Thanks Shaun,

I did watch the 8 (or 9?) videos on processing the parts in SketchUp on the Support DVD, and I found that helpful. I used SketchUp to make the CarBEN EV model, but I was not able to fully model the interior surfaces (though I did a fair bit of them), so I am doing the slicing (aka sectioning) in DataCAD, cleaning them up and adding the interior surfaces there, exporting them back to SU (via DWG, though DataCAD also can export SKP files).

Now I'm learning about the process to make the GCode -- I'm glad you put the link in your post, thanks again.

 

Okay, I've gotten the GCode to load into CNC USB!

I did two things, and it may be both or one that got things working: I exploded the component in SU, and I set the Safe Area to 93" x 23.25" which is the actual safe area on my 2" Dow EPS T&G 2'x8' sheets.

Here's a screen capture of what I'm seeing in CNC USB:


I have a few questions:

What is the cyan/blue rectangle? It seems to be part of the CNC USB Settings, but I don't know where to change it, or get rid of it.

The Safe Area that came in with the GCode has the same lower left corner as the Settings in CNC USB but I don't know if I need the Settings one or not?

The GCode paths and Safe Area appear to be below the one from CNC USB rectangle -- is this correct; would it work?

Oh -- my support rollers came today! Looks like I'll be trying my first cuts this weekend!

 

I will do at least one dry run (without foam) to see if I can spot any problems. Since I used the 93" x 23.25" Safe Area, I should register the foam (when I do use it) so that the origin/zero point is 1.5" from the short side and 0.375" from the long side, at that front right corner, right?

Other questions:

I will be making a way to square and true the sheet in the PhlatPrinter 3 -- any hints on how to do this?

Since I have the stock 1/8" cutting bit extended out as far as I can -- it is about 1.75", and I think the Z-axis has to be lifted as far up as it can in order to clear the foam; I set the overcut to 100% and I am not using any tabs. The foam is actually 1.9375" (1 15/16") thick (maybe it is really 50mm?) so that should leave 0.218504" (3/16" or 5.5mm) on the entire bottom of the foam. What is a good feed rate to keep the bit from bending too much?

Do I have to be careful to set the zero / home point at the right height?

 

Okay, I did a dry run without any foam in the PhlatPrinter -- it looked great up until the 3rd pass, which plunged the cutting bit way past the bottom of the foam, between the rollers. This is good in one sense in the it could cut all the way through -- BUT the tip of the chuck jaws were only about 1" above the rollers, so it would have been tearing up the foam!

So, something needs to be different: do I need to enter in the tool bit length? (I seem to remember doing this.) It is actually 1.75" long sticking out of the chuck. The cutting burrs cover about 0.875" (7/8") so I was hoping to get away with 2 passes, though it generated 3 paths.

I set the Zero/Home point at just about 2.0625" above the rollers and the 1st pass seemed like it would be a little less than an inch into the foam.

If I set the depth of the passes to larger (I have it set to exactly half of the actual foam depth which is 1.9375" / 2 = 0.96875") say 1" if this only generates 2 paths, then maybe the it won't plunge past the bottom?

Any thoughts or hints or answers?

Or maybe I have to set the Safe Area depth to exactly the thickness, and see if that avoids the 3rd path?

 

Okay, here's what I did, and the GCode *looks* better -- I'll have to wait until tomorrow to see how it works on the PhlatPrinter:

Material Thickness 1 15/16"
In/Outside Overcut 99%
Multipass Depth 1"

We'll see how it goes!

 

That is something I had not thought of -- I'm using the light blue Dow EPS and I was hoping that it would shred and get sucked away by the vacuum, before it could melt? Maybe a short shroud to focus the air flow would help cool the bit?

So, I should set the multipath depth to 1/2" for my first real run?

I think I need to set the overcut to 95%, as the foam is 1 15/16" and the bit is ~1 3/4", which is about 5% less. I's rather not have pieces come loose, and have to cut things out, than having the chuck jaws hit the top of the foam.

 

How do I increase the voltage / power of the X-axis? Which trim pot, the upper one nearer to the parallel port or the lower one?

My first cut has some wobbles because the X-Axis can't move the foam well. I've adjusted the rollers some and I take a second pass...

Edit: The foam is slipping in the X-axis towards the back, so that subsequent passes are not tracking in the same cut.

I think I need to slow down the feed and go to 2 passes only; and even that could be risky. I'm going to try and find a new bit with a full 2" of cutting surface so I can do just one pass.

Also, I will try putting the foam *centered* on the X-axis rollers, in case the pressure isn't equal, causing the foam to creep, possibly?

 

Thanks Shaun! My other issue (that may be related?) is though I *swear* that I re-zeroed the bit before each run, there were a few that were at least 3" off...

 

I tried to zero it at the same relative place on the foam before each retry (the foam is getting cut up!) and on several runs it was off by that much right at the beginning.

I may need to slow down the feed rate even on the 4 pass GCode -- maybe it is pulling on the foam as it cuts? This could skew the speeds enough to throw it off.

I might need to put the grit tape on the pressure rollers/bars?

And, I need to know about what the two trim pots do -- does one work for the stepper motor in each direction? Do they need to be "balanced" so the motor runs the same speed in both directions?

I was adjusting the heights of the support rollers as the foam needs to move freely and smoothly, and some of my early issues might have been because of these being a little too high.

 

The feed rate in SketchUCam says 8' 4" -- what does this mean?

I'm trying the 4 pass GCode with 4' 4" feed rate. And I'm trying a 2 pass version with 1' 1" feed rate. It remains to be seen if fewer passes at a really slow feed rate can reduce the error / slippage.

Also about the two trim pots on the X-axis channel on the CNC USB board (I'll read the manual again, but it was not obvious) does TP1 control one direction, and TP2 control the other direction? Do the voltages on both the pairs of wires going to the stepper motor need to be the same? What are the safe voltages? If the X-jog speed is *very* slow, how do I speed it up, and how do I get it to not "jump"?

 

Okay, there have been a lot of dead ends today.

Problem #1 has to do with X-axis "jumping" -- I may nee more support rollers, but man I think that the drag on the sheet is pretty minimal, and I cannot figure out a way to get it to move consistently. The first piece that is getting cut is along the bottom of the car, and when the x-axis slips/jumps/or doesn't move correctly, the width of the iece is severely affected. Like by inches.

I tried adding grit tape to the two pressure rods/rollers and this seem to make it worse. But the foam cannot shift which is good.

How can I get the X-axis stepper motor to consistently move the foam? If the tension wheels were bearings instead of plastic, that would greatly reduce any friction they have. I will order 2 or 4 more rollers to get as much "droop" out of the foam when it is sticking out of the PhlatPrinter.

I have tried the TP1 (which seems to be the voltage adjustment) and the TP2 in a bazillion settings and I cannot get enough power/torque out of them at slow RPM's! However, when it is moving fast, they seem to have plenty of power. If I set the cutting depth shallow, then I can keep the feed rates high, but *any* little slip equals BIG error, and it *must* track in the same cut 4 times in a row, which is a LOT of chance for errors.

If I set the feed rates slow, and have just 2 passes, that reduces the chances for error, but it seems to have more skips/jumps this way...

Problem #2 is that I got a MAJOR cotton candy affect 3/4 of the way through my best pass so far -- it had been tracking very very well. The ball of melted goop was over 1/2" in diameter. So I am trying another bit -- it is still 1/8" diameter, but is about 3/8" longer, so I can extend it ~1 7/8" and still have more in the chuck jaws. It is a Dremel brand and it has steep spiral flutes -- it this going to work better or worse? The direction of the spin means it is pushing the cuttings down into the groove, unfortunately...

I will look fro a larger diameter bit, so that heat will build up more slowly. Any hints on where to look for these? My local hardware store has the Dremel, but nothing bigger. The knurled Dremel they had seemed slightly longer than the stock one, but it had shorter cutting area. and slightly deeper knurling.

So I am fight with two interactive/conflicting problems. The main thing is to get accurate pieces, but it has to also make it all the way through the GCode file without getting screwed up in some way or another.

So, I'll order more support rollers -- I have 4, and will get 4 more, cuz' there is no messing around! The foam needs to move freely, and the least bit of friction screws it up.

 

I found some 5/32" (4mm) bits that have a reverse spiral (Roto Zip) that will lift the cuttings out of the groove; and also a 5/32" that is knurled like the stick one. The spiraled bits are about 2 1/4" long which lets them bet a secure grip in the chuck and still be ~1 7/8" long. The knurled one is the same 2" length as the stock bit.

I'll try the new settings, for sure! Where can I get the Sharpie holder?

Yes -- the acceleration may be the issue! About half the time on the startup when the bit moves from the zero point to the first cutting point, then motors made a lot of noise and the cut would be started too close to the end of the foam.