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    Default Planning a new build. CNC laser cutting in Brisbane?

    Hi All, I am planning a new build for a mill with a working volume of about 200x200x150 mm. I am thinking of building with aluminium and filling with polymer concrete. Can anyone suggest a good CNC laser cutting outfit in the Brisbane area who could cut parts from 4-6mm aluminium sheet?
    thanks and happy new year, Rob

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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    don't have anyone for laser cutting but could you share more details as to what you are planing to do like spindle power, expected speeds, rigidity, purpose, accuracy all the gruesome details



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Hi nicklefish, It is in the pretty early design stage. I have already bought closed loop steppers, 0.5 and 1.5 kw spindles, ballscrews, rails etc. so I have some design constraints. I have done watch repair for some time as a hobby and now that I am retired, I would like to design and make one.



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Hi,
    there is really only one question...'do you wish to cut steel or not?'

    If you do that determines that the machine be extremely rigid, if not then the pressure is off.

    Craig



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Hi Rob - Try Gold Coast Laser GCI they can cut 6mm al sheet easily. There will be a minimum charge.

    https://gcigroup.com.au/

    I'd forget about filling tubes with EC. Make the tubes bigger, stiffer and heavier in the first place much better solution. Epoxy is $$$ more then metal. Then this points at using steel if you want weight. Peter



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Hi,
    I made my mini mill (180mm x 180mm x180mm travels) out of cast iron elevator weights.

    The weights are nearly 1m long, 220mm wide and 120mm thick. I got them at the scrap yard for just a little over
    scrap value. I then proceeded to cut them up and make axis beds by milling them on an old Bridgeport copy
    at work. I made a lot of iron chips!

    The quality of the cast is questionable, I found a few inclusions and there was a 'rime' on the outside which was hard on tools
    when milling the rime off. None the less I ended up with two beds 480mm x 200 x 65mm and one about 600mm x 200 x 65mm
    for about $400NZD which includes the purchase of the weights and half a dozen 16mm HSS endmills.

    My wee mill does a good job for its size. The 24000 750W spindle I got from Germany and does a great job engraving, aluminum and
    plastics but it does not have the low speed torque that you need for steel and stainless. I made a second spindle from a Rego-Fix
    ER25 cylindrical toolholder, matched NSK P4 angular contact bearings and a second hand Allen Bradley 1.8kW 3500rpm 6.2Nm (cont)
    servo and drive. Its great for steel but shows up the rigidity, or rather the lack of it, in my machine. I would have sworn it was bullet proof....
    but its not!!!

    I am making a new and larger (350mm x 350mm x350mm travels) mill. This time I am going to get the beds cast in grey iron. The beds are
    750mm long, 250 mm wide and 130mm deep with minimum thickness of 50mm. They will weigh about 120 kg each.

    The frame that hold the XY combination at right angles to the Z axis bed is still in the design phase, but the rough sketches and wooden
    mock ups suggest two right angle flanges tapering to 75mm at the ends from150mm at the right angle and 50mm thick. The design
    of the webs is still under development. It will have to wait until the new year when I can sit down with the foundry man and get some tips
    on how the pattern and mold will work. I'm almost decided on SG iron for the frame.

    If you want to machine steel you need rigidity and cast iron is STILL the material of choice. Steel and aluminum sections are wonderfully strong
    for their weight but as flexy as hell, short of extremely thick sections, of epoxy-granite is not that much better.

    If steel and/or aluminum and/or epoxy granite were as good as cast iron then wouldn't you expect Hass, Okuma, Mori Seiki etc to be making
    their machining centers that way? They don't...they use iron...and lots of it.

    All of this begs the question....'do you wish to machine steel?'. If you do then you must learn the difference between rigidity and strength.....
    there is a world of difference.

    Craig



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Hi Craig and others - To explain conventional wisdom a bit. If you are going to make lots of something then its sensible to cast it, hence "cast Iron" is a good material to use as it casts easily. It also has the property of good damping and lubricity if you are using ways. Its stiffness is about half that of steel depending on the alloy so thicker sections are required due to the lower modulus and the casting constraints. Many precision machine builders choose EG as it is very damp and can be cast into intricate shapes easily. Its modulus is about 35GPa. Strength is rarely a concern in machine design due to the rigidity required producing parts that are so big the stress is very small. Big fast machines have very big inertial loads and this requires mass to produce stability so the machine does not dance. Even my small benchtop router will skid around if I ramp up its acceleration too far...So it is counter productive to make light machines. However if you secure the machine to the planet via a large concrete slab and make a lightweight machine it will move faster if you need speed. It can be as rigid as you like in aluminium, steel or whatever material you want. For instance industrial robots are very light and very very fast and they have to be bolted to the planet to function.Printed titanium is becoming very popular for many automotive and aerospace and sports products and I expect that will become common in high speed machines as it is stiff and damp by design. Ti is a bit stiffer then CI (<100GPa) around 110GPa. Steel is 200GPa and Al is 70GPa for general info.

    Modern analysis methods identify vibration modes and these can be eliminated in the design stage. Aluminium and steel fabrications use plate which is thin and these tend to vibrate. These can easily be found in modal analysis and eliminated. The major machine suppliers spend a lot of time analyzing rigidity and vibration. They use the best material for the job and that may not be CI every time. I think that an equal performance machine could be made in aluminium vs CI for instance as long as the AL machine was bolted down and adequate effort was placed into understanding its vibrations. CI is about the same density as steel 7000kg/m3 whereas aluminium is 2700kg/m3.

    So I dispute the CI is the best no matter what dogma. It has its place but other materials can be used if they are understood and used well. Peter



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Hi Peter,

    So I dispute the CI is the best no matter what dogma. It has its place but other materials can be used if they are understood and used well. Peter
    Yes, I understand and agree, if you are prepared to use thick enough sections you can make any material stiff enough for a CNC machine.
    The problem here is that many DIY designers will use say a 6mm RHS steel section, and it will be very strong but my 50mm x75mm x30mm thick casting
    is way stiffer, and not coincidentally 10 times heavier! The reason that cast iron is STILL the premier material for rigid machines is because the sections
    used are SO MUCH thicker than anyone would consider sensible if using steel, and its the thickness, or rather cross sectional area that is so critical to
    a stiff machine.

    The major machine suppliers spend a lot of time analyzing rigidity and vibration. They use the best material for the job and that may not be CI every time.
    No doubt you are correct, however the only machines that I have had the opportunity to look at closely have ALL been cast iron.....and big bits of it as well.
    I'm sure the manufacturers used the best most cost effective material for their machines and cast iron STILL PREDOMINATES.

    For instance industrial robots are very light and very very fast and they have to be bolted to the planet to function
    Industrial robots are a totally different machine, they need to be fast and so they are built as light as they can be. Even a large robot arm has a remarkably
    small rated load. Such an arm might be great for an automated welding process say but it could not hope to contain the cutting forces of a mill spindle.

    My post about using cast iron firstly in my mini-mill and now in my current build was to indicate to OP that cast iron is not absolutely restricted to
    heavy production machines and the 'Big Boys' of the CNC world, hobbyists can still, if determined, either use cast iron and mill or otherwise machine it
    to shape or have stuff cast. Further my post was cause him to think very clearly about whether machining steel is a requirement for his machine.

    It would appear that DIYers and Hobby CNCers have something AGAINST cast iron....like its not a kosher DIY material? Somehow Epoxy-Granite
    has assumed some sort of moral high ground as a hobbyist material.

    Many precision machine builders choose EG as it is very damp and can be cast into intricate shapes easily.
    Cannot iron be cast into intricate shapes? Of course it can and we have a long history of doing so.

    Epoxy is $$$ more then metal
    I quite agree.....epoxy in large volumes is not cheap. I have used epoxies a lot over the years from model aeroplanes to boat building and repairs,
    its an amazingly versatile material, but if I'm going to spend big dollars on a DIY machine, in parts and materials, then I want the best my money
    can get me....and that's STILL cast iron!

    When I first started in CNC it was mainly to make circuit boards but I wanted to machine steel as well. It was that requirement that took what could have
    been a simple and cheap router into something else entirely. I have enjoyed the learning process and have some creditable results but I have to admit
    in insisting that my machine be steel capable I have made a difficult project for myself....you might call it a mistake if were not feeling charitable.

    Craig



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    You may find laser cut steel is cheaper.

    No reason to use aluminium if you are getting someone to laser cut the parts.

    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)


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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Hi Craig - We all have favorite materials but I'll point out that industrial robots can now lift 1300kg, reach 3.5m (on a track this becomes infinite) and have a repeatability of 0.01mm standard. You can order precision grade that's even better if needed. I'm sure if you put a spindle on a titan it would cut steel easily. These machines are aluminium and many are now using carbon fibre arms.





    https://au.dmgmori.com/products/mach...4300-3d-hybrid

    There's many ways to skin the proverbial CNC. Industrial processes change very fast once economics, needs and technology fall into line. CI may be one of them now 3D printing is mainstream and machine envelopes are getting big enough to make large machine parts. Peter

    Attached Thumbnails Attached Thumbnails Planning a new build. CNC laser cutting in Brisbane?-titan-jpg  


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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    What an amazing response! Thank you for all of your advice. I will mainly mill various brass alloys. My main concern is accuracy because they will be watch parts, some of which fit in an area of only a few square milimetres. I have C5 ballscrews and closed loop servos which I hope will be enough.



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Another thing to consider, which I don't believe has been mentioned, is thermal expansion.

    Aluminum, having more than double the thermal expansion coefficient of steel or cast iron, will expand at a greater rate as the machine warms up.

    I have often wondered whether machines utilising steel linear rails firmly attached to aluminium frames are prone to the bi-metallic strip phenomon as they heat up.

    Whether thermal expansion is an issue for you will depend on the tolerances you are expecting to maintain.

    regards, Oz



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Hi,

    I have C5 ballscrews and closed loop servos which I hope will be enough
    Yes, C5 ballscrews are definitely up to the job as are closed loop sevos. Depending on speed and to a lesser extent load open loop steppers
    are also damned good.

    Accuracy for your purposes is determined by ballscrew accuracy, particularly cyclic accuracy, backlash and machine rigidity.

    My machine is intended to vigorously cut stainless steel with 16mm tools and is a far FAR cry from what you need. I need thick section cast iron
    (or other thick section materials) to get the rigidity required whereas you can go much MUCH lighter and still have a machine that is rigid enough for
    your purposes.

    I am tempted to agree with others that steel sections/parts maybe better, you are likely to have more resources and skilled individuals in your local
    area with steel whereas those resources and skills are rather more widely dispersed with aluminum.

    I also agree with Peeteng that thicker section steels will result in better overall performance than thinner section steel-epoxy combination.
    If you have not cast epoxies before there are a few surprises and techniques to be learned before you can get good results.
    One good epoxy exotherm event will prove my point!

    The only other recommendation, or rather observation, that I have is not to be tempted to make the machine too big.

    On this forum, and others, are any number of threads where the DIY designer has built the biggest machine he/she could but with
    material sections better suited to a machine half the size. The result is a substandard (in terms of rigidity) machine.
    If you double the size of the machine the cost goes up exponentially.

    Accuracy depends on rigidity. You can bolt on an upgraded ballscrew or upgraded servo but what you can't do, easily at least,
    is bolt on 'more rigidity'.

    Craig



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Hi Oz - yes thermal expansion is an interesting thought. CI is about 10x10-6 m/m/C Al is 24 and mild steel is about 11. So steel rails to CI is a good match. EG is about 13 I think....Peter



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Quote Originally Posted by peteeng View Post
    Hi Oz - yes thermal expansion is an interesting thought. CI is about 10x10-6 m/m/C Al is 24 and mild steel is about 11. So steel rails to CI is a good match. EG is about 13 I think....Peter
    Yep...that's why I wonder about the bi-metal effect with steel on ally.

    If I understand it correctly, a metre long piece of ally grows .023 (rough average, depends on grade) for every 1 degree increase in temperature but the steel rails only grow .014 (based on average for Nickel alloy). If the rails are securely fastened to the ally frame, one would have to assume there is some bending at least trying to happen.

    This would happen just with the daily temperature change, without even considering the heat being induced due to operation.

    PS.... sorry to OP, didn't mean to hijack your thread.

    regards, Oz



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Hi Robdon - One thing you will need to consider with watchmaking is runout. You can have lots of accuracy in your structure only to be caught out with some runout in your spindle. So you need an uber stiff z axis and structure which is pointing at steel (unless you go cast iron or solid granite) and very accurate motion parts. By the way I have been speaking to my local stonemason and cut pieces of granite seem to be quite economical. He has a big CNC wet mill and can cut blocks and drill to spec. Maybe there is one close to you? cheers Peter S



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    Default Re: Planning a new build. CNC laser cutting in Brisbane?

    Try Laserworx Australia, I had some motor mounts laser cut by them. Price was good and quick turnaround.



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