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    Default Re: Designing new Router called Maximus

    Hi Zorbit - List your questions here and maybe we can use Maximus as an example to answer these or I'll quickly answer them to get on our way. Thanks for participating. Peter



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    Default Re: Designing new Router called Maximus

    Re:Crossed Linear rails

    Hi Peter,
    I assume if one of the rails or bearings fail, the whole unit must be replaced?



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    Default Re: Designing new Router called Maximus

    Hi Sterob - Yes that's a thought. So better make it bulletproof. I suspect that cost will kill it but until the supplier gets back to me I'm not sure. Peter

    Last edited by peteeng; 04-15-2019 at 06:54 AM.


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    Default Re: Designing new Router called Maximus

    Hi Peter,

    is it possible to glue the gantry beam pieces together ? Strength won't be an issue, but I can't find info about the stiffness of the structure.

    I like the idea of glue because it means I can use a very flat front surface, and hold it straight, whilst assembling the back section and stiffening webs, with little distortion to that front face.

    Any thoughts appreciated on this, and also on a complete composite beam.

    Thanks,

    Steve



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    Default Re: Designing new Router called Maximus

    Hi Steve - You can glue any material together these days, even low surface energy plastics like polyethylene. So that's the go. One mantra I have with Maximus is to minimise bolts. That's one reason the gantry is made in two pieces. The rail bolts hold the rail on and hold the gantry together. A composite gantry is entirely possible and there are commercial examples out there. Some 20 years ago I helped in building a 100% carbon fibre 5 axis router with an envelope of 6m long by 3m high by 3m wide. All components were CF. There is great discussion in this forum on composite gantries. But you had better use a more descriptive word then composite. If I use an aluminium back plate and a steel front plate on Maximus it's a composite gantry. So you need to qualify your composite better: fibreglass, carbon fibre, timber/aluminium, etc. A glued structure is very stiff and damp. Planes and boats have been glued together for 50 years and now cars are glued together. In this forum there is a glued aluminium router/mill was very well documented. You need to start a thread and get some images & ideas up so people can comment if that's what you want to do. If you glue the gantry together I'd work with the geometric inertia of the gantry and neglect the gluelines. That would be very close to its real stiffness/rigidity. I would also be cautious in not mixing too many materials together unless you understand them very well. I encourage people to stay in fibreglass world or carbon fibre world or timber world etc. Combining lots of materials does not make it better...KISS Cheers Peter

    I have been working through the tutorials on bolted connections in simsolid. My aim is to fully simulate the bolted connections in Maximus. Simsolid will model the faying surfaces and predict if they gap or not. It will actually calculate the gap and shape of the connection and the area of influence of the bolt plus the load in the bolt. The images attached show the test bolt gapping and one image shows the area of influence of the bolt preload and connection traction. Looking fwd to Round 2. Back to designing a bench....Peter

    And Steve - You said you had lots of Q's put the list up...

    Attached Thumbnails Attached Thumbnails Designing new Router called Maximus-gap-jpg   Designing new Router called Maximus-traction-jpg  


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    Default Re: Designing new Router called Maximus

    Steve/Zorbit - Consider mdf or plywood as Gerry does so well. Here's a calculation to show it's just as good as aluminium. I did design a plywood router called BOXI prior to Maximus. But it did not fit my business model. I was thinking of releasing it as a plan set sometime. Having spent a lot of time with timber boat building/design even in survey and composites I'm totally comfortable with the idea of a timber machine. I see you work with titanium would love a Ti machine build!! Does your supplier have tubing? I used to make 6-4 bicycle frames. Cheers Peter

    Attached Files Attached Files


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    Smile Re: Designing new Router called Maximus

    Hi All - There's been a lot of discussion about damping in machines so I thought I'd write a little article on it. Now I can concentrate on the bench... Peter



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    Default Re: Designing new Router called Maximus

    Quote Originally Posted by peteeng View Post
    You can glue any material together these days, even low surface energy plastics like polyethylene.
    I have not been able yet to come up with a satisfactory glue solution for HDPE. I did not try the $200 or so glue from 3M though.



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    Default Re: Designing new Router called Maximus

    3M and others have expensive adhesives that do work. I used a scotchweld product to bond some PE inserts into a melamine panel mould. Then someone decided to change their place. We destroyed the melamine and the PE getting it out. There are acrylic adhesives for HDPE that are reasonably priced. Look up Crestomer.

    Recently I have bonded some HDPE "shoes" onto fibreglass springs for an undersea ROV that is used for a drilling sample rig. This is a very adverse environment yet they have performed as good as the screwed versions. In this machine which is about the size of a 20ft container they are slowly replacing all metal bits with composite and plastic. It journeys up to 3km to the bottom of the sea and drills deep holes for geotechnical data. I redesigned the 2.5m long carbon fibre springs for fibreglass to remove the electrolysis problem as most of the structure is aluminium. Peter

    Attached Thumbnails Attached Thumbnails Designing new Router called Maximus-shoe-jpg  


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    Default Re: Designing new Router called Maximus

    Quote Originally Posted by peteeng View Post
    I used a scotchweld product to bond some PE inserts into a melamine panel mould. There are acrylic adhesives for HDPE that are reasonably priced. Look up Crestomer.
    Thank you Peter.

    I did look up Crestomer. It looks like it is not available/can't be shipped to where I live. Your Scotchweld is interesting. It is a widely available manufacturer here. Do you happen to remember which type/number you used for the melamine plugs? Because I tried a few and the bond would come apart when a bit force was applied.



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    Default Re: Designing new Router called Maximus

    Look up Scotchweld 8009. I think it's that one. Been some years since I've used it. But all the major adhesive suppliers have similar product, just ask for low surface energy adhesives. Plus look up flame preparation of surfaces. Surface moisture is one of the biggest issues with bonding. A propane flame wafted over the surface removes moisture and can activate the surface. Look up videos of the bmw chassis manufacturer, they flame prep nearly everything before bonding... Peter

    More technical words are plasma treatment, corona treatment.



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    Default Re: Designing new Router called Maximus

    I've used Crestomer in place of epoxy / bubble fillets for joining grp sections on yachts. It's reckoned to be stronger than the epoxy for that application, much more flexible too. This stuff was translucent green, smelly, and came with a whole load of health warnings. I remember a bad batch that cracked as it cured.



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    Default Re: Designing new Router called Maximus

    Quote Originally Posted by davida1234 View Post
    Thank you Peter.

    I did look up Crestomer. It looks like it is not available/can't be shipped to where I live. Your Scotchweld is interesting. It is a widely available manufacturer here. Do you happen to remember which type/number you used for the melamine plugs? Because I tried a few and the bond would come apart when a bit force was applied.
    This is about as good as it gets for HDPE don't expect it to have a great bond this is not a material that bonds well, the best process for this material is fusion

    Attached Files Attached Files
    Mactec54


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    Default Re: Designing new Router called Maximus

    Hi Zorbit - Green and smelly says its a PMMA adhesive. Yep its acrid stuff!! But good...Crestomer is a brand name and covers several adhesive systems. The one I've used on boat structures is a hybrid urethane/acrylic stuff that is moisture tolerant. Urethanes use moisture as a curing agent so the surface moisture that is on everything is not a detrimental thing. It is with epoxies as they do not like water. We did several destructive tests with Crestomer 1152 and found it to outperform epoxy. No need for taping either and these were survey boats that we had to jump through lots of hoops to get it to the water. Surveyors and DOTs don't like new solutions.

    For routers in metal or timber simple epoxy with good prep is all that's needed. Use a hot air gun on metals or a flame before application... roughen surface with some grit paper, follow manufacturers instructions and all's good. Peter



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    Default Re: Designing new Router called Maximus

    Hi All - I've borrowed the bench and stand from Boxi a prior plywood router design to get Maximus grounded. Boxi used pocket screws and glue to hold it together. I'm now going through plywood supplies to decide on the biggest sheet I can get to create the the machine bed and get the 2400mmx700mm plus edge allowances or so bed size in one sheet. This will finalise the machine size. Once the machining size and footprint is frozen I can move along to Round 2. I know I've been talking about R2 for a while now.... I'm also still thinking about a metal bench, stiffness is king here...Peter

    Attached Thumbnails Attached Thumbnails Designing new Router called Maximus-max-2-jpg   Designing new Router called Maximus-maximus-1-jpg  


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    Default Re: Designing new Router called Maximus

    Hi All - I've done a bit more stressing and adjusting parts. Simsolid only displays values to 0.00 so I've been using 10,000N as the design load so I can see the differences to the third place so to speak. 10,000N is 1019kgf or 1.1 US tons. The structure would survive this with 314MPa being the highest stress in a small corner if we used G350 steel for the gantry front. But being a light router I doubt we will get past 100kgf tool load in reality. So we are now deflecting at 30% more than our 10N/um target with over 10X safety factor on stress. So you guys out there that keep saying its got to be "stronger" need to say it's got to be stiffer (there must be a joke in there somewhere) I have to widen the gantry and get the proper bench into the structural model. So I'll get the bench size frozen then can start the rebuild.

    I'll modify the comment about deflection. The force is being applied at the bottom clamp for consistency purposes. At the clamp its deflecting 0.95mm which is under the target stiffness ie 10,000N <1.0mm (10N/um) Happy Days...

    Currently in the simulation all faying surfaces are "bonded" which means they are more efficient than when we come to bolt them (maybe if we use the right bolts in the right places it will be equivalent) So the simulation is more like the structure is welded together at the moment. Ultimately I have to decide if the design is too expensive for the market that I target. But until we get to the design resolution that's a mystery. Peter

    Attached Thumbnails Attached Thumbnails Designing new Router called Maximus-maximus-1t-deflection-jpg   Designing new Router called Maximus-maximus-1t-stress-jpg   Designing new Router called Maximus-max-front-jpg   Designing new Router called Maximus-max-jpg  

    Designing new Router called Maximus-clamp-deflection-jpg  
    Last edited by peteeng; 04-18-2019 at 02:19 AM.


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    Default Re: Designing new Router called Maximus

    Quote Originally Posted by peteeng View Post
    Hi Zorbit - Green and smelly says its a PMMA adhesive. Yep its acrid stuff!! But good...Crestomer is a brand name and covers several adhesive systems. The one I've used on boat structures is a hybrid urethane/acrylic stuff that is moisture tolerant. Urethanes use moisture as a curing agent so the surface moisture that is on everything is not a detrimental thing. It is with epoxies as they do not like water. We did several destructive tests with Crestomer 1152 and found it to outperform epoxy. No need for taping either and these were survey boats that we had to jump through lots of hoops to get it to the water. Surveyors and DOTs don't like new solutions.

    For routers in metal or timber simple epoxy with good prep is all that's needed. Use a hot air gun on metals or a flame before application... roughen surface with some grit paper, follow manufacturers instructions and all's good. Peter
    Our destructive tests included chaining test pieces to a mooring buoy at low tide and leaving them there for several years. As far as I know, they're still there, checked yearly.

    More recently, I had to glue some 7075-T6 aluminium reinforcements into a hardwood frame and consulted the West Systems bible for advice. They recommend sanding the aluminium through the wet epoxy, to prevent the near-instant oxide layer from forming.



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    Default Re: Designing new Router called Maximus

    Hi Zorbit - the wet sanding method is tried and true. But immediately before you start, a waft with a flame or a heat gun to remove surface moisture is best. If you ever tig weld you will see the water leaving the surface of the metal ahead of where your are welding. We are on a water planet and water is everywhere. I also learnt about this when I was vacuum bagging various things and found that epoxy stuck to things like the polished surface of an extrusion like the proverbial. But if I had done this in atmosphere it would not have stuck. Under vacuum all the free water boils off so epoxy sticks to things exceptional well. When I was welding hovercraft parts we had hydroflouric acid to clean aluminium before we welded things. A very large tank of dangerous stuff. Anyways the oxide took about 4 hours to recover so it doesn't happen quite instantly.

    The aircraft industry does most of its secondary bonding hot, partially because of the epoxies used but also to boil off the water...

    To bring the day to an end I have turned the Z axis into a tube design. The back piece and front piece will be identical. I did have it as a shoebox fit but making such a fit in sheet metal is tough. So I shall use side straps and lots of bolts. Plus the spindle clamp can bridge across giving it the correct load distribution at the end. This one has 6mm thick bits vs the 8mm thick before and its same stiffness and weight. 0.98mm deflection at the clamp with 10,000N applied. Now the major deflection is in the gantry so need to tidy that up.

    I'm off for the weekend to do some towing launch tests on a flying trimaran, should be exciting.... Peter

    Attached Thumbnails Attached Thumbnails Designing new Router called Maximus-z-axis-jpg  
    Last edited by peteeng; 04-18-2019 at 07:32 AM.


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    Default Re: Designing new Router called Maximus

    Hi All - A brief summary of where the design is at. By the way the transverse rigidity is 4x the longitudinal rigidity. Peter

    Attached Thumbnails Attached Thumbnails Designing new Router called Maximus-max-transverse-jpg  
    Attached Files Attached Files
    Last edited by peteeng; 04-18-2019 at 08:13 PM.


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    Default Re: Designing new Router called Maximus

    Hi All - I'm back and the trimaran flew successfully and nothing broke!! Yeh, that's a 2 year project off my list. The 10 hour return driving time gave me lots of time to think about Maximus. I have been thinking how to evaluate and optimise the structure. With a stress domain object that is quit easy as you can work through the machine part by part, look at its stress state and do things to reduce the stress to the allowable limits. In fact several FEA systems can do this for you automatically. But with a stiffness domain structure no-one has given me a part by part deflection limit only a global limit. So reading Bamberg's thesis again he discusses stiffness or structural loops. I shall work it a similar way. He does the vector maths, I use simulation. I break the machine into its sub assemblies. The Z axis, the bearing plate, the gantry and the columns. I have isolated each assembly and calculated its individual Z deflection. Then I rank these against the global deflection as a %. This tells me the compliance contribution of each bit and therefore which bits to work on. Results:

    Global deflection 0.13mm in the Z direction from a 1000N load. This is at the collet by the way not the load application point.

    Z Axis 0.03mm or 23.1%
    Bearing Plate 0.01mm or 7.7%
    Gantry 0.08mm or 61.6%
    columns 0.01mm or 7.7%

    A bit glaring on what to work on!!

    The gantry contributes 62% of the deflection so need to work on this. I'm considering using a single SHS or RHS for this but need to talk to the laser people to find out if they can cut the size I want. (nope 150mm max so have to sheet metal the gantry )Plus I'm going to weld a full flange on the end vs the partial bolt up at present. I'm generally agin welding due to distortion but if they plug weld the flange on, distortion will be minimal (fingers crossed) I'd prefer to braze it but they don't braze so I'd have to pick the parts up, braze them myself and take them back and that's a 3 hour turn around so they can then paint the parts, too far to be economical... I also think the current column/gantry integration is poor. The other negative is that the Maker will have to tap all the holes if I use an SHS but then their time is considered to be free. The picture is becoming clearer... Peter

    Attached Thumbnails Attached Thumbnails Designing new Router called Maximus-3-z-axis-exagerated-jpg   Designing new Router called Maximus-2-max-z-axis-jpg   Designing new Router called Maximus-1-max-z-axis-global-jpg  
    Last edited by peteeng; 04-21-2019 at 07:52 PM.


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