About to fall down the rabbit hole ??

[JAZZCNC]

When beginning to draw up a design, is it better to find the sizes of linear rail and ballscrew that are readily available and size the frame to those existing components. Or just draw the machine out to the desired size and worry about those after?

Design the machine you want then have the components made to size. It's highly likely because of budget you'll buy Rails and ballscrews from China and they will machine ballscrews to your spec. Same with rails, they'll cut to your exact size or like Neale says just buy little longer than needed and cut your self.
The important part is choosing the correct diameter and pitch to suit your machine. Depending on length you'll also take into consideration end bearing type but don't worry about that yet your still some way off worrying about those things.

Are Nema 23 steppers a good fit for a machine of this size, 1200mm maximum assuming a twin ball screw design on the Y axis?

Yes perfectly fine but need to look closely at the spec because not all steppers are equal and come in various flavors ie: 4 wire 8wire.
Like Neale indicated the inductance rating is important but this rating changes depending how the phases are wired so you'll need to understand this to get full picture. Without getting too technical I'll explain quickly the differences and why one type/setup suits Router better.

The phases of Steppers can be wired in 3 ways depending on how many wires motor come with. These are Bi-polar series, Bi-polar parallel, Uni-polar. With Modern drives only the first two of those are used so won't explain Uni-polar.

Series Wired motors generaly provide high torque but require high voltage to achive high RPM. This is because the inductance is much higher.

Think of inductance like pushing car with sticky brakes and the people pushing being the voltage. The more sticky the brakes the more people needed to push car the same speed.
So lower the inductance the less voltage will be required to achive same speed as high inductance motor, or put another way, with same voltage the motor will spin faster if inductance lower.

So series wired motor are generaly best used for machines like Mills or Lathes which don't require high feed rates(rpm) but do require more torque due to heavy design.
Also because series wired motor uses roughly half the current of Parallel wired motor smaller lower cost drives can be used.

Parallel wired motors are pretty much the opposite. The inductance is half that of series wired so require less folks to push, down side being when going uphill those folks will need to be stronger. In real terms what this means is that double the current will be required when wired parallel.
In performance terms what this allows is that higher RPM can be achieved and they hold the torque further up the RPM range, down side being there is less torque at lower RPM.

Now this is where it gets little confusing to people because motors come in 4 wire and 8 wire(often called Hybrid).
4 wire motors are fixed by the manufacturer and can be wound either series or parallel, often they are series wound.
8 wire motors can be wired in either way by joining wires in certain order. (they can also be wired Uni-polar)

So cutting to the chase for Router builder your better using 8 wire motor with low inductance when wired Bi-polar parallel. This setup when combined with correct voltage(65-70Vdc) gives best performance.

Is there a best practice order of design? Z axis first, gantry (X) first or any other methodology?

Like any good structure it all starts with solid foundations. Design from the bottom up and each will form the other.

[routercnc]

In terms of the machine design process it is fairly iterative and you need to go around the loop many times as every choice has a knock on effect that ripples through the design.

Assuming you are building a fairly standard machine with moving gantry and raised X axis then I'd suggest you draw the spindle with your favourite tool in the collet and place the tip about 150mm above the top of the bed plane.

Draw the Z axis plate that holds the spindle and make it say 300-350 mm tall by 150 wide. The bottom of the plate should not be lower than the main spindle body. Add the Z rails to the back of this plate making them at least 300 mm long and ideally matching the height of the Z plate.

Add the lower carriages to the Z rail placing them no lower than the main body of the spindle. In the CAD program slide the Z axis (spindle, Z plate and Z rail) down until the tool hits the bed plane. The lower carraiges should remain in place.

Add the upper Z carraiges near the top of the rail, leaving 10mm or so if you want a bit spare to face the bed.

Draw the Y axis plate which hold the Z carraiges on the front side. On the rear of this plate add the Y carraiges making sure they do not clash with the Z carraiges and that it can be assembled!

The Y rails can then be drawn to fit the Y carraiges and the gantry drawn.

Add horizontal plates on the ends of the gantry and fit the X carraiges to the underside. This dictates the X rails position.

Draw the frames to hold the X rails and then add vertical supports under these frame sides to connect down to the bed frame.

Add the steppers, ballscrews, ballnuts, and ballscrew mounts and the fun starts. Things get tweaked and moved to get it to work. I would say this bit takes the most time so hang in there.

Finally plenty of advice on hand on this forum to guide you. Best of luck!

[Ollie78]

Thanks for the great responses to my questions.

I was thinking of starting with the Z or the spindle as you suggest routercnc. I can see what you mean about everything affecting everything else which was partly where my difficulty starting.
This gives me a good start.
Great tip about setting the height from the bed to the tool straight away.
I will remember Jazzcnc`s comment about starting with the strong base too....

Do you do suggest sort of rough drawing on fusion (or whatever software ) first just using plain rectangles etc, to get the shape and then do a proper one with the profiles of the extrusion and the carriages etc, or just go straight in with the full detail.

I have been attempting to gather dxf files of aluminium extrusions and the Hiwin stuff. does anyone have a source to a library of this sort of thing.


Thanks

Ollie

[routercnc]

I went to the Hiwin website and they have a selector program where you can select the carraige type the rail type etc and it will output a solid model in a range of formats. These are 3D models in a range of formats (e.g. step) not dxf which I believe are only 2D line drawings and not what you want.

When I used the Hiwin tool the model it exported was one entity and the carraiges could not be slid around once in the CAD program. I was Ok with that as I used simple surrogate rectangles and cylinders for the design and only added holes and details at the end. Saying this you do need to think about where the bolts will go so they don't clash when you model the holes at the end and have to make changes.

CAD for extrusions are usually on suppliers website but for initial design just use a rectangle with outer dimensions to match a commonly available size.

If you use steel rectangular hollow section in the design make sure you model the outer corner radius as leaving them square makes it look like you can bolt things right up to the edge.

[Ollie78]

Hi everyone, and thanks for all your advice so far.

Whilst planning my build I have still been checking on the used machines on ebay etc. One came up that looked sturdy and was about the size I wanted (actually a bit bigger than I was planning). Anyway I made an offer and now this lives in my workshop.








I put those wheels on so I can move it on my own, I might leave them on but if it causes problems then I can take them off once its fully installed. They are just sort skates that slip on to the frame.

It has Hiwin 15mm on the Y axis with central 25mm ballscrew
Hiwin 20mm on the X with 25mm ballscrew
Hiwin 15mm on the Z with 16mm ballscrew
Motors are nema 34 size not sure about strength of them
There is homing or limit switches on the x and z but none on the Y.

The electronics live in an old PC case
A Breakout board uniport from diycnc
2 leadshine SPS705 power supplies
3 Kimco stepper motor drivers



The frame is mostly 45mm by 90mm extrusion and the x and z plates are all 20mm.

The spindle is 2.2kw chinese watercooled, it is controlled by this thing.



However it only seems to be controlled by the small dial and switches at the bottom which adjusts the speed but reads in hertz so I will have to do some maths on that. The other buttons on the removable control bit don`t appear to do anything.

So now my new mission is to get this thing working perfectly so I can learn about everything and get productive, I would still like to build my own but this might be a better use of my limited time at this point.

I got the machine running with the PC that came with it mach3 was installed as well as Vectric aspire (which i never got a chance to use). I managed to get everything jogging nicely using mach3 so I know that the power supplies and stepper drivers are all working at least.
However before I managed to get much further, I was trying to establish a home position etc. The Machine stopped jogging and didn`t want to respond. The only evidence of an issue was a red light on one of the sps705 power supplies. So I rebooted everything and then I got this unhappy sight.



So I am a bit stuffed for now. However when I turn on the system all the LEDs in the control box are green again (not sure exactly what this means but I am looking at it positively).
I will try to recover the system with a usb boot recovery if I can ( it is running XP I think). If not its new pc time.

This leads to a question (first of many) .
Should I stick with an old system with parallel port and 32 bit or go for a more modern and thus hopefully reliable windows 8 or 10 system ?
I am thinking of a small media box type pc with maybe fanless design for less dust issues or even a laptop.
As I understand it this would require another board to communicate with the PC via ethernet or USB and the parallel port on the breakout board.
Any recommendations on best method for this?

Computer problems aside I started cleaning up all the ballscrews and tracks etc. I cleaned up the x axis ballscrew and track with some boeshield and it came up nicely.

What is the best grease to use for the ballnuts and carriages ?
The bigger 20mm carriages have grease nipples but the 15mm ones don`t have any. How do you grease these ones.



Also I have noticed that the bearing on the drive end of the X axis is a bit clicky and needs changing the same bearing on the Y is suspect too. Z is fine.

The blocks are these ones



The shaft has been turned down to 12mm just after the bearing before the coupler, the bearing block is 26mm wide and about 70mm high. does anyone know the name or type of this block bearing?



Can the bearing be replaced easily (ie without a press) or do I need to get the whole block?

What water/ coolant is best for the spindle, it has a small fishtank style pump. I am just using the same water (demineralized apparently) that was already in it. But I will be making a better tank arrangement before i use it again.
Oh and can you buy those green grommets for the rails separately? the holes were filled up with dust.


Thanks for reading all that.

Ollie

[Clive S]

I think you have done well if you bought it right. Now re the pc. first I would re-seat the cables to the hard drive and re-seat the ram as well. Before you start loading a new operating system try putting the drive (as a second drive) in another pc to see if you can recover any data from it like the XML file from the Mach3 folder as that will contain all the settings ect.

Bearings blocks you can buy the bearings (they should be AC bearings 2 No.) they should come out quite easily notice which way are fixed in there (ie back to back or front to front) the bearings will have numbers on one side to identify them. They also might have a shim between them.

The bearing block is known as a BK type It looks like a BK15 and the other end of the screw a BF type if it is floating.

[Doddy]

What water/ coolant is best for the spindle, it has a small fishtank style pump. I am just using the same water (demineralized apparently) that was already in it. But I will be making a better tank arrangement before i use it again.

My own system is a PC water cooling pump with integral tank, and a fan cooled radiator (also PC cooling). The story goes that a bit of car coolant/antifreeze will inhibit algae growth, which looks to have held true on mine for the last couple of years

[Doddy]

The bigger 20mm carriages have grease nipples but the 15mm ones don`t have any. How do you grease these ones.

https://www.hiwin.com/pdf/lubricating_instructions.pdf

Add a grease nipple.

[Ollie78]

Doddy, great link, thanks.
I think I should be able to add grease nipples to the end of the blocks as shown in the manual which looks the simplest method.
However I have not been able to find anyone who sells them separately yet. Found a company selling loads of different ones but couldn`t see the thread size of them in the hiwin document.

Clive S, thanks for the info on bearings, I think they are BK17 as 25mm screws. Glad to know you can change the bearings without getting new blocks which may save a few quid, I will take one off when I get time and have a look.
As for the computer I have had a wiggle with the connectors etc and blown all the dust out with an airline. Tried a CD with the recovery part of XP only ( no original disk) but it wouldn`t have any of it. I will see if my brother can help as he is very good at IT stuff.

I am thinking of getting a UC300ETH-5LPT ethernet motion controller which I hope could be installed with everything else in the control box remaining the same. ie between the PC and the BOB .
This means that it wont matter what computer I use in future.
I am planning to use fusion 360 for cad/cam (its free and powerful ) but it will only run on 64bit systems. Also moving forward more and more software is going to be like that.

It seems like the uc300 eth was made for UCCNC initially and has a plugin for mach3/4. As I will need to learn from scratch anyway (assuming the pc is dead) might it be better to just get UCCNC and learn that. I know mach 3 has huge user base and more history so might get easier support. Any thoughts?

Thanks

Ollie