joints you are using would respond very well, because the Loctite would be working in compression & shear ... which is, of course, exactly what it's designed for.
Obviously you would only make some areas "permanent" ... but I'm sure I don't need to tell you that.
|Rod Ashton||30/09/2012 06:54:27|
|324 forum posts|
The thread has morphed away from the original question.
How then, about the future for further Mach3 articles!!!!
|Paul Boscott||30/09/2012 08:02:07|
99 forum posts
I would like to see sometimes Mack 3 articles would an answer be to use this web site for the code to save column inches (mm) this would also cut and paste of the code
|Steve Withnell||30/09/2012 09:12:10|
825 forum posts
What might be usefuk is a short column on Hints and Tips, work arounds for known problems. May be a few interesting cannds cycles where the programming has some ingenious twist.
Longer articles might be "How to make x using a KX1 CNC", where x would be any of the popular engineering designs, not previously constructed using CNC. It seems that many people think that CNC is only for multiple parts, but when you have turned the handle on the mill 35 times one way , then back to the start, incremented 2mm across and then repeated whole thing 20 times, you do start to yearn for a Mach 3 wizard to magically appear...
|Michael Gilligan||30/09/2012 09:19:28|
17073 forum posts
You are right, of course; albeit the diversion has been rather interesting.
As I see it, the editorial problem is to find the right balance.
David's original series was exactly what you wanted at the time, but was despised by some others [whether a majority, or a vociferous minority, I know not].
I genuinely believe that we all should have some interest in CNC, whether we intend to use it in our own workshop or not. I am, however, less convinced that we need step-by-step instruction in the use of a particular piece of software.
In the magazine; let's have articles about the underlying principles, not "painting-by-numbers". Mach 3 may be a de facto standard for the model engineering community, but it is certainly not the only tool for the job.
Whilst hoping not to throw the thread off course again ... the same applies to articles about [say] wiring-up a static inverter, or using an LED as an indicator lamp, etc. etc. There are too many pages of MEW wasted on big pictures of trivial things.
Chorus: An Editor's job is not a happy one !
Paul' suggestion of posting code to a specific area this forum is excellent, and I think the same should apply to screenshots of the software. There may be an exception who proves-the-rule; but it's a good bet that anyone that is interested in running Mach 3 already has access to the internet.
So ... Let's have articles that explain CNC and how to use it; but don't fill the magazine with a serialized version of the instruction book for a specific product.
Edited By Michael Gilligan on 30/09/2012 09:22:53
|Stub Mandrel||30/09/2012 16:41:15|
4311 forum posts
I think Richard Gordon's article in the current MEW hit the spot. useful information without being a step by step.
|John Haine||30/09/2012 22:01:40|
|3551 forum posts|
Of course serialised instructions on how to make things on a mini lathe or a Myford are a different matter.....
Seriously, if you are starting in CNC, you have a choice of 2 programs to use - Mach 3 or LinuxCNC. Rather like having a choice of Myford or Boxford really, except that those lathes are very similar whilst M3 and LCNC are very different. Mach3 is sufficiently complex that a helping hand is very useful in the early stages - the documentation isn't bad but having someone who isn't one of the software designers explaining how to set it up is extremely useful.
I quite agree that this website should allow people to post files such as g-code. In fact like most other similar sites it should allow any file type. Then the CNC articles can relegate the supporting code to the site - IMHO anyone who is likely to be doing CNC in their workshop will have web access.
|John McNamara||13/02/2013 14:20:15|
1313 forum posts
This is a link to a short video of the CNC router I posted earlier..... working! in this case test engraving MDF board
The movies were shot with an Iphone and is unfortunately one is a biggish file 500meg. If you have fast Internet it will take a few minutes to download.
The machine is driven by Mach 3 using a smooth (USB) stepper driver board
Test 1: This was the first test Not Bad at all! Apologies for the portrait aspect.
**LINK** 123 meg
Test 2 at the opening of the Bright Men's Shed (North Central victoria Australia) where the machine is working.
**LINK** 500mb 1080p format
Most of the machine was made from laser cut 5mm mild steel plate. The rotating parts were made on a manual lathe using stock gears and Ball bearings. Every rotating element runs in ball bearings (Circlip and flange type ball bearings sitting in laser cut holes. Specified at .01mm oversize) there are no plain bearings.
A few hours maybe 4 were spent lightly filing and fitting joints and holes for bearings to fit in the steel plate.
Now that this one is finished I am starting on a new design 1200x2400 mm
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