Rapid height? Basic router setup help

[Ranscon]

Hello all,

I'm new to cnc (completed machine this afternoon). Hope someone can help me out a bit. (bit, wow, I'm a natural at this already)

Seriously, I have built a 24" x 48"(cutting area)router table with Keling 425 oz motors, 4030 drivers, c10 BOB. 10-Tpi Acme leadscrews, rotozip 6amp 33000 tool. Computer is an amd athlon 2.2ghz,512 ram, I have mach3 software. I'm losing steps. Could someone please give me some decent startup settings for the motor tuning? Or a particular sound to listen for from the motors.

Also, I'm trying to figure out the "write" wizard in Mach3. I cannot change the letter dimensions. What do the numbers refer to? Are they in thousandths? What is rapid height? I have already drilled a hole through my table trying to figure this one out. I think I,m losing steps because when I hit return to z after cutting the machine does not go to the home position(mostly z but x a little as well).

Any advice will be greatly appreciated, Jeff

[TOTALLYRC]

Hello all,

I'm new to cnc (completed machine this afternoon). Hope someone can help me out a bit. (bit, wow, I'm a natural at this already)

Seriously, I have built a 24" x 48"(cutting area)router table with Keling 425 oz motors, 4030 drivers, c10 BOB. 10-Tpi Acme leadscrews, rotozip 6amp 33000 tool. Computer is an amd athlon 2.2ghz,512 ram, I have mach3 software. I'm losing steps. Could someone please give me some decent startup settings for the motor tuning? Or a particular sound to listen for from the motors.

Also, I'm trying to figure out the "write" wizard in Mach3. I cannot change the letter dimensions. What do the numbers refer to? Are they in thousandths? What is rapid height? I have already drilled a hole through my table trying to figure this one out. I think I,m losing steps because when I hit return to z after cutting the machine does not go to the home position(mostly z but x a little as well).

Any advice will be greatly appreciated, Jeff

Hi Jeff, asking for help is a sign of true greatness. Anyone can sit in the corner and cry in their beer .(ruining it in the process).

Using the data that you have provided, which doesn't say what type of micro stepping you are using, or what voltage the PS is. I guessed at 10 micro steps( which I justed checked and is NOT one of the options) x 200 steps/ rev x 10 tpi = 20000 steps/ per inch. Insert what you are using for micro steps in the formula.

The only way to find the fastest speed that your machine can reliably go is thru trial and error. Try this for starters. 20,000steps per inch x 10ipm = 200,000/min or 333.333 per second or ten ipm. I forget how it is setup in Mach3 and I don't have Mach3 in front of me. If the motors are actually stalling, you willl hear a noise that will make you cringe, it is an ugly buzzing sound. If you are failing to return to zero by only .020" or so, you may have play in the system that you need to correct.

If it is off buy a huge amount say 1" plus, then you are in for some real fun. One way to make sure that you are not loosing steps is to make a mark on the stepper motor shaft and then run the code. When you get back to the starting point, the mark should be exactly where it started.

The 10tpi acme screws will limit you on fast you can ultimetly go, but as long as it is fast enough for you, then that is OK. If the motor can turn 500 rpm and not loose steps, your max carriage speed will be 50ipm. For some driver and motor combinations, 500 rpm is not possible. Similar motors on my Taig mill at ~30v will only go 10 ipm on a 20tpi screw which would be 20 ipm on a 10 tpi screw. HOWEVER I am not using the keling drivers and Your Mileage may vary.

[Ranscon]

Thanks TotallyRC,

I have it set on full step(4th and 8th dipswitshes are down) at 2000 steps per inch just to see if it would run. My power supply is 24vdc 8.3amp. I,m not sure how to microstep. It's the dipswitches correct? what microstep should be used for sign carving with graphics? (would 1/4 step be sufficient)Which pins are on and which are off if you know? The motors are at 30ipm and 30 accel. Sherline 1/2 step is on. Am I at full step or 1/2? I calibrated the axis' with a digital caliper and they are exact at 5.000 inches when not cutting. Please, What is rapid height? Is this where the bit is in relation to the table when moving from point to point?

Jeff

[TOTALLYRC]

Sorry, I forgot to explain what is rapid height.
Rapid height is the distance above zero you retract the z axis above the work piece to provide cutter clearance when moving to the next cut.

Zero is normally the top of the workpiece. I normally jog the machine to just above the top of the work piece by eye and then zero out the dro.

If I remember correctly, micro stepping (1/4, 1/8 and so on) will just slow you down, but it will increase the resolution. At 2000 steps per inch ( which is where you are now) each step is .0005" or 1/2 of one thousanth of an inch, plus or minus the error of the stepper motor itself and any other errors that might be there. I would think that would be more than sufficent for your machine. Most routers have much more flex when cutting than that. I think that you accel is very high, especially since it is in inches/second, not inches per minute, like the max feed rate. Try using a setting of 5 for the accel,and 10 for the ipm and try that. If it is repeatable you can go up on the ipm but be careful how much accel you use, it is what gave me fits on my big machine till I got it figured out. I am only using an accel of 12 on my big cnc with servo's and 100v PS.

If it is truly 24v and check it with a volt meter to be sure you, will not have the greatest rapids. If I remember correctly, and I have that same motor on my Z axis, it has max safe voltage is 60+ volts. 24 volts is less than half and almost 1/3 of max. Volts is where your rapids come from at the risk of over simplifying it. Since your drives will take 40 volts, and if you need to go faster, just by upping the power supply voltage the machine will rapid faster and probably work better.


Are you using this machine to cut vinyl with a drag knife? If so I think I would set the accel at 5 and leave it there because you have to give the knife a chance to align itself with the direction of the cut?
You could probably cut vinyl at slow speeds but my brothers profesionallly made (graphtec) machine goes about 60ipm at least,but I am just going by watching the machine.

If you are in fact using this machine to carve wood with a router or similar the higher the accel is,the squarer the corners. Within reason of course.

I don't know about the specific settings for those drivers. If you have it set in Mach3 for 2000 steps/inch then it sounds like you are full stepping the motors and I would probably keep it there. If you program a a circle of say 5 inches and then measure it along the x axis and then the y axis, you will get a good feeling for how ell everyhting is set up. A gentleman reminded me of this yesterday. When the motor reverse direction around the circle, you will get a variation from a perfect circle. If it a couple of thou no big deal. If it is.040" then you have more work to do. Please remember one thing, don't get crazy on the max resolution and repeatability vs what somebody else gets.

If the machine is good enough for what you do then use it and enjoy it. My router is +- .010, due to all the flex and it is more than close enough for all of my woodwork and stuff. When doing closer tolerance work on it, I go slower or run a finish pass at a few thou to get it within .003".

[ger21]

I'd set it for 1/8 or 1/10 step if it's available. It'll probably run smoother, and perhaps faster. Lower your accel and velocity by half and see if it still loses steps. You may be suffereing from resonance, also. If that's the case, you might need to make dampers to increase performance.

As for the write wizard, it's important that you set every option, or it won't work correctly.

[Ranscon]

Thank you for the answers to my questions. I'm sure I'll have more. Just wanted to let you know , I really appreciate the advice and I will try it and see what happens.

Thanks again, Jeff