Carving acrylic for lithopanes. You'll like this story but it's long

[RobertDD]

Posted last week that I was having carving Cast Acrylic. In the last month I replaced the brushes in my cut motor and then started having all kinds of trouble with the machine throwing up a Y stall code 0303. I was trying to carve acrylic, the machine would start, then stop but pressing enter would continue the carve, but I was still melting the acrylic? So I threw away my acrylic and purchased new CAST acrylic, was told (even buy the company that made it as I personally meet with a rep at their factory) that I probably had extruded acrylic instead of cast, I am a sign man by trade and was using old sign acrylic that I had. My cost on new acrylic was $160 for 4 x 8. Ok so new material, new brushes, still stalling and melting? So Y stall could be bearings in the Y motor, so I have now replaced them with the company suggested on the forum, but I got the sealed bearings instead. While I was in there I did a complete cleaning of everything. I also wrapped black electrical tape around the clear plastic on the Y motor that houses the white plastic gear, hoping to keep some of the dust out of the gears again. Why this wasn't done before I don't know? Now also while I was into cleaning everything, I thought I would check the cut motor brushes to make sure that they seated properly, as I know that that could be a wear in thing and maybe my cause of the starting and stopping when I first start a carve. I split the motor housing open brushes fine, and I thought since I was in there, I believe Al suggested to check the Cut sensor at the LED screen, no reading so the magnetic pickup must be bad, but I did have the cut motor all apart for cleaning when I first installed the brushes, so having machine version B I have the magnet surrounded by the full plastic. What if this magnet was reversed? What would this do? So I tried it. Now at the LED screen in sensor check I get a reading, yea finally on the right tract. Ok so time to carve.
Started the machine; now no stalling just running; yea again maybe it's fixed. Half way through the new acrylic, and the brand new 4-fluted bit started melting again. Now I'm mad as I run to the machine, lift the clear cover scrape the melted off the bit, hit enter and restart the carving where it left off. Try having this fun for 2.45 hours, boy was it fun.
Months back in the late end of summer I built a dust collector submitted by someone here on the forum, bought a large 2hp dust collector from Harbor Freight and was very proud of how well it kept my machine clean and have used it ever since. I have even customized it and now replaced the rear muffler with a hose that brings dust around front and into my made dust collector, in fact I was so proud that I also added 4 rows of LED lights that hooks to one 9 volt batter with an on and off switch, nice for adding light, start the carving and turn the switch off. I will post pics of this soon.
Why did I tell the dust collector story, was it to brag? No. So why? This is why, after fighting with the machine so long and the melting problem I thought I would start an acrylic carving without the dust collector and see what happens. WOULD YOU BELIEVE IT WAS FINE AND NEVER MELTED! So this is my problem. My collector is so efficient that with the garage temp being in the high 50's, the amount of air being drawn around from near the carving caused the hot bit to melt the acrylic around itself. FINALLY a reason why I was having this problem didn't happen in late summer, but the air was warmer, now colder.
I'm still using my collector to pull the air from within the cut motor, but the collector is not in the machine, so no melting, works fine with the wood carving though.
I have owned my machine for 2 years and I still learn more about it every day! Boy I'm glad I finally figured it out. I strive to learn more every day as this is just me. Well got to go another lithopone just finished.


Keep the forum going guy's it does work. And keep carving!!! RobertDD

[Kenm810]

A Big Double Thumbs Up to ya Robert,

Glad you kept plugging away at it, and found the solution.
Thanks for posting the Story and the results,
It's Really Great info to tuck away in my "What if folder"

[henry1]

A Big Double Thumbs Up to ya Robert,

Glad you kept plugging away at it, and found the solution.
Thanks for posting the Story and the results,
It's Really Great info to tuck away in my "What if folder"
I have to agree with Ken on this great story I will keep this in my folder
Henry

[cnsranch]

RDD -

I'm not a skeptic, I'm just slow.......help me get my mind wrapped around your findings -

If I understand what you just said (THAT would be a miracle alone), without the DC working, the temperature around the bit and acrylic is actually warmer than the ambient temp of 50 degrees in the shop, preventing any melting. With the DC on, it's sucking a lot of 50 degree air around the bit and surface, actually cooling the surface, which makes the difference between the temp of the bit and the temp of the surface greater, allowing the surface to melt.

Sounds counter-intuitive.

Sorry, got my thick hat on today.

[chebytrk]

RDD -

I'm not a skeptic, I'm just slow.......help me get my mind wrapped around your findings -

If I understand what you just said (THAT would be a miracle alone), without the DC working, the temperature around the bit and acrylic is actually warmer than the ambient temp of 50 degrees in the shop, preventing any melting. With the DC on, it's sucking a lot of 50 degree air around the bit and surface, actually cooling the surface, which makes the difference between the temp of the bit and the temp of the surface greater, allowing the surface to melt.

Sounds counter-intuitive.

Sorry, got my thick hat on today.

How about if you get the acrylic piece and put it in the freezer for a while. Then it would be cold (keeping the bit at a cooler temp), when you place it in the CW. : ) Ain't sayin'... just sayin' ....

[cnsranch]

JerryB - you're a genius!

I think you've solved a bunch of problems with one idea -

We got neighbors complaining about noise
We got spouses complaining about dust
We got hot bits
We got hot acrylic

Put the entire machine in the fridge, carve away, solve 'em all.

[chebytrk]

JerryB - you're a genius!

I think you've solved a bunch of problems with one idea -

We got neighbors complaining about noise
We got spouses complaining about dust
We got hot bits
We got hot acrylic

Put the entire machine in the fridge, carve away, solve 'em all.

You'll just have to wear sunglasses when your in the fridge carving away 'cause that crazy fridge light is always on. : )

[JLT]

RDD -

I'm not a skeptic, I'm just slow.......help me get my mind wrapped around your findings -

If I understand what you just said (THAT would be a miracle alone), without the DC working, the temperature around the bit and acrylic is actually warmer than the ambient temp of 50 degrees in the shop, preventing any melting. With the DC on, it's sucking a lot of 50 degree air around the bit and surface, actually cooling the surface, which makes the difference between the temp of the bit and the temp of the surface greater, allowing the surface to melt.

Sounds counter-intuitive.

Sorry, got my thick hat on today.

I'm like you, cnsranch... one would think that a draw of cooler air would prevent the problem...

I'm by no means an expert, but it sounds like the issue might be more associated with a static charge building up on the acrylic from the mass of air being drawn across it, with the charge possibly be dissipated at the point of the carve / cut?! And typically, lower humidity (which usually comes with lower temperatures) will bring a stronger static charge, which would explain why 50 degree air would exacerbate the problem as compared to warm summer air...

Take it as a theory...

[Ike]

Isn't this like a spark turned into a flame by the wind? As the DC very efficiently draws the dust and air and as the acrylic cuts. It cuts hot and as the air is drawn the hotter the acrylic becomes until it reaches the melting point. A lot like a wood stove damper the wider it is open the more the flame, less draft less flame. For those of us who have wood stoves know when the damper is closed while trying to start a fire it doesn't work!

Just my theory!

Ike

[JLT]

I think drawing more air across a spark or flame is a matter of increased rate of available oxygen to fuel the combustion... In the case of carving / cutting acrylic, there is no combustion (hopefully!). Probably a better analogy is a convection oven, whereby drawing warm air across an object increases the heat effect. On the other hand, with a draw of cool air, the opposite is should be the case, such as the wind chill effect or drawing air through a car radiator...

Probably need some clarification from Robert's experience. As I interpret it, when running the dust collection in the late summer, with warmer temperatures (and presumably higher humidity), it did not result in the acrylic melting...

[CarverJerry]

Maybe he can just decrease the amount of vacuum by opening or adding another vent before it get to the CW. I always use my ringneck blues vacuum with a 650 CFM machine and have never melted cast acrylic or corian. Just my 2 ¢ worth. Also too maybe your tool may be getting dull.

CJ

[AskBud]

Perhaps he has a bad batch, or they sold him the wrong material.
AskBud

[RobertDD]

No Jerry you almost have it right. The air at 50 degrees is now moving so fast with the dust collector that it was cooling the acrylic around the now warm bit.

[CarverJerry]

RobertDD, well I posted on this thread a while back. I have been a machinist for almost 35 years I just don't buy it, I may be wrong but I just don't get it. sorry to sound so negitive but it just doesn't make any sence to me at all as I've used liquid coolant on different materals, used air misters on all sorts of materials including different acrylics and plastics. Used vacuums on projects and never seen where the vacuum caused a problem. And I've machined in temps from 115° in Tucson to very cold shops in Ohio. But the vacuum isn't the cause of your problem. It has to be either or both the material or the tool. The vacuum isn't going to cause it to melt, unless it could be causing some sort of static charge build up and if that is the case you had better ground your vacuum ASAP before it blows out the machines computer. If I were you I'd try a new tool and a different material. Go on eBay and buy yourself a piece of corian and carve that. Just my 2¢ worth, and maybe someone like Ron Justice who is also a long time machinist will chime in and give his advise.

CJ

[Ike]

Jerry I have a question and by no means doubt your expertise, but wouldn't the frictions and the air flow increase the temp on the bit? I gave a basic example of a wood stove draft an amber becomes hotter when all the dampers are opened wide. Most of the time with the wood stove the outside air is cool the move draft the hotter the amber. With the bit spinning at a high rate the forced drawn air adds to heating the bit.

Like starting a fire with a bow and string you spin the stick and and blow on the area until it ignites. I can see it melting the plastic from just the speed of the bit, but without the DC he has no problems. I am just guessing it is so efficient it is making the bit hotter.

Unless the friction is the same as static? I am curious and just asking !

Ike

[CarverJerry]

Ike, well I may not be totally right, and I'm not saying robertdd is wrong, I'm just saying I don't buy it. But it was good talk'n to ya today and we'll see what others have to say on this. I may learn something myself here.....time will tell.

CJ

[RobertDD]

I too was also a machinist for 18 years and ran several pieces of equipment and at the last a CNC surface grinder producing the machine mounts for the Hummer and also getting into the precision of the Cat scan bearings, I can't explain it but with the carvewright bit, and the new 4 flute bit from Ron, it will carve almost perfect without the dust collector? Any other thoughts? Open for ideals? Thanks...RobertDD