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Circles not round...
#1
OK, so when I print any type of a cylinder, either just tiny 5mm hole or a 10mmx10mm cylinder they always come out just a little oval. For instance a part I was printing was supposed to be 14mm in diameter but ended up 13.8x14.2 oval which did not fit the tolerances. With this issue I can't hope to print any working gears.

Since, unlike a RepRap, we're limited at our ability to fine-tune the system I'm at a loss of where to begin looking. XYZ doesn't offer any info like belt tension or even maintenance info like how, when, and with what to grease the rods and gears.

Any thoughts to a fix for the ovals and maintenance tips?
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#2
Scott, given that there is no way for us to adjust the calibration of the printer due to its closed firmware the only way would be to modify the input file.

You could try to scale the STL file by the measured factors in x and y dimensions:
For example 14/13.8 = scale up 101.45%

You can do that in software like Repetier Host or Netfabb Basic.
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#3
Check all the belts. One is loose. From what I have seen their calibration is spot on.

More:Oliver is correct. As of now we can not adjust the firmware. You could hack the shape with re-size, but *if* I am correct and the firmware is OK, then the circle error you are experiencing most likely occurs during direction transitions - which is caused by incorrect backlash (loose belts.) Correcting backlash with resize is going to throw the entire print off...

BTW, My white idler wheel in the left carriage seems a bit loose. It doesnt seem to efffect anything yet, but I do imagine I'm going to need a new wheel/bearing soon. (FWIW, I have aprox 200 hours on the printer.)

Kieth
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#4
I was having a very similar issue with my printer when printing small circles. I found that the motor that is mounted in the top right side of the metal frame was not tight enough and the belt was somewhat slack. I removed the right plastic panel, used a torx screwdriver to loosen the screws holding the motor mount and tighten the belt. Now it prints perfect circles. The before and after is very striking in the difference. You must check that all of the belts are tight and fix them if there is any slack. Hope this helps!
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#5
Quote:I was having a very similar issue with my printer when printing small circles. I found that the motor that is mounted in the top right side of the metal frame was not tight enough and the belt was somewhat slack. I removed the right plastic panel, used a torx screwdriver to loosen the screws holding the motor mount and tighten the belt. Now it prints perfect circles. The before and after is very striking in the difference. You must check that all of the belts are tight and fix them if there is any slack. Hope this helps!

I've had these issues as well. I've checked/adjusted the tension for all the belts (X belt as shown in one of the XYZ Videos, and the Y belts by taking off the plastic shroud on both sides), but I'll have to check motor mounts next. Below is a before and after.

[Image: image.jpg]
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#6
I have the same issue of having small circles being slightly oval. I was trying to print a 1.2cm diameter rod, the print turned out to be 1.22cm on long axis and 1.18cm on short axis, it just won't fit into the 1.2cm diameter hole. I called the tech support today, they said the printer doesn't have the resolution of printing circle less than 2cm in diameter without distortion. And they would not recommend adjusting the belt if the oval shape only show up on circles less than 2cm in diameter. That's shocking because a 1.2cm circle isn't that small of a circle by any standard. Can anyone help confirm that this printer can't print a round circle of less than 2cm in diameter?
By the way, my x-axis belt tension seems to be less tight than the y-axis belt. I did try to adjust the x-axis belt per xyzprinting video, but there's improvement.
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#7
On the LH side carriage there is a small white wheel that the belt wraps around. Make sure that wheel is not moving up and down and the extruder moves left and right. The printer should be able to do the print you are asking - as a last resort someone else mentioned you could scale the print (within the STL) slightly X or slightly Y as needed to correct for the error.

Ive printed many thing with
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#8
Quote:I called the tech support today, they said the printer doesn't have the resolution of printing circle less than 2cm in diameter without distortion.

TJ, can you please post the tech support number? I thought there was only email support. Thanks.
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#9
Quote: I called the tech support today, they said the printer doesn't have the resolution of printing circle less than 2cm in diameter without distortion. And they would not recommend adjusting the belt if the oval shape only show up on circles less than 2cm in diameter. Can anyone help confirm that this printer can't print a round circle of less than 2cm in diameter?

I think the truth is it can't print a truly round circle at all, it's just that the limitations of the machine start to show up at smaller size. Oliver alluded to this in his message above that since we can't modify the firmware our precision is limited to the mechanics.

I found a link to another forum that details some work done on a printer of a similar design (2 Y-axis belts). [url=http://www.soliforum.com/topic/3621/another-yaxis-calibration/[/url] I noticed last night that my y-axis belts are *not* the same tension on both sides, the one on the right takes 110g more force to deflect than the one on the right, something the posters in the above forum are saying could be an issue.
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#10
The y axis is easy to get the belts even. After tightening all the belts my eye-gauge says my circles are *almost* perfect. The X is *slightly* off on the RH side of the print. This is because the white idler gear/roller is actually moving up/down slightly as the extruder moves left/right. when the extruder moves to the right the slop doesnt matter because the belt pulls directly from the stepper to the extruder. When moving left the stepper pulls the white roller which moves to take up slack before transfer to the extruder moves the extruder. I suspect fixing this will resolve the issue, but frankly it is so minor that Im not concerned.

Can others check the roller for what I am describing? Its easier to see if looking the the idler and slowly moving the extruder left/right by hand.

Kieth
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#11
Quote:Can others check the roller for what I am describing? Its easier to see if looking the the idler and slowly moving the extruder left/right by hand.
Kieth

Can you snap a picture of the roller you are talking about so that I can check?

Thanks!
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#12
SKEstes
You're right , the cicrcle can never be a perfect circle because it's approximated by a polygon. The smaller the circle, the less round it gets. When you factor in the belt slacks, the smaller circles will get more distorted than the bigger ones. I can understand that the circle can get distorted if you try to print a 5mm diameter circle, but it's ridiculous a 12mm diameter circle is visually oval. I just don't buy it when I was told by xyzprinting that their machine doesn't have the precision to print a visually undistorted circle less than 2cm in diameter. If xyzprinting think a distorted circle less than 2cm in diameter is a norm, then they have a serious quality control problem on all their machines. Or maybe this problem is so prevalent that they just don't want to deal with it.
I don't have anything to test the belt tension. But when I press the belt with my finger, I can tell my x-axis belt is less tight than both y-axis belts. Visually I can't tell that x-axis belt is loose. Both y-axis belts seem to be equally tensioned. Does that mean all my belts are properly tensioned? I did the belt tension adjust on x-axis as instructed by xyzprinting video, the x-axis belt is stll less tight than the y-axis belt. They use a spring to set the tension on the x-axis belt, I can't tighten the belt any further than what's being pre-set by the spring. I think I will loosen th screws on the motor to see if I can tighten the belt further.

Aside to Kieth,
Thanks for your suggestion. I moved the extruder left and right, the idler wheel appeared to be pretty stationary, I don't see it bobbing up and down. Today I printed a 30mm square, it turned out to be 30.32mm x 30.14mm. So I scaled it in the CAD per your suggestion, the square showed 30.06mm x 30.06mm . And I thought the scaling would solve the distored circle problem as well, but it is still distorted slightly, there is some improvement though. The funny thing is the oval's long axis is at approximately 135 degrees measured from positive x-axis, does that mean my printer has slacks in both x and y axes?

To Chris,
The tech support I called is in Taiwan. I'm not sure if you have customer service number where you at?

I appreciate you guys help!!
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#13
Quote:I just don't buy it when I was told by xyzprinting that their machine doesn't have the precision to print a visually undistorted circle less than 2cm in diameter. If xyzprinting think a distorted circle less than 2cm in diameter is a norm, then they have a serious quality control problem on all their machines. Or maybe this problem is so prevalent that they just don't want to deal with it.

I suspect you're right. I was up late last night with weights and a spring scale setting each belt to where there was 400g of downeard force when the top part of the belt just began to touch the bottom part. I accomplished this, in part, by replacing all of the "plastic biting" screws with 3mm bolts, washers, lock washers, and nuts. I'm still getting ovals but they're a little different this time.

I think that since the hardware is limited in its ability to be calibrated and the firmware is closed without any optional modifiers the only way ahead is to replace the main electronics with an open source solution (RAMPs, RAMBO, etc) that allows for modifiers to compensate for hardware issues.

This printer is designed to be mass-produced, not to be precision calibrated.
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#14
Quote:The y axis is easy to get the belts even. After tightening all the belts my eye-gauge says my circles are *almost* perfect. The X is *slightly* off on the RH side of the print. This is because the white idler gear/roller is actually moving up/down slightly as the extruder moves left/right. when the extruder moves to the right the slop doesnt matter because the belt pulls directly from the stepper to the extruder. When moving left the stepper pulls the white roller which moves to take up slack before transfer to the extruder moves the extruder. I suspect fixing this will resolve the issue, but frankly it is so minor that Im not concerned.

Can others check the roller for what I am describing? Its easier to see if looking the the idler and slowly moving the extruder left/right by hand.

Kieth

The idler is attached to the plastic bracket that holds the tension spring so you might check to see if the set screw that is supposed to keep that bracket from moving. The tapping screw that XYZ is using to hold plastic parts in place can easily strip out allowing the bracket to slip little. If you're brave and have a steady hand you can replace that screw with an M3 bolt, a lock washer and a nut.
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#15
SKEstes wrote:

I think that since the hardware is limited in its ability to be calibrated and the firmware is closed without any optional modifiers the only way ahead is to replace the main electronics with an open source solution (RAMPs, RAMBO, etc) that allows for modifiers to compensate for hardware issues.

This printer is designed to be mass-produced, not to be precision calibrated.


I agree that you can't have high hope for this printer to be precison calibrated, it is built to a price point and targeted at people who's less technically inclined and just wants a turn key solution. And you're right, the way the printer is built just makes fine tuning so much more difficult. I think I'm going to give up on fiddling with the belt tension. Replacing the controller with open source solution to compensate for hardware error is a possible solution but it also means major modification and more money. Scaling the print in CAD requires no modification to printer and its free. I will play with the CAD and see how much improvement it will bring.
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#16
Since the Da Vinci is a modified copy of the Solidoodle I started looking solutions for that unit.

Step 5 of the Solidoodle adjustment guide mentions this:

"Using your hand, lift the y motor enough to take the short loop of belt off the pulley attached to the motor. This belt is the source of most trouble with printing circles. If this is the only belt you wish to adjust, you can skip to step 11."

The DV and the SD share this design characteristic so I'm going to make sure the drive belt is tight and at a 90 degree angle to the carriage belt.
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#17
This is exactly what I did and it seemed to correct much of the oval-ness of the small circles.
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#18
Hi I had the same issue when I first started the printer, I started by checking the mechanics and found that the Y axis belts were not in line i.e. the X axis was not running parallel to the bed, in my unit the right hand belt was two teeth out of align with the left hand belt this is easy to check just lift the top door and look down on the X axis and see if it is parallel with the lines in the heated bed. to correct this I removed the right hand cover released the sprung idler pulley and moved the belt round two teeth I now have round circles down to 2mm / 3mm and this has also given me square prints not parallelograms!
I hope this helps
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#19
For what its worth, i had oval circles aswell. i found out that the screw that is responsible for holding the white X-axes belt wheel was not tightned at all, i pushed it back until the beld had the same tention as the Y axes belts (pushed it back far enough so that the spring determents the tention) and put a washer around the screw and secured it. the printer head is moving much better now and the circles are once again, circles.
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#20
Quote:For what its worth, i had oval circles aswell. i found out that the screw that is responsible for holding the white X-axes belt wheel was not tightned at all, i pushed it back until the beld had the same tention as the Y axes belts (pushed it back far enough so that the spring determents the tention) and put a washer around the screw and secured it. the printer head is moving much better now and the circles are once again, circles.

My Da Vinci developed oval circles the other day. I checked all the belts and they seemed tight but I went ahead and tightened them anyway.
The one that made the most difference was the small one in the top right corner attached to the stepper motor.
My X axis belt seems tight enough but I can't tighten the screw as the thread is worn but my circles are good anyway.
Is that screw really necessary ?
Davinci 1.0 with repetier 0.92 & E3D hotend
Slicer - Simplify3d 


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