Starting spot makes bit sized indent

[DannaT]

Hey everyone,
I have some issues I was wondering if anyone could help me with.

Firstly,
The starting spot makes bit sized indent into the material of the item I am cutting. It doesn't happen on all the items cut but it seems to be getting worse. I am not sure if it because my collet need replacing but I am in the process of getting a new one.

Secondly,
After I have Cut my items I sometimes notice that some corners(usually few if any, doesn't always happen) that are supposed to be sharp are kind of rounded, like the turn for the cut stuttered.
I am thinking it might be connected to the first issue and I hope a new collet will fix it.
Will update when I get the part in.

[pkirby]

For your first issue, try either a ramped start or a lead in from the side. That should take care of the bit indention. I'm not sure about a solution for your second issue.

[garyc]

Danna....
Assuming that your machine is a PRS model. If so, then both your symptoms can be attributed to mechanical adjustments. Look in the manual for adjusting the X, Y and Z pinion to rack (motors) and make sure that the pinion grub screws are tight also.

The lower V rollers on the YZ car as well as those on the Z could also be out of adjustment.

If a PRT, then the Z rollers would be the first suspect, second the pinion grub screws.

[DannaT]

I finally did another job and I am still having issues with the bit making rounded corners where it started the cut and goes down.


For your first issue, try either a ramped start or a lead in from the side. That should take care of the bit indention. I'm not sure about a solution for your second issue.

I have not tried this yet but I will be cutting soon so I will try this on the next cut. Since it is the started corner that is also the problem I am not sure if it will help but will try none the less.


Danna....
Assuming that your machine is a PRS model. If so, then both your symptoms can be attributed to mechanical adjustments. Look in the manual for adjusting the X, Y and Z pinion to rack (motors) and make sure that the pinion grub screws are tight also.

The lower V rollers on the YZ car as well as those on the Z could also be out of adjustment.

If a PRT, then the Z rollers would be the first suspect, second the pinion grub screws.

Sorry for not clarifying, I have a PRS Standard shop bot.
I have tightened both X and Y pinions to the rack and the grub screws on them as well. I have been doing this for awhile so I didn't think the problem was that. I have not tightened or even checked the Z motor in fear of messing it up. It came attached with the shop bot So I haven't touched it.
The rollers on the YV car are on with good pressure so I think I am good there.
Just to clarify my problem I have a picture added in attachments. The image is of the worst cuts in my tool path jobs but I sent it to give you an idea of what the problem is.
I don't have the vacuum so I use clamps instead. I am thinking the material gets loose as the shop but cuts but I still get little indents in the corners even when the shop bot does the first cut into new material.
I need some advice on how to fix this.
Thanks again,
DannaT

[Brady Watson]

Put on those safety goggles and get in there and SEE what is going on. You should be able to tell immediately if the material is lifting or moving.

If the material is stable, drop & re-seat the X&Y motors like Gary posted. It doesn't matter if you just did them an hour ago or if you are a hard boiled SB veteran. Do it again. I can't tell you how many times this has happened over the years where people were 1000% sure...and then it turns out the pinion grub screws were loose OR the motors simply are not fully engaged in the racks. Try it again & take NOTHING for granted!

The other thing could be that you are running the tool too fast. Pull down the speeds to 2,1 and re-cut. Still doing it? If no, then you can lower your speed or lower your Slow Corner Speed in VR to cushion direction changes like a corner. Pull it down to 40 and see if that helps.

Then of course, close SB3, Goto->Program Files/ShopBot/Diagnostics and run the SpeedTest.exe. If your number is lower than 70%, then you need a self-powered USB hub in there...Search this board - plenty of info on doing this.

-B

[jerry_stanek]

check to see if yours has 2 grub screws one on top of the other.

[twelchPTM]

most of these guys know alot mor e then me but looking at the pic you posted its seems possible that your corners are getting clogged up with chips and pushing the bit (or the entire axis)off to the side. I had a simillar issue where even though my xy feed rate was fine it was to fast to allow proper evacuation.

[DannaT]

I just ran off one more test job and it all looks good.
What I did:

I changed my toolpath from .25 pass depth to .125 and added a ramp like Paul suggested the other night. Worked like a charm.
My thoughts are; I think the material is to hard for my settings so an added ramp and change in pass depth helps keep it smooth.
When I removed the material it was a bit hot.
Maybe the friction caused the tool to warp while cutting?
Your thoughts would be appreciated.
Thanks,
DannaT