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581

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: August 22, 2012, 03:27:39 AM »

Good point.
The Delta VFD-m uses an input, usually a proximity sensor for indexing. You can tell it what angle from the sensor you want it to stop at. This is the same drive that David DeCaussin uses on his machine. If you watch the video you can see it stops, then turns to index. Not sure if it locks the position though.  My thinking at this point is to ultimately have the VFD dictate whether or not the draw bar can engage. That may be a dream or something as simple as using an intelligent output on the drive. I'll have to see what I can come up with when I get the drive.

If the drive can signal, that would be a good option to consider. Most likely I will do my own setup that way, but it is useful to get as many ideas on the table as possible and then pick up the one that best suits each machine.

If you don't trust Mach-pokeys-smoothstepper to not turn on (or off ) an output then you can't really trust it for any other method to prevent unintentional draw bar movement.

It is not possible to get MACH out of the loop completely since the tool change command initiates in the G-code and (typically) MACH is controlling the spindle. My objective is to have, in addition to an 'enable' function, a positive mechanical interlock that will prevent the drawbar from moving unintentionally, regardless of the source. I suppose the reasoning would be similar to the folks who have their E-stop setup outside of MACH, but still triggerable by MACH.
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582

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: August 21, 2012, 01:20:00 PM »

If the relay turns off the drive and allows the drawbar to move simultaneously, there will still be a 'danger zone' if the spindle was running a 7K and the drawbar was set to move. The adapter would release as soon as the VFD was disabled, but it would still be spinning at 7K.

The Tach idea would eliminate that possibility. Also, as mentioned previously, I don't see how you can disable the drive and then change the tools. What would keep the spindle stationary?

It occurs to me that there has to be some sort of home sensor on the spindle in order to change tools that have drive dogs, so unless I am missing something, why not just watch the home signal? i.e. WHILE <continuous home sensor signal>, do the tool change, WEND. The spindle would have to be stopped and any movement would halt the tool change . . .  which would be a good thing, presumably.

I think this is the hot setup for the spindle, so that just leaves every other movement . . .  LOL!  Actually, I have magnetic sensors on the air cylinder, so it will be fairly simple to detect that the rod has reached the correct release and grab locations. If it fails to pick up a tool, it would move past the correct grab spot, and that should be pretty easy to detect also.  

583

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: August 21, 2012, 10:37:18 AM »

ah i see it's the need for the spindle to be stationery for the drawbar to operate you'tre worried about. Add a tacho to the spindle and use this to operate a relay that disables the drawbar.

There is a spindle lock that the motor cannot overpower, and the motor actually has a tacometer built into it. It puts out 7V per thousand RPM if I remember right. That is an interesting option, thanks!

For BT30 or any other scheme that has drive dogs, the spindle must home and stay homed. Not all spindles have locks and I am looking for the most universal solution . .  i.e one that the typical mill could use . .  although really I don;t know what 'typical' means 

There is that functional issue, certainly, but what I am focused on is preventing the adapter from being ejected unexpectedly at 7,000 RPM with a sharp tool in it. I am beginning to get the impression now that a safety interlock is a foreign topic.

584

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: August 21, 2012, 10:26:20 AM »

The only reasonable thing I've been able to come up with is making the ram button on the end of the air cylinder rotate. Then have a wire that the 24VDC that runs my estop system run through it like it was another estop switch. If the ram comes down while the spindle is turning then the button will turn break the wire or contact and kill the 24V. My estop system is totally separate from Mach. when you kill the 24V you kill everything. Servos, VFD,coolant and the air valve for the draw bar. The air valve is a spring return so when you kill the power the default is up.
Not elegant but for an electronics ditch digger like me it will get it done. I've been working with Mach daily since it was master5 and never witnessed it activate an output on its own.
Having said that it wouldn't surprise me at all if it happened tomorrow. That's why my estop has nothing to do with mach.

I am running 62 dev version because that is what works with the PoKeys board that I am messing with. You cannot use the 'stable' version with PoKeys and 62 has broken B and C axis feedrates and also has a tendency to either have fatal errors or just up and quit without warning.  I have a screen macro that simply lights an LED and activates an output. The LED always lights, but the output would go high sometimes and sometimes not.  When Mach starts and exits (intentionally or otherwise) andwhen the PC starts up or shuts down, or when Smoothstepper has a tantrum, it is hard to predict what any pin is going to do.  My safety interlock will be a mechanical device which will provide a positive physical impairment of the drawbar movement. I just have not decided how to arrange it.

Speaking of drives what are you running? I'm looking at the Delta VFD-M series. it's in the right price range , takes single phase input and has simple indexing to align the drive lugs.

My spindle motor is using a Copley Controls Xenus drive. 165V 40A on single phase 120V. Will also run on single phase 220V, but the bus voltage also doubles. The motor is 140V 37A peak.

585

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: August 21, 2012, 10:14:45 AM »

the relay that enables the vfd/spindle drive can be used to isolate the solenoid operating the drawbar.

In this case, I think the drive would need to be disabled in order for the drawbar to work. With the drive disabled there would be no mechanism (other then a spindle lock) to make sure the spindle is stationary.

586

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: August 20, 2012, 05:34:43 PM »

Question to anyone: What are you using for a safety interlock to prevent the power drawbar from releasing if the spindle is turning?

Speaking for myself, I do not trust MACH with such an important job, so I would be looking for something autonomous, or activated by the servo drive and not by MACH. I am thinking about a spring loaded solenoid that must retract a mechanical interference from the mechanism before the drawbar can release. Perhaps steal some energy from the motor to drive a relay to keep the 'lock' in place until the motor has zero energy. 

The drive I am using can sequence everything with an internal program, but I am looking also for a more 'generic' and autonomous solution which would work with less sophisticated drives.

587

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: August 18, 2012, 06:06:12 AM »

Just a FYI I'm running the same setup as you except all my parts are heat treated and tempered A2 ( I seem to recall your using A2 and S7). I just finished a run on a bunch of castings with over 400 tool changes and it never missed a beat. I have another set to run and after that I'm going to do a tear down and see how everything is looking.

Each tool steel, or any material for that matter, has characteristics that are good in some applications and not-so-good in others. A2 when hardness is the primary requirement. S7 is tougher and shock resistant. A2 would outlive the S7 (used for the ball holder), but would be more likely to fracture. These are not super stressed parts, and should not break nor wear out in our lifetimes, so either is acceptable. The pull stud is the only scary part of the mechanism as a whole. 

I watched your video. Very clever indeed. The opening lid was really a surprise!  You should spice that up just for fun. Paint it green and put some big teeth and some crocodile eyes on it. I have to build the spindle and the pneumatics, which are fairly straightforward tasks, and then attack the ATC. I have looked at a lot of arrangements. Mohammad comes to the mountain and vice-versa. Somewhere between ideal, realistic and practical is where It will probably end up. 

588

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: August 18, 2012, 05:37:41 AM »

The Bellevilles are working and there are ways around the spring-to-spring friction issue, but I still do not like the whole concept. The BT30 is so small that the gripper sleeve has to be installed from the opposite end of the spindle, which leaves a much larger hole in the spindle leaving the need for a 'platform' to be created for the base of a coil spring. Plus I would have to reanalyse the stresses for a thinner spindle wall (larger hole). There was a spring washer available which met all of the requirements and has a path to a heavier 'sister' as an upgrade path, so that was the easy way out for this first iteration. As you can see from the video fragment, the assembly releases at .20" with the stack set to 1,000lbs and there is an additional; .135" of travel after that. The spring pack binds at about 1,940lbs. It should take about 1,400lbs to release. I have not calculated the max available pull, but I know it is way above what is needed, so the heavier sister will not be needed and I will design the pneumatics for  a 1,800lb release @ 90psi.

The gripper will normally run at about 600lbs. I have tested the gripper mechanism to 3,000lbs and there was zero dimensional change, so I'm calling it a done-deal. I will be making a much larger spindle immediately following this one and I will use the coil spring in that design. Interest seems to be waning in this project, so I may not post beyond this, but I will be making a video of the entire development process. After I have presented it to the folks who are behind this whole effort, I will post it up on YouTube.


www.thecubestudio.com/BT30SpindleProject/BT30GripTestFragment.wmv

589

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: August 17, 2012, 06:04:15 PM »

The entire Gripper assembly is now completed and tested. Here are some photos of the complete assembly and the test rig.  I will be doing a full YouTube video on this project, and I have a small fragment showing the testing of this completed gripper. I'll post a link when I have it on my site.

590

Show"N"Tell ( Your Machines) / Re: Success! Mini Machining Center under Mach3 control - Video link

« on: August 10, 2012, 05:10:51 PM »

The video:

http://www.youtube.com/watch?v=TlQgMk6te_Y