8x4 Build based on plans by Joescnc Hybrid R&P

[GrahamWhite]

Hi all :)
My name is Graham and I'm new to all things cnc,got a 3d printer I built from a kit though so cnc on a very small scale then!
I'm starting a build based on plans I bought from Joescnc website- now I know not everyone will like or agree with the build materials and I definitely would like to spend a lot more on the build .... the wife says no!
So in the whole it will come from the plans but I'm hoping maybe there will be some input along the way as well.
As I said it's based on plans that once bought gives access to the builders forum and has approx. 250 machines built or being constructed all based off of the plans- giving dxf files/templates for cutting various parts etc.
The plans suggest a welded steel box frame base ,but as I don't weld I opted for a timber base.
Constructed out of structural 18mm ply ready to take the aluminium rails when they arrive.
so a few pictures of things so far then...

As you can see I doubled up on the ply thickness and the box section rails really improved the stability and strength.

The rails fit together like mortice and tenon joints, the long sides are glued to the legs.

The side rails are 10ft long so I extended them on opposite sides at the ends.
The width is 5ft.

I again doubled the ply for the cross rails and screwed them in dry so take down is possible for relocation if needed.
so this is where I am at now-

The front rails are bolted with nylock nuts.
I also scooped the front rails to allow an 8x4 board to go between the legs for storage, still need to add some rails yet.
With a few sheets stored under there is should add some considerable weight.
The legs have screw adjusters on them for levelling.
So that's where I'm at now, I have some aluminium profile on order which I'm hoping will be with me soon.

[JAZZCNC]

I posted on another thread but I'll comment here as well.

Somewhere else I see you mention £3k. With that much you can get long way to building proper machine made from steel.
Yes, it would be basic to start off with because of low budget but you would have a good foundation that truly can be upgraded as you go along without wasting money.
For a fully finished machine with decent quality components and few bells whistle you'll need about £4-5K but this will give you a machine that will last for years even in small production enviroment but more importantly be reliable and repeatable/accurate.

You will regret building this machine at some point that's for sure.

[GrahamWhite]

So after much thought ,I have decided to go with the original plans- which are V bearings and Rack and pinion.
This is purely a cost thing for me - the entire build should come in at under £2k. I can understand peoples views on linear rails and ball screws but as pointed out by some ,it would take the build cost to nearer £4k which I am not prepared to spend.
Also the fact that this is an 8 x 4 machine for that price I can't see me having any 'Regrets' building it! like I have said before I would rather have a cheaper machine running than no machine at all.
If there is some upkeep to maintain performance then so be it.
Speaking to one of the guys who have built this he said he would build it again in a heartbeat.... but no need as its still running 7 years later ,now upgraded to aluminium carriages but still running V rails.
So bearings are ordered and aluminium profiles and angle iron are in this week :)

[GrahamWhite]

So after my rails apparently having had a tour around England before reaching my supplier, I finally managed to pick them up Wednesday ... a 9 3/4hr round trip:(
So busy day today fitting them:)


Bearings for V rails are on their way from USA so hopefully things will start moving soon!

[CNCKitMan]

Hello fellow adventurous newb,

I'm doing the same thing as you it seems (well it is a CNC forum).
I wish i had more input for you , to help you on your way.
I'm looking at purchasing Linear rails as i've used them before and the seem to give a better result (V Bearings on my Laser CNC work ok thou).

My input is i've searched and searched and think i've found a supplier of rails which don't cost the earth.
How much is the rack and pinion costing you??

[GrahamWhite]

Hi,
I just couldn't justify the cost for linear rails I'm afraid :(
I have been looking at a UK supplier that is selling the rack MOD 1.0 at £74.99 for a 2m length pre drilled.
I'm hoping that's a fair price as when I google rack and pinion I get car steering racks a lot!
For the pinion drive i'm looking at a 3:1 drive plate module that I will probably order from cncrouter parts in the USA. No one over here seems to make them :( I think they are about £60 each+ postage and import tax.- I need 3

[GrahamWhite]

So I'm looking at motor/driver choices and yes while i'm after advice can I ask that you switch off the 'best possible solution 'head and use the 'I expect that will be suitable' head!
This is a kit for nema 23 4Nm with 48 psu instead of the 36v they offer with other kits.
https://www.cnc4you.co.uk/CNC-Kits/P...4-Axis-Nema-23
I know I will need screened cables as well but is there anything glaringly obvious missing?
Sorry if it seems like i'm doing it all wrong but I'm loving my build so far as it's starting to take some shape :)

[driftspin]

So I'm looking at motor/driver choices and yes while i'm after advice can I ask that you switch off the 'best possible solution 'head and use the 'I expect that will be suitable' head!
This is a kit for nema 23 4Nm with 48 psu instead of the 36v they offer with other kits.
https://www.cnc4you.co.uk/CNC-Kits/P...4-Axis-Nema-23
I know I will need screened cables as well but is there anything glaringly obvious missing?
Sorry if it seems like i'm doing it all wrong but I'm loving my build so far as it's starting to take some shape :)

Hi

Graham White

People here like to go for 68v diy psu and 80volt digital drivers.

And you can too, for about the same price.


Grtz Bert.

Verstuurd vanaf mijn SM-A320FL met Tapatalk

[JAZZCNC]

Sorry if it seems like i'm doing it all wrong but I'm loving my build so far as it's starting to take some shape :)

Your loving it now but you won't be if you keep ignoring advise cutting corners trying to save a few extra pounds. It's very easy to spoil a machine when just few £100 more would make a great machine and unfortunatly you only realise this after the money is spent.!

I won't give Bum advise so I'm not giving you a "just good enough" solution but will give you solution that is what's required for good machine.

Because your using R&P which is only 50-60% efficient compared to ball screws which are 90-95% couple this with linear rail system that's is even less efficient then you'll need extra power to deal with lower efficiency. Also because you'll be using ratio 3:1 then you'll want motors which spin little faster but still have torque higher up the RPM range and 50V drives with 48Vdc won't provide enough power. (Also 48V is too close to the Drives 50Vdc max so you risk blowing drives up)

Ideally, with R&P setup, esp one that isn't very efficient then you'd run Nema 34 motors with Mains voltage or higher Dc voltages around 100Vdc.
So if you must use Nema 23 motors then you want to be running them around 70Vdc with 80Vdc drives.
Also you want Unregulated PSU not Regulated Switch mode supply. Reason for this is that under de-acceleration the motors become dynamo's and dump the power back to the drives which then dump this back to the PSU (Back EMF) and if the PSU as protections built into it then will shut down which is bad news.
On Small slower machine with light gantrys then can sometimes get away with this but on large machines with heavy gantry traveling at higher feeds whcih routers tend to do then it will become a problem.
The PSU you want is Unregulated toroidal PSU which use capacitors that store energy and absorb any Back EMF. These are actually very easy to make and will work out cheaper than buying a large PSU, it also means you can tailor Voltage and Amps to your exact needs.

So the setup I suggest with nema 23 motors is this.
4Nm motors
80Vdc Digital drives running motors at 68-70Vdc.
Toroidal PSU transformer spec'd to output 68-70Vdc

With Nema 34 Motors:
4.5Nm Nema34
80Vac (100Vdc) Drives
Toroidal PSU transformer spec'd to output required.

Stay away from kits they are always compromised in some way.

[GrahamWhite]

Appreciate the info:)
I can understand all you have said and will take it on board and not order the kit :)
so the steppers are fine ,will have to go with the 4Nm 23's as the mounting holes are already drilled.
An 80vdc board
https://www.cnc4you.co.uk/Microstepp...r-60VAC-CWD872
I have no clue on building a toroidal PSU!! lol so would need a touch of help there!