[jsantos]

Hi All,

It's been 4 years since I built my first woodworking CNC. The first one was an 80/20 build using rack and pinion drives running on cncrouterparts bearings mounted on cold-rolled steel. Ever since I completed that first one, I've wanted to have a CNC on linear rails and running on ballscrews. To that end, I've been collecting the parts since the completion of the first one.

While the first CNC served me well, it's been acting up in the last few months. The shaft of one of the motors broke while it was routing a mahogany tea table. Luckily, it was one of the x-axis motors and the other x-axis motor was able to carry the gantry and complete the work. Otherwise, the table would have been ruined. Also, repeatability and accuracy has gone worse as the days gone by. Okay, I have not been very diligent on the maintenance aspect of the machine.

But since I've moved my woodworking workshop from my garage to my basement, it's now time for a replacement.

[jsantos]

The new CNC will be built from the following:

1. 80/20 3030 frame. I would love to have a steel frame but I don't know how to weld, so I'll have to stick with 80/20. The size might be a problem with the 80/20 as far as sagging is concerned.

2. 35mm THK linear rails on both the x (3000mm) and y axis (1650mm).

3. 32MM (10mm pitch) ballscrew from AutomationFor Less for the x and 25mm (10mm pitch) ballscrew for the y, also from AutomationForLess. I'll have more to say about AutomationForLess' outstanding customer service later on.

4. DMM Tech 750W AC servos , drives and BOB.

The attachments are what the new machine will look like. As I mentioned earlier, my biggest concern is the possibility of sagging. I'm keeping my fingers crossed that the 35mm linear rails will stiffen the 3030 enough to minimize sagging to an acceptable level. If not, I might try to sandwich the 80/20 extrusion between the linear rail and the cold rolled steel I have from the original machine - kinda like making a torsion box.

I've been putting together the machine on Sketchup for the past month. Now it's time to start putting it together for real.

[jsantos]

Have been noodling with the design and have made more changes:
1. I lowered the gantry by a foot so it doesn't look so tall now. Reduced weight and cost too. :-)

2. I was shopping around for aluminum for the uprights and found some 1 3/8" that I was able to get cheaper
than I would have paid for a 1" so I will be using a much thicker upright.

The first attachment shows the redesigned gantry.

The second attachment is the completed frame. To make it easier to mount the rails, this was assembled
upside down. I then had a friend help me turn it right side up.

The last attachment are some parts for the x-axis. I milled channels in them to make aligning the parts easier -
easily the smartest decision I've made on this project. :-)

[jsantos]

It has been a long day but I wanted to finish the horizontals for the gantry. I was worried that my uprights are not perfectly aligned with each other and the only time I'll find out is when I fit the horizontals. The pictures below showed the process I used to test fit the horizontals.

First I mounted and screwed down the extrusions on one of the uprights. Once I've tightened down the screws, the extrusions are now rigid and as I squared the ends, they should also be perpendicular to the upright. The third picture shows how it looked like.

I then fitted installed the second upright on the x-axis carriage and see if the horizontals would fit in the slot of the second gantry. And they did!!!! I was shouting and jumping with joy. I didn't have to force fit the horizontals. They easily slid into the slots of the second gantry. That's the second picture.

The slots are 7mm deep. That's the first and last pictures. Looking at this now, I'm not sure that my Z axis would have twisted back and forth without using plates. But since I've already made the plates, the plates are going on. They will just make my Z axis much better. :-)

The pictures I uploaded seemed to be out of sequence and I can't seem to control the sequence in which they are shown. Does anybody know how?

[jsantos]

Hey Gerry,

What version of Mach 3 was I supposed to use for your Screenset? Also, what is the latest version of your screenset? I have 1.09.

Thanks!

[nlancaster]

I would fear with that design your going to get alot of sag in the middle of the bed. That is a huge span. But maybe others with more experience with 80/20 could correct me. Having the CRS flat between the rail and extrusion will not do you any good. If you do ad CRS to the design to stiffen it up, attach it to the side of the 80/20 vertically. That will for sure stiffen it, I do not know if it would be enough.

[jsantos]

Finally completed the x-axis. I can rotate the ballscrew shaft with my hand and move the linear rails very smoothly from end to end with no binding at all.

I'm surprised at how well everything is fitting together. So far, all the parts have fit perfectly. I relied entirely on Sketchup Pro for all my dimensions and it seems to have done an excellent job. Now if someone will only come up with a CAM that works with Sketchup Pro. :-)

I've also started laying out the electronics. I'm going with DMM Tech's AC Servos, DYN3 drivers and their BOB. It looks like I'll end up with a panel that's about 2' X 3'. This is a lot bigger than I expected! Oh, well. Based on my calculations, I should be able to get like 750 ipm out of servos. Don't know if the other mechanicals will be able to handle that much speed. I'll soon find out.

[jsantos]

Here's the gantry installed. That is one heavy gantry! The plates made it so much more beefier. That baby will never twist. :-)

When I ordered the plates, I took the measurement of the back plate from sketchup and use that to order the plates. I forgot that the back plate is an inch shorter because of the y-axis plate. Now my front plate is shorter by an inch too. Sigh...

[ger21]

As shown, I think you'll get a substantial amount of flex in several places.
As was already mentioned, it's going to sag a lot over the 10' span. I'd drive it from both sides and fully support the table.

I think you're two separate gantry beams are going to allow the Z axis to twist back and forth (front to back). Tying the two together into as more rigid box beam would make it much stronger.

Hanging the spindle down below the gantry beams like that will surely flex quite a bit. You're relying entirely on the stiffness of the plate which looks rather thin. If you insist on this design, I'd use at least a 1" thick plate to mount the spindle to. But, my preference would be to add something to stiffen that plate, oir get your bearings down lower.

35mm thk rails are way overkill for this design. 20-25mm rails would still be plenty strong enough, and should be a lot cheaper.

[nlancaster]

For Z-axis stiffness I would lean towards mounting the rails on the actual z-axis and the bearings for them on a plat. then the z-axis is always supported by the rails and the bearings can be fixed and further apart. may cost a bit more on having the longer rail.

[jsantos]

Thanks for the suggestions guys! Really appreciate it.

1. x-axis - I have 2 motors and drivers that I can use for the x-axis but only one ballscrew. I debated whether to drive it from both sides or just center and decided to do just the center since I only have a single ballscrew. But given your comments, it looks like the best course of action is to get another ballscrew and drive it from both sides.

2. 35mm THK rails - I was able to get the rails on eBay for very cheap over a couple of years ago, so I'm not complaining. :-)

3. gantry beams - Thanks for the suggestion. I'll change it to a plate. I've seen people use 1/2" plates. Would that be thick enough? Speaking of gantries, any thought on the extrusion uprights? Should I change those to plates too?

4. spindle plate - My z-axis is about 10" deep and the y-axis bearings are as low as I can get them and keep the 10" z. Attached is a close-up of how the z-axis is setup. The spindle is going to be attached to a 5/8" plate (spindle plate) that in turn is attached to another 5/8" plate (z-axis plate) that's attached to the z-axis linear blocks that are inside the 'green box'. The green box is a 'sealed' unit (acquired from Techno-Isel thru eBay about 4 years ago) that contains the rails and ballscrew for the z-axis. There's quite a bit of overlap between the spindle and the z-axis plate. Do you think that there will be a lot of flex on the spindle plate?

5. z axis - Also attached is a picture of the z-axis unit. There's nothing I can change here. The 2 black stripes are rubber seals that does a pretty good job of keeping the dust out of the ballscrew and rails. The black plate is the z-axis plate and is attached to the 4 mounting 'doodads' in front.


Keep comments/suggestions coming please.

[dodger889]

If you drive each side with two separate drive system and move them to the outside of the frame. Then you could add some middle supports. You asked about your gantry uprights I would do some plates for them. Now to address the gantry I would add some sorta boxing to it. that would give you a much stronger gantry then drawn.

[jsantos]

By boxing, do you mean putting a plate in front and behind the gantry extrusions?

[jsantos]

More of my learning on machining...

I was going to machine a channel on the front plate for the rails to sit on. The machining of the first tile went great. But when I machined the second tile, the depth of the pocket was not the same as the first tile! Nooooo! So I tried the 3rd tile. The same thing! I had the plate sitting on stand-offs because I was also drilling. I thought that I might be having problems with the pocketing because the plate was not sitting flat on the stand-offs or the stand-offs were not even. I finished the drilling and then took the plate off the stand-offs and set it on the tooling plate. My tooling plate is supposed to be flat to 0.003".

I tried the first tile and then the second tile. The same problem - the pockets for the first tile was not the same depth as the first tile! What's going on! Then I noticed that the plate was not sitting perfectly flat on the tooling plate! Oh! I removed the plate and saw that there were some chips on the plate. Argg!. Cleaned up the chips and make sure the plate is sitting flat. No, it wasn't! Double Arrgggg!

The gantry plate is against 2 locator pins on the side and another index pin in the center. I also drilled another hole in the center for my clamp. I was only using a single clamp on the center to hold the gantry plate down. Now I put 2 clamps each on each side where each tile ends. This time, it looks like the gantry plate is sitting flat. Try again. Success! While I can see where the first tile ends and the second tile begins because of the tool swirl marks, I cannot feel any ridge.! Anyway, I was going to have a 2mm channel that ended up as a 3mm channel but I'm happy with the result. Lesson learned.

Finished products shown in pictures below.

I will talk about my rail cutting experience in the next post.

[jsantos]

Done with the mechanical! Well, almost. A machinist friend of mine who came over was very impressed with the rigidity of the machine (thanks to those who provided some very good advise) but said that I should pocket the big plates in a truss pattern. He said that doing so can reduce the weight of my gantry by over 50% without sacrificing structural rigidity. He even offered to machine it for me on one of their big CNC. :-)

I also don't have a second ballscrew yet, so I will have to live with a single ballscrew on the x-axis for now.

Here are pics and commentaries on them:

1. z-axis front plate - This is the only plate that I didn't put a channel in so I can tram the spindle by moving it from side to side.

2. z-axis motor mount from the back. The sides are screwed to the y-axis plate to also support the motor mount.

3. z-axis motor mount from the front with the pulley attached to the z-axis ballscrew.

4. spindle plate - I followed Gerry's advise and went with 1" plates. I tapped 4 6mm threads in them for setscrews that I will use to for tramming the spindle from front to back.

5. the spindle attached - As expected, the whole z-axis drops like a rock. I asked DMM for a motor with a brake but they don't have any. My machinist friend says that their machines use springs of the type used in tape measures but don't know where to get them. Does anybody know where?

6. the y-axis motor/ballscrew mount - This one does not flex at all.

7. the y-axis ballscrew installed. It turned out that my fears about the y-axis linear bearings are unfounded. Turning the y-axis pulley moves the linear blocks and the whole z-axis very smoothly from end to end. pippin was right.

8. last two pics - supports for the x-axis ballscrew plates. tahustvedt and widget were right. The plates will flex when moving the gantry. After I reinstalled the ballscrew and the pulley, the plates flex visibly when I rotate the pulley. Supporting them at the bottom stopped the flexing. Thanks guys!

[jsantos]

I finally got hold of DMM Tech and told them the problems I'm having. They asked me to return the BOB and the offending driver and said they will send me a new BOB right away. A few hours later, I got a notification from their shipping company that I have a package coming! Now that's what I call service! Thanks DMM Tech! I must say that I have been very impressed with their support. And their patience because I have asked some pretty dumb questions!

Since I'm really motivated to get my CNC up and running so I decided to give it one more try and figure out what's happening to my BOB and one of my drivers. Checked out all the wiring connections and measured voltages at the terminal blocks. All checked out. I then removed the driver that I was having problems with. All of a sudden, the BOB came to life! Hooray! Forget the problem driver. I'm installing this on my CNC!

Even though my cables are short, I decided to hook them up to my CNC anyway. I won't have a lot of slack on my z-axis but I can move the controller close enough so I can make the short cables work. Finally completed the wiring. Turned the controller on, start up Mach3 and lo and behold, Mach3 has control of the system!

Jog the x-axis. She moves! Jog it the other way. It did not go the other way! Brought up the DMM software to look at my driver settings and the x-axis was set to CW/CCW instead of Pulse/Direction. Change that and try again. She moves backward and forward! Try the y-axis. She works! Try the z-axis. She really works! I'm very pleasantly surprise how smoothly the machine moves. The motors, though, seem a little too noisy. That might be a matter of tuning.

Another thing I did noticed is that I will still have to stiffen up my x-axis support. While the support itself is not flexing, the 80/20 1530 that it's attached to is flexing when I start and stop the jogging very quickly. I'll get some 3030 from the local surplus store and see if that helps. In the meantime, I'll look at tuning the servos. DMM has some very nice write-up/calculation on tuning their servos. I'll find out how good they are.

[jsantos]

Been busy machining the gantry uprights and the front and back plates. It's been an experience learning how to machine parts that are larger than your table.

I'm using Vectric's Aspire to machine my parts and since Aspire has the tiling option, I thought that I would use that to machine the parts. I first did the uprights. Although Aspire's tiling option have quirks, it worked. I do have a concern that the top and bottom might be a little off because there is a ridge on the side where the first tile machined and the second time machined met. I'll find out if it's a problem when I add the horizontals.

While Aspire's tiling option seems to have worked on the uprights, I did run into all sorts of issues when I worked on the plates. The plates are 1700mm long and my table is 600mm on the x-axis.

The first problem with Aspire's tiling option came when I tried a toolpath to trim the edges of the plates. If I don't have the tiling option on, Aspire happily shows me how it will trim the edges. Once I turned the tiling option on, Aspire doesn't do anything. It gives me an error saying it couldn't save the toolpath. I emailed Vectric support and all I got from them was that my toolpath was outside my tiles, no other explanation. After I mentioned on the Vectric forum that I wasn't getting an explanation from Vectric support on what's happening, Brian of Vectric finally explained it. But it looks like I POed them off. Other emails about other issues I'm having with the tiling option have since gone unanswered.

Because the toolpath that's being generated by Aspire looked weird, I decided to do some experiments before I started machining the gantry plates. Here's what I found out. Some of these issues may be because I don't know what I'm doing, so take these with a grain of salt.

1. The drilling toolpath also retracts to the safe Z instead of retracing to the retract gap. Since my safe Z was 2 inches high because of my clamps, it was taking a long time to drill. Since I had a lot of holes to drill, that was a problem. This was the last issue that I sent to Vectric support. And like I said, I never got a response back from them.

2. I turned ramping on my pocketing toolpath and Aspire happily did ramping on the first tile. It forgot all about rampng on the other tiles.

3. With the tiling option off, Aspire would rapid down from the safe Z to the plunge Z. Then it would come down on the material on the specified feed rate. With the tiling option off, Aspire would come down on the material at the specified feed rate immediately! This makes for a very long machining! Oddly, it seems to only do this on the first plunge.

4. Aspire pockets the first tile perfectly but does not completely pocket the other tiles, leaving ridges in the pocket.

While I am a fan of Aspire, I thought that the tiling option is not ready for prime time. As I did not want to ruin my plates, I decided to do the tiling manually.

Now, I'm ready to machine the plates. This is where more learning experience came in!

[jsantos]

Vectric Support Update:

As I mentioned in an earlier post, I had given up on hearing from Vectric Support. A few days after that, I heard back from another person from Vectric asking if I was satisfied with the answers that I got from Vectric Support. I answered back that I haven't received answers to the last 2 emails that I sent them. I then sent back the list of issues that I had with the Aspire tiling.

Although, I didn't like some of the answers I got (Essentially, some are 'that's the way it works'), I'm very glad that they did get back to me. As I also mentioned before, I am a fan of Aspire and I was glad to also get the support.

[jsantos]

Started installing the cables and found out that the cables were too short. Arrrggghhh.

Had to order longer cables from DMM Tech. They were good enough to ship it immediately.

Having to change my cables, took down the motors to do some more testing and start looking at motor tuning. In the course of testing, one of the drivers started acting up. Turned off the controller and turned back on again. This time, the status light on the driver did not even come on. :-(

To make matters worse, my DMM BOB does not seem to work anymore. I used to hear the charge pump relay turn on and off and I also get power to my limit switches. Now, I don't hear the charge pump relay turn on at all and I don't get power to my limit switches. I wish the DMM BOB have some status LEDS on them.

I'm now trying to get hold of DMM to at least get them to ship a BOB to me. I still have 3 working drivers so I can at least get my CNC up and running.

I've done our Woodworkers' Guild trophies for the past 3 years on my old CNC and was supposed to do it again this year, thinking that I will have my CNC up and running in time. But now I'm running out of time. :-(

[jsantos]

Thanks, Gerry! I did a search for disabling limit switches too and didn't find anything either. I was hoping that you'd have the answer off the top of your head. :-)

On a more positive note, I was able to jog the machine at about 700 ipm with no problem, unless you consider the machine walking a problem. :-) I will definitely have to bolt this one to the wall. Since the wall I'm attaching this to is a stud wall that's nailed to a concrete wall, I just hope it doesn't tear the stud wall away from the concrete wall.

Now to check out my probe and attach my spindle.