I've built this machine 100 different times in my head!!!

[JAZZCNC]

#1: This guy is ok. Most of them are the same spindle and probably out the same factory.?
2.2KW WATER-COOLED MILLING AND GRINDING SPINDLE MOTOR WITH 2.2KW INVERTER VFD q3 | eBay

#2: Honestly there is no solution to match driving from both sides whether twin ballscrews, R&P or belt drive it's by far the best and easiest way to get accurate stiff machine. The wire/drum is just a bodge and best doing it correctly first time.?. . You'll only end back there in the end.!!
Unless your machine is narrow format, which it doesn't look, then single screw just won't work good. Making gantry wide helps but there's a limit before it gets unusable or feasible.

#3 Can't answer that question without knowing which make and what size linear rails. What I can tell you is even the lower quality units are capable of handling forces far beyond what you throw at them or what your machine design will handle, so it will fail long before they do.!!

#4: No contest here linear rails win hands down in every department by a very big margin. They can't be compared really in accuracy and performance terms.
The other advantages are longevity, they will easily last several years longer than supported rails, even in very harsh conditions. Hassle free usage, fit grease occasionally and forget.
Disadvantages over linear rails is they don't tolerate poor workmanship and misalignment.

#5: Show us and will comment but until then not sure what you mean.?

Now your design.?? . . . You have a problem Houston (several actually).!!! . . . . but this one Is a common mistake easily missed.!
The linear bearings on the Y axis can't possibly be fastened like you have them drawn.? Chicken and egg problem.!! Fasten plate on one set and you can't access the bolts for the other bearings.!!

I'd also consider using different thickness material for the Z axis.? Those thin plates, even with the bracing will resonate while cutting which will affect quality of finish. Don't rely to heavily on the Cad simulation, without inputting all the variables and cutting forces then it won't show this. I know from experience that if you plan on cutting hard woods or hard material like aluminium then your Z axis just isn't strong enough.
Just remember no matter how well built or how strong or accurate the rest of the machine is it's the Z axis that takes all the cutting forces
and if this flex's or resonates the rest don't matter a jot.!! . . . The machine is only has good has it's weakest link, this Z design is weak.!
( Also Don't rely on the Linear rail adding strength they don't really add much.!)

[GTJim]

Hi Adil, this is a very interesting build and a great deal of care has been give to getting the design right.
One question regarding the electronics, do you have a wiring diagram/schematic that you are using? If you do, could post it up as I'm currently struggling with this.

Jim

[Iwant1]

Hi Bart, welcome to the forum mate and don't stress over hijacking the thread, someone needed to bring it back to life.

Jim, honestly everything is as it was few months back, i.e. in pieces. Once I've got the control panel built and I'm happy the way it works, I'll make a schematic and post it for you. It will be quite tricky though coz' it uses a few linked relays.

Jazz, nice to see your back and in full swing.

[JoeHarris]

Hi Bart, welcome to the forum mate and don't stress over hijacking the thread, someone needed to bring it back to life.

Jim, honestly everything is as it was few months back, i.e. in pieces. Once I've got the control panel built and I'm happy the way it works, I'll make a schematic and post it for you. It will be quite tricky though coz' it uses a few linked relays.

Jazz, nice to see your back and in full swing.

Adil, what's occurring mate, still building this thing ??!


Sent from my iPhone using Tapatalk

[Bart]

Hi,
Thank you for your interest in my design

I guess I should have started with some spec of the design.


Frame dimensions
W x L: 1400mm x 1800mm

Red and Blue is steel
Yellow is aluminium 10mm thick

Linear rails
X: 1800mm x 25mm
Y: 1350mm x 20mm
Z: 380mm x 20mm

Motors:Four Sanyo Denki 103H7823-1730@$80 each - 4A, 2,2 mH, 0,65R, ~2 Nm up to 600 RPM
http://www.plccenter.com/en-US/Buy/
any suggestion of better value for the money?

Driver :TB6600

Gantry
Steel square profile 80x200x (4 or 5)mm

Z axis aluminium plate is all 10 mm

#1: This guy is ok. Most of them are the same spindle and probably out the same factory.?...

That's what I'm hoping for but almost every seller has a picture of slightly different design so I was wondering if any of them is better or more reliable then other.

#2: Honestly there is no solution to match driving from both sides whether twin ballscrews, R&P or belt drive it's by far the best and easiest way to get accurate stiff machine. The wire/drum is just a bodge and best doing it correctly first time.?. . You'll only end back there in the end.!!
Unless your machine is narrow format, which it doesn't look, then single screw just won't work good. Making gantry wide helps but there's a limit before it gets unusable or feasible.

I've just google wire/drum and it's called cable drive and it's not as easy and cheap as it seams - if it is to be precise.
Belt drive is ok but it has a disadvantage of not reducing the moment of inertia of ballscrews. Right now, one ballscrew
has an equivalent mass of 60 kg, that is as mach as moving mass for X axis and same moment of inertia as motor.

#3 Can't answer that question without knowing which make and what size linear rails. What I can tell you is even the lower quality units are capable of handling forces far beyond what you throw at them or what your machine design will handle, so it will fail long before they do.!!

Yes, I've seen the spec for the linear rails and linear guideways and bot of them are pretty strong for the size.
So for the X axis, moving mass is 60 kg and max force when cutting would probably be around 500N which gives (simplifying) 125N per linear bearing.
However, when i asked about flexing of open bearing, what I had in mind was an order of magnitude. Is it 1 um, 10 um or 100 um of flex.

#5: Show us and will comment but until then not sure what you mean.?

Homemade PCB milling machine - YouTube
start watching at around 1:35

Now your design.?? . . . You have a problem Houston (several actually).!!! . . . . but this one Is a common mistake easily missed.!
The linear bearings on the Y axis can't possibly be fastened like you have them drawn.? Chicken and egg problem.!! Fasten plate on one set and you can't access the bolts for the other bearings.!!

Absolutely right :) - I've noticed it some time ago but i was too lazy to change all the constraints :)
here is an updated photo

I'd also consider using different thickness material for the Z axis.? Those thin plates, even with the bracing will resonate while cutting which will affect quality of finish.

It's 10 mm aluminium plate - what do you think it should be?
I was thinking about making a sandwich of wood and aluminium to dampen vibrations. What do you think?

Sorry for slow replay but i was too busy to write a post

Best regards
Bart