New build – input/comments appreciated

[kingcreaky]

Well done sir.. Salute.

only thing I can suggest, is, instead of driving each shoulder of the gantry with its own stepper motor, connect the two ballscrews with a long belt to one stepper. you wont regret it. That way you can calibrate it square once, and it remains mechanically fixed that way going forward.

I think a few of the boys have done it, most recently mr njhussey look at his thread

matt

[ngundtoft]

I don't know if it is necessary, but I think the cover plate over the X-axis ballnut holder will stiffen the holder in the x direction.

Kingcreakys suggestion to use only a single Y-axis motor and use a belt instead, sounds very interesting. Obviously you save a motor and a driver and you avoid any misalignment between the two gantry sides. This is a fairly heavy machine.
Do you think that one Nema 23 motor is sufficient to do the job?


Obviously the top cantilevers at the rear of the machine, after having extended them, will obstruct a belt. Extending them gave me an extra 153mm, so that the spindle could Work 70mm in front of the frame, which is a fairly small work area for dovetails. So I was thinking if I only extended the front end rails I could fit a belt and I would have 153mm length for the dovetails, which I think would be plenty.


JAZZCNC - I noticed on your Pictures, that you are using a lot of proximity sensors. I was planning on using micro-switches, but maybe the proximity sensors are more reliable? Do you prefer magnetic, capacitive or inductance types?

[JAZZCNC]

I think a few of the boys have done it, most recently mr njhussey look at his thread

What you mean a few have done it I practicly invented it, all them other buggers just copied me. .

But he's right it does work well.! . . . . Not pretty but affective.!

I don't know if it is necessary, but I think the cover plate over the X-axis ballnut holder will stiffen the holder in the x direction.

Yes it's very necessary and I'd suggest something a little stiffer than that thin plate. Look a pic #2 and you can see the kind of stiffness i'm talking about.

Kingcreakys suggestion to use only a single Y-axis motor and use a belt instead, sounds very interesting. Obviously you save a motor and a driver and you avoid any misalignment between the two gantry sides. This is a fairly heavy machine.
Do you think that one Nema 23 motor is sufficient to do the job?

No for gantry this weight you'll really need nema 34 around 6nm with high voltage drives. The machine in Pic 2 uses twin screws joined with belts running a nema 23 on 70Vdc and while it very works well this is about the size limit of machine I'd fit it on.

Obviously the top cantilevers at the rear of the machine, after having extended them, will obstruct a belt. Extending them gave me an extra 153mm, so that the spindle could Work 70mm in front of the frame, which is a fairly small work area for dovetails. So I was thinking if I only extended the front end rails I could fit a belt and I would have 153mm length for the dovetails, which I think would be plenty.

Personally I would have a little at both ends. Think about the future or upgrades like 4th axis.? Passing the front with enough length will allow a very easy and neat 4th axis to built into the machine without impacting the cutting area.
The extra cost of longer rails or ballscrews won't be that much and usabilty of the machine is much higher. The extra functionality will return the cost 2 fold when you come to sell it or pay for it's self within a few jobs.

JAZZCNC - I noticed on your Pictures, that you are using a lot of proximity sensors. I was planning on using micro-switches, but maybe the proximity sensors are more reliable? Do you prefer magnetic, capacitive or inductance types?

Prox switches I use are inductive and they are much much better than low/mid end mechanical switches. Cheap as chips and very accurate.
I posted a video showing how repeatable they are.! . . Excuse my horrible voice!!

[njhussey]

What you mean a few have done it I practicly invented it, all them other buggers just copied me. .

But he's right it does work well.! . . . . Not pretty but affective.!

Unashamed copy in my case and proud of it.....I can vouch that it's not pretty but it will do until the machine cuts it's own replacement part

[ngundtoft]

I have stiffened up the X-axis ballscrew nut mounting by increasing material of bracket to 30mm, increasing cover plate to 10mm and inserting a 20mm triangular support.


I feel somewhat uncertain with respect to using a single motor and belt setup for the X-axis. I remember reading that the Nema 34 motor should normally be avoided because acceleration is much slower than the 23. So do the advantages (better alignment, single motor) make up for the drawbacks (lower acceleration, long complicated belt)?

Maybe a long belt could just go below the top cantilevers (and the bed) by using some extra idler pulleys?

[njhussey]

I have stiffened up the X-axis ballscrew nut mounting by increasing material of bracket to 30mm, increasing cover plate to 10mm and inserting a 20mm triangular support.

Image: http://www.mycncuk.com/attachment.ph...id=16043&stc=1

I feel somewhat uncertain with respect to using a single motor and belt setup for the X-axis. I remember reading that the Nema 34 motor should normally be avoided because acceleration is much slower than the 23. So do the advantages (better alignment, single motor) make up for the drawbacks (lower acceleration, long complicated belt)?

Maybe a long belt could just go below the top cantilevers (and the bed) by using some extra pulleys?

If you look in my build log you'll see me jogging my long X axis (your Y) at 10m/min. I had it up at 15m/min and it was fine so I've n9 qualms about using the 6Nm Nema 34 with the 230V driver, it's plenty quick enough. My belt is 2525mm long and again I've no problem with it (so far!!!)

[JAZZCNC]

Neil I don't mind in the slightest and consider it a compliment with anything taken from what I offer or show. Also wasn't mean your machine wasn't pretty but the fact long belts in general are messy.

[njhussey]

Neil I don't mind in the slightest and consider it a compliment with anything taken from what I offer or show. Also wasn't mean your machine wasn't pretty but the fact long belts in general are messy.

It's messy, I don't mind admitting it, as I've a just got a temporary plate and pulleys on it to get it going.....

[Neale]

..and once the machine is set up and working, you'll use it to remake components to look better? That's what I keep telling myself!

[Clive S]

I think you will need more teeth in mesh on the motor there are several examples of how to do it on the build logs.