CNC Build: The Bed and Breakfast at 4 years and 40,000 miles

[capnTelescope]

I did that several times when...

It must be something that's going around. This wasn't the first time the machine has surprised me.

Yikes, I was more worried about your right hand!

One hand on the mouse to push Cycle Start, and (from now on) one hand on the e-stop. My right hand was a good 2 feet away from the bit, in the supposedly safe direction. Examining the block of code that actually executed, the router was moving at a rapid traverse. You'll notice the mouse stayed behind when I went for the e-stop. No mice were injured in the making of this video.

Dang that was scary, glad all is fine….

Scairt me too. Right after this, I decided it was time to eat lunch and find something else to do.

[capnTelescope]

Hey! I'm back. Two weeks without a post. Did anybody miss me?

This post is dedicated to those of you who are wanting a hobby CNC, just to get you a flavor of what you can be getting yourself into.

As I noted in my Jan 7 post, I'm having a problem with the CNC missing steps. It shows up on the Y axis by the gantry gradually drifting in the plus direction, and the 2 X axis motors miss steps and rack the gantry out of square. This is why I had to make the cut that resulted in the gash we've had so much fun with. I still haven't fixed the problem, but I think I am close to a solution.

Quick review for the uninitiated: My machine is controlled by a software package called Mach3, which reads the toolpath directions contained in G-Code, and sends precisely timed pulses out the parallel printer port to move the stepper motors to cut the part.

There are known issues with printer port voltages sometimes too low to drive the machine electronics. Also, background programs on the PC can foul up the timing. So I tried a parallel port card recommended on the Mach3 forum. $15. No improvement. Then I found a write-up on the forum on how to optimize your PC for Mach 4. $0, but now the machine moved at absolutely a snail's pace. After that, I posted an SOS on the Mach forum. When you get into this hobby, you do have a lot of support available. If you read that Mach Support thread, you'll see that we decided it was the PC and its Achilles heel, the parallel port.

Rather than buy a new PC, with no certainty of a fix, I'm going with another product that bypasses the dreaded parallel port, and sends those pulses via Ethernet. The vendor says things work much better (what else is he going to say?). $200. The parts came, and a proprietary cable that was ordered was not in the box. Probably Monday-Tuesday.

In the meantime, I've wired up the starboard wall so it's ready to go in the vac bag, stained and varnished 3 coats on the interior paneling, celebrated Mom's 92nd birthday, caught the flu (ate up last week), improved the dust collection on the table saw, and generally putzed around.

[dustboy]

Hmm. I'm running WinCNC, which has a proprietary card with two parallel (?) ports to a control box. Not sure if that gets around your problem or not. I'm finding some inconsistencies with the sizes of parts that it cuts. Haven't decided why it happens, I don't think it misses steps, maybe it's deflection or parts are shifting on the vacuum table.

[capnTelescope]

Not sure if that gets around your problem or not.

It probably would. It looks like the PCI card does much of the timing function and sends pulses to the stepper controller. It does raise another problem, though... $1260.00

I'm finding some inconsistencies with the sizes of parts that it cuts. Haven't decided why it happens, I don't think it misses steps...

Mikeschn seems to also have a similar complaint. My exact problem is that my machine can go from X0Y0 to x96y48 and back, and it actually returns to x<=>0, y=.030, even though Mach says it's at 0,0. Sometimes. Other times, it's right at 0,0. Y seems only to creep in the + direction and x creeps mostly in the + direction. This is while traversing in air. Does the same while cutting.

maybe it's deflection or parts are shifting on the vacuum table

A few well-placed pencil marks where part meets vacuum table should give you a better feel for whether parts are shifting. Likewise, I use dry-erase marker and a scratch awl to check if the machine is where it thinks it is.

This pic shows Y creep from successive runs:


It all boils down to Windows computers make marginal CNC controllers, and we're too poor to afford dedicated made-for-purpose computers.

[KCStudly]

I missed you!

[capnTelescope]

Thanks, KC. (edit) I missed you, too! (/edit)

[capnTelescope]

Progress at last! Got my SmoothStepper and the stray cable, got 'em wired in, passed a smoke test and got things running without too much drama. Tested while cutting air and things seemed to go fine. Fingers crossed, I'm going forward.

When I left off, I was ready to do the finishing of the profile at the ceiling, spar pockets and the outside roofline. I'm happy to report that I have now successfully completed those operations. The left wall is now semi-finished and off the router:


You can now see the front end profile:




I retrieved the wires that go to the fan, dome light and reading lights, and the wall switch wiring:


I now have CNC-located pockets for roof spars...




that have a corner relief for the spar lumber, so that the spar sits in the bottom of the pockets:




that hold the spars tightly, and make room for the ceiling and roof insulation:




Some pieces of 1x3 lumber fit in the pockets, but some didn't because they were slightly oversized, ...


... but not because the pockets were undersized -- they weren't:


The next steps are to repeat the process on the other wall, and to cut some parts for the galley walls to fit up the hatch. I'm waiting for warm-enough-to-glue temperatures for the wall, and working to finalize the hatch design.

I've got video to edit, coming soon.

[KCStudly]

Good progress!

[aggie79]

Brad,

It's good to see that you are back at work. I also appreciate your frank discussion of your CNC experiences and have filed them away for the day that I get serious about a CNC machine.

Take care,
Tom

[capnTelescope]

Good progress!

+1, I agree. (Is it OK if I +1 when someone complements me?) Thanks, KC. I was starting to get worried that I would be stuck forever where I was. It feels like a milestone. I have half a wall completely done!

I also appreciate your frank discussion of your CNC experiences...

My pleasure. It's a big part of the adventure for me, so I'm glad to share. CNC isn't for the faint of heart, mind or wallet.

I think the CNC started acting up after I replaced the original computer that died. It just finally became a really big PITA problem. I couldn't really pin down what the cause might be. Could it be that stepper I dropped once, the motor wire that got caught in the gears, weak stepper driver, the breakout board (a real black box for me), bad connection, the PC? How can it be a computer and be an intermittent problem? It was like staring into the abyss of a huge time and money pit. What if it needs another new computer? Do I go to the same store for another cheap used one? What if that one doesn't work either? Do I upgrade to a new desktop and put the one I'm using now to run the CNC? What if it doesn't work? What if I don't want a new desktop? What if Mach doesn't run under Win 7 or 8? What if none of this works? Aarrrrrrrghhhh!!! ( I want my mommy!) While I'm in the middle of this meltdown, the Ethernet SmoothStepper came to my attention. The size of the bet was a little bigger than another used computer, but I was disillusioned with the parallel port thing. Fortunately, the SmoothStepper appears to be working very well. (Knock on wood. ) I did have to install a second network card so I won't have to run SneakerNet for drawings, g-code, etc.

[capnTelescope]

Progress keeps happening. Today the temperature got up into the 60's, and warm enough to glue. I finished getting the starboard wall ready for the vac bag:


smeared some glue around and applied the interior oak veneer ply. Into the vac bag and let it sit overnight.

The weather is supposed to turn bad again tomorrow. Hopefully it will hold off long enough to wrestle the wall into the shop. Wind is the big factor here. 4 x 10 foot plywood assemblages make good sails in a stiff breeze. Stiff breezes seem to always accompany these weather fronts moving in.

If the weather fails to cooperate, tomorrow will be a drawing board day. If it does cooperate, I get to start cutting on the wall.

Thanks for stopping by!

[bc toys]

keep up the good work we are following your build and you are dong great

[capnTelescope]

keep up the good work we are following your build and you are dong great

Thanks, BC. I appreciate the encouragement. Hardly anyone's saying much, but when I post, I get a couple hundred views. So there's quite a few folks that are interested and lurking. I lurked quite a bit in the past. Y'all are most welcome to post comments, questions, etc.

There's more progress to report today. I got the starboard wall out of the vacuum bag:

and moved from the garage to the router table. Weather cooperated enough that I didn't freeze and the wall didn't blow away.

On another note, my Timbren axle-less suspension arrived:


I need to get busy on getting a trailer built.

Tonight I'll work on getting some g-code whipped out, and I can start making router dust again. Mostly, all that needs to be done is mirror the cuts from the first wall, so most of the hard work is done.

[KCStudly]

Cute dolly.

Any idea what one of your walls weighs?

[capnTelescope]

Cute dolly.

Thanks KC. It wouldn't have been possible to move that wall by myself without it. It still needs some design work. It took me an hour and a half this morning to get the wall moved, cuz the dolly broke on the first try. Two 6" lawnmower wheels and a 4" swivel caster from HD for under $25.

Any idea what one of your walls weighs?

The left one is probably 50-75 pounds. I lifted and moved it in the shop today, with one hand thru the door opening and the other hand steadying. I think it's a little less than a sheet of 3/4 ply, which I could carry in my mis-spent youth but no longer. More framing will get added in the galley, later. The right one probably weighs around 100# uncut. Just guessing. Wisht I had a bathroom scale.