CNC Build, Day 8 – The Rain on my CNC is like a baptism

Posted on September 15, 2011 by jimbo

My assault on the wood begins now.

…

Couldn’t help it. It started raining about 5 minutes after I got the CNC machine inside this evening. But I’m skipping ahead.

I decided to give the CNC machine a tuneup before continuing with the cut on board 2.

I used Simple Green to clean the grease and sawdust off of both X and Y axes, and then put on white lithium grease instead. I ran both axes back and forth a couple times to get the grease nice and evenly spread. The axes sounded a lot better, and were running pretty smoothly, too.

I also swapped out the “somewhat dull” endmill for a brand new one. I set the machine up to cut, and left to go make dinner. I checked it several times, and everything was going smoothly, right up until the big parts had been cut out and the little parts didn’t have enough “meat” left on the board to hold them together. They rocked and rolled around a bit, finally jamming into the bit, so I stopped.

Man, the CNC workflow is complicated. I can understand how long it must take to get really good at it. I mean it’s not just getting the graphics right and the MOP right, you have to make sure the toolpath is going to work, too. There’s a lot to it all.

Anyway, the parts that were left to cut out were all more or less rectangular, so I decided to finish cutting them with the chop saw. That went quickly, and reminded me what a nice clean cut looks like. I was working pretty fast, so there’s a lot of tearout on the backs of the parts, but I got it done.

Board 2 is finished. Halfway there!

I may have to re-tune the machine before I’m done with board 3. I have a feeling that sawdust is really not the friend of those exposed drive screws.

Here’s a photo of the front of the Y gantry, with the gantry sides:

It’s pretty big, wider than my shoulders. Here’s a “for scale” photo:

I suppose it was supposed to be; the Y gantry is going to be 52″ wide after all. It’s just good to see the thing start to take shape.

I have a bigger pile of parts to process now. All of it needs to be sanded, and several pieces need to be recut or need more work in one way or the other. But I’m getting there.

I got the saw put away, the dust vacuumed up, and the table moved inside, when it started raining. Let’s hope I can sneak in a few more dry days to get this done. Maybe I’ll put up a canopy.

I’m really looking forward to being able to retire the Book CNC. And I’m hoping that the Blackfoot will be as accurate as I hope. I have a feeling that the first job on the new machine will be cutting out another copy of itself, because the first one is going to be a little ragged. 🙂

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CNC Bling

Posted on September 14, 2011 by jimbo

There are a number of little accessories that would make my CNC life a little easier.

First, some kind of pendant / MPG to move the axes around manually. It would be best if it worked without Mach3 running (I often find that I need to raise the Z axis a little to change tools or boards…)

Second, some method of finding “home” on the table, whether it’s with touchplates, switches, or some other sensor (Hall Effect perhaps).

Third, some method of finding table limits (Is this necessary if home switches are installed?)

Fourth, router speed control (and computer control of router on/off power). If I use SuperPID, do I still need a 48v relay?

Once those “basics” have been solved, some “pie in the sky” nice to haves include:
– automatic tool changing
– vacuum hold down (does this automatically include vacuum dust collection?)

In addition, once I get settled with a table, it would be nice to have a full set of configuration in Cambam and Mach3 so that things act a lot less manual.

For now, I concentrate on just getting the big machine built. But pretty soon, I will want to feel a little more “moved in” with my machine.

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CNC Build, Day 7 – fighting the machine

Posted on September 11, 2011 by jimbo

I set out to cut Board 2 today. I moved some things around, hoping to help myself get through the cuts more easily.

I tried to set up a 1/4″ drill bit to do the initial drills, but the runout was extremely bad, so I decided to try out the straight-flute router bit. Also a bad idea.

I went back to the endmill, and it cut all the small drills without a problem.

I decided that I’d like to be able to see the parts on the board earlier rather than later, so I built a 1/4″ deep profiling pass to “outline” the parts. It was during this procedure that I realized that I really need to be doing 1/8″ passes with the little router.

I didn’t get as much done today as I had yesterday; there was a lot of stuff going on in the house, and I’m increasingly worried about the machine, the mills, and everything.

I discovered that the X and Y axis nuts were pretty loose, causing some chattering in the cuts. I tightened them both up. But, in the process, I overtightened X, which caused it to start missing steps. a few holes got bored in the wrong places before I figured that out. argh.

I am hoping that the new machine does more repeatable work, with less flexure. This job is by far the largest cut that I’ve done with the Book machine, but I am finding myself continually worrying over it, and for good reason. It will be nice to (hopefully) have a machine that can just do the job. I can’t imagine just walking away from the machine during this cut.

I got all the “small drills” done, the outlines cut (a couple of them look bad, but nothing major I think), and was working my way through the “large drills” when I ran into the X axis error. I was able to quickly edit myself a new set of “large drills” to finish off that MOP, but I ran out of time and had to stop for the night.

Here’s what I have so far:

I modified the machine to do 1/8″ passes, so everything will take a lot longer, but I think that it will make my life a lot easier. The palm router just isn’t doing the job at 1/4″ per pass.

Next up, I need to finish the large drills, do the pockets, and then parts cutout for this board.

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CNC Build, day 6 – cutting started

Posted on September 10, 2011 by jimbo

Since I’d done most of the prep last night, I was nearly ready to start right up this morning.

I had to move the rig out of the shop and onto the driveway (I am so done with sawdust everywhere), and I decided to add a spoilboard, as I worried that I might end up hitting a screw head or something. I had enough left over material from the Trixie rebuild to make a nice spoilboard, and I made sure to screw it down outside the cuttable area. I am going to have to be more careful with my holddowns once I can use the whole board…

I got rolling around 11:30 with the first boardful of cuts. Doing the drills first, then pockets, then cutouts, made for a nice accurate set of early holes. I ran into a problem during the cutout, though, and needed to take a break and rehome everything.

Quick aside.

I really need to get an auto homing system in place. If anything messes up mid cut I am in bad shape. Also, I need a more repeatable router mount. The current one allows too much flexure. Of course, there are several places where I get flexure in the current machine. But the router mount is the one that bothers me when something goes wrong.

Oh. And I will be using a larger router on the new machine. The little guy bogs down doing 1/4″ passes.

Back to the show.

I got things lined up again after the fail, and continued to cut out the parts. By the way, it failed because of the clearances around the parts, and my failure to leave any holding tabs. More stuff to learn.

I ended up losing 2 parts off of the board; nothing major, just need to be re-cut.
Even so, at the end of the day, I had a nice little pile of parts! 1 board down, 3 to go.

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CNC Build, Day 5 – rails and prep work

Posted on September 9, 2011 by jimbo

It took me a bit, but I figured out what rails I need for the new machine (T6 6061 structural aluminum, as opposed to 6063 architectural aluminum), and was able to order and pick them up from Online Metals.com (which turns out to be Seattle-based, over in Ballard).

While I was there, I met another customer of theirs who was, by chance, also picking up 6061 rail to build a CNC machine. Small world, I guess. Hes building an Adruino-based desktop style machine, so we had a blast chatting about steppers and motor drivers and G-code and software and &c.

When I got home, I realized that if I was going to do any cutting on Saturday, I needed to get the CNC machine all set up. So I spent a couple hours getting the motors installed, getting the computer all hooked up, and generally making ready to cut for the weekend.

I eventually found most of the required parts (still looking for the teflon grease for the axes), and the machine is ready to go in the morning.

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CNC Build, Day 4 – parts ordered

Posted on September 8, 2011 by jimbo

I put in 2 separate orders this morning; one to Pointe for ~$50 and the other to BuildYourCNC for about $450.

The Pointe order includes 1/4-20 and 3/8-16 bolts and nuts, and a couple pieces of 1/4″ allthread. I found some even cheaper bolts to use; they are socket head instead of philips (which I like, actually), and I hope they’ll work out. I’m slightly concerned that the heads will be too tall, but I can fix that by counterboring, or by using panhead screws in places where it’s problematic (of which I hope there will be few).

The BYCNC order has all of the drive mechanism parts that I’ll need; sprockets (drive and idler), roller chain, v-groove bearings, and couplings.

I still need to source small amounts of parts (eye bolts, aluminum rails, hose clamps, and washers). And I’m going to reuse the Z-axis screw for now. I’ll pull a few bearings off of the old machine by the time it’s over, too.

One thing that I’m worried about is that they call for a NEMA 34 motor for the X axis on this build. I will start out using the 425 oz in NEMA 23 that I have, but I may have to spring for the bigger motor sooner rather than later, a $125 proposition ($89 for the motor and $20 each or so for 2 new couplings). When I put in the order for that, I’ll probably pick up the new Z axis screw and maybe another endmill. Call it another $200 and I’ll be loaded for bear.

The hardware should get here early in the week, if all goes well. I hope to have a pile of wood sitting here waiting to be bolted together when they arrive.

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CNC Build, Day 3 cont. – Testing the CAD

Posted on September 7, 2011 by jimbo

With the CAD drawings all converted to the cuttable area of the Book machine, I needed to confirm that all the parts were placed properly. I scratched my head about how to do this, and then hit upon an easy and straightforward way to do this.

I just moved on and created all the machining operations (MOPs), and generated the toolpaths for the boards. Since the cuts define where the tool will go, a quick visual check of all the cut lines (to confirm that they never “cross” each other) is sufficient to see whether the parts are all spaced properly.

I think that the .nc that came with the plans showed cutlines that are right on top of each other (ie the parts are set as 1/4″ apart). I had been trying to use more like an extra 16th (3/16″ spacing) instead. I ran just the part outlines on all 4 boards first, and only found one part that needed to be moved 1/8″ in the whole mess. Not bad.

Then I went through and selected the various cut types and put them into MOPs. I broke things down into “small drills” (places where the hole is 1/4″, to be cut by the endmill in one plunge), “large drills” (places where the endmill will need to bore out a larger hole for some reason, such as the 7/16″ holes for cross-dowels, or other “inside” profiles), “pockets” (where the area is not to be completely drilled through, for counterbores, or for the decorative logos), and “parts cut out” (for “outside” profiles). Of these, the parts cut out is the only one that must be run last, for obvious reasons, but other than that, one could theoretically run any of the other MOPs in random order (they are not dependent upon each other). However, I decided to run the MOPs in the order listed here, with the hope that by going (more or less) from “smaller” holes to “larger” ones, the machine would have an easier time cutting, and the toolpathing would have an easier time calculating.

There were a few parts that didn’t set up properly; most of the “keyhole” shapes didn’t work right. A small amount of tweaking (I did essentially the same thing as a “join all gaps” function, which I can’t remember the name of, in Cambam) fixed these, and again they were pretty easy to see by inspecting the toolpaths carefully. Oh, there were 2 or 3 holes that showed up as 0.249999″ instead of 0.25″ (the diameter of the endmill), so I had to round them up so that the toolpath generator would allow those cuts.

I spent quite a bit of time checking all the gaps between parts, and checking for bad-looking (or missing) toolpaths. I am fairly certain that I’ve found all the problem areas, and I now have 4 .nc files, ready to cut!

If all goes well, I should be able to start cutting in the next day or two, and perhaps even finish this weekend.

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CNC Build, Day 3 – hardware pricing

Posted on September 7, 2011 by jimbo

I more or less know what I’m getting into this time; the structure will be built of 1/4-20 bolts and cross dowels, with a small smattering of larger bits (to hold on bearings and stuff), some angle aluminum, and a handful of washers and nuts.

I went through some thrashing last time around about whether I should buy hardware at the store or buy “the kit” from BuildYourCNC. Because I didn’t really know what I was getting into, and because I was otherwise going to be buying all the bolts at retail, and because I couldn’t find a cheap source of online cross-dowels, I decided to buy the kit, even though I felt it to be a bit overpriced at the time. Without a CNC machine (or drill press, or …) at the time to back me up, I felt that there were some parts in the kit that I would have problems dealing with on my own.

This time, it’s different. I mean, I ended up having to “top off” the kit at retail prices anyway, when I ran out of 1/4-20 bolts a couple times. And unlike the BRAs from the Book machine, there are really not that many parts in the new build that are “strange”.

Also, I found cheap cross-dowels online (amazon has them for 29.9 cents each).

So the hardware breaks out this way:

Roller chain and its components, plus the V-bearings, should be bought from Patrick.

nuts, bolts, cross-dowels should be bought in quantity online (I use 1/4-20 hardware all the time anyway).

aluminum angle, threaded rod, washers, and any “off-size” bolts can be bought at retail (I don’t foresee this being more than $100 in bits and bobs).

So, here’s a rough analysis of the price breakdown:

Patrick parts:
– Roller chain (#25, 2×12′, 1×5′ @ $2.40/ft) = $70
– drive sprockets (1/4″ bore, 9 tooth, 3 @ $11) = $33
– idler sprockets (5/16″ bore, with bearing and bolt, 5 @ $16) = $80
– 1/4″ to 1/4″ rigid coupling (2 @ $21 ) = $42
– 1/2″ collar (2 @ $8 ) = 16
– V-bearings (16-pack) = $128

Patrick subtotal: $370
If I decide to upgrade to ACME screw for Z, and spring for a couple of new bearings and a bracket for the screw, this adds $75 = $445)

Nuts, Bolts from Pointe Products:
– 15402-AV 1/4-20 x 1.5″ ( 200ea = 4bags @ $8.76 ) = $35
– 15404-AV 1/4-20 x 2″ ( 100ea = 2bags @ $11.08 ) = $22
– 10-10001 1/4-20 hex nut (100ea = 1bag @ $1.55 ) = 2

Pointe Products subtotal = $60

(they also sell 1/4-20 threaded rod in 3′ lengths for $1.70 per, I would need 2)

Angle Aluminum for the rails from Home Depot:
– 1 1/2″ angle aluminum, 8′ length ( 4 @ $18.50 ) = $75

Home Depot subtotal = $75

Total is $560. This compares to BYCNC’s price of $923 for the same set of stuff.
I am reusing the Z-motor coupler, which saves $10 or so. Ordering the rails from BYCNC would mean they are pre-drilled (I think). And his parts list as listed on the BF webpage only adds up to $850 if you use the prices he has there, and only adds up to $700 if you use the updated prices from elsewhere on the site (he’s found much better prices on roller chain and sprockets). So there is about $200 in markup over just buying the parts piecemeal from him (for his time and effort figuring out the parts list, I suppose), and a 60% markup over buying stuff a la carte and sourcing nuts and bolts myself.

The Book machine was about $200 in the hardware kit, and included bearings, couplings, and BRAs that I wasn’t going to be able to figure out on my own. This kit is 4x as much, but I can source the “easy to find” stuff on my own and save a bundle.

I think that I’m going to go it alone on this one, unless Patrick decides he can sell me the hardware kit at half price, too.

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CNC Build Day 2, The Rhino in the Beetle

Posted on September 5, 2011 by jimbo

The plans for the 4×8 machine require 4 quarter-sheets of ply, so I went to McLendon’s to pick up some 3/4″ Birch. Their stuff is really pretty compared to Home Depot. $19/sheet, though.

I briefly considered getting 4’x4′ sheets and then ripping them with the new tablesaw, but I chickened out; it’s only $6 more to buy 4 2×4 sheets than 2 4×4 sheets, and who needs that stress?

The tablesaw will get a good workout building the table for the 4×8 machine — plans call for a torsion box to keep the surface dead flat and properly supported. Not to mention a stand (made of 2x4s) to support it all.

I spent the rest of the day and well into the evening pushing the parts around in Cambam to get them to fit into the 18″x36″ cuttable area of the CNC machine. This presented several challenges.

First, the graphics included plans for the v4.0 Blackfoot, but also a sheet of revised parts to bring the machine to v4.1.

Second, the pieces for the 4′ wide Y table (actually 52″ ID, and even wider OD) take up a lot of room on the plans, so they have to be carefully placed in a way that can cover all of the parts.

Third, there are 2 pieces that simply can’t be cut on a 36″ table, namely the Y axis top and bottom, which are ~3″ wide by 46″ long. I’m going to have to fab those on the tablesaw, or else I’m going to have to find a different way to create these.

Finally, I need to make sure that all of the parts have sufficient spacing between them so that the toolpath creator can do its job. I also have to figure out all the parts that have pockets and make sure that I’ve covered them all properly.

Once I started working through the various constraints, I was able to get everything pushed and shoved into place, and I now have a set of drawings to create a v4.1 machine in 4 quarter sheets of ply, with a cuttable area of 18″x36″ on all sheets (ok, one sheet needs 18″x38″, but that’s not a big deal)!

I need to do some final sanity checking to ensure that all the parts have proper spacing. Then I’m ready to start cutting.

Once I finish the 4 sheets, I’ll have a bunch of scrap left over, as each sheet will have about 3″ on each side left over, and about 12″ at the end. From that set of scrap, I need to cut the following parts (moving the parts around on the diagrams as appropriate):
– the aforementioned Y axis top and bottom (2 parts)
– the router shoe (2 parts)
– the lower vacuum mount (2 parts)
– router mount rings (2 parts)

The router mount rings I’ll have to design myself, as I’m using a different type of router than the Blackfoot plans ship with. I already have a CAD that I designed earlier, and I should be able to modify that pretty easily to create the required part.

I have some work to do to turn these drawings into machine operations, and I’ll have to do some additional cutting once it’s all done. And I will need to buy hardware to put the whole thing together. But for some strange reason, I feel like the hard part is done.

Onward.

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CNC Build Day 1, Moving on up

Posted on September 4, 2011 by jimbo

I’ve decided to upgrade my trusty CNC machine to a larger unit. There are several small problems with the current machine, some by design, and some in my execution.

By design, the machine has a 24″x48″ table, but it can only utilize about 20″x40″ of that. My machine is slightly more restricted because of the way I built it, and I can only achieve 18″x36″ cuttable area (ok, it’s closer to 19″x38″, but if I need to get “outside” a part to cut it, then this is about the limit of part size).

Because the machine was hand-cut and hand-drilled, there are several places where bolts aren’t going through exactly where they should, which in most cases is not a severe enough problem for me to worry about it, but in a couple of places, I needed to re-cut the parts (with the CNC itself, naturally) so that the cuts were more accurate.

In short, I was about ready to cut out a new machine anyway, and was deciding on a full 24″x48″ machine, when Kristi mentioned that she had a couple project ideas in mind, all of which would require a larger bed than that.

So, the 4’x8′ project was born.

I bought the plans for a Blackfoot v4.1 router today, and I’m looking the plans over to see how to compress the 4 sheets of parts into 18″x36″ areas.

I also put the frame of the CNC machine back together. I still need to install motors and get the computer hooked up and running, but I’m getting closer there.

I need to start working on this now so that I can get the machine up and running in time to fab some holiday decorations and Christmas presents.

Sawdust is in the near future.

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