4' x 4' x 8" Router Build

[Kitwn]

Tha's reight old lad, cummin from't God's own country a shuda known bet'ta, but think tha'll fi'nd it's spelt ha'peth.!!. . . . cos we'll av non that posh "orth" rarynd here si'thi.

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!

Kit

[JonnyFive]

Mrs J5 is a Yorkshire lass, I’m going to have to ask her to translate.


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[Gustave]

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

[JonnyFive]

Hello JonnyFive, finally have you done the assembly of 2 x 120x80 suggested in the discussion or do you stay with 160 x 80 ?

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.

Cheers.


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[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.

Cheers.


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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

[JonnyFive]

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?

[routercnc]

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.

[JonnyFive]

That makes sense, thanks! I knew there was a reason I hadn't seen anyone else doing it.

[JonnyFive]

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!

[JAZZCNC]

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

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.
If not lowering the screw speed just go with a 1:1 ratio with a 10mm pitch.

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!

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.
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.

Pulleys - are HTD5 the ones to go for? I've modeled 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.

HTD 5 x 15mm wide is perfect for this job.
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.

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?

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.
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.