speeding up my cnc machine?

[Splinter120704]

Im using a homemade Cnc machine with Mach 3, im using a 1/4" router bit and am cutting on a project that's almost like a 20oz pop bottle cut in half. Im cutting at 100% feed rate and its almost been 3 hours and its maybe 1/4 of the way finished. Any way of speeding up the process without it effecting the project in a bad way?

[ger21]

What do you mean 100% feedrate? What is your velocity in motor tuning, and what is the feedrate in the g-code?

Assuming you're doing 3D work, what is the stepover?

You need to give us a lot more info.

[jpike10]

as stated you will need to provide more info:
Spindle speed
feed rate
depth of cut
radial depth(step over)
If you can use a larger diameter to do the roughing then finish with the 1/4".

[louieatienza]

Sight unseen, you should use the deepest pass depth and largest stepover you can for the roughing cuts. Of course this might leave too much waste if you're using a smaller bit for the finish pass. Also if possible use a straight endmill or bull endmill for the roughing pass, it will remove about 40% more material than a ball endmill...

[dooms_pr]

I have being trying to speed up my machine too. My setup consists in the following:
1. Machine Type: Moving Table Homemade CNC (MDF)
2. Driver board: 3 axis HobbyCNC EZ driver board.
3. Motors: Stepper Motor Model # 57BYGH303, rated at 208 oz in
4. Software: Mach3
5. Lead screw: 5/16 18 Thread
6. Driving nut: 2x wood brass inserts oposite to each other and adjusted to minimize backlash
7. Motor Tuning Velocity: @ full step (3600 Steps/in) 75 ipm
8. Motor Tuning Velocity: @ 1/2 step (7200 Steps/in) 50 ipm
9. Motor Tuning Velocity: @ 1/4 step ( 14400 Steps/in) 45 ipm
10. Sheerline 1/2 pulse enabled.
11. Kernel speed: 6000 Hz
12. CV option enabled.

I would like to run my machine at full step with 75 ipm velocity but this seems to cause too much jerking on the motors. The machines runs smooth at 1/2 and 1/4 steps but Im not too happy with these speeds. I machine mdf at 35 ipm with .1 depth cuts with a 1/4 in router bit. Im going to experiment with shallower cuts at higher speeds to see if I can speed up the process.

I was wondering if there is a way to set the machine at full step without the jerkiness, for lack of a better word, or if I need to change my hardware ( i.e. motors, board or lead screw). Any advise? Thanks in advance!

[nickswimsfast]

First, let me say I am not an expert. But I do have some ideas how you can speed up your machine.

- raise the dv voltage (so long as it is allowable for your control board. ) I believe the hobbycnc board is rated to 36 vdc. You can upgrade your board to a gecko 540 which I believe is rated to 50 vdc.
- introduce a gear ratio - optimize it for you torque/power curve. This should take into account your desired cutting/jog speed. I've done this for servos, not a stepper system, so maybe someone can chime in. You can change the gear ratio with belt/pulleys, or by increasing the pitch of your screw.
- obviously you understand the mechanics of microstepping.

Those are some ideas, hopefully that gives you one to move on.

[Walky]

I'd start by upgrading those screws; changing from 18 TPI to something 10 or 5 TPI should speed your machine up dramatically. At 18 TPI you advance way too little with each revolution, and it's worst considering that steppers' torque curve drops at high speeds.

[ahren]

I second Walky's advice -- for steppers, you really don't need or want too much mechanical advantage in most cases. Most folks running screws on DIY machines gravitate towards multi-start screws like 5 start ACME -- this has an effective ratio of 2 turns per inch, and is significantly faster than even standard 10 turn per inch ACME, sometime 2-3X. Definitely upgrade the screws first -- the higher pitch and higher efficiency will both work to your advantage.

Best regards,

Ahren
CNCRouterParts

[jimmyjames1981]

dang at 18 tpi that machine is painfully slow, like mentioned before, change over to a multi step acme screw and dumpster cnc nuts , like a 2 rotation per inch and that will make your machine capable of going 8x faster. it will stress your steppers more, and at 208oz im not sure if i would change it that drastically, if you had 465oz steppers i would go 2 turns per inch, with yours maybe 4 turns per inchu