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My dad was pure-bred Yorkshire (though he was born in Karachi, only because his mother was there at the time) but was educated at Cambridge so the odd posh turn of phrase was known to escape his lips. Not often, mind!Quote:
Originally Posted by JAZZCNC
Kit
Mrs J5 is a Yorkshire lass, I’m going to have to ask her to translate.
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Hello JonnyFive, finally have you done the assembly of 2 x 120x80 suggested in the discussion or do you stay with 160 x 80 ?
Gustave
Hi Gustave, I haven’t done any assembly yet, I haven’t been able to spend any time on the project recently and I’m still tweaking the design. I will be using the 120x80 when I get around to it, the maths says it will be a lot stiffer.Quote:
Originally Posted by Gustave
Cheers.
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Quote:
Originally Posted by JonnyFive
Thank you, I think I will also going on L shape based on 120x80.
I am designing a nearby machine and I have the same R&P and ball-screw dilem ! For the moment I think going on ball-screw for price (Fred BST), precision, easy to achieve. The X is 1800mm length and I plan to use 2 x 2510 ball screws. I bought servos motors (Simdrive AC system 750W, Holding Torque (N.m)
2.4, Peak Torque (N.m) : 7.2, Rated Speed (rpm) : 3000) and I hesitate between direct drive or the use of pulley with a ratio 2: 1. Do you have any advice for me?
Best Regard
Does anyone have any thoughts on mounting the rails as below, it gives a slightly greater distance between the rails than mounting the lower one in line with the top one - is it likely to be a pain to get everything parallel?
Attachment 28977
There is probably a theoretical small gain with the rails set such that the line between them is somewhere around the centre of the overall L shape, and they are furthest apart. But I can’t help thinking you would loose more in the box plates around the outside with vibration and flex. Personally I would put the lower rail directly below the upper so they are close to the front where the Z axis is.
Also the top and bottom plates look a bit thin. 20mm is ideal then the closer plate on the back is less critical. You can delete it, or if you still want it then 6mm would be fine.
That makes sense, thanks! I knew there was a reason I hadn't seen anyone else doing it.
Finally some progress! This project has been rolling along slowly in between the many other things that I've had going on, thought it was about time for an update.
This is where I'm at:
x-axis:
2010 x 1480mm ballscrew geared down 2:1 from 4Nm NEMA 23 motor
2 x 20mm x 1450mm HIWIN rails + 4 x HGW20HC2R carriages
y-axis:
2 x 2010 x 1750mm ballscrews geared down 2:1 from 4Nm NEMA 23 motors
2 x 20mm x 1900mm HIWIN rails + 4 x HGW20HC2R carriages
z-axis:
1605 x 412mm ballscrew geared 1:1 from 4Nm NEMA 23 motor
2 x 20mm X 400mm HIWIN rails + 4 x HGH20HCA1R carriages
Frame:
The frame is a mixture of 60 x 60 x 5 and 60 x 120 x 5, possibly overkill with the bracing so might think about simplifying it a bit.
I am planning to use a strip of steel with rivnuts to secure the y rails to the frame rather than tapping the frame - thought this would give a bit more adjustment.
Gantry:
2 x 160mm x 80mm in L configuration
Intermediate mounting plates for squaring the x & y axis
I'm at the point now that I really need to tie down some key components so that I can finish detailing everything and have a few questions for the hive mind:
Motors - Are the CNC4YOU 4Nm NEMA 23s the way to go for all 4 motors? Electronics is definitely not my strong point, I'm going to need a lot of help to get through that part of the project!
Pulleys - are HTD5 the ones to go for? I've modelled up 14T & 28T (copied from Joe's amazing design) and there are a couple of things I'm not so happy about. Firstly the motor shaft is not long enough for the pulley when using one with a boss, it overhangs the end which doesn't seem ideal. The alternative is to use a pulley where the grub screw is on the toothed part and it seems like that will munch through the belt as it rotates - anyone got experience of this pulley type? My second concern is fitting the smaller pulley onto the 20mm ballscrew - the shaft is nominally 12mm which looks too big for the pulley to fit, turning the ballscrew down to 8mm or so seems like it might be too weak? The alternative to this is increasing pulley sizes which will make the motor pulley quite large.
Cable chains - What size do I need (I'll be using a water cooled spindle)? Should I use the same size for all 3 chains or should they get progressively smaller?
I appreciate all the help, cheers!
Attachment 29695Attachment 29701Attachment 29696Attachment 29697Attachment 29698Attachment 29699Attachment 29700
Why are you gearing 2:1 if using a 10mm pitch.? It's not required and would actually be detrimental to the machine as it will be slow. If you are trying to lower the screw speed then go with a 20mm pitch and then use the 2:1 ratio, this will give the same travel velocity as 10mm but with half the screw speed.Quote:
Originally Posted by JonnyFive
If not lowering the screw speed just go with a 1:1 ratio with a 10mm pitch.
Yes, they will work but if you are going to this trouble then I would go with Closed-loop steppers as the price difference isn't massive and they are much more accurate.Quote:
Originally Posted by JonnyFive
Also, it's not just the motors you need to decide on, the drives which control them and the voltage you run them at are important. Don't go with any drives that are rated, 50Vdc Max. To get the best from 4Nm motors you'll want to be running them around 60-65Vdc or 50Vac if the drives support AC voltage which many do these days. You also need a safety margin on the drive's Max voltage or around 10%, so if using 60Vdc you want drives with a max voltage of 70Vdc or more.
HTD 5 x 15mm wide is perfect for this job.Quote:
Originally Posted by JonnyFive
Regards the grub screws then turn the Boss inwards so it's on the shaft if possible, if not then it's ok to drill between the teeth provided you remove any burrs. However, you say you are putting the small pulley on the screw.? You have this the wrong way around, you want the small pulley on the motor and the large pulley on the screw if you want 2:1 ratio.
Larger is better, the worst thing you can do is use too narrow cable chains and have the cables rubbing against each other, worse still if your running noisy cables like the spindle cable with signal cables like limits, etc, which you will be.Quote:
Originally Posted by JonnyFive
You also don't need 3 chains, on the machines I build I only fit chains on X-axis and Y-axis, the Z-axis which is mostly just the spindle cable and water pipes, I run thru flexible conduit.
The energy chain I supply has internal dimensions of 25 x 58mm.
This pic shows the flexible conduit and energy chain, there is the same chain at the rear of the gantry.
Attachment 29717
Hi Jazz, thanks for the reply, I appreciate the help.
I thought I'd read about gearing the motor / ballscrew to lower the screw speed to prevent whip whilst keeping the motor running at it's most efficient speed? Maybe I've got it all wrong. So 1:1 is the way to go is it?
As I mentioned the electronics side of things is really not my strong side, the more I read about it the more lost I get. Could you point me in the direction of some suitable closed loop steppers? I've had a look but they seem to be around £200 each? I had been thinking of going with a UCCNC ethernet controller, is this a good option? Do closed loop steppers need a different controller & drives?
I had put the big pulley on the motor based on what Joe did in his video: https://www.youtube.com/watch?v=gQz9G_Dlv3w about 45 seconds in.
The cable chains I have modelled are 50 x 17.5 internal - I'll increase this to 25 x 58mm as you suggest.
Thanks again :beer:
Yes this correct but the way you had it was doing the opposite, this would double the screw speed not half it.Quote:
Originally Posted by JonnyFive
The reason Joe used a large pulley on the motor with a small one on the screw was to increase the speed because he only had 5mm pitch ball-screws. So he needed the 1:2 ratio to get the extra speed but in doing so he doubled the screw speed which increases the chance for the whip.
As the above demonstrates, Be careful with blindly following someone else's component choice or build thread if you don't fully understand what or why these have been used.?
It's very easy to select the wrong components and end up with an unbalanced machine or worse completley unusable machine.!
You can get them cheaper than that, but if you are not in a rush I can supply you with 4.5nm and drives from Lichuan that I fit on machines I build. Unfortunately, at the moment I only have enough stock for the machines I'm building, however, I have an order being produced at the moment and will have new stock in about 10 weeks' time.Quote:
Originally Posted by JonnyFive
Yes, it's very good, I use it on the machines we build and fit the AXBB-E ethernet controller. Again I can supply you with UCCNC and Controller if you want to PM I will give you prices.Quote:
Originally Posted by JonnyFive
They don't need a different controller but they do need drives that are matched to the motor/encoder. They are often sold in matching sets.Quote:
Originally Posted by JonnyFive
I think part of the problem is I don't have the motor performance curve, I have worked out the ballscrew critical speed is about 1000RPM (end fixity type C - right?) but not sure what speed the motor should be going.
I'd definitely be interested in motors, drives & controllers - I'll PM you. I won't be ready for them for a few months yet so no major hurry on my part, I just need to know what size to design brackets to at the moment.
I think I've remebered how I got confused with the 2:1 gearing, think I read somewhere about using 2020 ballscrews and then gearing them for lower RPM. 2010 seems to be the norm for a 4' machine so will go with that.
I've made a bit more progress on the design......
I have removed the gear reductions, now the x & y axes are geared 1:1 with 20T pulleys and the z is direct drive. I am still working with the 4Nm Nema 23s on all axes.
I have also tidied up the end stops and proximity sensors.
The x & y cable chains now have inner dims of 25 x 57mm (I couldn't find 25 x 58mm).
Think I'm nearly there with the mechanical design, soon be time to concentrate on the electronics - not looking forward to that one!
:beer:
Attachment 29768Attachment 29769Attachment 29770Attachment 29771
Looks good to me. The only thing I would point out is that you have the proximity sensor end-on. There's very little room for deceleration between detecting the gantry and being smashed by it. A safer option is to have the sensor pointing uipwards so that it detects the gantry riding above it. You already have a non-smashable mechanical end-stop in case that fails.
Kit
That’s a fair point, I’ll look at moving them through 90 degrees. Thanks!
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I personally would turn the Z axis sensor the other way round ie. fit it on the back plate. This will make the cable neater.
You could just drill the back plate.
I like the sound of that! Thanks.Quote:
Originally Posted by Clive S
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Thinking about it, I think the reason I didn’t do this is because the sensor would have to be where the lower target thingy is now and there isn’t enough depth to fit it between the gantry and z plate. Unless I’ve misunderstood what you’re suggesting?Quote:
Originally Posted by JonnyFive
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I haven’t looked at the data sheet for the sensor but. I’d assumed that it would be triggered 2 or 3mm before contact and I could then have the hard stop almost flush with the sensor z. How much overrun should I allow for? I guess when it’s travelling at speed something like 5-10mm would be better?Quote:
Originally Posted by Kitwn
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You need about the same length as a piece of string! All depends on the weight of the gantry, your approach speed for homing (crashes at rapid speed will hopefully be avoided by soft limits once the machine is homed which is the first thing you will do after switching it on) and some stuff to do with drivers that other regulars will understand better than me.Quote:
Originally Posted by JonnyFive
Your Z and other axis (it's Y on my machine but X on many) sensors are right. In practice the overlap of the sensor and your target will not be very much when it triggers. I put slots in the mountings of my targets to make things adjustable but this does increase the risk of something moving and messing up the repeatability of homing.
Kit
The distance is determined by the sensor spec, if using just for homes then 2-3mm won't be a problem but if using for limits then usually you will be traveling at fairly high velocity when tripped so the inertia will easily travel 1-2mm if at high feeds.Quote:
Originally Posted by JonnyFive
Also, the accuracy and sensitivity are affected by distance, so it's best to keep the distance on the smaller side of the sensor spec. This way it will react faster but obviously if end on you have less room to stop. 90deg is a much safer setup.
Finally got around to sorting the proximity sensor bracket:
Attachment 30001
I think I'm finally there with the design, still need to finalise the motor choice and sort out some sort of levelling feet - can't decide whether to add levelling casters, they're pretty expensive but probably worth the money if I ever need to move the machine. At the minute I've just got M12 nuts welded on to the base of each leg - they look a little small to me but it seems M12 feet are good for 1000kg each - should be enough!
Attachment 30002
I made some steel discs as targets for mine as the sensor will be more sensitive than on aluminium, but both will work.
Just been pricing up the steel to make my frame, the price has gone through the roof!! Almost double what it was when I last looked!! Ouch!
Tell me about it, and it doesn't just stop at the steel, aluminium has also gone crazy. The price of steel is also driving up the price of motors, ball screws and anything else made with steel. Then on top of this shipping costs have gone crazy.Quote:
Originally Posted by JonnyFive
That’s all I needed to hear, how am I going to explain it to my missus?!?
Do you need to tell her :surprise:Quote:
Originally Posted by JonnyFive
I am in the same boat as you. 2018 was the last time I was on here and almost was ready to start it after 2 years of learning and designing from some really top guys on here. It was so easy to source materials and mild steel box sections was cheap as hell but now as you say they have doubled in price and I can't even find any suppliers for ball screws and the ones I have for linear rails they only stock a few. Not even looked at the electronics side yet. Dont know if I should just save money and wait to see if things go down and new suppliers start selling or keep searching and hoping for the best.
Jazz - do you have a feel for how much things have increased overall? Has everything doubled? Just trying to estimate how much extra I need to find.Quote:
Originally Posted by JAZZCNC
Oh Yes, I certainly have a feel for it, every month I feel like I've been Butt F^@£ by one supplier or another. Steel has indeed doubled at least and Aluminium tripled for some grades.Quote:
Originally Posted by JonnyFive
This isn't just in the UK either, Even China and Asia are struggling with the rising material cost's. I have never had a Chinese or Taiwanese suppliers apologise because they are increasing prices and in the last 3 weeks I've had 4 suppliers all say the same thing.
On top of this, the cost of shipping has gone crazy, container prices used to be around £2000, now they are anywhere between £10,000 to £12,000 and taking longer to arrive IF you can get them on a ship.!
Airfreight you need to sell a kidney if it weighs more than a mouse. I've just paid £560 to fly 2 ATC Spindles over that would have cost £120 before Covid started, Why when planes are sat on the ground with no passengers.?
I used to fly most of my stuff over a few machines worth at a time, Now I'm shipping by sea freight 20 or 30 machines worth at a time and motors etc by the 100's just so I can keep continuity and be sure prices are kept sensible. The downside being I'm weeks and months behind waiting for stuff to arrive and I'm paying more for the privilege.!
It's the same with Steel and aluminium, I used to buy steel box section 5 or 6 lengths at a time, enough for a couple of machines. Now the only way I can get sensible prices is to buy 30 lengths. Sheet steel is even worse, I'm paying the same now for 3mm as I paid for 10mm 6 months ago.
I would allow at least 40% extra to what you probably think was going to cost.
If you are serious about building then I wouldn't wait for prices to come down either because I don't think it's going to happen any time soon and it's still going up with no sign of coming down.
Careful Dean we will be adding to your delivery soon �� I am hoping mine doesn't come to more then £6k if I'm honest but if it does I'll sweet talk the Mrs a little more
I was thinking the same, I could be waiting for years for prices to come down, best to just crack on and suck it up.Quote:
Originally Posted by JAZZCNC
Oh, and don’t tell the missus [emoji6]
Usually telling them after it is built works best...:highly_amused: Esp, If you want a divorce..:stupid:Quote:
Originally Posted by JonnyFive
I'm trying to finalise the ball screw design and noticed that the standard dimensions from BST don't seem to be compatible with the FK15A bearings - looks like the spacers eaither side of the bearing are too long and there's not enough length to get the locknut on the end:
Attachment 30108
Am I missing something? Do I have to turn down the spacers? I'm planning on tweaking the end to have 2 locknuts rather than using the grubscrew, just want to make sure I'm doing it correctly.
Cheers,
Have you purchased the ball screw and bearing FK15A from Fred if so he should have machined it to match the bearing.Quote:
Originally Posted by JonnyFive
Also did you tell him the "F" length you wanted it is normally 15mm as standard but I usually tell him to make it 30mm so as to get more space for a pully.
I am not familiar with that bearing.
It's been slow progress over the last few months. I've spent the last month or so trying to work out how much this thing is going to cost me, looks like it's going to be around £5.5k.
Here's what I got so far:
Steel box section for the frame:
I have scavenged some 80x80x3 box section from work; I have redesigned the top of the frame and the main leg uprights to use this, the rest will be 60x60x5 & 60x120x5 as previously planned. The price of steel is insane at the moment, it's going to cost £750 for the rest of the steel I need - my original cost was £500 when I priced up the entire frame a couple of years ago!! I've been trying to figure out if I've over engineered it, compared to most other designs I've looked at I seem to have an awful lot of steel in there.
Parts from BST:
Original HIWIN Brand Linear guide
2pcs HGR20-L1900mm Linear rail
2pcs HGR20-L1450mm Linear rail
2pcs HGR20-L400mm Linear rail
8pcs HGW20CC-ZA-C Carriage
4pcs HGH20CA-ZA-C Carriage
=USD629.00
Our own Ballscrew Assemble Set
2set RM2010-L1770mm ball screw with SFU2010 Ballnut
1set RM2010-L1480mm ball screw with SFU2010 Ballnut
1set RM1605-L322mm ball screw with SFU1605 Ballnut
All with end machining according your need,1770/1770/1480/322mm is the TOTAL length for each
3pcs 2010 Ballnut Housing
1pcs 2010 Ballnut Housing
1pcs OD25-8x10mm Jaw Coupling
1pcs MBA12 Motor Bracket
USD182.00
2set FK15/FF15 End support-Superior type,FK with P5 grade Angular contact bearing and FF with better deep groove ball bearing
1set BK15/BF15 End support-Superior type,BK with P5 grade Angular contact bearing and BF with better deep groove ball bearing
1set FK12/BF12 End support-Superior type,FK with P5 grade Angular contact bearing and BF with better deep groove ball bearing
6pcs M15x1 Locknut
2pcs M12X1 Locknut
USD145.00
1set 2.2kw spindle motor set=1pcs 2.2KW 220V 4 bearing motor+VFD+80mm Clamp+Water pump+Pipe
USD265.00
6pcs HTD-5M-20Teeth-15mm Wdith Pulley
4pcs HTD-5M-15mm Width-250mm Belt
USD22.00
1pcs 1000mm 25x38mm Cable chain with end connector
2pcs 1300mm 35x75mm Cable chain with end connector
USD26.00
Weight is about 57kg,discounted freight is USD650.00,so totally is USD1919.00.
= £1417
Aluminium extrusion for gantry:
2 off 160 x 80 x 1620mm (with drilling / tapping) = £1064
Aluminium tooling plate:
I've calculated approx £500. I was hoping to get these made for me but there is a maker space recently opened up near me that has a CNC mill so I am thinking it will save me some cash and be a good introduction to CNC to sign up and make them myself.
Closed loop steppers & drivers = £500
Electronics:
I've estimated £500 to cover the PSU, enclosure, cables etc - is this about right?
Miscellaneous:
Estimated around £500 (not including PC and software)
Is there anything obvious I have missed? Are my estimates about right?
I have reworked my frame to include the 80 x 80 x 3 that I have, I used it on the machine bed and the main uprights - I figured the bigger second moment of area compared to 60 x 60 x 5 would make these parts stronger. The frame now looks like this:
Attachment 30747
Attachment 30748
Attachment 30749
Attachment 30750
I am also pondering whether to have just a single aluminium extrusion for the gantry to save a bit of money. I can see that it adds a lot to the stiffness to the gantry but £500 each piece is a big investment. I have seen people get pretty good results on lesser machines with far smaller gantry sections. For example a single 160x80 section has a second moment of area 22x greater than a gantry made from C-beam. I'm not 100% convinced the extra cost will result in a significantly better machine - interested to hear what people think of this?
This is how the machine looks now:
Attachment 30751
Attachment 30752
Things just got very real, just ordered all the steel for my build!!!
Finally the first step to making this thing a reality, excuse the terrible welding!!!
Attachment 30944
Attachment 30945
Attachment 30949
Attachment 30946
Attachment 30947