Purple heart


#1

I know, you’re thinking it’s Henry, it will be some snarky anatomical pun on heart since he did cut into a real heart today… But nope (well I did, but that’s not this - although I did leave the title in 2 words to make people wonder).

I stopped off today at Rockler today between my two anatomy sessions, and decided to get some exotic stuff to try something artistic.

I hear you cry: “What, @henryhbk be artistic? That’ll be the day”. I will have you know I have a fine sense of art, and like both kind of dog-poker posters, both velvet and plain!

So I got some really nice purple heart (very purple) and some African orange Padauk including a block of each (for bowl turning, but I intend on inlaying for desk awards) and a short 1x3 board of each to try out on before using the blocks, along with a 1x3 3’ board of really nice walnut for something at some point. I also got a variety pack of exotic and american veneers.

So took a small chunk off the end of the 1x3 to experiment with settings. Just my initials in a scored square.

Score: 85/150
Engrave: Dark 5/300

(note the crack happened when I dropped the little test chunk on the floor). Also note the engrave is at the low-res setting, since this wasn’t a real test for outline quality just a proof of procedure.

which actually came out really nice (there is a fair amount of oil splatter around the engrave) which I would clean if I cared about this piece. But most importantly the depth seemed about right.

Next decided (even though not probably the veneer of choice for looks) to try the proof grade walnut veneer. While I struggled the other day with engraving the veneer, cutting works well.

Yeah, but if you cut something this small (see with penny below) it is virtually impossible to get the adhesive off without tearing up your letter. So the H cross bar tore, the point of the J tore off, but eventually got all the parts in place (and I was using very very fine tweezers and a razor blade to separate the adhesive backing) and peeled off the protective paper. The serifs on the F tore off when it cut (really?) and fell down the grate, so that didn’t happen. But I sort of see how it’s supposed to work. Need a lot more refinement.

The good news is the top is pretty flush and would clean up nicely I think once I finished it (again this is simply test V1.0)

For finishes I got some nice tung oil and some wax for a shine.

All suggestions welcome, especially from any PRUs out there who have inlayed…


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#2

Looks great! :relaxed:

If you lose a piece or two down the grate, take it out of the machine, hold it over the floor, give it a little shake, and retrieve your bits. They can frequently be used with a spot of glue.

Then clean up the floor. Chuckle!

(And try a scalpel instead of a razor blade…you get more handle to work with.) :wink:


#3

Looks good.

Not sure the masking buys you much more than pain with most veneers. Cutting it is very, very fast so not much smoke. Mostly using my own unmasked veneer. Just cut some bleached Anigre. It’s a light parchment color. The edges come out noticeably black like all woods but masking would not help with that.
The top and bottom have very little noticeable smoke stain even on the almost white veneer. The bleached Anigre is the white veneer in this pic.


#4

Yep. Really nice writeup. That’s how I went about it. For the lettering, to get a sense of what will happen after cutting them out, I make the path width the full width of the kerf and then I can see what is left of the serifs to hold. Getting the right typeface also helps because the serifs on some go down to nothing pretty quickly. But it looks great from the start and is smaller than what I have tried.

I’ve also used a hat pin to clean out the engraves, especially the serifs.


#5

Oh, didn’t know you were supposed to do that. OK, V2.0 will have to try that, thanks.

Cool, the ones I bought at Rockler don’t have masking, so will try that. Probably way easier to figure out which is front vs. back in that case.


#6

Lay something below it on the bed to avoid flashback.


#7

I’ve been laying a piece of card stock underneath but it doesn’t completely prevent flashback. Do you have something better?


#8

Wasn’t having a problem just laying it on a manila folder material. Guess you could raise it 1/4" off the bed with some Proofgrade cut offs. Had the head running like a bat out of hell at very low power. My veneer is thinner than the Proofgrade version. (Needed to slow the head down just a little because of a little ringing in the head motion at one spot)


#9

I wonder if GlowForge suffers from resonance like 3D printers. It probably does with stepper motors and belt drive. I fixed it by automatically slowing down when the movement frequency got close to resonance. See http://hydraraptor.blogspot.co.uk/2010/12/frequency-limit.html. This never made it into the common RepRap tool chains because it falls between two stools, i.e. slicer and firmware. Instead it is prevented by limiting acceleration but that is a blunt tool.


#10

Not sure, but it’s definitely a motion ringing at the higher speed limits. It is very repeatable. Now keep in mind that the head and gantry are moving quite fast when this occurs. Enough that it bumps the machine when the combined head and gantry change direction at those speeds. Slow the speed down a little and the effect goes away. Doesn’t surprise me. This is something that I often need to compensate for on my X-Carve CNC.

Here is the inlay cut at 100, 133, 166 and 197 inches/min. The effect is not noticeable at 100 inches/min.


#11

Aren’t these the jerk setting on most CNC controllers. You can definitely tweak jerk settings on my printer (I let others who know about such things generate the settings) and same with most CNC mills…


#12

Depending on the motion control S/W you buy it could probably be set. The stock company provided motion control S/W for the XCarve doesn’t have settings for it. I can think of a dozen ways it could be done that I’m not particularly interested in worrying about. And of course it’s all done elsewhere with the GF system. I’m sure it’s one of those things they will continually tweak. Doubt we will ever have control of that.


#13

Jerk is supposed to be rate of change of acceleration in maths but in the 3D printing world it is the instantaneous start speed. I.e. instead of proper trapezoidal acceleration (which becomes S shaped when jerk is limited) 3D printers have a vertical step at the start of the ramp.

Limiting acceleration and its first derivative will reduce overshoot and vibration. However if the problem is caused by resonance at a particular frequency that is hit by short zigzag moves then limiting the acceleration to prevent it is suboptimal. You are limiting acceleration everywhere when you only need to to limit the frequency of moves, which only affects short zigzag paths.

On my 3d printers controlled by Marlin firmware I have to set the acceleration to about half the value I can achieve on my machines controlled by my own tool chain that has a frequency limit.


#14

I have a design that really jerks the Glowforge around. I’ll cut it and video it. Be interested in having you analyze it. I’m reminded of Rhett Alain’s column in Wired. He’s pot a dot on the head and one on the bed and do motion tracing.


#15

Update:

So changed fonts to a more robust serif, and it worked super well (ignore the slight scratch on the H, I did that moving something before taking this picture)

Also since purple heart is so oily it leaves a lot of splattered oil on the surface, so I wondered if an alcohol pad would clean that off, and it works great.

Proofgrade Walnut veneer (note with the flashback it can be really hard to determine which is the adhesive back and which is the masking if there is none of the green logos on the back paper…)


#16

You do know that’s a valuable penny, right?


#17

Why is it valuable? It’s only a few years old…


#18

Really? That’s what pennies look like these days? :flushed: The last time I handled a penny it looked like this:

Wow, I am apparently about seven years out of date! I thought you had some ancient penny. My bad. Why don’t they just retire these darn things, anyway?


#19

Here’s the front of my “GlowForge Scale Penny”


#20

I stopped using pennies in my art fair business in the '90s. Gave change rounded up to the nearest nickel after that. Then everyone started using cards, so not much cash exchange after that.