CNC Workshop CNC Lathe Build

[dieselpilot]

Did you find what caused the axis error? I've not seen a situation were the screw pitch and step angle didn't result in proper step increment.

[kvom]

I have tweaked the steps/unit in M4 but haven't yet tried a new thread.  We've had house guests this week.

[kvom]

Ran a threading program today on brass rod for a 3/8-16 thread.  Got a nice threadform but it was 32 tpi.  There's a software bug here somewhere, but not sure if it's M4 or my control.

[jschoenly]

Are you using the threading cycle or G32 moves?  I posted a thread from Fusion which uses G32's and It ran just fine on my Mach4 Hardinge lathe.  I haven't tested out the G76 but it's high up on my list of things to try. 

I'm really surprised to hear you coming out a a factor of the pitch.  Is the encoder setup correctly on the spindle?

[kvom]

I tried it both ways and got the same result.  I prefer the G32 because I can single step it when setting up to do a new thread (i.e., check pitch with a thread gauge).  I also have had problems with G76 retracting too far so that first few passes just cut air.

I suspect a controller issue rather than mach4, but debugging is out of my hands.

[Admiral_dk]

Is the encoder setup correctly on the spindle?

Having the wrong number here will certainly "throw a spanner in the works" ... 

Flip that coin and it can be an easy way to get the right pitch without changing anything else .... 

Ehh .... correction, if all other things are as should be - not a good solution.

I would check that your feed is correct - or is there another way where you can check how many pulses you get from the encoder for one full 360 degree of the chuck. I have a very old version of M3 and you can check many things in the diagnose section - I would expect M4 to be a lot better. If so - have a person counting the pulses shown on the diagnose page (if not done by M4) while you turn the chuck exactly 360 degrees in one direction only. There is a high probability that this is a nice binary value (2, 4, 8, 16, 32, or 64) - is this the same value you got in the setup for the encoder in M4 ?

[kvom]

There is no M4 encoder setup to my knowledge.  The encoder output feeds to the control box, which uses Pokeys.  I don't know whether M4 or the control box is the one coordinating movement, but there is also Pokeys motion control software in Windows between M4 and the control.

[Admiral_dk]

There is no way that any CNC program can do threads on a lathe without reading an encoder ....

The encoders I have encountered give between 1 and 6400 pulses per revolution - you therefor need to be able to tell the software this number (unless the software is locked to one particular encoder type).

I would be rather surprised if a professional general type CNC software like M4 should be lacking these fundametal functions .... but I have no clue where you find the correct setup menu.

[RonGinger]

Mach4 uses a hardware motion control board, in this case a PoKey57e. For this lathe we selected a 500 line per rev encoder. This is configured in the plugin for the PoKey device.

The PoKey does support a mode to use only an index pulse for threading as was done in mach3.

I have been trying to test kvoms code to see if I can duplicate the tpi problem, but I am having a problem with my encoder. I do know that the last time I made a thread, using the G76 it ran fine. We also had everyone in the class making threads and all came out right, as I remember even kvom made a thread then. A test machine in Brian Barkers shop, with a PoKey motion control makes fine threads. I suspect something has changed in kvoms config.

[kvom]

I didn't do any machining in the class.

I installed a newer version of M4 from the test FTP site per support's recommendation, and that required running the pokey install script supplied in the class.  Other than that, the only changes were modifying the steps/unit to make the axes moves more accurate.

[Admiral_dk]

Mach4 uses a hardware motion control board, in this case a PoKey57e.

OK - so Mach has moved the control software from the computer, into firmware inside a "black box" ....

I just checked the PoKey57e - very smart device - and in this case it need to be told the encoder data ....

But I'm sure that you already knew that Ron, so I should probably just stay out off the conversation ....

Best wishes

Per