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Author Topic: 4x4 CNC Journal  (Read 9696 times)

Chorca

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4x4 CNC Journal
« on: June 19, 2012, 07:28:46 PM »
Editing this post to keep the thread relevant with the current "things we're doing" and "ideas for what to do".

Things we need to do:
  • Clean up wiring, mount control box, install e-stop buttons and on/off switch and relays
  • Possibly acquire cabinets and install them in the frame to store materials
  • Install either a simple toggle switch w/box ala RepRap Table, possibly with cover to prevent oops, or SSR-controlled router, or both? SuperPID is on the way for accurate control
  • Get mount for computer/monitor/keyboard and attach to frame somehow Building CNC cart
Done:
  • Install Igus chain
  • Acquire servomotors
  • Acquire servodrives
  • Purchase replacement leadscrew for right side of machine
  • Locate wrench to operate collet on router
  • Acquire other collets which will fit in the router to let us use a wider variety of bits
  • Locate a more permanent home (and power source) for the machine
  • Install power distribution onboard (Power strip) for simple on/off of entire machine

Things that would be awesome, which are being discussed or can be done:
  • Extending the bed to make it a full 4x8' cuttable area, so we can load full sheets of sheet wood into it
  • Overhead projector to show cutlines and assist with positioning
  • Rebuild the gantry for mo' betta' with some sort of metal or otherwise

Older info below this:



I realize that while we already have two threads that were merged about this, technically this is more about how we make it work and evolve the machine, so I'm going to fire up a thread here to show what we're doing to it and where it's at currently.

(I'm just going to keep editing this post since that'll be easiest)

A few things have happened so far. We have

  • Gotten the CNC
  • Gotten it mostly working
  • Gotten it cleaned up some.

I will expound up on some of the latest things, as the whole 'setting it up' is kind of boring.

My friend (Adam) and I had originally set up the machine and gotten it to a working state, but we had some issues and it was neglected for a few years. Now we have to basically finish it up, get it working, and calibrate all the goods.

After getting things assembled, we found that the same issues we had before were present, namely, issues with the leadscrews on the Y axis (gantry movement) stalling the stepper motors. I played around with the motor drivers, and even using 1/2 step to get more current (up from 1/4 stepping) it is still having issues driving the axis.
We played around with the rod, getting it aligned properly with the leadscrews and found while that helped a bit, there were still resonances that were happening causing the steppers to stall.

At the same time, I fixed the distance issues with the leadscrew on the X and Z axis, and they move perfectly now. The Y axis is still the difficult one. I have been exploring some other options, and while the gantry rides easily back and forth, the issue appears to be with the motors not having enough torque, or setting up resonances (stepper motors, because of their design, have certain resonant frequencies they lose torque at) in the motor and leadscrew which cause the motor's torque to drop. The options are to spend more time troubleshooting and perfecting the stepper drives, or to move to something different.

We had used Cat5 cable and connectors to hook up the stepper motors, and to remove any issue they may be causing (and were causing) with connections, I switched everything over to fixed wiring. I purchased about $50 worth of 8-conductor cabling at Skycraft and used a thick Monster Cable on the two moving axis (X and Z) and used the thinner cable on the other two (Y/A axis).  I also bought four terminal blocks to stick on, which I did, and then wired them between the stepper motors and the wiring. I drilled out the holes in the box to enable me to slide the larger diameter Monster cable into the box, and then attached the wires into the motor controls. I used a standard wiring pattern, which I will post as well, so we know what goes where.

I went through after this and cleaned off the table. I removed all the junk from it, all the extra hardware went into the plastic drawer, all the larger parts went into the cardboard boxes and I used one of Waterbury's brushes to sweep the entire table free of three years worth of dust, wood shavings, and dirt. The cables are laid across the table for now as we do not have the Igus chain installed and connected yet. The lengths I cut the cabling to should be long enough to support using the Igus chain as well. We have three pieces of it, but I am not sure how much needs to be used and what sizes. I assume the small chain should be enough to carry the two cables on the X axis and the three cables on the Y axis. (Z/Router on the X, Z/X/Router on the Y). We will need support brackets to be made for the chain to hold it up as it rides back and forth, and also some way of mounting the chain to both the moving axis and the stationary point.

I am currently investigating a way to make at least one of the axis, if not two, work much better. I have found a relatively inexpensive source of ball screw, which we may be able to use in order to increase the amount of torque the motors have available, as well as make the screws turn much easier. I have also been looking into using servomotors for at least two of the axis, Y/A and X. I am trying to spec out motors, but the same place that sells the inexpensive ball screw has reasonably-priced servomotors that have quite a bit of peak torque, almost double what the current steppers have. They're also made for Geckodrives, so we could use the step/dir outputs from the parallel port to feed into a set of GeckoDrives to handle moving the servos. For at least the Y/A axis, this would give us closed-loop positioning. We could possibly use the smaller motor homeshopcnc sells on the X, or a similar one from ebay.

Here are some prices. This is to do the Y/A axis with ball screws(Gantry movement):

NamePriceQuantitySubtotal
1605 Fixed End Machining$75.002$150.00
1605 Free End Machining$25.002$50.00
1605 Screw Stock$1.89/in144$272.16
F1605-4-C7 Flanged Ballnut$89.002$178.00
BF12-C7 (Free End)$45.002$90.00
BK12-C7 (Fixed End)$105.002$210.00

Subtotal:    $950.16

Now, prices for upgrading two axis (Y/A,X) to servodrive:

NamePriceQuantitySubtotal
Nema 34 850 oz/in Peak Servo$235.002$470.00
Nema 23 350 oz/in Peak Torque 60VDC Servo $150.001$150.00
GeckoDrive G320x$121.003$363.00

Subtotal:     $983.00

This is not taking into account any things that may be purchased from eBay for cheaper or something, just using things that can be purchased right now if we wanted to.

It does seem a little steep, but I think for now the best option is more powerful motors, since we get two things with that: more power to fix the issues with resonances, and closed-loop on the two most important bits. The Z stepper has more than enough torque as it is to lift the head, now that it has been aligned properly, and it has not stalled once since then.

Any ideas, feedback, are great. I'm going to continue my search for motors on eBay every couple days, and if I can find a cheap auction selling a few of the same motor that meets oure requirements, I'll prolly pick it up, even if it's a non-standard frame size. If someone would like to help out with the GeckoDrives or has any of the materials that we need, feel free to help. I will post a list of the things that we need done (in no particular order):
« Last Edit: May 26, 2015, 01:41:29 PM by Chorca »

f00bard

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Re: 4x4 CNC Journal
« Reply #1 on: June 20, 2012, 09:20:05 AM »
Chris, apologies if this doesnt belong here.  I looked at the Igus chain again last night.  We have two different sizes.  The larger of the two has one "mount" or something approximating one.  We'll need a couple more of those.  The mount has holes for screws as well as something to tie wrap cables to for strain relief.  I'd like to use the proper parts, of course.  Should we use just the smaller sized chain?  There's more of it, and it's probably enough for our needs (fixed point to Y gantry, Y gantry to Z).

Do you think it's worthwhile replacing the leadscrew on the one side?  Is it as cheap as you were assuming?

I'd like to see us cutting first before seeking more investment, but that's me.  I figure we can get more people interested in investing in the CNC if we can show it running.  I do like seeing our options, though.

On a related note, Bob and Dave laid out a plan for power last night, and we should have word back from the electrician soon.  Then we can get the power in place and start moving tools where they belong.  Exciting!

Chorca

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Re: 4x4 CNC Journal
« Reply #2 on: June 20, 2012, 12:49:22 PM »
I'm totally down with getting whatever we need to get the Igus chain working. If someone wants to go ahead and order it and install the chain, I'm totally fine with it, and I trust someone to figure out how to get it done.

We can prolly get it cutting with a minimal investment, $80 or so should get us a new precision leadscrew for the side, which would hopefully prevent most of the stalls we're seeing. We can also set it to full step instead of 1/2 to get more current, and slow down the moves to keep it from dropping steps.

I'd say top priorities to make it "cut":

  • New Leadscrew
  • Wrench for router
  • Igus chain mounts
  • Install plug/switch for router
  • Calibrate/setup Mach3/EMC2

Those are small, somewhat easy things that we should be able to get done in the next week or two, and perhaps we can have a working machine by the next open house.

I still don't know how loud the router is, but I'm pretty sure it's not quiet... Also, if we can get some sort of dust collection set up, that'd be awesome. There are some CNC-able designs, and it's usually one of the first things that people make on these (like the handle on the makerbot) is a dust collection skirt to ride around the material.

Also, we have a set of T-slot nuts to use on this, but no hold-downs. Does anyone know what hold-downs we should use on the table or have links to some we can buy?

Simply7

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Re: 4x4 CNC Journal
« Reply #3 on: June 20, 2012, 03:26:24 PM »
I have that same router and its. not that loud unless you are loosing a bearing. The real noise is when the blade starts cutting. You probably will not hear the router over the cutting sound. I may swing by tonight tonight and see if I can get something together.

AtomicProf

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Re: 4x4 CNC Journal
« Reply #4 on: June 20, 2012, 04:58:56 PM »
We may be able to make hold downs with simple wood wedges.  They work great and are often overlooked as a lost technology.


One wedge needs to be connected to the T-bolt, the second wedge goes between the work piece and the wedge attached to the T-bolt.  A tap with two hammers locks them into place with friction.  Several of these around the workpiece will hold just fine.


They are quick to disconnect with just a tap of the hammer.
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Chorca

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Re: 4x4 CNC Journal
« Reply #5 on: June 20, 2012, 05:00:53 PM »
We may be able to make hold downs with simple wood wedges.  They work great and are often overlooked as a lost technology.

If you'd like to take this on and build some, we'd be grateful. I can give you one of the nuts if you would like, and you're welcome to work on it.

The only thing is that they need to not be susceptible to vibration, as the bit will definitely impart plenty of that into the workpiece.
« Last Edit: June 20, 2012, 05:22:17 PM by Chorca »

AtomicProf

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Re: 4x4 CNC Journal
« Reply #6 on: June 20, 2012, 08:55:01 PM »
Two finished hold down wedges are in the lab.  Let me know your thoughts.
Photos show the wedges in progress.
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Pitbull

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Re: 4x4 CNC Journal
« Reply #7 on: June 28, 2012, 10:23:24 AM »
I think getting rid of the cat5 cable was smart, that is to thin a gauge  for heavy steppers imo . I do not know what size motors you have or how big a power supply..but combined it might not have been supplying enough juice.

Any chance that you can redesign to get rid of the lead screws and ball screws and go with rack and pinion. Its a wash money wise but you will get rid of a lot of issues a larger machine has with long runs and lead screws, not to mention pick up jog speed.

If you are going to overhaul it...all options should be on the table. But I agree with f00bard, Getting it operational at this point goes a long way to showing need for more investment.

Servo is a nice upgrade, but before going that route it might be wise to get a better drive such as a geckog540. It sounds like more than anything you are having electrical issues. Power from the steppers could be increased dramatically if the demons are exorcised.
« Last Edit: June 28, 2012, 10:27:53 AM by Pitbull »

Chorca

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Re: 4x4 CNC Journal
« Reply #8 on: June 28, 2012, 10:50:05 AM »
The driver we're using is http://www.hobbycnc.com/products/hobbycnc-pro-chopper-driver-board-kits/

If someone wants to pitch in $300 for a G540 I'd be down for it, they're pretty nice.. I'll even find a power supply to use for the thing so we dont' have to use the crappy one that came in the hobbycnc kit.


However, I think for now I'm going to investigate a belt-drive system for the leadscrews, using servomotors. I can use the belt to gear down the motor, and at the same time, use a smaller servomotor than would be required for direct drive, and still get positional feedback so it won't lose it's spot. It would also shrink the size of the machine as the rather bulky motors can be moved to inside the frame. A large-tooth GT2-style belt would work well.
« Last Edit: June 28, 2012, 11:18:55 AM by Chorca »

Chorca

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Re: 4x4 CNC Journal
« Reply #9 on: June 30, 2012, 04:04:11 AM »
Success!

The PreciseBits collets and nut came in for the router, so I cleaned up the chuck on it with their cleaner and recommended process, and then began testing bits. I attempted some simple cuts by hand using the jogging on the machine, just to see how well it would work. The cuts were clean and seemed to work pretty well, so I began working on getting Mach3 set up with the right calibrations and such for the machine.

After much tinkering, I got it working properly, and moving the correct distances and at speeds that would keep it from stalling. I then worked on getting PyCAM working with a simple set of circles to cut, but then realized after spending an hour making it work, that Mach3 (being in demo mode) would only allow 500 lines of G-code to be executed. Milling three small circles took over 2000 lines. This clearly would not work. The options were to buy Mach3 ($170) or use EMC2, which I already had running on the Zen quite well. I decided to do the latter.

After finding out that the Sony Vaio would not boot off of the USB drive, I decided to just steal the Zen's computer and set up a second config for the large CNC. After getting the settings right once more, and tweaking a few things to account for how the CNC worked, I was able to finally cut the three small circles. This was the first thing that had been ever cut in an automated fashion on that machine.

I then decided to immediately go to the big stuff, and worked for the next hour or so getting a 1'x1' FamiLAB logo run through PyCAM in order to make a raised cut. After plenty of frustration, and tons of time spent having it write the gcode, I finally had it finished, and ran off the first pass to hog out the bulk of the material so the second pass could more finely clean it up. ( Video )

This mostly worked. The router mount came loose during cutting (seems we never tightened it up, should have checked that) and led to some interesting offset in the second pass. After that, I re-homed the second bit (1/4" endmill) and began the second pass. It went quite well, and while I did not have a ballnose to get a quality finish, the end result looked like a FamiLAB logo. The milling process itself went smoothly and we made a huge mess.

After milling that out, i wanted to try adding the FamiLAB name to it, sideways. I began working with FreeCAD and fighting PyCAM to get it to do what I wanted, only to find that it was basically impossible, as pocketing non-concave curves was impossible so far. Swinden and I began exploring the Vectric line of software that Ian had recommended, and decided to check out a trial. While I didn't have windows on my machine, I did have Wine, so we decided to give it a go.

The install and such went fine, and aside from a small hiccup with the window decorations that was fixed by updating Wine, the sofware ran flawlessly under it. We checked the price, and after a bit more tinkering, I decided it would be worth it if the gcode was half as good as PyCAM's.

$150 and a few minutes later, and we had Gcode of the FamiLAB text ready to cut. After a quick setup, we did another cut. ( Video ) It came out awesome! Really really nice. Very impressed by the software and how it plans it's moves and such. Really works great with the CNC.

We decided to do one more before heading home for the night, and etched the "CNC" letters into the top of the board as well. I used a two-bit setup this time, hogging out the material quickly with the 7/16 bit, and then going back to clean it up with a 1/8". The end result was good, even if there seemed to be a slight misalignment.

Overall, the CNC is operational. The first order of business is going to be dust collection, as it makes a HUGE mess. We need a dust shoe and Thien Separator very soon. I'll start working on a design for the dust shoe, and keep working on getting it tweaked up.

If anyone would like to experiment with the software we are using to generate G-code, you can download it here. Just click on the download button by Cut 2D, and install it on your system. You can run it in trial mode, the only limitation is that you can't export G-code that's not from the built-in example files. This is fine, since you can stlil save your entire project out with the trial version, meaning you could set the entire thing up at home, bring the Cut 2D save file to the lab, and use the copy there to generate the G-Code for the machine. I will be setting up Wine and Cut 2D on the machine we use for the CNC soon, so that it can be used right there. It is very fast at generating G-code.

If anyone has a pressing project that NEEDS to get done, talk to me and I will help you out getting it set up and cut. We really should not cut MDF until we have a proper separator and ventilation system, so I have been using plywood.

On the electronics and drive front, I am going to begin ordering the parts to convert the machine over to servo drive. I will be picking up a few motors and possibly another pair of GeckoDrives shortly, and PockyBum has purchased the necessary parallel port breakout board we will need to run the new drive system. Each axis will be driven by pulleys and a belt, providing both remote location of the motor, as well as reduction for better torque. Small pulley driving a large one)

Pics at the bottom!
« Last Edit: June 30, 2012, 04:06:39 AM by Chorca »

digitalman2112

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Re: 4x4 CNC Journal
« Reply #10 on: June 30, 2012, 08:52:42 AM »
Awesome work guys!

Pitbull

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Re: 4x4 CNC Journal
« Reply #11 on: June 30, 2012, 09:22:36 AM »
Glad to see it cutting! I just got my collets from precise bits as well...and for the same router you are using on your CNC so this definitely gets me excited. I am still a good 2 weeks away from being operational on my project..... :(

However, I can help by giving you a heads up on a good source for parts. The link below is for Kelling's new store front. Very well known and regarded supplier of steppers and servos.
http://www.automationtechnologiesinc.com/products-page

I bought a lot of stuff from them for my project and they shipped same day. They also happen to be one of the largest volume Gecko dealers and Mach3 dealers...both of what you can get here cheaper than what you have listed above.

Lastly, I have a SuperPID on its way from Australia (takes a little less than 3 weeks). If you are not familiar with this product it seems it would be right up your alley for what you have going on....especially if you plan on milling plastics and aluminum on the CNC router. Its not cheap, about $180 shipped for your arrangement, but allows full control of speed with 100% torque at any rpm (closed loop feedback). Also control readout and operation from within Mach3 which makes it safer (complete shutdown in an instant).
http://www.vhipe.com/product-private/SuperPID.htm

This is a now hidden video on youtube (probably because it displays unsafe practices) showing it chewing through wood at 5000RPM with no torque loss. Extremely impressive imo!
http://www.youtube.com/watch?v=85L050QcsYI&feature=plcp&context=C3435faaUDOEgsToPDskJ1QNMyghWqKOCXsnNZo_vV


Looking forward to the open house-

Jason


Chorca

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Re: 4x4 CNC Journal
« Reply #12 on: June 30, 2012, 09:48:39 AM »
Awesome, I've actually looked at Kelling for some of the motors and such that they stock. Seeing as i'm not going to go direct-drive, the smaller MCG motors from ebay should be fine. The SuperPID looks pretty awesome, but the Hitachi router that we're using has a speed controller built in that monitors the speed and increases current to maintain RPM already. There's a ramp start function built in and the speed changes are actually done quite well using the dial. I'm not sure that PIDing the power into the controller would be the best thing...

Hope to see you soon!

P47

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Re: 4x4 CNC Journal
« Reply #13 on: June 30, 2012, 10:02:26 AM »
Great to see it cutting. Awesome job in putting this together.

Pitbull

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Re: 4x4 CNC Journal
« Reply #14 on: June 30, 2012, 10:25:58 AM »
The soft start and speed control on the router would actually get bypassed all together if going with the SuperPID. However you can come close to somewhat stalling that router or any like it at low rpm with a decent feed rate using factory speed control.

The SuperPID is certainly not necessary by any means, but it will go along way toward helping to not melt plastics while keeping a fast feed with full power
« Last Edit: June 30, 2012, 06:19:58 PM by Pitbull »