Height detector needed

[JoeJakey]

I am in the planning stages of a modified MechMate. For starters, I only have room for 24" of Y travel. That's all I need, because I am planning on using it to surface solid wood panels/lumber/logs, and 24" x 96" should cover my needs. My question is this: since I will be starting with rough, uneven lumber in many cases, does anyone have a suggestion for a way to automatically set the cutter height (Z-axis). I want to be able to lay a workpiece on the support table, secure it as necessary, then turn on the machine and go do something else. This means the machine must be able to find the high spot(s) before beginning cutting. I want to minimize the time it takes to do this. In other words, I don't want to lower the cutter in small increments and hunt back and forth, I want to do it quickly and accurately (initial height accuracy to within 1/16" is probably sufficient). And I want it done without my oversight.

I have considered laser beams, microswitches, etc., but I'm afraid dust might eventually foul the works. Any ideas?

[smreish]

Joey,
The quick answer is maybe....I am going to try something in my shop in the morning and let you know.
Quick question:
Does the log differential...IE small log to large log fairly consistent window? Like 4 to 8 inches, or do you need to look at the entire Z window of travel?
Sean

[JoeJakey]

What I will probably do, given the potentially wide range of thicknesses involved, is build an elevator table to bring the workpiece to roughly the correct height, then use the Z-axis to do the actual surfacing. But because the rough workpiece is, by definition, rough, I think I'll probably raise it manually to approximate work height (+/- 1"?), then turn the router loose on it. Obviously, if it turns out to be too high, I don't want the cutter trying to bite into, say, 3/4" of oak. Rather, I want to build a machine that will see the problem and set the Z height accordingly, and then proceed to traverse at a reasonable speed and depth of cut. By your question, I think you're asking if I intend having a long Z-axis travel. No, I do not. I think less here will be more rigid.

[Richards]

Joe,

You've got an interesting problem. As I see it, if you used a laser beam connected to the Y axis, that was a specific distance, let's say 1", lower than the bottom of the cutter when the cutter is in the Up position, then you could raise the elevator until the rough material broke the beam. When the beam was broken, you would lower the elevator a little and then move the carriage along the length of the table to see if any other part of the rough material was high enough to break the beam. Each time the beam was broken, you would have the elevator lower the material. After scanning the length of the material, you would know that the highest part of the material was exactly 1" below the cutter. Then you would lower the cutter and start the cutting process.

A blast of air to clean off the laser emitter and receiver should be sufficient to clear off any debris each time you added a new piece of material.

[revved_up]

Genius!! Mike that deserves a Guiness!

[Marc Shlaes]

How do you detect if a laser beam is broken over the entire surface of a board? What device "sees" the laser beam over that width? Special laser scanner? Special receiver? Combo unit?

[Alan_c]

How do you detect if a laser beam is broken over the entire surface of a board? What device "sees" the laser beam over that width? Special laser scanner? Special receiver? Combo unit?

My guess to keep it simple would be optical orbs (otherwise known as eyes) :)

[Marc Shlaes]

Didn't think of that! :eek::rolleyes::cool::p:D

[JoeJakey]

Mike, I like your train of thought. Perhaps one of those laser levels that seem to be sold in every hardware store nowadays. I think Alan_c is probably right - keep it simple, slow down and use my eyes. Thanks to all who responded.

[Kobus_Joubert]

Hi Joe, just my 5c worth. Why don't you use a mini mill attachment connected to a power saw to surface your log
1116 or the bigger brother 1117

Once you have a flat surface, the MechMate can make it look nice.

This is something I made a few years ago...without a MechMate, but with the little Mini Mill 1118

Good Luck

[Doug_Ford]

I bet your wife doesn't rearrange the furniture much.:D

[JoeJakey]

Kobus, we're on the same wavelength. In fact, I've just finished milling about 600 board feet of oak that fell on my house last January. It's mostly in 2" slabs, stacked and drying. Thanks for sharing your furniture. Looks built to last!!!

[Kobus_Joubert]

Hi Joe, I don't like the Oak that we have over here. If you don't properly dry it in a kiln, they keep on 'MOVING' The other hardwoods I milled is stable after about 2 years stacking.

What type of mill are you using to make your lumber

This is a lounger..made from a SOLID Oak tree trunk. When I started this weighed about 800 kg. After a few years it is not so heavy anymore and 4 people can carry it.

1119