Web Goblin cnc has begun

[Web Goblin]

Andrew, the kinco drives are good. I have Nema 34 motors on them and they are fine. The only problem is that the drives generate alot of heat but a couple of cooling fans will take care of that.

Guys, thanks for info on cutter loading/feed speed. I willl have to play with it to get a feel for the right speed and loading. The step over and feed speed was what cut2d generated when I picked that cutter. They can be modified but I decided to go with the stock option as a first timer.
I do have plans for two spindle mounts but havent gotten round to them yet. I have ordered some of the single flute cutters off ebay so that could be a good test when they arrive.
Jonathan I am using USBCNC not Mach3. It has something called look ahead feed built in to it. I think this looks ahead of the block you are running and looks at the program to see what is coming up. It then tries to calculate the optimum speed for those upcomming blocks to keep the machine moving smoothly, well thats what I got out of reading the manual anyway!

[JAZZCNC]

Jonathan I am using USBCNC not Mach3. It has something called look ahead feed built in to it. I think this looks ahead of the block you are running and looks at the program to see what is coming up. It then tries to calculate the optimum speed for those upcomming blocks to keep the machine moving smoothly, well thats what I got out of reading the manual anyway!

Mach also use's look ahead.
CV (constant velocity) and Exact stop are Gcode commands which basicly tell the control software how to react.
If your code outputs G61 then the look ahead won't apply because it's been forced into exact stop mode and look ahead only works in CV mode.

If your code breaks arc's down into tiny lines(like lots of software does) then this will have the affect of jerky movements, it will also have the affect of stopping and starting between arcs and straight lines as exact stop accelerates and deaccelerates point to point, this affects cut quality badly. (Plus it's bloody annoying)

Exact stop will not round tight corners like CV does at high feeds but it can cause the machine to run very slow and quite rough as it accellerates then deaccelrates between each point.
As you can imagine at high feeds this will hammer the machine and motors as it flys upto the corner at high speed then jumps on the brakes for the tight bend.!!

I think if you check there will be settings within USBCNC to help control CV's angular distance where it changes for tight radius and controls rounding at high feeds.

But I think even USBCNC can be put into exact stop mode so G61 will apply basicly cancelling look ahead and CV mode. . . . . Worth checking out.!!

[andrewbond]

Thanks for the info,

I'll probably go for these as I won't have to buy seperate power supplies (I'm going to be using the 8nm nema 34 motors)

Did you mean the drives themselves generate alot of heat, or that they cause the motors to get hot?

Andrew

[Jonathan]

Did you mean the drives themselves generate alot of heat, or that they cause the motors to get hot?

It's probably both - running the motors at a high voltage tends to make them hot, but as long as it's below about 80C it's not a problem.

[Web Goblin]

Andrew,
the motors get warm to touch but nothing bad. The amplifiers do get quite warm so if you are going to mount them in a cabinet forced cooling would be required.

Ian

[Web Goblin]

Had a shot at cutting some new spindle motor mounts today. The first one is cut and it came out well. I used one of the single flute cutters from ebay.


There is a litte bit of marking on the third photo at one of the corners but its nothing to worry about. This is cut from 25mm thick alu. Inner size was programmed to 80.5mm and it came out 80.4mm so thats fine as well. Just need some more time to get the second one done and get them drilled and tapped out for fitting.

I also did some testing on my tool height setter. Fitted a new 6mm single flute cutter and ran 10 measurement cycles of the tool height routine. The results are below.
1, 30.5087
2, 30.5037
3, 30.5012
4, 30.5012
5, 30.4963
6, 30.5012
7, 30.4963
8, 30.4988
9, 30.4988
10, 30.4988
From min to max the difference is only 0.0124 so thats good enough for me.

Regards

Ian

[JAZZCNC]

Hi Ian,

The corner marking is chatter probably due to radius being the same size as cutter, if you can make your radius just slightly larger than the cutter this won't happen.

Nice job as well by the way.! great aint it watching the machine build it's own bits. .

[Web Goblin]

Jazzcnc,
thanks for the info on the cutter radius. It was a 3mm rad and a 6mm cutter. I will alter the drawing for the inner radius corners for the next one. I have alot to learn about milling, this is not something I would have to worry about in profiling.
Your right, its great watching the machine cut its own parts. I wonder if I can get it to build a replica of itself:lol:

Ian

[Web Goblin]

I have been cutting two new spindle mounts this week to reduce the vibration of the spindle motor. After finishing the second one I had sent the machine to the home position which is where I usually leave it when switching it off. On travelling with the X axis I noticed a grinding sound. On further investigation I found this:



Looks like the shaft I used to join the motor to the pulley had been working its way through the bearings and had the coupling rubbing against the motor mount.
I need to strip this out and make two locking collers for the shaft to stop it moving.
At least it hasnt done any real damage.

Ian

[JAZZCNC]

Ian there's a big gap between the worn coupling and the bearing mount has it been floating.?
Sorry but I'm not familiar with your setup and can't tell from this close up pic but that looks like it's an FK bearing in the mount so it shouldn't float at all.?

Edit: Ok I stopped being lazy and went back and looked thru the thread I understand now, they are FK bearings but also fixed at the other end.!. . . . Still looks like float thou.?