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11
CamBam help (General usage) / Re: Machining Polycarbonate
« Last post by Tool-n-Around on Yesterday at 00:26:37 »
Polycarbonate’s super power is impact resistance, scratch resistance not so much. There are formulations, where a thin glass hard like layer is applied during manufacture
to help this.

I may need to look at using acrylic. I thought the toughness trumped the scratching but pc scratches easily. Since they're just display pieces, durability may be more a matter of scratch than impact resistance. Not sure it will change the machining issues much though.

I don’t know if it’s my imagination or not, but looking at the tool marks at the bottom of the cuts (on the outer periphery) it looks like the tool is digging in at times, so the tool is porpoising along as it’s making the cut, It might pay to check the backlash in the Z axis, on your type of machine the Y axis can contribute to this as well, if you look at the wheels on the Y axis and they appear to have a white ring around them, then they have worn in a little and need a snug up.

I’ll check both. It may also be the stock getting lifted off the table by up shear. I’d probably need vacuum hold down if so. We’ll see how much pc I do in the future. I need to get through these two peices in the present.

The z-axis is just an acme screw with kind of a hokey backlash anti-device but it’s on linear rails. The wheels on the rest may very well may need tightening. That darn foam has quite a charge when cut and that which escapes vacuum collection clings to everything including the v-grooves for the wheels which compress the fluff with cycles into much harder interference. If I don’t wipe (especially the underside that I can’t see) it can build up enough to cause step loss. I was considering adding some air jets to keep/blow the fluff out of there, but I need to modify the machine for more Z-axis travel and when I do so, I’m giving serious consideration to upgrading everything to linear rails (versus wheels) and ball screws (versus rack and pinion). It would just be imported rails and screws, but I can do the whole machine for $350. The rails have wipers that will probably handle the foam dust fine, not sure about the ball screws. Re-engineering my cnc machine hardware for such would be no big deal for me. While I was at it, I would probably fill the aluminum extrusions for stiffness…….but maybe not the one on the moving gantry to keep it light. Even with the cheap imported linear motion stuff I bet it would be a significant improvement for the machine and probably good value for money.
 
Love to see your work, always puts a smile on my dial.

Me too, I really enjoy it. I’m working on a couple projects now that will be my most complex and best work so far. Right now it’s being paced by my CAD learning curve to model the projects, not cut them, but I’m getting there. Th efoam patterns should be some pretty impressive (at least for me) 3D machining work. When I do, I’'ll stop back and share. Heck, I'll probably be back for help. I still have great appreciation for all the help and patience this forum provided to me when I was just starting out.

Best,
Kelly
12
Installation Help / Re: Reinstall CAMBAN and the serial number/key seems wrong - SOLVED
« Last post by WireCut on November 26, 2022, 23:52:50 pm »
Hi David,

many thanks for your suggestion.

Running CAMBAM as administrator, the license key is accepted.

 :) ;) ;D


Ciao

Leo
13
CamBam help (General usage) / Re: Machining Polycarbonate
« Last post by dave benson on November 26, 2022, 22:59:22 pm »
Quote
May it have served as cutting lube? What do you think?

I don’t know, sometimes I have to machine a pre-existing object, so the paper
has been removed, and at other times use virgin stock with it on.
In practice, I haven’t seen much difference, although in the back of my mind
I’m thinking, that paper is stuck on with adhesive so would it stick the light weight
chips to the cutter.
Polycarbonate’s super power is impact resistance, scratch resistance not so much.
There are formulations, where a thin glass hard like layer is applied during manufacture
to help this.
Polycarbonate starts to slump at 140 Deg C and melts at 300 Deg C.
This is one of the reasons that 3D printed “under the bonnet” items are made from
ASA or some other higher melting point plastics are used.
If you want to remove the tooling marks in the bottom of the cut, there are two
common ways to do this, Flame cleaning where you use a very gentle lpg gas flame
and pass around the cut surface, I’ve done this and it works but you have to keep the flame
moving at a consistent pace.

The other method is to use Vapour cleaning, the 3D printer crowd use this method to
cleanup and eliminate Layer lines, I haven't done this as I looked at the materials safety
data sheet, and thought I’d give it a miss.

I don’t know if it’s my imagination or not, but looking at the tool marks at the bottom of the
cuts (on the outer periphery) it looks like the tool is digging in at times, so the tool is porpoising
along as it’s making the cut, It might pay to check the backlash in the Z axis, on your type
of machine the Y axis can contribute to this as well, if you look at the wheels on the Y axis
and they appear to have a white ring around them, then they have worn in a little and need a snug up.

Love to see your work, always puts a smile on my dial.

Dave
14
CamBam help (General usage) / Re: Machining Polycarbonate
« Last post by tau on November 26, 2022, 20:05:48 pm »
Kelly,

Quote
May it have served as cutting lube? What do you think?

IMO, it does not make any difference. I did make many successful cuts ands engravings with and without the protective film without any difference. When optimal cutting speeds and feeds are chosen (as well as a sharp and polished tool is used), the  results came out always perfect.
15
Installation Help / Re: Reinstall CAMBAN and the serial number/key seems wrong
« Last post by dh42 on November 26, 2022, 16:06:21 pm »
Hello

You must run CamBam as administrator for the license key to be accepted.

https://cambamcnc.com/support/FAQ.aspx#2

Quote
I insert the key but is not acceped.

Did you try to use the license file instead to type the key ?

++
David
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CamBam help (General usage) / Re: Machining Polycarbonate
« Last post by Tool-n-Around on November 26, 2022, 15:37:36 pm »
I forgot one important detail. I machined that previous lid with the protective film in place. Not so on the most recent effort. The film adhesive seems to be waxy feeling. I did it to prevent scratching while handling because that is how the professional friend of mine I previously mentioned did it. May it have served as cutting lube? What do you think?

Best,
Kelly
17
CamBam help (General usage) / Re: Machining Polycarbonate
« Last post by Tool-n-Around on November 26, 2022, 15:24:38 pm »
.......I did everything wrong to make an acceptable cut.....Wrong speeds and feeds........Crappy work holding (sitting on parallels in the vice) so no support at all......Wrong type of endmill (it was a well-used one for cutting AL, four flute).......No air blast. Short of spinning the endmill in reverse, I could not think of anything else to do wrong. ;D

The only thing I did was lubricate the cut with straight dish washing liquid at
the start of the cut with my finger......Tooling marks aside, the piece came out optically clear, I can see straight through it
(40 mm) to the woodgrain of the table.

Wow! I must say, I went back and looked at the pics of one of the other polycarb lids I did. Ignorance was bliss. I paid no particular attention to anything and just cut it at an arbitrarily lower speed than I was cutting polystyrene casting patterns foam. The logo had some burrs stuck to it but they came off with a wooden pick. Those were the cut speeds I started with on this filter, however, the cutters may not be the same....cant be sure on that. Attached a picture of the resulting air filter assembly with both aluminum and pc lid.

I’m not suggesting that you use the dish washing liquid, just that if you are still struggling to get an optically clear surface to your satisfaction, after taking all of the above advice (which is good) then it’s well worth considering. Dave

Well if not suggesting it's sure making a strong case for it! I have not gotten back to experimenting with it because I had family visit and they stayed....so will be back at it when they depart.

Best,
Kelly
18
Installation Help / Reinstall CAMBAN and the serial number/key seems wrong
« Last post by WireCut on November 26, 2022, 09:10:14 am »
Hello,

I have reformatted the PC and I re-install CAMBAM.

Is installed:
CamBam plus [1.0] x64
Copyright © 2020 HexRay Ltd

CamBam.CAD : 1.0.7389.20585
CamBam : 1.0.7389.20589
Build Date : 25/03/2020 11:26:10
Framework Version : 4.0.30319.42000
Evaluation Copy : 36 evaluations remaining

I insert the key but is not acceped.

Any suggestions?

BR

Leo
19
CamBam help (General usage) / Re: Machining Polycarbonate
« Last post by airnocker on November 26, 2022, 03:56:03 am »
Thanks, nice test Dave.
20
CamBam help (General usage) / Re: Machining Polycarbonate
« Last post by dave benson on November 26, 2022, 03:29:55 am »
Yes Nocker, it was a full depth cut along the edge face.
I took quite a few pic's, one of the pic's is looking down through roughly
40 mm, I did not machine the face that is sitting on, it was sawn and dressed,
still a bit opaque though.
The reflection of the crazing from the front and back faces of the material, which was scoured, can be seen
reflected in the face I machined.

Dave
 
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