Member postings for sam sokolik

well - for linuxcnc it depends on the realtime latency of the system. I have been running the PI4 with linuxcnc for a long time - but using a mesa ethernet card to do the heavy lifting. (step generation and such)

The maximum jitter I get is around 50us or so. This is perfectly fine for external interfaces like mesa.

Linuxcnc does have a gpio driver for the pi - but again you are limited to how fast the realtime kernel can twittle bits. I I goofed around with it a while back - and was getting about 10khz step rates. Not stellar...

I would just use the motor that is on it... I have.. With a decent drive - they work great..

The masso controller seems to have css and fpr but you cannot run them at the same time..

**LINK**

Css is awesome - surface finish and tool longevity...

Linuxcnc (is free) does threading - css and fpr.. (and to start - you could use the printer port...) In the dev version of linuxcnc (well - the pre-release version) there is also roughing/finishing cycles.. (G70,71 and 72)

sam

also - things like constant surface speed and feed per rev are really nice things to have..

I Know linuxcnc has it - I assume Acorn does.. Don't know about planetcnc..

sam

Getting closer.....

Where is your sense of adventure?

I think it only comes with a 50ft cable and you can get a 150ft cable..

If you want to check it out - Starlink has an app that uses your cell camera and location to see if there are obstructions...

good riddance. My parents only decent internet was dsl (copper phone lines) (here in the US) and it sucked. They were lucky to get 1mbsX128kbs. (and it was down all the time)

The second starlink came available - I told them to sign up for the beta.. They got in and have been using it for the last few years. I can count on 1 hand how many times it was down (that we noticed) Speeds are variable but are around 100mbsX10mbs (at least) They now don't worry about the internet. It just works.

Do you guys have cell service that allows calling over the internet? That is what I use. I can make cell phone calls from within the machine shop at my parents - 0 cell signal - all through the internet. (starlink) works great also.. (so my parents cut the cord)

sam

Why not use something that has been improved on for years and being used daily for real machines?

Linuxcnc will allow you to do true closed loop control.

I am even doing it through the the printer port (obviously speed limited) but very accurate using PID.

Using basic pwm amplifiers - My lathe currently uses $5us drives from amazon.

It has 9 axis of coordinated motion..

You can start as simple as this for closed loop... (replace the amc drive with the $5us drives from amazon.)

Plus you can buy inexpensive external interfaces that do hardware encoder counting, high speed step/dir and high speed pwm (among other things)

+/- 10 volts out of the printer port..

Found some circuits here.. **LINK**

The first one from the forum seemed simple enough to try - although it took me a bit to figure out the filter was setup as a high pass - not low pass.. After figuring that out it made sense..

It should be more than good enough to do closed loop spindle control - and constant surface speed...

usb to parallel port adaptors will not work in this situation...

sam

Finally had a little time to work on this project. I got the X ball nut assembly done - it took some creative machining...

an hour you won't get back...

A bit of ladder for testing...

Finally scored a compact 5 turret!

Edited By sam sokolik on 29/11/2022 18:11:46

been really impressed with my pixel phone... (4a 5g)

Saving a pin on the printer port using missing tooth functionality.. (to create an index pulse)

Very cool! Yes - the hard part is making it deterministic... I can't say I fully understand how linuxcnc does it. It uses the rt_preempt kernel (which is now part of the Debian repository)

They use the real time api to create the threads.

You can isolate cores for real time - it helps but you won't get mhz thread. (at least in my experience)

For machine control - most of the 'control' can be done in a relatively slow thread. (1 - 10khz) calculating the PID, Trajectory and stuff.. The faster stuff can be moved to hardware. (but again - still doable in the computer as long as 50khz works..)

sam

There is also an RTAI patched kernel which is still available - but requires a bit more work. It used to be that it performed better than the rt_preempt kernel but in my experience they usually have similar latency now.

sam

Little update.. Made some 3d printed parts to mock up the new ball screw.. Looks good. I think all I have to do is move the ball screw out about .050" or so.

With the courser ball screw (2.5mm -> 4mm pitch) the input scale went down (50800 -> 31750 pulses per inch ) This and using a pci-e printer port which seems to allow for a slightly faster realtime thread - I can get easy 90ipm.

The base thread is running 18us or 55.5khz. 55,5555/31750 = 1.75 in/sec (if the quadrature of the encoder is perfect and counts every base period) giving a little headroom - 1.5in/sec or 90ipm.

Edited By sam sokolik on 09/09/2022 15:42:33