Pumelloman Solysylva 25x37 Router Build

[CarveOne]

I would bet money that your machine will run faster than that if you find and fix anything that is binding. Change to 2 start ACME if you can.

I had similar problems with my first machine. I snagged a motor cable while it was powered and blew one of the three drivers on the Xylotex board. Of course, the remaining two good drivers had to go back with the bad one.

After that was repaired, I had all sorts of binding problems. Now the red oak machine runs 250 ipm on the X and 300ipm on Y and Z with the repaired Xylotex. Sounds a lot quieter too. I have redesigned the bearing supports and changed the 1/2-10 1 start ACME screws to 5 start. The machine still flexes more than I like, so I started building a steel channel replacement for it.

For my 6' work table machine I bought G203V drives, 72vdc PSU, and a C11G breakout board. That machine has evolved into a 50" x 144" steel frame machine with R&P drives on X and Y. Actual travel is a little over 11 feet. It jogs the 180 pound gantry around at 1,400 ipm. Check out this YouTube - A walk around the CarveOneCNC machine showing four CNC calendars. I been busy while you were not looking....

I ordered a G540, four 380 oz motors, and 48vdc 12.5amp PSU last evening for my latest steel channel build. Should be here around Wednesday or so.

CarveOne

[pumelloman]

Very nice CarveOne!
Also, where did you find that 48VDC amplifier at?

I'm pretty sure you're right about the binding. Today I came into my shed and the machine was like "RAWR!!!!" It was strongly unhappy about being run at such miserable temperatures. So, I warmed the shed up with my heater, and after a while it was back to being happy. In other words, binding is a huge issue, and temperature differences of less than 10 degrees can make all the difference in the world.

Although binding can be fixed a bit, it might be difficult for me to run it much faster until the temperature stabilizes, as I have essentially 0 temperature regulation capabilities. I'm pretty sure though that I can run faster, just like you said. I set the accelerations to well over 10in/s^2 today and the machine had few problems with that, it only started locking up when I reached 29in/s^2 or so. Even the belt driven axis ran pretty well at high accelerations.

I'm running 5 start screws, which helps a lot, since the turning speed is lowered quite a bit.

You blew up a driver too eh? I'm not alone then !

I tried doing some test cutting today, and was promptly reminded of why I built a vacuum adapter for the last router I had (I changed to the Hitachi M12VC 2hp one with a K2 mount). Dust. Everywhere. Gotta fix that soon.

What's more concerning is, at high feed rates, I noticed quite a bit of chatter. I also noticed that either there's a lot of backlash or it's still skipping steps, because the position slowly drifts over time. I pushed on the carriage and noticed that the rigidity isn't quite what I'd like it to be. Fortunately, I have extra bearings since the bearing supplier sent me the wrong hole pattern. I might be able to modify my carriage and put another bearing block on to compensate a bit. Flexible leadscrew couplers might also help cause some of the chatter, but far less so than the carriage lacking carriage stiffness.

For now though, I think this is where she'll stay for a while, I'll just have to make do until I graduate and then decide what to do from there.

[CarveOne]

48volts dc, 12.5 amperes.

I made my bearing plates out of 3/8" steel bar stock and counterbored a pocket slightly less deep than the 5/16" thick bearing. Then used two pan head screws to hold the bearing in place. The plates are screwed to the ends of the oak frame at each end. There is just one bearing at each corner instead of two like the plans called for. Originally, I was planning to modify the frame to use cncrouterparts.com carriages with 1/4" cold rolled steel bar stock rails and make a new Z assembly, but by the time I started on it I decided to use channel instead. Because wood moves a lot out in my shop also. So will steel though. Now I wish I had used steel box tube instead. The channels have a bow of about 0.080" in the middle of the 48" sides where the rails are mounted. I added some threaded 1/4-20 grub screw holes in the channel for adjusting the rails to a straight line with no twist. Shimming the rail would work also.

If your lead screws have any rust on them it will cause drag, and will wear the lead nuts excessively. You may want to use some teflon spray lube that dries without being greasy on the rails and lead screws. Garage door spray lube will work.

I went back and looked at your last machine photos. I don't see any reason why you can't get it to work normally. Only thing I noticed is that on your gantry the Y axis lead screw is above the centerline of the Z assembly movement. Mine is centered between the Y axis rails per the Solsylva plans. You may be getting some lever effects that make the Z assembly want to tilt left or right under cutting loads and cause binding on the Y rails. I see others that were done that way and the owners haven't complained about it that I know of. It seems to me that pushing and pulling the Z assembly should be done nearer to the center of the rails that it moves along.

CarveOne

[pumelloman]

Small update since I haven't updated anything for a long time. School is definitely destroying me and my free time...

Here's a few things I changed
- Swapped to 2.25hp Hitachi router with K2CNC mount (works fantastic)
- Changed out HomeshopCNC delrin clamps to steel ones after I broke one on accident (tightened it too much)
- Put the new Anaheim Automation linear bearings on, pretty slick, I think I mentioned this before

But by far the biggest thing I've done is I drilled out the carriage to put in 3 bearing mounts on the Y-axis. There were originally just 2, one of the top of the bar, one on the side of the bar (facing you in the photos typically, middle of the yellow carriage). But with the massive moments around the tool tip, the deflection was enormous, there was huge chatter and it caused backlash. Now that I have two bearings on the side of the Y-axis, the deflection is much smaller.

I also did some testing at school with the stepper motors. I found that the maximum frequency of pulses for the hobbycnc 305oz-in steppers with no load is 9kHz (that's 900Hz I think in full steps, the geckodrive G540 does 10 microstep automatically). It can go higher yet (I think.. up to 12-15kHz?), but beyond 9KHz if it stalls it cannot get back into step again. There's some hysteresis as well, it has to go back down to 9kHz before it'll start moving again.

I did some calculations at the time, and what I found was, with my current setup (1/2-10, 5start leadscrew), that's something like 60ipm, I don't remember the exact numbers. That makes a lot of sense, I've experienced a lot of stalling with higher load past 60ipm.

Then.... I hooked up the motor in parallel, since I've been running them in series for the longest time.

In parallel I could get over 70kHz, with no signs of stalling... It went so high that I didn't want to go any higher because it was actually pretty scary.

So, it looks like I know what's wrong now with my machine, the motors are in series, rather than parallel. I have 3 motors though running at 3A or more, so I don't think I can hook up my motors in parallel without first replacing my power supply with a much bigger one like the kellingCNC one.

In other news, I'll likely be returning to Japan to take my Master's in Engineering. I talked with my supervisor and it seems like I might do something like 5-axis CNC toolpath generation. Looks like my cousin will be inheriting a CNC machine.

[CarveOne]

You may want to reconsider going back to Japan anytime soon, now that they are dealing with such a devastating calamity. Do you know the status of the area that you were in?


CarveOne