Lines are still jagged.

[Austin Shafer]

Hello everyone! I changed the pinions on the machine and the lines have gotten cleaner but they are still jagged in some spots and I have been running it a little slower what should be checked next?

Its a shopbot buddy PRSStandard and we have had it since 2009.




On another note my new controller card should be in from shopbot today to fix the input issues I am having!

[scottp55]

Austin,
Got another pic like this one you posted in the original thread of how it's currently cutting?
http://www.talkshopbot.com/forum/showthread.php?21896-Jagged-lines

[Austin Shafer]

I do not have a picture. It is happening the exact same way though only on diagonal or circle cuts just not nearly as bad as in the pictures.

[Austin Shafer]

Here are some updated pictures. I have been messing with the feeds and speeds to see if I could make the cuts perfect but it is seeming impossible.2612926130

[Brady Watson]

What is your XY, Z Move Speeds? (MS values in cut files)

What diameter tool & geometry? (how many flutes, regular spiral, straight or spiral-O?)

What RPM are you running?

-B

[Davo]

I had cut plastic with similar looking results on the piece that was cut out

I used the 1/4" end mill at 13k

[Austin Shafer]

I mainly use the 1/4" single flute upcut spiral O flute onsrud bit and for cutting it usually runs at 13000 RPM X,Y is at 2.0 and Z plunge is 1.7. It seems that the jagged parts are worse where the tabs are.

[Brady Watson]

With a single flute tool, you are going to be limited to around 1.5 IPS in XY. You can go faster with a 2-flute spiral-O, same RPM. Onsrud & Harvey have them.

HDPE/Playboard is going to telegraph every little reverberation in the machine. The only way around this is to cut with allowance and come back full depth @ 0 allowance to clean it all up. You are going to have more marks at the tabs because of the sudden stop, lift and move again.

Reduce your Z speed to 0.7 or 1 IPS. It is too fast and it is probably causing the jaggedness & tool marks in those areas.

Try to get your vacuum up sooner than later. Tabs suck for several reasons in plastic. Strong hold down is absolutely essential to quality cutting, especially in plastics. Tabs with screws or clamps are horrible...There's plenty more quality you can squeeze out of that machine.

-B

[Austin Shafer]

I will try and devote most of my downtime to researching vacuum tables. I will try changing the speeds and update you guys with pictures. Would 3D tabs work better?

[Brady Watson]

Would 3D tabs work better?

Maybe...but they will probably need to be longer than the 2D tabs.

-B

[Austin Shafer]

26131
This is the 2.0



26134
this was at 1.5. Ended up about the same as 2.0


2613226133
these are at 1.0 and the lines are looking way cleaner.

[MogulTx]

Looks like you may have solved your mystery with a speed adjustment. Good for you. The last couple of photos look pretty good. You might also ( depending on material being cut, depth of cut, etc.) want to use (1) multiple passes to the bit is not getting deflected or bogged down (2) use ramping of the cut so that it gradually lowers itself into the cut, and thus, you get a smoother cut (3) modify Z feed rate in your bit profile for different materials (4) modify router or spindle speed to alter chip size for best removal and to keep bit and work piece cool while cutting.

[Brady Watson]

Good...Looking much better.

-B

[Austin Shafer]

Thanks again for all your help guys!

[Brady Watson]

Austin,
Check out "Last Pass Allowance" in the VCP/Aspire help file in the program. Give this a try and see if it cleans up those waterline marks. I'd try .02-.03 to start.

This will cut your part 'big' that .02" and on the last pass, come in to the actual part size and shave off .02" from the edge at full depth, eliminating the waterline marks. The tab areas will still not be ideal, but the rest of the part should be cleaner. Try a little test part and see if it helps.

-B

[Austin Shafer]

I have never paid any attention to that! I have it ready for the next program. I will let everyone know after I run it and see how it does.

[shilala]

It's weird that that single flute is deflecting so much.
That'd take a lot of torque.
For sh1ts and giggles, I'd try taking thinner passes and release some of the torque and vibration Brady mentioned.
Then you may be able to be able to bring up your speed.
In the end, it may be a wash, but it's always best to know the limitations of your bits. Especially ones you use a lot.