Things we have learned that where not immediately obvious.

Okay all,
this is a thread that everyone should participate in. what have we learned weeks in either from another thread or from experience that was not obvious the first few days? Let me get it started with a few:

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* You don't have to have 0,0 at the lower left. Offsetting x and y works great for jobs that are just drop where the pencil marks cross and cut.

* It is better to use an allowance to fit stuff together than to try to tweak the vectors.Just remember to use a negative number to make the pocket bigger

* If you will click material setup over on the tool path side, the right, you can make the handi park where ever you want at the end of a cut, very nice when tiling.

Okay, what have you got?

* Zero Z by shutting off power and pushing router body down until contact. Then turn on power.

If you Zero the Z that way, don't forget to do a ZZ or use the Zero button in the Keypad to tell the software that that is where you want the Z Zero to be.

I move the router bit to the center of the cutting area and then stick a piece of paper under the bit. Then I set the Fixed distance to .05 and bump it down until the bit deflects the paper. Then Zero the Z there.

We also learned that, sometimes, you need to have the shaft of the bit not as far in the collet so that you have enough travel in the Z to reach the cutting depth. Especially true for a V bit, but also true when cutting deeper than .5" with a bit with less length on the cutting area.

0,0
Good one, original manual left out that critical step, you have to turn it off!

Sally,
Both good ones, I often zero that way.

Keep em coming, I guarantee whatever it is, someone, probably me, will slap their forehead and have a new trick.

* If you are going to have to index more than once in either direction, mark the whole job before the first cut, that way small errors average out instead of multiplying.


which lead to this riddle:

what do you call a board that you totally biffed the index on?
..
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.
.
.
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fire wood....

0,0 Wrote:
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> * Zero Z by shutting off power and pushing router
> body down until contact. Then turn on power.


I love this tip !!! Thank you. Works awesome !

I found the following info on the Shopbot Tools site and wondered if the same applies to the HandiBot. This info is from the PRS Assembly Manual.

Quote

INDUCED CURRENTS - The stepper motors on your tool become significant little generators if they are manually turned. They can generate sizable voltages in your control box if you push the X or Y-axis of your tool around physically. Occasionally it may be necessary to move the tool by hand, but try to minimize such movement and when you must do it, make the move slowly. If you need to do a lot of manual movement, unplug the motors on the axis you are moving - having shut down the power first as noted above.

While intresting, I doubt moving the Z an inch or less at slow to moderate speed will cause any problems. The stepper motors on the handibot is about 1/3 the size of the bigger units.

On pushing the motors around --

As per the website reference above, in general pushing stepper motors is a bad idea because of potential damage to drivers. That said, it is the case that the Gecko drivers in the Handibot are pretty robust and will stand up to some gentle pushing around. So it is a reasonable way to do the Z-Zeroing. It is also the case that just moving the tool about in the world when it is not powered will inadvertently result in some movement of the carriages -- and we expect the drivers to stand up to these challenges as well.

We are evaluating various alternative stepper drivers (e.g. based on specialty IC's) for Handibot that would offer some cost savings. One of the issues in our analysis will be the vulnerability to damage from back-driving. We have about 4 years experience with the drivers we use in the Handibot. They power our Desktop ShopBots and have now stood up well on a lot of tools. In fact, our policy with these current versions of Handibot is to over-build -- using components we have confidence in from bigger tools and providing capabilities that may be more than are ultimately needed for Handibots. But our idea has been that we do not want to limit the kinds of applications that early users will want to explore with a new type of tool.

Ted Hall, ShopBot

I didn't realize that pushing the bot around when it's off isn't good... Is that because like any DC motor when it's electrified it spins, and when you spin it, it creates electricity?

* It is better to use an allowance to fit stuff together than to try to tweak the vectors.Just remember to use a negative number to make the pocket bigger

Where exactly is this explained? I need to know how to do this.

First off, let me modify my statement with -where possible-, I'm working on a project just now that is all profile cuts and trying to use allowance won't work as it makes one part bigger than the other, not just the part I need to tweak.

So, anyway, it works great with tab and slot, tongue and grove, and the such.

Short answer, When you open up the pocket or profile tool paths there is a numeric box that says "pocket allowance" or "offset allowance" for the profile.
These read 0.0 by default, you can grow or shrink your stuff just enough for a good fit by tweaking these. So, you have a 1 inch wide tab and it will fit into a 1 inch pocket you can draw it just that way and without any allowance it is going to take a big hammer to get them together. Put a -0.01 into the form for the pocket and there you have it, a nice fit without having to fool with the drawing.

Allowance offset apples to several other tool paths as well but profile and pocket are the only ones I have messed with so far.

Oh, and you can get more from the help pdf file, just search for "allowance".

aileron Wrote:
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> * It is better to use an allowance to fit stuff
> together than to try to tweak the vectors.Just
> remember to use a negative number to make the
> pocket bigger
>
> Where exactly is this explained? I need to know
> how to do this.



Edited 1 time(s). Last edit at 04/14/2014 12:39AM by Mark Evans.

Hey Eric,

Just to clarify on the moving around issue (with maybe more detail than needed) ... We believe that the motor drivers in a Handibot should stand up to the backdrive currents that are generated by pushing the axes around. The way we expect Handibots to be handled and moved around, back-driving is going to happen. We've totally abused dozens of them ourselves by now, and I'm not aware of a blown driver. So we are feeling pretty good about the ones we are using now ...

However, I can tell you that those little motors can generate quite an electrical pulse! And, over ShopBot's 20 years, a perpetual struggle has been with the robustness of stepper motor drivers. Not only is back-driving an issue, but any sort of even trivial short or disconnect of the wiring to the motors can cause a driver to implode. They are actually pretty sophisticated little devices because they are working to provide the motor with the maximum possible voltage at each step (which represents a re-loading of coils as current direction reverses) while at the same time limiting current by chopping the output as current goes high (that's thousands of times a second). {This is why you'll notice that stepper motors are usually nominally rated at only a couple of volts, even though we throw much higher voltages at them to get them to move quickly ... voltage determines how fast a coil will reload.}

If you take a look, you'll see that even though the (Gecko) drivers on the Handibot are small, they are built up from a number of individual current-drive components. Even though we get them at commodity prices, they are still expensive compared to stepper drivers that are just an individual IC chip. There is a new generation of these IC-drivers, and we will be seriously evaluating them as an option to help reduce the cost of Handibots. But our experience with the lack of robustness of IC-drivers in the past, makes us pretty skeptical about whether they will stand up to a Handibot environment and abuses. We'll keep you posted ...

Ted Hall, ShopBot