Thread: How to stop the spindle falling

Originally Posted by saczel

I used to use a few early Multicams and they did exactly what you said. The first day on the job and the guy said to use the piece of mdf just the right size that was already prepared for when it goes home it sits at it's free height and the mdf was about 6mm less so when we turned it off for the day it slowly sank down on it. Not on the cutter but the block that the spindle is bolted to. Works every time.

I understand that saczel, but when the head is allowed to sink down under its own weight, the read outs on Mach3 are then wrong and I need to reset the height again.

Quite apart from that, I just don't like it doing it.

Not sure if this is an option with mach3, but can you save your absolute X, Y and Z positions at the end of the day, and then send your machine to a known "home" position to park for the night? Next morning you just return to your saved position and resume?

That might work around the descending head issue.

You should be homing when you start the machine as with micro stepping when you power off you'll lose position within the full step

Originally Posted by foobillious

Not sure if this is an option with mach3, but can you save your absolute X, Y and Z positions at the end of the day, and then send your machine to a known "home" position to park for the night? Next morning you just return to your saved position and resume?.

I do save the positions, but to then send the machine to a home position would lose the Z height because I would need to remove the tool in the spindle to have a consistent Z

Originally Posted by pippin88

You should be homing when you start the machine as with micro stepping when you power off you'll lose position within the full step

Thanks pippin88

That is the point, I won't lose my position enough to worry me if I can just stop the head from falling.

Originally Posted by Bob Willson

I do save the positions, but to then send the machine to a home position would lose the Z height because I would need to remove the tool in the spindle to have a consistent Z

Why do you need to remove the tool?

I use LinuxCNC which won't let you run code without homing, but my procedure is:
Machine on.
Home all axes - Z goes up, X and Y to front left corner.
Then move to where I want and set zero.
Cut some stuff.
Power off.
LinuxCNC remembers where I set my zero (where it is in relation to home / how far each axis moved).
When I turn machine back on, I just home and can start cutting from the same point.

And from memory Mach 3 was the same when I was using it.

if your worried about tool height when parking the head you could use a tool height probe to set a consistent height. plenty of examples on youtube of people's home built ones if you don't want to spend any money on it.

Pippin's method of homing the Z axis up would allow you to block the descent (chunk of wood, ratchet, whatever) to prevent the bit being damaged by descending into the table surface. You could leave the bit in and just re-home in the morning.

To further explain my setup:

Z home switch is at the top of Z travel.
After homing the machine, I set Z0 with the tool at the top of the material. All cutting Z moves are negative Z.
I can turn the machine on and off and not lose position / need to rezero, but do home every time I turn the machine on. (LinuxCNC works on the safest priniciple - that the machine may have moved since being turned off, and home position must be confirmed).
If I change material thickness (say for a different job), then I need to re-zero Z.

I use a zero height tool made from a piece of PCB - when the tool touches it, it completes a circuit and triggers an input on the G540. Very simple and reliable.

Ogura Clutch Brake RNB 0 2ZG 03 DC 24V | eBay

Hi Rod
That looks to be just the thing Rod. I wish I hadn't ordered the spring lift now.
If the spring doesn't look easy to install or looks stupid when it is in place then I will get this anyway. Teamed up with this power adaptor I could just take 12v from the angel eyes and boost it to the required 24v.
I cannot see how to fix the brake to the motor as the brake assembly seems to have only three holes while the motors all have four fixing points. It may require an adaptor plate.

Hi Pippin
I do have several zeroing tools, but I really just want the head to stay where I leave it when I turn the power off.
The Ogura brake is just what I wanted but couldn't find. Russell very kindly offered to see me his for a price that was only exorbitant, but I had to refuse because the bank wouldn't give me an unsecured loan to pay for it.

Originally Posted by Bob Willson

I cannot see how to fix the brake to the motor as the brake assembly seems to have only three holes while the motors all have four fixing points. It may require an adaptor plate.

Hi Bob,
An adapter plate would be easy enough to fabricate. They do make square design brakes to fit Nema motors but I couldn't find any at a reasonable price so settled on the link in my previous post. 86 days till I retire - wohoooo.

Originally Posted by Bob Willson

Russell very kindly offered to see me his for a price that was only exorbitant, but I had to refuse because the bank wouldn't give me an unsecured loan to pay for it.

You should have haggled the price... I would have caved at $194.00 !

Originally Posted by rodm

86 days till I retire - wohoooo.

Oh no, that is a Friday 13th. Make it a day earlier.

Originally Posted by epineh

You should have haggled the price... I would have caved at $194.00 !

I would have bought it at that price. If only you had come clean just a little earlier about how much you would accept.