thought on simple type of homemade setworks

bruce29 · January 12, 2012, 01:52:10 PM

I have a home built bandmill that I would love to have setworks on but i am sure most would . I had a thoght that since my head up & down travel is controlled by a 12 volt dc gearmotor, that if i controlled the run time of the motor with some type of simple on time timer ,I could have a simple 1 or 2 inch drop of the head. I know this would be a long way from setworks but would increase accuracy & save some time from jogging the switch to position the head for the next cut.I could ahave a simple toggle switch to engage the timer circuit maybe. I have limited knowledge on this type of electronics, but would be interested in any info or thoughts about this idea.

Magic Smoke · January 12, 2012, 02:05:12 PM

Because the speed of a DC motor is controlled by the voltage applied, it would be difficult to obtain any kind of accuracy due to variations between the engine running/not running and battery conditions.

eastberkshirecustoms · January 12, 2012, 05:06:56 PM

Also if the load changed due to temperature, dirt, etc, your movement versus run time would change. You could install a simple cam to your lift mechanism that actuated a limit switch- one revolution=one inch or two inch, depending on cam profile.

pineywoods · January 12, 2012, 05:34:14 PM

Timer on a dc motor won't work. What about full versus empty fuel tank or water tank? What you need is some type of revolutions counter on the head lift motor. That's basicly how setworks functions...There is a good reason why modern day setworks is electronics...

bruce29 · January 12, 2012, 06:17:23 PM

Thanks for the info. I can see how my idea wouldn't work now. The cam interupter switch is something I may put some thought into.

eamassey · January 13, 2012, 10:25:43 PM

The way to get position indication-- this is not quite the same as setworks, is to get a scaleable (programable) counter and send it signals with either an encoder or a proximity switch. This can be really cheap equipment if you can find either some used or surplus. Use an encoder if you have a shaft end accessable (or you can chain drive to another shaft to get to an available space or better position). The easiest way is to use a proximity switch that can count the teeth on a sprocket, the spokes on a sheave, or bolt heads on something that turns in the lift mechanism. ------Then, scale those pulses to get real numbers on your counter display. By scale--I mean that you set the counter to: "for every pulse you recieve, increment the display by some number (best to get one or more pulse per 0.001" lift/lower)".

These counters, proximity switches, and encoders are usually 5 to 26 volts, but make sure any item you are buying will work at your available voltage.

To my understanding-though I have not used setworks myself--setworks allows "go-to"s. That is, drop down one board thickness + a kerf, etc. Of course you previously would have had to set numbers for the board thickness and kerf. Such capability requires position feedback and control of the raise/lower motor.

Woodwalker · January 14, 2012, 08:20:10 AM

Sorry,rotate the screen 90*
Starrett Digi tape. It ain't a set work, but it's a lot cheaper, off the shelf, reads fractions or decimal, less than $20.00.
Installation was tough, had to cut a piece of thin 1 X 1 angle (sheet metal). Screwed that to the head and slipped the tape on it with the belt clip. Pulled the end of the tape out and secured to the frame with a plastic clamp. As the head travels up and down the tape extends and retracts. Zero the reading on the tape after each cut and drop the head the desired distance.

bruce29 · January 14, 2012, 08:27:46 AM

I guess what i would like to come up with is a way to drop the head a certain amount with the push of a button or switch.I know thats not really setworks , but hopefully accuracy & speed would be better than just reading a scale.

Cutting Edge · January 15, 2012, 05:35:46 AM

Woodwalker....pretty slick...sure beats straining to see the little lines on a rule and splittin 'em with a needle. Might do that myself! Thanks

bandmiller2 · January 15, 2012, 06:51:10 AM

Bruce ,prehaps if you had a bar with spaced drilled holes and a limit switch that would contact them.Pull the pin and put it in the next hole be it 1" 2" est. Myself I have a aluminum yardstick and pointer have found it plenty good enough and it dosen't screw up,of course my up and down is hydraulic and very controlable. Simple is good, the less complicated electronics the better as its just a matter of time before problems. Frank C.

Brucer · January 15, 2012, 08:01:29 PM

Quote from: bruce29 on January 14, 2012, 08:27:46 AM
I guess what i would like to come up with is a way to drop the head a certain amount with the push of a button or switch.

For accurate thicknesses you should always drop the head below the next cut and then come up to the reading. If you don't you may find the head slowly settles in the cut due to vibration.

Also, when you drop to the cut you may find momentum in the drive system will let the head coast past your target thickness. This is much less likely to happen when you're raising the head to the target.

mikeb1079 · January 16, 2012, 09:45:58 PM

QuoteFor accurate thicknesses you should always drop the head below the next cut and then come up to the reading. If you don't you may find the head slowly settles in the cut due to vibration.

good point. this is much like tuning a stringed instrument. you drop below pitch and tune up to it to take any slack out of the system.

Brucer · January 19, 2012, 12:34:21 AM

Perfect example, Mike.

pyrocasto · January 21, 2012, 04:30:06 PM

Working on my version now, but as mentioned it's not quite a simple as timing it. It would have to have something to reference off. A notched bar and switch of some kind, or a wheel that counts rotations of the acme screw if you're using one. Few different ways, all require a little work.

firecord · January 21, 2012, 08:51:41 PM

has anyone tryed a robot motor? they have built in encoders which are
sealed so no problem with dust or water. there are several freeware programs which could be taylored to fit any application. you can get used ones off ebay. fanuc or kuka

pyrocasto · January 22, 2012, 09:13:28 PM

firecord, I think you're referring to a stepper motor, which is what they use on cncs as well. Finding some large enough at a decent price may be the only difficult task. My head motor hits almost 700 watts when raising, which is almost 1hp.

Then, you still have to program a microcontroller to run it. Def a good way of doing it, just seems a little more complicated than the OP seemed to be looking for.