[wjbzone]

I am still adding to it. Need to get a better table top. Travel is 24 X 13 X 7. The Kress router is great. 6000 to 26000 rpm - very quiet.

Hobbycnc driver with 125 oz. in. steppers. Turbocnc. travel speed at 40 ipm with no problems.

Just wanted to show off one of my first programs...

Bill.

my web page

[JOE65]

Wow looks really great Bill

How did you machine your alum. plate?

[balsaman]

Very nice machine. Looks great and looks like it works great too!

Eric

[wjbzone]

Thanks Joe,
I did most of it on a Haas VF1.

I have access to the machine shop (where I work) on weekends for personal projects.

Bill

[boxwood]

Looks great Bill, I have a hobbycnc board and getting 22 ipm with 24v supply and 8 tpi screw, curious what you are using for power supply and lead screw
Ray

[wjbzone]

Ray,
I am using a 35VDC power supply.

The ballscrew is a 5/8 OD x 0.201 lead. McMaster Carr PN 5966K26. (cost $1.07/inch)

The ballscrews nuts MMC PN 5966K16 (cost $20.63 each)

Bill

[wjbzone]

I've seen some posts of the costs in different machinines.

Here is my break down:

Aluminum ($1.00/ pound at scrap yard) $105
motors / driver / wires $180
ballscrew $77
ballscrew nuts $62
drill rod (guides) $55
igus bearings $68
misc bolts $20
transformer $36
case $45
turbocnc software $20
kress router $437

TOTAL $1105

Plus the computer (that I already had. )

I don't know yet what I will spend on a table top. The lamanited insert for a kitchen table is working so far. Any suggestions?

I estimated about 200 hours work. (very rough estimate)

Bill

[anoel]

Have you measured your accuracy yet? That ballscrew+nut combo produces a really funky inch per step number (0.001015625) I think turboCNC only supports 7 decimal places. So over 120 revolutions you'll be off .0006". Simple contouring should not be a problem but I wonder if a part that requires a "lot" of back and forth movement across each axis (like a large 3D part) would end up being a little goofy with the error being additive over the course of the run. (Again not a problem for something like sign/decorative work but might pose a problem when trying to do precision machining.)

I just wondered because that particular screw and nut are so much cheaper than the rest of the ballscrews in that category. I'm just wondering if the accuracy trade off is signifigant over time to not consider it.

[wjbzone]

I thought the same thing about that screw when I first priced it. Why so cheap? I assumed it was rolled vs ground?

It does have an odd lead value (about 0.201 inch/rev), but If my thinking is right, any inaccuracy caused by a difference in actual lead vs the lead that Turbocnc is given, would not be cumulative. Parts would be scaled up or down by a constant factor.

I have only checked the repeatablility of multiple movements over a 2" distance. It repeats within .001. I think I will check my accuracy by boring holes near each limit and checking hole locations on a CMM at work.

If my accuracy is off 0.0006 over (0.201x120) 24" I would be very happy. I probably have more inaccuracy due to the drill rod I am using for guides.

That screw vs an acme thread seems to me to be a good choice.

Bill

[wjbzone]

I checked out my accuracy by boring holes in a piece of wood and checking location.

Hole 1 at 0,0 - origin
Hole 2 at 10,0 checked 9.996,0
Hole 3 at 14,0 checked 13.995,.0012
Hole 4 at 0,-1 checked .0008,-.9999
Hole 5 at 0,+1 checked -.0016,.9990


Looks like I am out about 0.004" over a 10" distance.

These holes were bored in a 1 x 4 piece of pine side clamped in a vice then checked next day held down by one strap clamp. Some of the error could be due to clamping and some due to humidity (a lot of that around here lately)

It would probably be a better check in a piece of plywood, but I am OK with these results.

Bill

[anoel]

4 thousandth's of an inch certainly does not suck. I'm running at about 8 thousandths tolerance right now. (I've not really dug into finding out where the error lies, but I'm pretty sure that the fact that my machine is not as rigid as it could be has a lot to do with it.

8 thousandths is enough for press fit parts to not fit together. (so therefore I've been avoiding dong them.)

[wjbzone]

I just got my router on/off hooked up to the computer M3/M5. I used a Crydom solid state relay (model D2440-10) that switches up to a 240Vac 40Amp output based on a 5vdc input. Cost about $24 at a local electronics store.

It works great. I have several programs that I have been watching the time so I could go switch the router off. Now I just progam a M5!!!

Thanks to Jeff (homecnc) for the inspiration in getting it working.

Bill

[pminmo]

Looks nice, what could I expect to pay for 6061 aluminum?

[wjbzone]

Buying 6061 depends on where you get it, what size you get and how much you get.

I got mine at a scrap yard for $1.00 per pound. I bought 105 pounds and had some left over. (you can see my parts list on my web site - components list ) I had to modify my design a little based on what material I could actually find. I still havn't got the table top (labeled base on my component list)

If you buy it new, It can cost around $4 to $6 per pound (last I checked).

Bill

[cbcnc]

pminmo,

Check out Online Metals. They have an advertisement on this site. That will give you an idea of what the retail costs are. The only other way is to visit some surplus yards and suppliers to see what they have around. Also look for recyclers that deal in scrap. It all depends on where you live and what is around.

Chris

[wjbzone]

I need to backup a step on that M2/M5 switch. That Crydom solid state relay operates the power to the router, but when I get in a heavy cut, the power is limited.

I am thinking of using the relay to operate a solenoid to open/close a relay that will not limit the power. I can get 120Vac solenoid for about $4 and make the linkage to a switch.

If anyone knows a better method, I would like to hear from you.

Bill

[balsaman]

If it's a regular solid state relay I don't see how the power is limited. It should be close to zero resistance when closed... Are you sure the relay is the problem? You could put a volt meter across it while the router runs and see what sort of loss you are getting. It should be close to zero volts.

Eric

[balsaman]

A tip as quoted by a smarter guy than me:

"If the LED inside the Solid State Relay is not fully on, one half of
the TRIAC will not fire. The noise from the motor can also cause
problems. If the motor tool has a built in controller you need to put a light bulb across the motor tool . This allows current to flow.
A resistor will also work. Turn the relay on using an external
battery. Parallel ports don't always have enough output to run a
Solid State Relay."

Eric

[wjbzone]

Thanks for the info Eric.

I checked the voltage across the relay while the motor was running and am getting about 12Vac. I want to try it again using a battary as the power to the 5Vdc side (instead of the computer parallel port).

The relay is encased in plastic so I don't know if there is any way to see the LED.

Bill

[balsaman]

Nope, you won't see the LED. A battery will let you know if it's the parallel port or something with the relay itself.

Eric