MechMate CNC Router Forum - Now has AC SERVOs #111

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- MechMates already cutting (http://www.mechmate.com/forums/forumdisplay.php?f=78)

- - Now has AC SERVOs #111 – Georgetown, TX (http://www.mechmate.com/forums/showthread.php?t=1227)

Update questions

Bill,
It has been a couple of years since you have posted. do you have any updates, observations or reliability issues to report .

Thank you for posting your work and experiences. John Higgins found me up here in WV and he pointed me to this thread. This information was exactly what I was looking for. The specific Clearpath motors being used on a Mechmate with belt drives. the simplicity of the hookup really appeals to me (simplicity = solid) also these servos are quieter than steppers (something almost never addressed) I am a bit sensitive to high frequency noise. I have seen these servos run in person and they are really quiet.

Thank You
archie

Archie,

WOW! It HAS been two years..

Archie, Thank You for the query!!!

The MM started out as something I was interested to build, and I had a specific purpose for it. That purpose still remain, however, I am not using the machine for the original purpose.

The MM is being used to manufacture aviation parts. I'll explain briefly. A few years ago, a friend asked if the MM was capable to cut and form the die blank tooling with precision, for the ribs, bulkheads, etc, necessary to build a high performance experimental aircraft. At the time I said, 'NO', because the terrible Hobby Class controls. But I did confidently say at the time, the MM is robust enough to accomplish the task with professional controls. So I set about making the control change.

I rebuilt the controls, and we went about designing parts, and cutting the tooling necessary for the airplane. The plane is still under construction and will be delivered, perhaps summer this year, 2018.

Word got out to the local aviation guys about the machine, and I am now cutting aviation instrument panels for glass cockpit upgrades. So far I have redesigned and cut new panels for two Citation corporate jets, one corporate King Air twin turbo prop, and a few smaller aircraft. The guys tell me they are extremely happy with the panels the machine produces, and there are more big jobs coming.

Additionally, I am using the MM to cut motor and fixture plates for my Bridgeport Knee manual mill conversion to CNC.

Today, the MM spends about 80% for the time cutting aluminum. I have cut mounting brackets from 1" aluminum stock, no problem. Granted, this is not a milling machine, so you cannot take deep cuts. But it cuts 1" aluminum stock, no problem. Don't forget, the machine is driven by NEMA 23 servos.

There are no plans to upgrade the servos. The servos as they are, provide more torque than tool deflection can deal with. So there will never be a reason to seek a larger ClearPath driver for this machine.

I have a redesign of the gantry in drawing. This includes the replacement of the router for a spindle. Just waiting for enough money and time to implement.
The machine works well as it sits. I have stripped all unnecessary controls from it. I only use hard stops for X and Y zero reference. To begin a toolpath, I manually set the machine X and Y axis against the hard stop plates. Then I reset the Zeros for both in Mach. I don't use switches. They are not accurate enough. And I use stop blocks at the ends of the table. The ClearPath servos have an automatic shutdown built into the controller should the machine strike a stop block. So there you have it. There are no switches on the machine at all, except of course the manual emergency stop, red mushroom.

More info and photos later

Regards,

BillT

Bill,

Great to hear from you. I told Archie that you were a no-nonsense kind of guy.
Sounds like you are really getting a lot out of your MechMate. I look forward to those additional details and photos you mentioned. If you have any videos of #111 cutting aluminum, I would love to see them.

What MechMate-111 has been up to..

From the four following photos below you can see what the MM and I have been up to. Sorry for the photo size, they are as large as allowed.
Photos:

1)High performance fuselage under construction, outside view. This photo looks forward. The firewall begins as a circle, 36" in diameter and transitions slightly to elliptical shape moving to the cockpit. From the cockpit the strong elliptical shape transitions aft to the empennage. This offers a much lower drag coefficient than others.

2)High performance fuselage under construction, inside view. The camera view is two bulkhead stations behind the cockpit. It looks forward to the firewall. Shown are some 40 bulkhead pieces, others out of view, press formed, jigged and assembled as the fuselage. With the bulkheads precisely built, no shims were required as the skin was fashioned and fit.

3) A view of the Co-Pilot instrument panel. Five aluminum panels make the Main Instrument Cluster of the Cessna Citation jet. The two shown in front of the yoke, panel four and five are the Co-Pilots instruments. Many instruments from panel five were incorporated into the Garmin panel, partially in view far left. These panels are made of aviation grade 2024-T3 heat treated aluminum, 1/8". The MM cuts this material easily.

4) A motor plate for the Bridgeport CNC conversion. This is just a simple photo. It shows a ClearPath servo mounted onto a belt transmission, very similar to the ones used on the MM. The motor plates are 1/2"-6061-T6. The MM cuts this material easily.

These four photos are from three projects that would not be possible without the MM. The machine and the controls work well.

One final note on controls. As shown in this build thread I use the Hicon Integra. It is a six axis controller and quite expensive. Hicon has now a less expensive four axis controller; but still expensive. Over 400 bucks.

Recently however, Centroid, the big daddy of all CNC controls introduced a new controller, Acorn, specifically to attract the hobby guys. Yes, I advocate professional controls and the Acorn is truly a professional controller. Centroid gives the same core CNC processor to the Acorn board found in their high end boards. So the hobby guy gets the best. You will not find a better processor for the money. Did I mention the Acorn is about 300 bucks from some vendors. It comes complete with the controller, power supply, cabling, and their light but very robust control software.

Be on the lookout for a MechMate controller upgrade to Centroid.

I have also been reviewing the Acorn controller. I was wondering if the 23 motors needed any gear reduction. I see here that the 23's with our belt drives work great.

Just what I needed for info THKS WilliamT !!
I'm in the....thinking & search process to upgrade from my initial & old ( but still useful) PMDX+ SS + Mach3 set up !!
Wondering on & about Acorn or UCNC !?...but that's another questioning debate out of WilliamT thread @_@ !!
Cheers

Is it possible to get the resolution fine enough without gear reduction with servos?

Hmmm, one of the main reasons to go with servos is the ability to use the encoders for feedback positioning. According to Centroid's specs, the Acorn does NOT allow for true closed loop operation:

http://www.centroidcnc.com/centroid_...d_diy_cnc.html

Brian

"Beating the dead horse again" none of the low end products close the loop at the computer there are some cards that can be put in the computer that allow closed loop at the computer. Gallile comes to mind http://www.galilmc.com/news/cnc
but the common servo's that are used with Mach3 close the loop at the drive there used to be a plug in for mach3 for the gallil card but I digress

Happu Hunting
archie

I am very impressed with how you have been using your MM for building aircraft parts. I have used mine for making rib forms and plotting out cut lines on sheet metal. I have never had any success cutting sheet metal directly.

What type of aircraft is being shown in the pictures?

<Chuckle> I'll take a swing at that horse, too, as has been done in the past.

The key here is really to think of the entire motion control system. The Acorn is a step/direction interface, which means that closed loop is irrelevant: whether it's an actual stepper motor, or a servo driver which is emulating the behavior of a stepper motor you still have the failure mode that the control system cannot adapt to the feedback that a single axis is running slow and thus the workpiece and possibly the tool are already ruined when you get the feedback.

As Archie points out, if you have a full servo drive system without a step/direction interface in the middle of it, plus a trajectory planner than knows how to use the closed loop feedback it's a different game - as long as you never demand more torque than the servo can provide, which would be the comparable failure mode with the same outcome.

A well designed Step/Direction interface based system will never lose steps, generally by applying more torque than you need at all times. Tech marches on, so now we can construct systems that use single-axis feedback to emulate an open loop stepper using a less complicated/expensive servo motor. That's attractive even without a true closed loop as a drop-in subsystem to provide a certain amount of torque with a Step/Direction interface, which is what Teknic/Clearpath is offering - they've effectively extended the low end of servo technology down to 100W or so in a way they competes with steppers.

Ultimately it comes down to whether the entire system offers sufficient torque for a given demand at a reasonable price, regardless of step/dir/stepper, or step/dir/servo, or closed loop/servo. It appears that for the MechMate, the Acorn/Clearpath combination is in a sweet spot - a similarly priced system gives you the overflow torque advantage of a servo, without the runaway threat of a servo, without the waste heat of a stepper. Sure, it's not a fully closed loop, but if you can never exceed it's torque capacity, who cares? And if you can, well, "you're doing it wrong".

Brad,
Thank you for explaining it in a way even I can understand and much better than I could ever articulate (big word) it

Happy Hunting

archie

dbinock

Thank you for your comments.

Work holding is the key to cutting any material. Thinner material, as with sheet metal, is much more difficult to cut. I don't have vacuum, so I once sandwiched thin material between two pieces of MDF. The cutting process worked and the part looked good, but at what cost!

The aircraft is a two seat, inline full metal fuselage. The engine is a nine cylinder air cooled radial, 450hp. The aircraft will be fitted with fully retractable landing gear to minimize drag.

bradm and jeep534

Thank you guys for your comments too.

I really opened a can of worms here, bringing up the Centroid Acorn. Truth is, there are a large number of Break Out Boards and combination of Stepper motors that work very well for the MechMate application. For software some guys use Mach, some use Linux, and some have adapted Tormach Path Pilot. Parts are parts, are parts. Find a combination that works well for you and learn from the experience.

One guy recently asked me, regarding my comments on professional controllers, "What do I consider Professional Controllers?" You know what, that was an excellent question!!!

My references to professional controllers regards the 'hardware' side only. With better professional equipment you get other features specifically designed for big machines. But these features are not necessarily needed for the MechMate. I was after good hardware only.

In the video that follows, Alan explains why he changed to the Acorn controller. He begins explaining at about 3:20 his hardware failure problems, and the time and the money trying to get it resolved. Same thing happened to me and this is why I moved on to better hardware.

https://www.youtube.com/watch?v=4QqVa2lgU7U

You guys are way above, my knowledge level of machinery. I just keep reading, and learning little bits. After a while it sinks in, and I have that AHha! moment.

excellent build, love the upgrades, sounds like acorn and the clearpath are a good combination. The video of the knife builder was compelling. I think im gonna go this route