Messages

801

General Mach Discussion / Re: Need Guru input on an idea: Using Mach as dynamic balancer

« on: May 15, 2010, 03:19:13 PM »

Simpson,
Just a thought, but look into what the RC helicopter guys do. Balance is lost once you put something into the spindle.
Make note that the active system must be looked at, not just a single item, so even tool chatter can create a condition for resonance.

There is nothing attached to the rotating part. The sensor goes on the housing (magnetic usually) and measures the movement. The balancing is done with the spindle running free, so there is no cutting chatter or other influences. 

As it happens, I used to be an RC helicopter guy. I flew a gasser. Goal was a camera ship. but I started tinkering and next thing I was into aerobatics. Still have it on a shelf in the garage.

802

General Mach Discussion / Re: Sprial Cutting A Hole

« on: May 14, 2010, 04:50:23 PM »

Here is something to play with.  No warranty, use at your own risk.

This is a fragment of some G-code that I made up a while back to do spiral cutouts. You add your data to the variables labeled 'INPUT' in the comment line. I just extracted if from a larger program and added the lead-in and lead-out for this thread, so set your Z above the piece and 'cut air' to be sure everything is working as planned. I think it works OK, but it is not tested in its current 'universal' form.

Comment out the G4 codes unless you are debugging. Just move the '(' ahead of the G4.

Holes are cut around X0 Y0. You can move to the hole center and zero your DRO, use offsets to get to the desired location, or set up variables in the program to hold coords other than X0 Y0.

Have fun . . .

803

General Mach Discussion / Re: Need Guru input on an idea: Using Mach as dynamic balancer

« on: May 14, 2010, 04:31:19 PM »

http://www.datastick.com/products/bal2000.html?gclid=CKjJ_LO3zaECFR5rswodFXUafA

If one has USD$6,000 burning a hole in their pocket, the solution is easy. Actually I just watched an old analyzer/balancer sell on eBay complete with sensor, strobe and 'lots of cables' . . . but the fellow did not know if it worked or not and I don't have the resources to fix something like that if it didn't, so I passed on it. It sold for $135

Most likely I will end up with the USB scope which has outputs and a scripting language that allows it to be read and programmed from a PC. Add an accelerometer (or two) and a strobe and it's Miller time. Plus then I have the scope for other uses.

I though it would be interesting and useful to use Mach3 since it seems capable of the task and everyone already has it, but so far it seems there are no Gurus up to the task. 

804

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

« on: May 14, 2010, 02:32:29 PM »

Here is an update: I am going forward with the trunnion table project. The tailstock will be integrated with that project, so I will be doing both simultaneously. I am still planning to make the tailstock from a 5C spin indexer so that long material can pass thru both the 4th axis and tail stock spindles.

Today I purchased the materials and new heavier ball slides beef up the mill and build the trunnion table.

As part of the shuffle, I am selling off some of the other new ball slides which I aquired and will not be using. You can find these in the bargain basement if interested.

I will document as much of the project as I have time for. Photos and text in this forum and videos, of course on Youtube. Nothing is cast in stone at this point, so any 'wish list' or other interesting ideas are welcome. I am of course especially interested in any problems with current trunnion tables or indexers that might be overcome in a new design.

805

General Mach Discussion / Re: Need Guru input on an idea: Using Mach as dynamic balancer

« on: May 14, 2010, 01:56:46 PM »

Thanks for the replies. I am interested in balancing R8 and 5C machine spindles running in the 8,000 RPM range.

'Spin' balancers for tires (fairly crude actually) and similar devices for industrial dynamic balancing are designed to balance a 'disembodied' rotating part. There are balancing services that do this, the most obvious would be a tire store, but there are balancing shops where I could send the spindles out to be balanced . . .  but where's the fun in that? It seems to me that it would be very useful for the Mach community to have an inexpensive but effective way to smooth out the operation of their CNC machines.

Strain gages are used for low RPM unrestrained shafts. A tire 'spin' balancer actually has one end of the shaft completely unsupported, but that application is under 1,000 RPM. I am not an expert in this field, but to my knowledge, higher speeds are done with constrained shafts and rely on vibration analysis.

In-place or 'field balancing' (pumps, motors, fans, etc) relies on vibration analysis. This is done with accelerometers which detect minute movements . . probably several orders of magnitude more sensitive than a proximity sensor, I would imagine. There are basically two methods (that I know of). Both methods use accelerometers attached to the machine. The more sophisticated method uses two accelerometers 90 degrees apart and also a photo (or proximity) sensor to count revolutions (and create a ref azimuth). These devices then tell exactly where and how much weight to add, and can do each end of the shaft separately, but simultaneously.

I am not expecting to mimic this type of balancer. The simpler form has one accelerometer and a strobe. It simply fires a strobe in responce to the vibration, thereby identifying the imbalance spot, but without quantification. In the hands of a very experienced person, only a few 'better/worse' iteration usually get the machine dialed in pretty close.
 
Accelerometers can be digital or analogue. A simple analogue 3 axis accelerometer is contained in a single IC and is about 20 bucks. These can be hooked up to a scope and the magnitude of the imbalance read directly. What is needed then is a trigger for a strobe. I have been talking to a company than makes an inexpensive USB oscilloscope and that looks promising, but I think it can be done for 'free' with Mach if there is someone out there with the combination of electronics and Mach3 knowledge to do it. I would be willing to work it out and share the process, but while I can contribute to the project, I do not have all of the knowledge needed, hence this thread.

806

General Mach Discussion / Need Guru input on an idea: Using Mach as dynamic balancer

« on: May 13, 2010, 12:10:49 PM »

I am looking at acquiring the capability to do some simple dynamic balancing, and I need some help from the electron guys who are also familiar with Mach scripting.

A very simple form of dynamic balance is simply a sensor (accelerometer) that triggers a strobe light. The light is pointed at the spinning object and similar to a timing light, the strobe freezes the part at a specific point. You throw on some weight and go thru "worst/better" iterations until the balance is close enough. Not efficient, but it does work if you have the time and patience.

A new USB based balancer that runs on a laptop is over $6,000 and has capabilities far in excess of what I need, so I am looking at DIY (read cheap) alternatives. Basically, all that is needed is to fire a strobe based on movement (vibration) of the part.

First, are there any oscilloscopes or other off-the-shelf devices that can do this?
Second, how difficult would it be to design a circuit to do this?

Third, it occurs to me that Mach can take an input (tachometer) and of course can generate outputs. I think I can figure out how to fire a strobe from a 5v output pin. How would one go about connecting a digital or analogue accelerometer to Mach as if it were an index? And can the index input signal be detected by script?

807

General Mach Discussion / Re: Rotary Axis Blues

« on: May 12, 2010, 05:52:33 PM »

Just an FYI about computers running Mach3.

I have discovered that the built in PP can cause symptoms that look as if the CPU is not fast enough when actually it is the PP chip, (sometimes built into the bridge).

My current computer misbehaves if I use the built in port, so I disabled it and use PP port one and two from an add-in PCI card. Works fine that way.

You can check this out easily by watching the task manager. If the CPU is not pegged, but the machine starts acting up, it may be the PP, which is semi-autonomous and can cause problems even if the CPU is humming along fine.

Also don;t assume that the drivers that come with an add-in card will work with Mach3. My card has the Mos chip and the drivers that come with the card do not work. The drivers from the Mos site, however, work fine.

808

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

« on: May 12, 2010, 04:56:50 PM »

These pictures show how I set my X2 4th axis up for Tools. I mounted the quick change tool post on the side.

Two of your photos are not showing up (at least for me)

Awesome idea! A lathe quick change (or a somewhat less versitile 5C collet holder) is what I had in mind to do until it occurred to me that I might be able to clamp something to the spindle and rotate it to bring multiple tools to bear. I would need to replace the current spindle lock with the new Super Duty lock and perhaps replace the lower ball bearing with a tapered roller.  

Another related plan I have is to add a high speed spindle to the head in a horizontal orientation. I have aquired an ER32 spindle for that project. Currently I bolt my die grinder handpiece to the side of the head. It is visible in the last video cutting the pulley teeth with a tiny ball end mill. The X2 is long gone though.


Bob, there is an advantage to keeping the 4th axis free for indexing and to drive a trunnion table (probably my next project after a tail stock) I am currently in the process of reinforcing my mill for heavier work. I have already braced the column and now am moving on to add two more trucks (bearings) to the Y axis ball slides. This will singnificantly increase ridgity as well as add another 4+ inches of Y travel.  Nothing like a few hundred pounds of 1/2" and 3/4" 1018 steel plate to stiffen things up.  

809

General Mach Discussion / Re: Spindle

« on: May 10, 2010, 05:01:07 PM »

The way I read this, the OP wants Mach3 to do something with the reading. I don't see a purpose for that other than for Mach to slow the feedrate or something. I've asked this question several times and the consensus is that feedback to Mach3 for the purpose of reacting with adjustments to a running program is not doable. However, it still seems to me that is would be if the right avenue could be found.

Speaking to this particular thread, 'Pressure' is undefined. methinks. If this means spindle load, that's one cat. If it means the downforce on the head, that's a differnent cat. There are lots of ways to skin them, but skining the wrong one is not particularly useful.

810

General Mach Discussion / Re: Encoder motor control

« on: May 10, 2010, 04:49:22 PM »

There is a saying in engineering circles that states 'you can't polish a turd', yet is sounds like that is what is being attempted here.
 
You cannot make a stepper do the job of a servo motor, not even with a steel belted BandAid.

So stop polishing and just install a servo motor and be done with it.