So far none of my cuts on my mk3 have been accurate. I think I have narrowed it down to the x axis as it will not return to zero perfectly when i jog it and return to zero. I have tried most of the things suggested in the forum such as checking the pulley and belt adjustment. These adjustments did make it better but the problem is still there. The only abnormality I see is one of the drive roller bearings sticks out about 3mm further than all the others. It also seems all my circle cuts look like eggs. Any Ideas? Thanks Guys!

Eric

 

How have you gone about doing a calibration check? What software are you using? We need a little more information in order to give an opinion.

Edit: Looks like we posted up at the same time.

 

I used a yard stick on my x and y, calipers on my z. Maybe I should calibrate again since i messed with the x axis stepper. Speed does not seem to help, I have tried to slow it down the feed rate to 50 with the same results. What exactly is backlash?

I am using cnc usb.

 

Ok, I callibrated x, it was off a bit. Its dead on and repeatable. all other axis were spot on. I load a piece of foam, center it and punch a zero position. I then jog the x back and forth and comand back to zero, my zero changes very slightly to the lower right direction?

 

I cut another piece of foam, same skewing issue. The foam is moving on the grip rollers. It does not end up in the same place I clamped it down on. This happens even if im not cutting and just jogging the x axis. Im thinking one or both of the grip rollers may be bad. Any Ideas?

Eric

 

hawk flyer, I too have had a skewing issue from day one. I have never been able to get my machine to return to zero on the foam. I have talked to Mark a couple of times on the phone and he has no idea whats wrong.

If anyone else here has any idea what we can try that would be great. At this point, I'll try anything. :roll:

 

Yeah I have seen this problem pop up once in a while on the forum. From my limited experience with this machine my best guess is a slight warp or inconsistency in the x rollers. I completely removed my rollers and found that one of my endcaps is broken. I will ask Mark and Trish for a replacement quote. I think I will replace them both and try again. Ill post my results Craig, so you can decide if you might try the same.


Eric

 

I have always had the the new style of rollers. The only material that doesn't scew is Dallor Tree foam(with the paper on).

 

I also have the new rollers. Funny enough my skew is also less with dollar tree foam. Maybe because it's not as long as blue protection board.

Eric

 

Eric, that's good to know. I would like to see if you get your rollers fixed, it indeed reduces your skew.

 

It may not be your X-Axis, or the rollers. :questions: :think:

It could be a slight forward or backward movement in the tool holder.
I had some skewing in my X-Axis. After a lot of tracing things back and forth,
I found that the Z-Axis slide rollers were not clamped tight enough against their guide rods.
I tightened them up. That pretty much fixed the problem.

If you are using the cutting tool that came with your pp, make sure there is no
back and forth play in the bearings next to the chuck. That can be a gotcha as well.

Make sure that the cutting tool is clamped tight into the tool holder and there is no play.

Make sure that the tool holder attachment is also mounted properly to the Z-Axis slide.

Hope this helps.
GHB

 

Thanks Thunder Hawk for your feed back. My gantry is all tight. I can put a mark where the foam is on the pp table, then jog it back and forth a few times, go back to zero and foam has moved in relation to the line.

 

Hey Craig, due to obvious reasons I have not got a response from Mark, I can totally understand. So I took it on myself to repair my broken roller. I was able to hammer and epoxy it back together. A few swear words later it looked good as new. I then switched the two rollers arround. Ran a few tests and it looks like the skew has gotten much better. I tested it with the bit above the foam and not actually cutting. Surprisingly Depron showed the least amount of skew. Also positioning the foam at different points on the rollers will yield different results, look for the sweet spot. I still have a slight amount of skew, maybe 2mm or so, I think this is a good machine but I dont think it's a perfect machine by any means. I guess it will require some amount of tuning but for what we paid it's still the best deal out there. I hope you can try what I just described and it works for you! I know how frustrating this can be! Let me know what happens, hopefully we both get through this skewing issue, I will try to cut some depron and see what happens. :think:

Eric

 

I'm having problems with my X axis as well. I had problems with the pully not being solidly mounted to the stepper and it moving a bit but rocking it back and forth while tightening seems to have gotten it firmly seated now.

My circles are still showing signs of backlash but I havent been able to figure out how to correct it properly in the software.

 

Hey Helno, my kit came with the metal pulley and two set screws. I also used non-permanent locktite and have not had a problem with it coming loose yet. Now that I fixed my roller I will try a circle again, If I cant fix it with backlash ill just incorporate ovals into all my designs! Easy fix.

Eric

 

My two cents... Wavy fan fold moves in the rollers and will not return to zero very well. Calibrating with a ruler is not accurate. The cheapest most accurate way to do it is to use a pair of dial calipers. I have had good luck with this method. But using a dial indicator is best.
Caliberate several time back to back till the caliberation becomes consistent.
I had some slight accuracy issues but after carefully making sure all the guild rollers were tight, belt tensions were right and the machine was well caliberated, my machine can run 500 lines of code and return to zero within roughly .020.
Just keep working with the machine and you will get it cutting the way you want it.

 

I did calibrate mine with digital calipers using a nice long piece of plywood. I measured the backlash and after entering the value my circles got worse so I am going to wait a bit and try again.