Sherline Lathe Conversion ?

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03 Feb 2017 09:44 #87197 by verticalperformance
Glad to see you got it going Hugh.
Note that there is still a bug I think in 2.7.8 (since new trajectory planner in 2.7.0) that causes a little hiccup in the synchronised motion G76 during the thread runout motion.

Workaround is to in do an F0 prior to the G76, as the feedrate is essentially set by the sync with the spindle speed anyway. If the thread runout is into a relief groove, you will not notice this.

See topic: Pause during exit taper, G76

Fringe benefit of NC threading on the sherline, is that you can leave the headstock riser blocks in place too! Haven't used the thread cutting accessory since!

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07 Feb 2017 01:45 #87431 by currinh
Replied by currinh on topic Sherline Lathe Conversion ?
Andy: I believe you're right. I haven't used the threading attachment on my Sherline though it came to me with one. I think you need to put the back gears in place and a turn handle on the spindle. The feed is then tied to the spindle, no half nut so you need to retract the tool and back up for the next cutting pass. This seems non-functional to me after using a 14" gear head lathe. But with CNC and an encoder on the spindle it works very well.

Probably the wrong forum, but if anyone is interested in buying a threading attachment for the Sherline let me know.

Vertical: Thanks for the heads up. I didn't notice a hick-up but will use the F0 when threading.

I ran a batch of 12 small parts over the weekend. The Sherline made short work of it once I figured out the G-code. I use CamBam for milling but find it lacking for turning. It's OK for outside profiling, maybe CAM the outside with CamBam then hand modify for holes, threading, etc. Is it common to hand code lathe work? I really need to figure out better tooling, maybe gang tooling or additional QC tool holders.

Next will be spindle control and likely homing switches.

Thanks.

Hugh

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22 Apr 2017 13:33 #91840 by RJTeeter
Hugh, your spindle setup looks great. i'm piecing together a setup similar to yours and I'm looking for cog wheel specs. What diameter/pitch are your cog wheels and what length belt did you use?

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01 Apr 2020 20:02 #162368 by rocr
Replied by rocr on topic Sherline Lathe Conversion ?
Hello,

this might be a little late, since it is a 2016 thread. But I have approx the same equioment.

I have a Sherline mill and lathe (both in Paxton Patterson enclosures), replaced all electronics, upgraded stepper motors etc .. and both work fine with linuxcnc.

I am using a breakoutboard (bob) and everything seems to be working.

The encoder is a different story. I tested it with a test-bed setup, seemed to work when connected to a stepper motor.
(I have the exact same encoder omron encoder E6B2-CWZ6C 60P/R)

The problem I have is that at low speed the rpms seem like they are ok, at higher spindle speed/rpms, the speed dial in lunuxcnc goes down, towards 0.

I have the 5V and 0V hoked up to the BOB/par port (maybe that is the issue. and does the shielding need to be connected to ground?
or is it better to use a different power supply for the 5V and connect the cable shielding to the parallel port ground?

hope someone finds this,

thanks,

Ron

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01 Apr 2020 20:07 #162369 by andypugh

The problem I have is that at low speed the rpms seem like they are ok, at higher spindle speed/rpms, the speed dial in lunuxcnc goes down, towards 0.


How many pulses per second would you be expecting at the speed where the problem is seen?

The parallel port can only count edges as fast as the base thread runs.
So, the supplementary question is, what is the base thread period. (It will be in your INI file)

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01 Apr 2020 20:31 - 01 Apr 2020 20:33 #162374 by rocr
Replied by rocr on topic Sherline Lathe Conversion ?
well.. the speed seems somewhat erratic, but if the thing reports speed I can see that. the speed display indicates the speed that seems ok, approx 350-400 rpm. but changes "wildy" a couple of dozen rpms at a time, up and down. over 400 the speed display goes down and when at full speed goes down to 0.

the encoder is a 60 ppr. is has an A, B and Z signal.

I had a discussion with someone about the max pulses a linuxcnc machine could "handle"

I wonder if the power the parallel por delivers to the encoder might just not be enough?

Ron

PS: I also have a 1024 PPR one, but was toold it was going to be way too many pulses per per second that Linuxcnc would receive and was told that a 60ppr would work.
Last edit: 01 Apr 2020 20:33 by rocr.

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01 Apr 2020 20:38 #162375 by andypugh
Yes, 60 ppr should be OK normally

60 slots x 4 for quadrature X 400 rpm = 625┬ÁS per pulse.

Is the encoder counter function definitely connected to the base thread and not the servo thread?

Can you attach the HAL and INI files?

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01 Apr 2020 23:53 #162410 by rocr
Replied by rocr on topic Sherline Lathe Conversion ?
Ok, so I am a newbie, when it comes to linuxcnc, well the cnc part. I have an idea what that means, but that's where that stops.

I'll attach the hal and ini files that I am using for the Lathe.

thanks!,

Ron
Attachments:

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02 Apr 2020 00:23 #162414 by currinh
Replied by currinh on topic Sherline Lathe Conversion ?
Ron:

I can't help much. It's been quite awhile since I set this system up and my memory is terrible.

But I do remember working to connect the encoder to the parallel port. It wasn't trivial and I was making slow progress. Then I checked the specs on the Gecko G540 which I used. The I/O for the G540 does some electronic magic which allowed the encoder to connect directly. It also provided a power supply I used for the encoder. So it could be your BOB? Sorry, I'm fuzzy on details, as I said, I haven't messed with the connection for several years.

But to work at low RPM and cause problems at higher, I'd suspect timing errors first. Andy has infinitely more experience that I and can help you with linuxCNC configuration.

I hope this is of help.

Hugh

I am using a breakoutboard (bob) and everything seems to be working.

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02 Apr 2020 02:42 #162425 by rocr
Replied by rocr on topic Sherline Lathe Conversion ?
well,

thanks for replying anyway. I thought since you had the same stuff, that you had figured it out.

thanks!

Ron

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