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Ermm to me by arranging the profiles at the top of the 160 side pieces your wasting 80mm of height that could be used to lower the gantry height and increase stiffness or keep as it is and gain clearance.
The gain in having the motors under the bench isn't worth wasting stiffness, also moving the motors to the outside will shorten the belt length.
Also, the slightly elevated sides put the rails up higher and stop debris from hitting them directly and building up against the rail.
Those are some extremely good points..Quote:
Originally Posted by JAZZCNC
By moving the motors to the outside of 160x80 profiles, the belt lengths will be shorter and I will be able to move the 80x80 profiles down 80mm. This in turn will decrease the needed height of my gantry sides by 80mm while also protecting the Y-axis rails.
There is no doubt, I will make those changes. Maybe I could even change the sides to 200x80 and be able to make the gantry sides even lower! Now it starts to turn into a raised gantry design. The drawback will be that it becomes more difficult so access the machine table from the side, when e.g. fastening the workpiece.
Thanks JAZZ!
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Yep there's always going to be some trade off with design like this, you just have to decide which is most important to you.!Quote:
Originally Posted by NordicCnc
Yes.Quote:
Originally Posted by JAZZCNC
If I think about it, side loading would not be too complicated with only 200mm raised gantry sides. You can still reach for all the clamps quite well and large wooden sheets can be loaded from the front.
The purpose of the high gantry sides was exactly for that reason, to simplify side loading. But now when analysing the problem closer, this will probably not have any impact to me at least.
Time to modify the design... again!
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Hello, I like the way you're showing how your design is evolving, it's great for other people to learn from.
I notice your servo mounts for the x axis (long axis) are separate pieces. Could they be combined into the aluminium end plate you're using to hold the profiles into a 90degree corner?
Regards
Bob
Hello,Quote:
Originally Posted by BobTSkutter
Thanks for your feedback! I am glad that you appreciate it.
About the servo motor mounts (the long axis is the Y-axis in my case). The servo motor mounts and the BK15/BF15 bearing spacers are exactly the same as the ones used in the X-axis (gantry). The goal here is to have as few different parts as possible (commonality and re-usability).
Yes, it would surely be possible to have the motor mounts integrated into the end plates. The design of the BK15 bearing plate would perhaps need to look a bit different and. The servo motor axis length and the end plate thickness are the constraints. Machining is needed in the servo motor mounts in order for the motor axis to align with the ball screw (the F-length can be machined longer but the motor axis length can't be changed) and also allow for timing pulley mounting. Too thick end plates or too shallow motor mount machining, will make the motor axis length to short for mounting any kind of pulley. I also like to have the motor mount bracket separated from the machine. This way I can design new brackets later if I want to change the servo motors for some reason, without tearing down the machine itself and then having to realign the axis/ball screw.
Good point anyway and I like your idea. I will have to check the feasibility of this!
If you are bolting into the 80x80 ends through the 160 sides then I wouldn't waste the aluminum on those endplates because they offer very little to the stiffness, There are no forces involved in those areas so they are more cosmetic than structural.!
Quick update based last feedback collection. Many thanks to everyone contributing with their opinions!
- Raised gantry design with 200x80 item profiles. This allows for significantly lower gantry sides and will increase stiffness. It will also protect the Y-axis rails when they are further away from debris.
- 120x80 item profiles as table bracing, bolted through the 200x80 using counter bored holes. Alternatively I will use some item equivalent connectors, but I think bolting through is better in terms of rigidity.
- Motors on the outside, to allow for shorter belts and also lowering the table bracing to the bottom plane.
- End plates replaced with end caps from Item. These are only for aesthetics.
Attachment 27649 Attachment 27650 Attachment 27651 Attachment 27652 Attachment 27653
Next up will be figuring out cable routing and placement of proximity sensors. Is there any significant difference in terms of tolerances when comparing mechanical and optical sensors?
Its coming along very nicely Nordic.
What software are you using?
Thanks Sterob! I am using Siemens NX for CAD. I would probably use Fusion but I am lucky to have a work computer with a NX license. In the future I plan to move to Fusion, to ensure that whatever happens with work, I will still have CAD access, lol.Quote:
Originally Posted by Sterob
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Home & limit switches
Z-axis home switch at the top end of the travel. Soft limit will be used for the lower end of the travel.
Attachment 27667
X-axis home switch & limit switch on the moving part. Adjustable bolts in the t-slot in the lower right and upper left of the picture. The lower right will be used for home & limit switch and the upper left will be used for limit switch.
Attachment 27668
Y-axis home and limit switch on the moving part. Adjustable bolts in the t-slot on the left side of the base frame. Upper left one is used for limit switch and lower right one is used for home & limit switch. On the opposite side (right side) is the second home switch. The purpose with 2 home switches is to be auto to auto square the gantry when homing the axis.
Attachment 27669 Attachment 27670
Alternatively I could have all the proximity sensors fixed and not on the moving parts. Then I could use soft limits for all axis's in the opposite end of the homing position, same way as with the Z-axis. Would that be a bad idea? It would be less cable routing of the sensors in the cable drag chains,
I'd recommend having the homing positions on the dual screw axis finely adjustable - like how your Z position can be adjusted by turning that bolt. At the moment you'll have to loosen that bolt and t-nut and just hope you can push it accurately back and forth. It'll help when trying to square the gantry, where you need (ideally) sub-mm changes to switch triggering position and I wish I'd thought of that earlier. I've had to do quite a bit of back and forth trying to get the gantry squared.
You can work around it in software (I can't remember what controller software combo you're planning to use - but generally speaking its possible), but easier done once in hardware.
I personally would have the switch fixed and have the target movingQuote:
Z-axis home switch at the top end of the travel. Soft limit will be used for the lower end of the travel.
Yes, that is how the Z-axis switch is planned in the picture.Quote:
Originally Posted by Clive S
Extremely good point, thanks for letting me know. I will make some changes to the design to allow for fine adjustment.Quote:
Originally Posted by AndyUK
The proximity sensor at the top of the Z-Axis appears to be very close to the grease nipple on the bearing block. Could the grease nipple cause interference with the sensor?
Adjustable bolts looks like a clever way to adjust the trigger point but are the bolt heads big enough for the gantry limit switches to "see". The sensor is round and I think you're using set screws which appear to be the same size as the sensor with the hex indent in the middle. It looks to me as though the hex indent is exactly where you want the sensor to trigger. Would using a conventional hex head bolt instead of a set screw be better?
Regards
bob
Yes sorry I was looking at it wrong.Quote:
Originally Posted by NordicCnc
Good catch, but this is just a 3D error that I didn't correct yet. I plan to have all grease nipples facing inwards and with a common lubricating hose and nipple externally mounted.Quote:
Originally Posted by BobTSkutter
As for the screw heads, I am not sure really. This is something that I can easily fix later if it turns out it is not working as planned. I have access to both lathe and mill so manufacturing a better target, e.g. with a flat surface for the sensor will be possible.
Don't waste your time, the way you have it now will work fine, that's exactly as I do them. It's simple and works. If I was to make a suggestion it would be to move the switch onto the side, fastened to the ballnut bracket and use the top slot for targets. How you have it now leaves the switch wide open to debris when cutting and if you cut steel or aluminium then could get false triggers when blasted with chips. Also the crap from cutting aluminium with lube can build up on the sensor.Quote:
Originally Posted by NordicCnc
Again exactly as I do them and they work fine, the round head doesn't cause any issues. The only suggestion I'd make is to stiffen up the bracket. The one I use are 3D printed, You can just see it between the mass of pipes and wires in this pic.Quote:
Originally Posted by NordicCnc
Attachment 27671
For users of LiunuxCNC with the option to auto-square the gantry it is essential that the switches cannot overshoot their targets during deceleration and reset themselves before the whole sequence is finished. In this case you may need a larger target, especially with a large and heavy gantry.
Thanks for the suggestion. I will check the feasibility of moving the sensor to the ballnut bracket! I was also thinking that for fine adjustment with this simple setup, one could use a dial indicator when adjusting the target.Quote:
Originally Posted by JAZZCNC
Looks good.I think I could make a stiffer bracket out of aluminium without any problems. That X-axis ballnut bracket looks interesting. If I am not mistaken I would think you are using a rotating ballnut. Any chance I could get a closer look at that? :eagerness:Quote:
Originally Posted by JAZZCNC
I see, I didn't know that! Luckily I will be using Mach3! If I still need a bigger target for some reason then I can lathe a new target.Quote:
Originally Posted by Kitwn
The devil is always in the detail.Quote:
Originally Posted by NordicCnc
You won't need to adjust it to that degree. I don't use Linux CNC but believe it just works like any other gantry squaring routine in that it sees the switch and you tell it in software how far from the switch you want it to move so it squares the gantry. The switch is just a trigger, the closer you get to square the better because your not loading the bearings, etc, but you don't need it to be to the micron.!Quote:
Originally Posted by NordicCnc
The size of the target shouldn't make a difference if the switch distance is set correctly. What a larger target does allow is more room for clearance, basically, it allows more room over shoot, which you don't want anyway because of the twisting gantry.
Also if you are using Servo's then it's all immaterial because you'd use Home-to-Index, so again you just using the switch like a trigger, then the servo will Index to the Encoder.
Yes I used to make them out of aluminium but I prefer to 3D print them now because if anything hits them the bracket snaps off and saves the switch. The bracket is strong enough so it doesn't flex causing false triggers etc but yet weak enough to snap if thumped with somthing heavy.Quote:
Originally Posted by NordicCnc
Regards the Rotating Ballnuts then yes your right. All Axis except Z-axis are using rotating nuts but I cannot take any claim for the design, Jonathan designed them and kindly allowed me to use.( I actually bought some of the parts from him and made the others) If you search the forum you'll find a thread about them.
Attachment 27673
@NordicCnc
Can I ask you a couple of questions regarding your CAD drawings that you're posting here...
1. Were they done using Fusion360?
2. Have you modeled all the elements yourself, like the carriages and rails etc, or have you just found existing DXF files and imported them?
3. If imports then could you share the source?
I'm asking because I'm using F360 and am having real problems with the dimensions of my imported DXFs. I've been using DXFs from the HiWin website, but whenever I import them into a design the dimensions are all out. The imported DXF are never the same dimensions as they are on the 2D drawings, so aren't really useful.
All I'm doing at the present is just using solid shapes to represent the items I want. So a HGH20CA carriage for example is a block 77.5 x 44 x 25.4 with a channel running through it to represent where the rail goes.
Looking at your design drawings, you seem to have everything fine?
Cheers
I don't use F360 but would imagine it works just like Solid works where it will allow you to import Step or Stl models which if Hi-win don't supply a direct F360 format like they do for SW you could use. DXF is mostly a 2D format and you want a 3D model.
Also for Component models I use Traceparts
https://www.traceparts.com/en
I use Siemens NX which I am lucky enough to have a work related license for. If I wouldn't have that I would probably be using Fusion 360.Quote:
Originally Posted by joe.ninety
The linear rails and blocks are downloaded as STEP files from the hiwin configurator: https://motioncontrolsystems.hiwin.c...near-guideways
The ballscrews I have modeled myself without any threads. This is because I want to model the ballscrew F-lengths myself, and I have no need for the thread visualization anyway
I also use traceparts and grabcad for other models like servo motors. I like the STEP format best, no issues so far!
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@NordicCnc
Thanks for that tip re the Step files. I went back in and re-downloaded all the files as 'Step' and my problems went away.
The only problem with the rails is that you need to specify a length before the website will create the 3D file for you. Think I'll knock up my own version and just keep that as a 2D drawing that can be extruded to the length required. Although it will obviously lack the actual positioning of the mounting holes.
Cheers
Thanks for that tip. Looks like an interesting site.Quote:
Originally Posted by JAZZCNC
Cheers
Just get a few different lengths and lay them on top of each other, aligning with each bolt hole to keep the spacing. It's always better to work accurately and mate the bearings to the surfaces of the actualy rail they would run on, this way you don't get accumulative errors building up as the model grows.Quote:
Originally Posted by joe.ninety
Short update:
No progress for the last 2 weeks on the router design. I have been really busy with other projects and commitments. I had already bough 180W servos but those I already returned for some 400W servos with integrated drives. Those servos are now fitted on a Hitachi Seiki lathe (huge lathe with 400mm 4-jaw chuck) with a 1:1 ratio on the X-axis and a 2:1 ratio on the Z-axis. Ballscrews are 2005. WOW, I can now run the lathe at 10m/min without any problems. Ballscrew whip is no problem. I am very happy with that upgrade.
Anyway back to the router. Since I will be using servo motors with a 3000rpm rated speed, I thought I could take full advantage of that. I plan to do the following:
- Swap the 2010 ballscrews to 2020 on the Y-axis and X-axis.
- Swap the 1605 ballsrew to 1610 on the Z-axis
- Change gearing ratio from 2:1 to 3:1 on all axis. This will give me more torque, with lower ballsrew rpm while increasing the ballscrew pitch.
- Add belt tensioners to get more teeth engaged because of the 3:1 gearing.
This will limit the ballscrew speed to 1000rpm, and increase the Y- and X-axis maximum feed rate to 20m/min. Z-axis feed rate will stay at 10m/min. I feel like this is a better idea than trying to spin the ballscrews at 1500rpm with the 2:1 ratio. I want to take full advantage of the servo motors RPM.
On another note I was planning to use 400W (maybe even 750W) Delta servo motors, with dual motors on the Y-axis. I need to do some calculations if it would be a good idea to go for 750W. Anyway I saw on YouTube that there is a auto tuning function available in the software but I am not sure how to tune the dual motors on the Y-axis.
- What do you guys think about the increased ballscrew pitch, 3:1 gearing and belt tensioners?
- Is it possible to auto tune 2 motors at the same time?
- Perhaps I could change the design and use only 1 servo motor on the Y-axis with belt drive connected to both sides. This in turn will not allow for squaring the gantry with motion controller but I think i can get it square any way.
- How wide can the gantry be without having to use dual slaved Y-axis motors?
So machine design is now what I consider 99% completed so that I can start ordering parts. Since none replied on the ballscrew change I've decided to do the following:
- Keep the 2:1 ratio
- Change Y- and X-axis ballscrews to 2020
- Keep the Z-axis ballscrews as 1605
- No belt tensioners
- Double Y-axis motors will be used
I will put together a shopping list for all components so that I can get as much as possible in one order without missing anything. The final piece of design was to find a good location for the Y-axis home/limit switch. Cable chains I will fit later and wont add those to the 3D at all. Please ignore that the screw is not in the center of the limit switch. I will lathe and mill some custom screws but I could not care to design those yet. :victorious:
Attachment 27849 Attachment 27850 Attachment 27851
Final assembly!
Attachment 27852 Attachment 27853 Attachment 27854 Attachment 27855 Attachment 27856
Some things still bugging me is the 120x80 for the gantry. I hope that those will not be too weak for machining aluminium with the ATC spindle. I am still consider changing to 160x80. JAZZ, if you read this, I remember that you wrote somewhere that for larger machines you use the 160x80 for the L-shape gantry. Since my gantry is 1200mm wide and I am using an ATC spindle, would it be wise to go for 160x80 anyway?
Can I just ask what the benefit is of using blocks of profile to sit the gantry profile on, as indicated in the picture?
Attachment 27859
It seems because of this you were forced to place the bottom linear rail on the front, thereby pushing the spindle further away from the gantry. I'd always though that the idea is to try and keep the centre of gravity of the spindle as close as possible to the bearing blocks the gantry rides on.
This is not in anyway meant to be a criticism, but just me trying to understand if this design means there are benefits to it that outweigh the spindle being pushed further outward.
Cheers
As a rule you ideally want the spindle IN the same envelope as your X axis bearings, i would make the distance between these bearings further apart.
Those block are used to increase the gantry clearance. I want to build machine out of aluminium profiles and the 200x80 profile for the Y-axis sides are not high enough. Also by placing the linear rail on the front of the X-axis will allow me to use the work area fully, without increasing the footprint. If I were to put the linear rail on the bottom of the gantry profile I would lose approximately 160mm in the X-axis travel.Quote:
Originally Posted by joe.ninety
You are right about the overhang, but I would claim that it is not that critical. As long as the Z-axis and gantry is stiff enough, it should not be any problem at all. If you check other builds, the overhang is similar!
Thanks for your comment.
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Ok well I'll answer this question seen as he's mostly following my design.!
It always makes me smile when I see comments like these because while the physics shows that what you are saying is the ideal location the reality is that it makes no difference to the machine and how it works.
To prove this point I'm going to give you a challenge.! . . . Industry demands the highest cut quality and performance, so logic dictates that they would follow the physics and optimum location very closely.?
So go find me a machine from the major manufacturers that place the spindle smack between the bearings.! . . . If you find one then I guarantee you'll have seen ten before it that don't.!! . .. In fact, you'll be lucky if you find any with spindle inside the bearings.!
You all need to stop worrying about the physics and virtual world so much and get building so you can realize just how little if at all, these affect a real-world machine.!
Exhibit: A
Attachment 27860
To answer you directly Joe, then to place the gantry further back to bring spindle into line with bearings would actually weaken the machine not make it stronger. To do what you suggest without getting into complex gantry side designs means using plates for gantry sides that can flex side to side and introduce vibrations at the tool.Quote:
Originally Posted by joe.ninety
I can tell you from building many different designs of router that the design he's using is the best possibly way to build a router without getting silly about.
Mike is correct in that having longer distance between the bearings is good but thats a trade off between travel and foot print of the machine. In the grand scheme again it makes very little difference.
Quote:
Originally Posted by mekanik
Can you explain what you mean? I am not sure I follow.Quote:
Originally Posted by mekanik
Edit: I think you meant the spacing between the Y-axis bearings? Doing this would also decrease the Y-axis travel. I also want to be able to machine dovetails at the end of the table, so overtravel is a must!
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I was working on the assumption X was your Base and Y your Gantry, Dean is the go to man for advice and if he says it's OK just crack on.
Regards
Mike
I see! My design is defined with Y-axis on the base frame, X-axis on the gantry and then Z-axis on the spindle. Anyway thanks for checking in!Quote:
Originally Posted by mekanik
I have started thinking about precision tools that I will need for the build. I have a post already on the forum where JAZZ explained the tolerances very well: http://www.mycncuk.com/threads/13435...hinists-square
I already own a good dial indicator so now I need a set of straight edge and/or machinists square.
- Do I need both a straight edge and a machinists square, or would just a machinists square be sufficient?
- What straight edge length is required? Linear rails are 1500mm (Y, base frame), 1200mm (X, gantry) and 500mm (Z).
- What machinists square dimension (height x width) is required? Linear rails are 1500mm (Y, base frame), 1200mm (X, gantry) and 500mm (Z).
Helios Preisser straight edges:
- Steel square straight edge, cross section 40x8mm, length 1000mm, DIN874/2, @44,40€ https://online.helios-preisser.com/p...1050432013%5D)
- Stainless steel square straight edge,cross section 40x8, 1000mm, DIN874/2, @98,00€ https://online.helios-preisser.com/p...4973167720%5D)
Helios Preisser machinist squares:
- Steel square with base, cross section 30x5mm, length of beams 1000x500mm, DIN unknown?, @57,00€ https://online.helios-preisser.com/p...1027812493%5D)
- Steel square with base, cross section 50x10mm, length of beams 1000x500mm, DIN 875/2, @165,00€ https://online.helios-preisser.com/p...4525824975%5D)
- Steel square without base, cross section 30x5mm, length of beams 1000x500mm, DIN unknown?, @24,50€ https://online.helios-preisser.com/p...0938670859%5D)
- Steel square without base, cross section 50x10mm, length of beams 1000x500mm, DIN 875/2, @135,00€ https://online.helios-preisser.com/p...0456342882%5D)
So many options, but I think that the DIN874/2 and DIN875/2 would be sufficient. Then it is only about with or without base and the length?