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

[AlgoDan]

If you don't mind me asking Brad, what is the cost of a kit like yours?

I don't mind. The basic machine is a CNCRouterparts CRP4896 with a base price of $3795. With NEMA34 upgrade, prewired electronics (strongly recommended), cable tracks, dedicated PC, software (CamBam and Mach3), spoil board, router bits, spindle motor, so on and so forth, you need to be able to budget around $5,000 for the whole project as a minimum. YMMV.

The basic CRP machines are open source. You can download the plans and build from scratch. They also sell their proprietary parts for the machine. Think teardrop build, as far as getting all the materials and parts together, and it's a zillion times easier to buy the kit.

CNC Router Parts has earned the CapnTelescope Seal of Approval, but there are other good sources out there. Poke around http://cncZone.com for more/less expensive alternatives.

Good luck with your Finance Committee!

Great Brad, I will see what the finance committee (thinks) of this idea LOL…They are slick machines no doubt, I figured it was around 5K.

[mikeschn]

I can second that. I lost a year building my CNC. And the CNC machine still not where I would like it to be in terms of precision. But I could not justify a shopbot at many times the price. But if all I am going to do is cut teardrop parts every now and then, what I have will work just fine. And it's paid for!

Mike...

First, do you want to build a CNC or do you want to use a CNC? If you want to build from scratch, you're a better man than I am, Gunga Din. Just realize that it's going to take you longer to get started on those pet projects you're dreaming up. Probably a lot longer. If you want to use one, consider a turnkey kit or go with a ready-built. Mine's a kit, and I have no doubt I made the right choice for me.

[aggie79]

Brad,

Seeing the CNC machining of the parts was awesome! Right now, my envy quotient is real high! The sidewall came out great!

Regarding the bit, have you ever thought about using a solid carbide spiral bit. I use this type of bit quite often in an old school router or router table. You can get them in downcut, upcut or both. The only negative I can say is that they are expensive.

Take care,
Tom

[KCStudly]

Tom, I've seen these mentioned before. Could you please expound a little on what the advantages are, when is it appropriate to use this style of bit, and when to use up vs. down?

[capnTelescope]

Hey Mike & Tom. Welcome back from Lurkerville.

And it's paid for!

You can't beat paid for!

Seeing the CNC machining of the parts was awesome!

Thank you. Thankyouverymuch.

have you ever thought about using a solid carbide spiral bit.

Yes. The Freud (frood/froid/free-ud?) I used was about half the price, and I already had it. t is not center-cutting. The quarter inch I used on the first cut is a solid carbide center-cutting upcut. A downcut would be better on the veneer ply. I have a lot of fuzzies sticking up. Less expensive bits were a priority when I was first getting used to the machine. I broke several before they had a chance to get dull.

Could you please expound a little...

I know you asked Tom, but I like expounding. Tom can add anything I miss. Up- or down-cut refers to the way the top of workpiece "sees" the cutting edge of the bit as it approaches. A downcut bit will slice downward as it rotates, pushing the topmost fibers toward the workpiece. An upcut is vice versa. Up- or down- is vice versa on the other side of the workpiece, if the tool goes thru. That is, on the bottom, an upcut slices toward the workpiece. And then they have up/down cutting bits that cut up on the bottom and down on the top. These are also called compression bits. Theoretically, you don't get fuzzies on either side. They're even more expensive.
(/expound)

Look for more video later tonight. I did more cutting on the wall today, with much more to go.

[capnTelescope]

Here's today's video I promised earlier. I made more cuts on the port wall. The pucker factor remains high. Any mistakes are going to show.

Expect the video to be available on YouTube about 9PM CST.



For an anticlimax, I also got the starboard wall glued and into the vac bag.

Wiring, then one more bagging left on this wall. Then on to the CNC.

Thanks for stopping by!

[aggie79]

Could you please expound a little...

I know you asked Tom, but I like expounding. Tom can add anything I miss. Up- or down-cut refers to the way the top of workpiece "sees" the cutting edge of the bit as it approaches. A downcut bit will slice downward as it rotates, pushing the topmost fibers toward the workpiece. An upcut is vice versa. Up- or down- is vice versa on the other side of the workpiece, if the tool goes thru. That is, on the bottom, an upcut slices toward the workpiece. And then they have up/down cutting bits that cut up on the bottom and down on the top. These are also called compression bits. Theoretically, you don't get fuzzies on either side. They're even more expensive.
(/expound)

Brad summed it up. As I noted before these bits are solid carbide which translates to . As you know that also means they are brittle and can fail if you apply too much side loading from too fast of a feed rate. That said the single upcut or downcut bits are pretty durable. The compession bits are the ones you need to watch out for. I'm not sure of the technical term but with the dual helical cutting edge directions they have a smaller cross-section and can snap on you pretty easily. I've witnessed how much energy a small piece of metal has when it comes apart while spinning at 20-25,000 rpm. They do make nice clean cuts though.

[KCStudly]

That all makes perfectly good sense. Thanks for clarifying. I guess I thought there might be more to it. I can see for fragile/thin veneer plywoods and woods like Red Grandis that tend to splinter out it could be worth the extra cost and effort.

For my needs, novice skill level*, and the materials I've been using (maple and Okoume... not counting the Red Grandis hatch ribs), the straight flute carbide insert bits seem to work fine. And they have proven to be quite durable.

(*Razz me if you must, but I still maintain that, prior to the TPCE project, I had very little wood working experience, and even less in wood finish work.)

[capnTelescope]

... my ... novice skill level*

I would never have guessed, reading your build journal. You do good work. Careful and easy does it.

... they are brittle and can fail if you apply too much side loading from too fast of a feed rate

Like hitting something at full rapid. I haven't had that problem as much (knock on wood) since I learned how to set the speed limit on the CNC. Now there's more time to react to impending disaster.

Meanwhile, back at the drawing board, I spent my day programming the next sequence of cuts on the wall. I'll be trimming framing edges down to finish dimensions. This series of cuts determines how well the Tear fits together at final assembly. Every cut will be a locating/attaching surface for something.

After that, it's only a quarter inch to go to get to the spoilboard! That will be the end of the cutting on the port side cabin. Then I think I'll catch the other wall up. After that comes cutting in the galley area for both walls.

[capnTelescope]

Lots of ground to cover tonight. Some good, some not.

First rough cuts on wall
I'm making cuts into the framing under the interior ply all the way sown to the inside side of the outside ply. (Was that the least bit clear?) Just to be sure, I took the first rough cuts planned for the 1/2" cutter with the 1/4" cutter so extra meat would be left in case something went amiss. No problems. No video, either. Just the opposite af this morning. Keep reading.
Nose:

Roofline:



CNC down for maintenance
The CNC was down for maintenance yesterday. My Y axis kept drifting in the Y+ direction. I'll bet you don't have that problem. I contacted CRP to see what they said. Make sure the motor set screws are tight. I just did that for the same problem, but what the heck, I'll try it again. The Y motor set screw's hex hole was munged up. I couldn't get an Allen wrench in it well enough to tighten it any more. Off to HD with setscrew in pocket to get a new one. So I'm trying to compare my set screw with the screws on their thread finder, and drop the d@#% thing, and it is lost down in the crack where all the washers & stuff fall. Gone, never to be found again. Now I must come home with the right screw. So I made a couple of guesses, then stopped by the paint department to pick out a wood stain, then off to checkout. Luckily one of my guesses was right. I got that done and my Y axis worked fine this morning. I still can't figure out how it would drift only in the Y+ direction and not the minus.


Wood Stain
Had to try out my wood stain to see how it looks. Stained the end piece of the cabin cabinets. I like it. The interior will get this and 2-3 coats of wipe-on polyurethane. Here's the stained wood next to unstained:



The Bulge

Remember the bulge at the bottom of the door?


Here's a view from the bottom after cutting out the door opening. Light shines through!


I don't know what I want to do with this. I can just leave it alone, 'cuz it ain't hurtin' nobody. I could try cutting through and under with a coping saw, and try gluing it down. It'll leave a line, but less bulge. OK, do nothing just won. I've already done enough repair work today. Read on.


Disaster strikes!
I managed to steer the router waaaaaaaay off course.


Another long story. I got the baseboard bottom rough cut and started on the cut for the aft bulkhead. These are the two most critical cuts of the whole project. If they aren't right on both walls, the Tear is going to look like my only tools were a dull hand saw and a rusty hammer. On my first rough cut for the aft bulkhead, the gantry was out of square and so was the cut. That won't do.

So I squared up the gantry, and I'm ready to make another cut. I want to pick up where I left off, so I position the tool where it needs to be and scroll to the line of G-code I want to run next. At this point, I need to digress for the sake of the non-CNC reader. To pick up and continue from a particular line of g-code, you first scroll to the line and then you have to push a button to tell the computer that's the next line. Ok, now even the non-CNC readers can guess that what's about to happen isn't going to be the desired result. From a tool position 3/8" below the bottom of the interior ply, the router takes off at full rapid for parts unknown. Based on the length of the gash, it took almost 3 seconds from stuff starting to go wrong to my recognizing bad stuff is happening to hitting the Emergency Stop button. You don't want me tailgating you in traffic. Ever.


Disaster Recovery

Here's a closer look at the carnage.:


I started off by making a series of cuts to expose the baseboard and straighten out the gash, which was at an angle.


Did a little chisel work to square the corners on the one end. Note the round tool marks in the corners.


Dry fit a patch piece:


Just add glue and 220 grit:


It'll probably have a dark stain line around it, but it's down in the footwell, and I bet no one will ever know it's there. Except you, Dear Reader.

Stay tuned for more excitement.

[KCStudly]

Now you are truly a TD builder! Welcome to the club.

Someone here once consoled me, and I think it suits, something to the effect of, "the difference between a craftsman and a hack is how well he hides his mistakes".

Not sure I am following some of your issues, so it is kind of hard to offer suggestions. Maybe step back and frame the problem some; close ups don't give the perspective needed to understand the big picture of the problems.

Is the door warped up in the middle and down at the top and bottom?

Could the +y issue be related to the direction of the cutter rotation (no idea here what you are on about, but am taking a stab)?

Trials and tribulations. At least you aren't having trouble with tribbles!

Keep hacking away, you are doing great!

[mikeschn]

I hate starting in the middle of a toolpath.

I either start over at the beginning and cut air, or I generate a new toolpath that starts in the middle of the work...

Mike...

[capnTelescope]

I hate starting in the middle of a toolpath.

You know that I do, too. You really have to have your head screwed on tight to get this right every time.

"the difference between a craftsman and a hack is how well he hides his mistakes"

'S truth. Word. Amen. Etc. Even the craftsman makes mistakes.

Is the door warped up in the middle and down at the top and bottom?

Let's take a look at the pictures.

This one is taken from farther back, looking from the bottom edge of the wall. From the bottom of the pic: router's way (where the gantry goes back & forth), Darkness, the MDF spoil board, 1/4 marine ply with about 1/2 inch of surface exposed, poplar baseboard framing edge, glue line, 1/4 oak veneer interior ply. misc. tool, door opening.

Second pic:

from bottom: Darkness, router way, a little bit of baseboard framing, daylight, interior ply. The interior ply is bowed up from the framing, with little pillars of glue between it and the framing baseboard. The baseboard is basically straight, but the bowed ply causes it to bend upwards a little bit. To get the ply to lay flat, the compression of the ply must be relieved by cutting out a small section, and the glue between removed. This was caused by not having any support under the door opening while glueing the top layer in the vac bag.

The best way I can explain the Y drift is that if you start at Y=0, go do some stuff where Y gets changed, and you go back to Y=0, you actually end up at Y=0+something. The drifting to Y+ is intermittent, and it appears to be a configuration problem with the Mach3 software. I can change settings and make the problem worse or better, but how do I know when it's cured? Rhetorical question. This stuff makes my head hurt.
I 'ed around with this problem all day today.

[capnTelescope]

Keep hacking away, you are doing great!

Thanks. This time I feel like I took an axe and really hacked at it. At least it's hid.

At least you aren't having trouble with tribbles!

If I were a Tribble psycho-therapist, would I have Tribbles with troubles?

[KCStudly]

Okay, that's great. I get it now. Thanks for the extra explanation.

On the door sill inner ply skin, can you slide a thin filet knife or recip saw blade in there to cut the glue stalactites? Then slip some more glue in there using the same technique (as shown in my build... got the idea from Doug Hodder), then just clamp the ply down?

Is a relief cut truly needed? My guess would be no.

y+ ... so more like the embezzler rounding pennies that add up to dollars... some little bit of math code to not enough significant digits? You would think that that would have been solved long ago.