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

[JAZZCNC]

I was getting all worried at one stage that my 5mm pitch screws would mean I was going to be burning up the wood I was cutting due to the low feed rates then I remembered back to when I started getting into all this lark seeing machines that cut wood pretty reasonably being driven by threaded rod with pitches so small you can hardly see them! Reckon our 5mm screws will be all right.

Ermm Ye understand what your saying Joe.!!. . . BUT don't be fooled.? . . . If truth was told there bull shitting you.!! . . . You'll see many examples of flimsy machines cutting Aluminium with dremels etc but what they don't tell you is the finish is shit and the machine/spindle curled up and died 2hrs after the video.!

Same goes with threaded Rod machines the finish is rubbish the cutters wore out in 30mins and the machine fell to pieces 10mins after that.!!

Your correct thou that 5mm will be ok if you already have them but if your mainly cutting wood then I'd look at gearing at least 1:1.5 or 2:1 has that will allow the speeds needed to cut MDF/plastics at correct feeds.

[JoeHarris]

Oh yes I moved away from threaded rod a LONG time ago!!! Just comforting to know my £500 worth of ball screws were not a waste of money!!

[Iwant1]

I too was worried, that my 5mm screws won't be good enough, especially when spending close to £2k on the build. But then there no point on wasting valuable sleeping time, lol. Just going to use what I have, and if its too slow, and whipping about, I'll buy the 10mm pitch and use these for my plasma, or laser, or 3d printer. Got a lot of plans lol.

[Danielroyal25]

Hi, was just reading through your post and its helped me out a lot with design ideas. I'm still at the design stage at the minute, can't wait to get started on building.
Just wondering how yours is going? Do you have any images and more advice - do's and dont's. cheers!

[Iwant1]

Hi Dan,

I'm just waiting on the aluminium parts to get machined. To be honest, I'm not pushing on getting them done quickly, as I've got too many things on at the moment. That doesn't mean my minds not thinking about it, lol.

Since I've decided to go with dual x axis drive, my PC case control cabinet is looking too small to squeeze another am882 driver in, and also the recent decision to go with an ethernet SS and PDMX 126 BOB. So another part on my shopping list was a PROPER control cabinet, which as of today, am the proud owner of a used 600mm x 400mm x 200mm electric enclosure with slotted cable trunking, on/off switch and safety locks. Bargain at £40 shipped. Everything should fit now considering its twice the size of my PC case.


As for advice, DON'T buy any electrical components till your machine is built. Mine are just sitting there, eating up their warranties.

[JoeHarris]

Since I've decided to go with dual x axis drive, my PC case control cabinet is looking too small to squeeze another am882 driver in.

May of missed this in your thread but why did you decided on 2 drives over the long belt option??

[Iwant1]

After spending so many hours deciding between the two options, and after some emails with Jazz, I just bit the bullet and decided with dual drive. The main points in my decision were:

with AM882 there wasn't any issue with the gantry racking from one motor stalling as they have stall detection alarms, and the machine will E-stop before any damage is done.

Next, as for sync issues creeping in, Jazz says with descent drives this is drastically reduced compared to cheap Chinese drives. Obviously with one motor and belt its completely eliminated and is only a problem on very long jobs, which I doubt I'll be doing. Though you never know.

Then with 2 motors tucked away in the corners, it keeps the far end of my router free from belts and motors and tensioning arrangements, allowing for sliding long materials through.

With the long belt and one motor, I reckon a larger motor like a nema 34 would have been needed, and since I prematurely bought a nema 23, thought I'd use it on one side and buy another 23.

Also I think the 23 motor can spin faster at the top end, which will be ideal for my incorrectly ordered 5mm pitch screws, when traversing.

This is how I came to my choice, but it no big deal if I want to change change later. And I'm sure someone here will snap up my spare driver and motor, lol

Adil

[Danielroyal25]

I have been pondering over the 2 motors v 1 motor decision too. I think I will be going with the 1 motor option. You know you mention there may be issues with long jobs, what is the reason behind this.
I wanted the ability to slide large boards through the machine but may settle for turning them through 180 degrees instead.

[Iwant1]

You know you mention there may be issues with long jobs, what is the reason behind this.
I wanted the ability to slide large boards through the machine but may settle for turning them through 180 degrees instead.

From what I understand, long jobs are when you machine for 10+ hours without homing in between. Imagine one motor is losing a step here and there, and over a all those hours the missed steps could add up to a difference of a few mm's of one side of the gantry, taking it off square.

Homing would normally square it up again, but I'm not sure why on long jobs, like 3d carving, why can't you program a homing function every hour, and then continue where it left off.

Adil

[Bart]

Hi,

I don't want to hijack this post but i have a similar design and I'd like to use your experience.

I've designed the frame etc. in inventor and from the simulation i get deflections smaller than 0,015 mm with the force of 500N excreted on a tip of an end mill. Thus, the design seems to be sturdy and good enough but I'm waiting for any suggestions.

My questions...

1. Chinese spindle - which one to chose
There is plenty of different looking spindles on ebay and even more sellers so I'm not sure where to buy and more importantly which model. Which one do you have or which one you know is safe to buy.

2. how to avoid two motors.
I tried couple designs of frames to hold one ballnut for one ballscrew in the center under the table but it's hard to get small deflection without making it very heavy. Do you have some ideas how to solve it without 2 ballscrews and motors on each side?
How is the solution, with line that winds up on a rotating drum, called?

3. what's the free play on a linear rail's open bearings?
Is there any free play on them, how much do they flex?
Also I saw couple times that max speed for linear rail bearings is 5 m/s. What happens above that speed and how does it affect service life.

4. whats the advantage of linear guidways over supported rails?
They would cost me at least 2 times more. I've read the spec and according to it they don't deflect almost at all. What are the other advantages and are there any disadvantaged besides the price?


5. End supports for ballscrew.
I saw a design where instead of end supports fixed to the gantry or frame there where bearings directly fixed to gantry/frame. It seams that it might be stiffer and cheaper. What do you think of it?

Kind Regards
Bart