Newbie looking at 6040 (China CNC) for polypropylene 15mm sheet

**Clive S** · 21-04-2017

1000/S ? Do you mean 1000mm/min

**JOGARA** · 30-05-2017

I'll try that method and see how well it goes.
Ta

Any recommendations on what I can put in my water cooling to prevent rust?
Not been able to work for 2 weeks and the outlet pipe is going rusty gold.

**Zeeflyboy** · 30-05-2017

you just got an open loop?

some antifreeze would probably do the job, and keep the tub covered and out of reach of any pets/children

**JOGARA** · 30-05-2017

Originally Posted by Zeeflyboy

you just got an open loop?

some antifreeze would probably do the job, and keep the tub covered and out of reach of any pets/children

Yes open loop into a tub.
Does it have to be just antifreeze or is screenwash okay?

**Zeeflyboy** · 30-05-2017

don't think screenwash has any anti-corrosion inhibitors which is really what you are after.

http://www.carparts4less.co.uk/cp4l/...FUg6GwodLDEB_A

something like that would do

**JOGARA** · 30-05-2017

Originally Posted by Zeeflyboy

don't think screenwash has any anti-corrosion inhibitors which is really what you are after.

http://www.carparts4less.co.uk/cp4l/...FUg6GwodLDEB_A

something like that would do

Ahhh okay.
Ill go see what they have at Halfords.

Needs to have some colour in it as I did not realise a few weeks ago that my pump was off >.<
Got a bit hot...

**Zeeflyboy** · 16-10-2017

Typical stepper is 200 steps per revolution. You have 5mm screws, so you move 0.025 per step (5/200).

Microstepping doesn’t really count, so the fact you have eg 320 per unit (can’t remember exactly what the stock setup is) isn’t really what you’re looking at, though you could argue with little to no load it won’t be far off.

That said, I can move mine in 0.01mm steps on the jogging button but I have 1.2 degree steppers (so 0.017mm per full step) with built in encoders and microstepping gives 800 per unit.

Just edit your jog values so that one of them is 0.01mm and it’ll do it’s best to match. If it is 320/unit then you have a base value of 0.003125 so any movement will be a multiple of that - that means the closest movement to 0.01mm you could theoretically get is 0.009375 which is why the value in the readout looks a bit odd - it’s physically impossible for it to move to any value that isn’t a multiple of 0.003125. Again though microstepping is not really reliable regarding accuracy so your “real” resolution is 0.025 as limited by the motor steps per degree and the pitch of the ball screw.

Btw I would try to use the least amount of travel on the dial indicator - those type can have a fair bit of spring push and you may be deflecting the probe rod slightly. No guarantee that the deflection is equal all the way around.

Do you actually need to jog into the dial for this? I just spin the guage zero so that it sits in the middle of the values for either side and then adjust probe until it reaches close to zero, then move to the next set of screws and repeat, then go back to the first as it may have moved slightly. That will normally get runout to less than 0.01mm for me. Definitely a bit of a knack to it but it only takes me a few minutes now.

Oh and finally have you tried calibrating the machine? Mine wasn’t exactly wonderfully accurate out of the box. I think mach3 even has a screw calibration wizard that saves you doing the maths.

**JOGARA** · 16-10-2017

I have not changed anything other than adding ProbeIt to the wizard.
Don't like messing with stuff.

This is default.

What would be the highest resolution I can get from this without it being too weak?
That and roundest number possible :p

I moved back on the indicator and got around 0.025mm so tiny bit of movement yes.

Ideally I want to be able to probe my soft jaws and just batch process a load of cases.
Changing tools all the time takes time.

**JOGARA** · 16-10-2017

The only way around this is to mill the outside and front of my case first, then flip and mill inside with the degree of error being around 0.05-0.075mm.
This would allow me to vacuum plate the first operation on the front of the case, removing the need for super glue.

I think I could live with that...

Ideally I could get it all bang on but that is not looking like it is going to happen on this machine any time soon... :/

**Zeeflyboy** · 16-10-2017

I wouldn't get overly obsessed with the DRO giving a round number read out - better that it is actually calibrated correctly.

After all, other than for reasons of OCD consider that your 17.9188 from the DRO above is only 0.0012mm away from the commanded 17.92 - 0.0012mm is roughly half the width of a typical bacterium (which are commonly 0.01mm long too for context!) Basically it's a level of precision that your machine couldn't possibly hope to achieve anywhere near so it's irrelevant for all but how neat the DRO looks.

When you correctly calibrate the ballscrews, likelihood is that you will end up with a horrendous number like 321.24 as your calibrated steps per mm which of course means you don't have a snowball's chance in hell of ending up at a round number on the DRO.

I'm not sure how you arrive at your conclusion that you will be working to an error of 0.05 to 0.075mm.... but 0.05mm is nothing to be sniffed at... it's a very good level of accuracy realistically speaking - less than the thickness of a typical human hair.

Increasing the microstepping won't really help... if anything it just makes it harder for your motion controller to keep up at high speeds. Microstepping really only serves to make things smoother, gains in resolution are mostly illusionary.