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  1. #1
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    Designing new Router called Maximus

    Hi All- I'm about to embark on designing and building a new router. I thought I'd record its progress here. I've had two starts at it but have been interrupted. I decided to start clean sheet as some issues with two of my other routers have highlighted some of the long term wear issues with some components. So I've rethought a few things:

    So the rules of engagement: 1) target working envelope is 2400x700x300. I'd like to make it a full sheet machine but where it will live will not have the width. 2) Must be simple. All of my machines have been very simple and reliable as I have put the time into reviews and contemplation and full 3D modelling. 3) This one must cut aluminium as I want to make some parts for the next machine. The next machine will be a 5 axis router and I want to make the machine head. I'm tempted to make it a mill with a sliding table design but I have some long hydrofoils to make and I need a 2400mm plus cut capacity. 4) I have researched rack and pinion (plain and helix) but have not found an economical source for these yet so my current thought is to use 25mm wide AT belt. Very stiff. 5) I usually start designing the bench or base and work towards the tool. This time I'm going to start at the tool and work towards the bench. The Z axis is very important for cutting accuracy and I find I eventually compromise some of the geometry by starting at the base. This is because its like a pyramid and you run out of geometry as you get to the top. So by starting at the top I may end up with a bigger pyramid then I thought but at least it will be very solid. 6) I usually use routers but it's time to graduate to a spindle. So I'll do some more research on that. 7) I have to decide whether to use 15mm rail or 20mm rail. I usually use 20mm but the cost has gone up. Waiting on more quotes from local OZ suppliers. This has made me look for an asian supplier. Anyone know of a good one? I've used PMI, STAF and now WON brands.8) I've attached the napkin sketch of the Z axis and will get this into CAD asap. I use Alibre for this sort of mechanical design. I also use Strand7 and simsolid for FEA analysis of various bits. This helps in deciding which way to go if I have two designs. The stiffer one wins. 9) I usually use stationary motors on the y axis vs having a moving motor design. This is to lessen the weight of the gantry, make the wiring slightly easier as the motors are stationary and it also removes one idler. Idlers are expensive by the time I get them bored and buy bearings. The downside is that the belt run is twice as long so its half as stiff. To counter this I intend to put a motor at each end of the run. The stepper is nearly the same cost as the idler and this will increase the belt stiffness as it will be pulled and pushed along the drive side of the belt. I've had a play with this and it seems to work. I wire the two motors in parallel and drive them from the same driver. 10) Most parts will be laser cut stainless steel or aluminium as is Brevis and Scoot my other machines. Powder coat works out more expensive due to the extra handling involved. Plus I've had trouble with thick powdercoat making assembly difficult. 11) I'd like to get something metal 3D printed so will look at these parts for an opportunity or I'd like to make some of the parts in carbon fibre so will look at that as well. I made Scoot to make moulds and I've only done one mould in 2 years of use!!

    That's about it for now, when I get the Z axis modelled I'll put it up here for comment. Cheers Peter S

  2. #2
    Community Moderator ger21's Avatar
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    Re: Designing new Router called Maximus

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  3. #3
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    Re: Designing new Router called Maximus

    I will be watching with interest Peter.

  4. #4
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    Re: Designing new Router called Maximus

    Hello GER21 - thanks for the BTS address. Prices look good. My usual supplier stopped stocking the economy bearings and the price then doubled! Which in a kit like Brevis 25% the cost of the kit is the bearings. The price hike then makes it a hard to sell kit. May as well be a bigger machine as everything else is still the same cost. But onward and upward to Maximus... Thanks All

  5. #5
    peteeng
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    Re: Designing new Router called Maximus

    Started getting into the Z Axis. The aim is to minimise the stack height of the Z Axis linear bearings and the Gantry Bearings. These stacks add up really quick and then the gantry has to be cranked to get the spindle near the forward bearing. Or you accept a big overhang in the structure. I saw a tool plate like this on this forum somewhere and it's the inspiration for the Max redesign.

    So the tool plate is like corrugated iron, uses a thinner 5mm sheet to mimic a thick sheet and allows the tool to sit in a recess closer to the bearings. All of this reduces the stack. I usually use 20mm linears but again to reduce the stack it's going to be 15mm this time. The calc sheet shows that the tool plate is equivalent in stiffness to a 17.8mm thick plate which is good enough for the moment. Haven't decided whether it's aluminium or steel yet. It's also 38% the weight of the solid plate so we are well ahead here as well. I have to model the spindle and its clamp to ensure it tucks into the current space. The conventional drive is down the middle of the bearings. Obviously no go in this design. We shall see where this takes us as it develops. I usually try for the smallest elements but this time big will be beautiful...

    The 15mm bearings have a static capacity of 1650kgf and a moment capacity of 0.115kNm while the 20mm is 2436kgf and 0.221kNm. In round figures the 15mm are half the strength. But the figures stack up, won't be putting anywhere near the static loads on them. So it will come down to the moments. Will calculate these when we have more geometry to work with.

    I've also attached an image of MaxNo1 but this is being thrown out as early designs seem to go... Peter

  6. #6
    peteeng
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    Re: Designing new Router called Maximus

    I'm torn betwixt a high rail design and a gantry on columns. This machine will be long and thinish. I want to do full length plywood sheets but don't quite have the room to do a full sheet width machine at the moment. The high rail design will mean I have to lean over the rails to do a lot of the stuff I do which would be a pain. But the high rail design is stiffer and this machine is also aimed at aluminium. I want at least 250mm Z as this is what my current router called Scoot has. See the photo of Scoot cutting a rudder for a boat, hence I need a longer router! Been handy with waste boards, fixtures and vacuum clamps taking up Z space. So I think I progress the Z Axis to 90% and the gantry to 90% then decide. Peter

  7. #7
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    Re: Designing new Router called Maximus

    FWIW if I were going to do a machine ground up, it'd be a "high rail" style. So much more opportunity to stiffen up the gantry. As far as I can see the only real downside is fitting in oversized stock but, when you consider the more standard moving tower gantry alternative, you're not fitting overhangs in there anyway.

  8. #8
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    Re: Designing new Router called Maximus

    If I was doing all long stuff the high rail is the winner. But I do a lot of small stuff as well. Where the machine is going to go would make end access awkward. I think it's pointing at having two machines! I'm building a big shed at the moment and that's the right way to go once I have space. The big shed is so I can build big machines. I'd like to go to a 4or5m long 3m wide 2m high 5 axis machine for car panel moulds and yacht parts. The small machines are sort of learner machines for the biggies to come. Peter

  9. #9
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    Re: Designing new Router called Maximus

    OK first snag with the Z Axis tool plate - Its fine for narrow spindles and routers but for a big spindle the "gutter" will have to be wider. Most spindle clamps are designed to bolt to the vertical tool plate surface. This design has the end plate in the way even for the small router modelled. So the gutter needs to be wider to take a big spindle clamp. I'll have to survey the clamps to see what sizes they are... I've modelled an Ozito spindle and a clamp that I have for one of the Brevis machines here. It fits, but this machine will take a big spindle so I've got to figure those out. Peter

  10. #10
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    Re: Designing new Router called Maximus

    So I've had a look and I think 100mm land between the humps may do it. Anyone have thoughts out there? Is 100mm (4") enough for std spindle clamps? So the beauty of the the thick tool plate is you can put a clamp or mount anywhere on it. Peter

    edit: better be 120mm wide

  11. #11
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    Hi Peter.
    Will be watching this thread too.
    I don't know what spindle you are getting but i think the chinese round spindles 1.5 and 2 2kw are 80mm dia. So 120mm should be ok for the clamps. I have a square body spindle and it has mounting holes in the body so no need for clamps. The chinese square body are the same too.

  12. #12
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    Re: Designing new Router called Maximus

    Quote Originally Posted by peteeng View Post
    So I've had a look and I think 100mm land between the humps may do it. Anyone have thoughts out there? Is 100mm (4") enough for std spindle clamps? So the beauty of the the thick tool plate is you can put a clamp or mount anywhere on it. Peter

    edit: better be 120mm wide
    Are you going to fabricate the corrugated section or can you purchse it?
    Interesting idea.
    Thought about fabricating a 'stepped plate'.....hard to explain what I mean. 'top hat" shape?.....lol
    Maybe a corrugated section would be alot stronger?

  13. #13
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    Re: Designing new Router called Maximus

    Hi All- I get this sort of part laser cut and bent at various metal shops. I have to get a minimum order value usually so get other parts for other machines or wait till other clients place a sheet metal order and I tag it on. Scoot my first router was stainless steel laser cut and bent. The corrugated Z axis plate saves 20mm stack but results in a wide plate. Plus I have to integrate a drive which may add more width. If it gets too wide then it's back to a thick plate. If a thick plate it may be a plywood/aluminium sandwich but not there yet. Also thinking through the gantry and bearing plate as this is next step.

    It's not about strength its about stiffness. Strength and stiffness are often mixed up. Peter

  14. #14
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    Re: Designing new Router called Maximus

    Been working on the bearing plate to sort out the bearing logic. Would be great to get a combined crossed linear bearing so a bearing plate would not be needed. I'm sure I saw some of these in a catalogue once but can't find them now. Or if the manufacturer of these carriages made the hole pattern square so you could bolt them back to back. The battle is to get the bearings apart a reasonable distance and have them be able to be assembled in an order that makes sense. ie so you can assemble and square the Z Axis assembly on the bench, then offer it to the gantry and square it easily there. (ie they can't be on top of each other as they can't be assembled) This model is to visualise the basic geometry and start to figure these issues out. I have used three bearings because square rails provide moment resistance so in fact you only need one line of rails to prevent twisting or torquing (but 4 is still possible) . I did this with Scoot, I used only one bearings on each axis but about 6 months in, the light preload bearings turned into clearance bearings and wobbles appeared. Even though the single bearings were well within their specified load and moment specs. So paired bearings are much better and standard practice. Plus I now use heavy preload bearings.

    This model is parametric so when I change the size of the Z Axis plate the rest changes with it. So the geometry will be massaged to get the Z Axis travel to spec, then the bearing spacing will be sorted and the assembly logic will follow. A quick calculation shows the bearing spacing minimum to be 50mm so spacing is Ok. I've placed the gantry bearings outboard of the Z axis bearings and made the bearing plate long enough so I have access to the bearing bolts. On Scoot I had holes through the Z Axis plate to get access to the bolt heads. Another aim is to use the large bolts only. I use flanged bearings so they can be bolted from each side. With the H15 cars the bolt size is M5 but an M4 can be use from the back. M4 is not very stiff. So I think I'll use plain cars so they are more compact. The flanged cars and plain cars have the same rating. Peter

  15. #15
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    Re: Designing new Router called Maximus

    I think it's time for a design review:
    1) The corrugated Z Axis plate does limit the width of the spindle clamp. A gutter width of 120mm seems to fit most clamps and square spindles up to 2.2kW
    2) The corrugated plate has the same stiffness as a 17mm thick plate. Simulation will be done to confirm this
    3) It's been decided to place the gantry bearings "above and below" the Z Axis bearings a) to improve stability with wide gantry bearings and b) to allow easy access for bolting up
    4) There still is debate over 15mm or 20mm bearings. 15mm gives a small stack and so far the strength works out. I don't like M4 bolts they seem a bit small for the job. So 15mm flanged cars with M5 bolts is the pick at the moment. I'll compare costs before I redraw the design.
    5) The corrugated Z Axis plate loses 20-40mm in stack which is a plus
    Actions
    1) Freeze the bearing size based on cost and bolt size H15 or H20. From bst motion H15 and H20 are nearly same price $193 vs $209AUD so lets try the H15mm
    2) Freeze the gutter width based on available spindle clamps, currently 120mm wide
    3) Detail bearing plate or plates. I have an idea in which it will be two plates giving room for a central screw drive. Time for a redraw, see attached - Cheers Peter S

    I calculated the equivalent thickness of the mini plate and its 10mm thick. The actual thickness is 6mm. May make this 8mm thick. Time to redraw, detail a bit better and run some simulations.

  16. #16
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    Re: Designing new Router called Maximus

    I brought the Z Axis model into simsolid and ran the assembly with it extended and 100kgf applied to the bottom. I applied it in both directions to check the corrugation did not produce an asymmetric response. It deflected the same both directions so thats good. Simsolid makes MP4 movie files which this forum does not upload. So I figured out how to convert it to a WMV file via videostudio. It shows that the mini bearing plates and bearings are very stiff and that its the cantilever bending. That's good news. So now I have to decide a target deflection for this assembly then change the plate thicknesses to achieve that. The simulation model gantry rails are held rigid and the load is applied to the bottom of the Z Axis assembly.

    The current design has the gantry rails 200mm apart which is quite a chunky gantry... Been thinking about the high rail vs the low rail design and stiffness wins over convenience. So high rail here we come. Peter

  17. #17
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    Re: Designing new Router called Maximus

    I've modelled a 1200mm long gantry and added it to the assembly. This is to determine what bits have the most deflection. The Z Axis assm by itself deflected 0.2mm under the nominal 100kgf load. Now it deflects 0.3mm attached to this gantry. The gantry back sheet was initially 2mm thick but I increased it to 4mm thick as the gantry lozenged under load. A circle is the only shape that is stable under torsion but circular gantries are hard to attach things to!! So some shear webs inside the gantry tube will help. Maybe 3mm is good enough.

    So to summarise:
    1) The Z Axis plate needs to be stiffer. 0.2mm is too much deflection for where this machine is going. The mini bearing plates seem to be OK
    2) The gantry is big and stiff which is exactly what was ordered. In this machine the gantry is the Y axis
    3) The structural concepts are falling into place and the least stiff areas need to be addressed

    Actions
    1) Continue and add the gantry X axis rails to start on sorting the high rail design
    2) Once the high rails are figured out then we can start from scratch again, detail out the structural bits much better and start on adding the motion parts

    Are we having fun out there yet? Peter
    Attached Files Attached Files

  18. #18
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    Re: Designing new Router called Maximus

    Ooooh Yeah.....

  19. #19
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    Re: Designing new Router called Maximus

    Jumping ahead a little to the bench. A while ago I put some time into a router made from Formply called Boxi. I think Boxi's bench will be a good start for Maximus. So I'll reconfigure Boxi's bench into a Maximus. Then we shall have the entire structural concept very close to TAG. Want to get onto the motion parts... Peter

    addendum: Boxi will be completed as a paper plan set for those timber types that want to build a CNC Router. Formply is very stiff and cheap. If you have a good set of carpenters tools or machines you can build this sort of thing quite quickly. They are very stiff and are great for timber, foam and plastics. I developed some aluminium/plywood/aluminium laminates for some of the parts for increased stiffness.

  20. #20
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    Re: Designing new Router called Maximus

    Quote Originally Posted by peteeng View Post
    Jumping ahead a little to the bench. A while ago I put some time into a router made from Formply called Boxi. I think Boxi's bench will be a good start for Maximus. So I'll reconfigure Boxi's bench into a Maximus. Then we shall have the entire structural concept very close to TAG. Want to get onto the motion parts... Peter

    addendum: Boxi will be completed as a paper plan set for those timber types that want to build a CNC Router. Formply is very stiff and cheap. If you have a good set of carpenters tools or machines you can build this sort of thing quite quickly. They are very stiff and are great for timber, foam and plastics. I developed some aluminium/plywood/aluminium laminates for some of the parts for increased stiffness.
    Similar concept to this which has been made in many different sizes and configurations that are here on the Zone also momus CNC | benchtop DIY router plans | home page
    Mactec54

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