Drilling problems with new BT32

[bahed]

I am attempting to drill 713 holes (roughly a 23" x 31" grid) into 3/4" MDF to act as my spoilboard on top of a another 3/4" MDF board that is my vacboard. I was using a downcut 1/4" spiral bit at 12,000 RPM, plunging at 1/3 inch/sec. After I had gotten about 56 holes drilled the machine decided to move forward a couple of inches, rather than lift up and move over - I had to shut 'er down really quickly and it kind of freaked me out - I had to stop scratch my head and figure out what to do. I couldn't get the spindle to move up without turning off the control software and the control box.

I figured ok, dummy - should have used a regular drill bit. So, I put on a using a DeWalt bradpoint 1/4" bit at the same RPM and also looked over the code created in ArtCAM just in case the code was teling the machine to do this, but saw nothing out of the ordinary so I started out again. This time I got 115 holes and this time it freaked out in the downward direction as well as continuing to move forward went into the Aluminum table below both MDF board. I don't know how the bit didn't break, but it got tempered pretty high and is likely of no further use.

No clue what's up !

Anybody ?

Bret

[seana]

Bret,

Were you using a dust collector?
If so make sure to run a bare copper wire inside the hose and make sure it goes to a good ground.

Check if the table is grounded.


Other then that i'm stumped

Sean

[bahed]

Yes, I was using a dust collector. Static charges may be an issue. Several times the job will get interrupted and I have to hit "Resume". I was told by ShopBot to run a shielding ground from my Columbo spindle to the frame to get it to stop this from happening - it hasn't. Perhaps, I need to ground the spindle/frame/dust collector to something else.

This might be the approach. Any ideas where I need to consider grounding the spindle and the vacuum ?

It's still baffling that the spindle would get confused and dive down plow forward because of a static charge. The scientist in me would like to better understand why this happening !

[Gary Campbell]

Sean...
Try this post for some grounding info
http://www.talkshopbot.com/forum/messages/26/23079.html?1194144245
Gary

[Brady Watson]

Bret,
It is possible that you are stalling out the Z. Drilling with a downcut is a no-no in thick material. There is no place for the chips to go. The drill bit is better, but it is surely dulling quickly in MDF and could also be causing the Z to stall (if a PRS standard then it will just loose steps, if an Alpha, it could be on the verge of tripping the 3-5 sec resistance trigger/fault)

The ideal thing would be to use a spiral upcut end mill, peck drill & just go over the top with an orbital sander with 220G when done.

-B

[gpari]

Also, I run my brad points at 3000-4000 rpm with a colombo spindle. They seem much happier at these speeds, 12K seems a little fast for a standard drill bit.

Gabe

[richards]

Your statement that the Shopbot moved without raising the Z-axis has nothing to do with the cutter. Even a dull cutter will NOT travel sideways while in the material - that is a probem with the machine.

Because the problem seems to be random, i.e., it didn't happened at exactly the same point during two separate runs of the same program, I would guess that you have an "electrical noise" issue. There have been a lot of posts describing how to deal with electrical noise on the Shopbot Forum. Read them and do everything recommended. (I have grounding wires running from every possible point on my PRT-Alpha to a common ground point on the controller's case. It worked for me.)

[myxpykalix]

Brett,
My first thought would have been to say ground your dust collector (as stated above). But when i was having static problems all it did to me was to stop the file at intermittent points but never caused it to make moves on its own.

[bahed]

I did the following for grounding purposes and it seemed to reduce the number of times that it hangs up - but not totally:

1. The ground that connects the VFD to the spindle then goes into the ground of my outlets, which are fully grounded.
2. The dust vacuum ground wire is tied into this.
3. The YZ car is grounded to the same ground wire.

I am sure I need to do something with my computer because after I turned if off and then back on, I was able to drill about 3/4 of all of the holes without a hitch, whereas I had 3 incidences with the first 1/4 of the holes. The problem was always the same - the bit decided to move forward without coming all of the way up and free of the spoil board.

I want to therefore, ground the computer but I am not sure about item No. 10. I see where the USB comes into the computer, and I know where the ground bus is, but I am not sure where the "serial to USB connector" is or where to attach the wire to it.

I will also do No. 8 to all of the chasis, and I was planning on running it to the same grounded outlet wire.

I have nothing for my Fein hold down vac, but I assumed that I am not really moving material through the hose, and shouldn't need it grounded.

I am sure that I will catch a lot of flak for not running a dedicated ground wire to ground lug of my circuit panel. So let me have it !

[seana]

Bret
Try grounding the dust vacuum to a different ground source.
You maybe making a bit of a loop with the static build up in the dust hose then coming back to the table through the ground line.

The dust collection hose should start inside the hose but not connected to the shop bot and come out of the hose and go to a good ground source just before it goes into the dust collector.

At one point i didn't have a section of wire inside the hose for the last 2' where my hose connects to the bot and it would cause issues. Once i added the wire the rest of the way issues went away.


Hope this helps

Sean

[beacon14]

Bret,

Check the switch that tells the ShopBot that the drillhead has returned to its resting position. I had a series of unpleasant movements just like yours until I determined the switch was false-triggering. If it is a ShopBot-supplied prox switch try tightening and loosening the little screw that holds the switch in place. Mine would trigger on when the screw was tightened a little too much. I replaced the switch and the problem went away.

[bahed]

David,
When you say "resting position" that would be 0,0 for my program (and most routines, I imagine) - is that what you are referring to ? Because there is no resting of the spindle bit movement until it is done completing each of the lines of code from the program. If you are referring to something else, please explain. I am far from an expert in this CNC world. Also, which switch are you referring to that was false-triggering - where is it located ? The only physical switches that I am aware are of are the 2 limit switches and the Stop button. I am not at my CNC computer now, but I seem to recall that on the control software GUI there are other switches, numbered 1 - 6, or something like that. Help me understand which one you replaced.

Sean,
I will take your advice on running seperate grounding lines for all of the items that need to be grounded.

Thanks to all,

Bret

[beacon14]

Oops, sorry Brett I should have re-read your post more carefully. I was referring to the auxiliary air drill. As was recently referred to, "never mind"