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Show"N"Tell ( Your Machines) / Re: BDG 672 CNC router 2450 x 1250 x 600 with 8 place Toolchanger

« on: May 29, 2013, 09:25:40 PM »

If you have access to the machines then definitely machine it in one piece or as few as possible. For stress relief try vibratory stress relief like Metalax.

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Show"N"Tell ( Your Machines) / Re: BDG 672 CNC router 2450 x 1250 x 600 with 8 place Toolchanger

« on: May 29, 2013, 12:57:56 AM »

There are a few ways to do it, I have used most. Yes welding on steel bar works but needs stress relieving.  Yes direct machining on thicker plate or tube works but can get heavy.  I have also done machines where I have bonded on aluminium or steel bar with epoxy and then machined the strip, I made the tapped holes go through both pieces to make sure there is no chance of a debond.  I have also done it by casting a bed of epoxy (filled with aluminium powder) and then machining that. That particular machine was done by making a dam on the edges of the tube and then pouring a self leveling epoxy to make a flat surface that we then just drilled and tapped holes in as a large mill wasnt available (well not a realistic price anyway) for when I wanted to do the job.  If you can get it machined its easier. A precision machine frame level and square comes in handy too.

I can sell you a full set of drawings and components at a reasonable price (or a complete machine), if you are interested pm me.

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General Mach Discussion / Re: Mori Seiki TL-5 TL5 Fanuc 2000 upgrade

« on: December 14, 2012, 12:48:22 AM »

Update on the TL5. Simon has been working on it and we now have X and Z axes moving, spindle turning and the tool turret indexing and most of the IO working. To give an idea of the work involved, Simon has been at it for 7 weeks full time. He is a Mechatronics engineer, new to Mach3 but I have been helping him out with lots of stuff. The big problem is the lack of complete documentation and working on a machine that has a had a few undocumented changes and repairs over the years, plus the whole Fanuc 2000 and spindle controller and drives are so old they are like they from a different planet the way stuff was done. Any way we are using the original Fanuc servo drives and Mitsubishi spindle drive. Currently we have issues with not seeing mpg input in mach3 (shows up as bit changes on the input lines in DSPMC status window) and figuring out a screen set to work with the existing hard switches on the old operator panel. Any help appreciated.

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dspMC/IP Motion Controller / Re: Plugin to load a file of points direct to DSPMC for High Speed Machining HSM

« on: January 12, 2012, 08:49:35 AM »

My interest is in high end high performance machining with high stiffness and high acceleration. Interestingly the trajectory planning requirements are similar for high end and low end machines but for different reasons. On high end machines the machining time and accuracy of complex surfaces is most influenced by the available acceleration. On low end machines the dynamics and stiffness are low and you need gentle acceleration and smooth motion so that you dont excite vibration in the structure, even at low feed rates.

I want to get to trajectory planning that will consider all of the limitation of the machine, not just the acceleration of the programmed axes. With five axis machines the acceleration and velocity of the physical axes (after transformation) is also important.

Rhino is a good starting point.  Have a look at MadCam.  Rhino has a good API, so you could get closely spaced trajectory points for both the tool tip and the physical axes (for machines with say 4 or 5 axes) directly from the surfaces and taking into account the local derivatives.  Its a good approach, but I need a solution that will work with other existing CAD-CAM packages.

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dspMC/IP Motion Controller / Re: Plugin to load a file of points direct to DSPMC for High Speed Machining HSM

« on: January 11, 2012, 12:05:45 AM »

The 1ms interval is because that is what the DSPMC is expecting, although it could also work at 0.2ms but its not set up for that from Mach yet. Its called the "interpolation cycle".  Trajectory planning is not easy because because you have to work out the accelerations over an arbitrary path, for both speeding up and slowing down. But Ive got a way figured out that should work, its kind of half programmed now and it will also let me do RTCP for five axis machines, or any other kinematics required.

Where are you Karl?  Moths are a good challenge.

Mould making with short G code segments is a challenge. Even expensive controllers can and do have problems. At the end of the day, the things needed are a rigid machine with high natural frequencies and high stiffness and a control system that looks ahead and plans a decent trajectory that takes advantage of the machines acceleration.

I am now machining foil moulds from aluminium and steel on a machine that weighs 6 tons. I started carving wood centreboards using a table saw and hand plotted NACA foils when I was a kid 30 years ago. Apparently I am still a kid, just the foils are better.

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dspMC/IP Motion Controller / Re: Plugin to load a file of points direct to DSPMC for High Speed Machining HSM

« on: January 10, 2012, 06:52:42 PM »

Got the plugin and am in the process of writing a trajectory planner to test it out properly.

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Show"N"Tell ( Your Machines) / Re: BDG 672 CNC router 2450 x 1250 x 600 with 8 place Toolchanger

« on: September 16, 2011, 05:04:07 AM »

Rufi says that feed forward works but it might need a really big number to have an effect. I will give that a try except that the machine is at the customers and I wont go there for a while yet.

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Show"N"Tell ( Your Machines) / Re: BDG 672 CNC router 2450 x 1250 x 600 with 8 place Toolchanger

« on: September 16, 2011, 05:01:33 AM »

Here are some more pictures

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Show"N"Tell ( Your Machines) / Re: BDG 672 CNC router 2450 x 1250 x 600 with 8 place Toolchanger

« on: September 15, 2011, 08:08:17 PM »

No I haven't tried the low pass filter, but I did see it. I will try it to see how it works. Thanks.

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Show"N"Tell ( Your Machines) / Re: BDG 672 CNC router 2450 x 1250 x 600 with 8 place Toolchanger

« on: September 13, 2011, 09:11:12 PM »

The servo noise is pretty common on a lot of servo systems. It depends how "hard" they are tuned. If you go for a soft tune, ie lower gains, lots less D, then the noise goes away but the response is nowhere near as good. Its all a compromise.  If you can use encoders with more counts per rev, then its less of a problem. These ones are 12 000 counts per rev (3000 lines) or about 1 micron resolution. The new Fanuc machines and some other systems Ive used use million count encoders or sine/cos systems like Hyperface or endat or BISS and they are a fair bit quieter and more responsive. But 10 times the price. Really they should be quiet but its hard to achieve in all cases. I did have an even "harder" tune but it was tripping the drives sometimes, so I pulled it back a bit and its ok now, but like you say a bit noisy. I will look into it a bit more.  Ive done lots of tuning with the DSPMC and havent seen much if any effect from the feed forward terms. Ive used feed forward (position control lagless they call it) on a big system with Beckhoff Twincat and its awesome. Hopefully Rufi can help us with the feed forward stuff.