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  #11  
Old 05-21-2020, 11:31 AM
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Gary Campbell Gary Campbell is offline
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This could also be as simple as linear bearings that are binding on one side at a certain place in their travel. As one side is held back from resistance, the other advances due to the pivot action of the center drive. It is highly unlikely that that gantry is racking due to misalignment, resistance is much more likely.

Set the gantry cross slide on blocks and move the bearings thru their full range of motion by hand. It is usually obvious if there is a mechanical bind. Also, make sure all the bolts holding the linear bearings and those between the gantry cross slide and the side plates are all tightened properly.
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  #12  
Old 05-21-2020, 03:20 PM
Guylaro Guylaro is offline
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Thank you for the replies. When I read Russell’s post I understood what he was saying and agreed with him. I think this machine would be way more accurate with a motor at each side of the gantry for the Y axis instead of just one in the middle and bearings on each side. I’m not sure I understand what you mean Gary by putting the cross slide on blocks. I know I have powered the machine all off and moved the Y axis by hand from one end to the other to see if I could feel a spot where there is resistance but all is nice and tight and smooth from one end to the other. I’ve checked the machine several times now with tech support to make sure nothing is loose. I’m at a loss. I’m kind of starting to think like Russell more less said that I just didn’t spend enough money. Am I expecting too much? Is everyone else’s Stinger I the same but they’ve never noticed? I’m at a loss. I might post something else here with pics that I sent to tech support to show what I’m seeing on my machine. You guys can give me your opinion on what you think. -Guy
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  #13  
Old 05-21-2020, 10:26 PM
Guylaro Guylaro is offline
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Here I have 2 machinists rulers that are identical. When I lay 1 over the other they are exactly the same. I place one on one side and one on the other side of the CNC bed as you can see in one of the pics. The bottom side of the pictures is the home side of the CNC machine. I zero the CNC on the 1" mark of one of the rulers (it doesn't matter which one, I've tried both and the outcome is the same). After I zero the machine I use my keypad and send the spindle to the other side of the X axis. I manually place the other rulers 1" mark directly under the bit point. So now I can send my spindle on the X axis from one side to the other and the point of the bit is directly over the 1" mark on each rule. Now using the computer I enter Y19 to send the Y axis directly over the 20" mark on each rule. In the pics you can see that on one side of the CNC it does exactly what its supposed to do but when I use the keypad to move the spindle on the X axis to the other side you can see that it is over the 20" mark by 1/16". In the last pic I drew the outcome of what happens. I hope this is clear enough for you to understand what I am doing. If I had longer rulers I could show you that when the spindle gets towards the upper end of the Y axis towards the 48" mark the error is just about gone. This error is greatest towards the centre of the Y axis and on one side. I'm showing you the 20" mark on the bed because that is where it is the worst. Its very bizarre. Its been this way from factory because the T slots that were cut in the phenolic top at factory are not parallel to each other in the centre of the table because of this error thats been there since it was born. Please don't ask me to check if this or that is loose. :)) I've been through the checking for looseness on this machine several times now. :)) The machine has hardly done any work since this is just a hobby. I'd just like others who have Stinger I to check if their machines happen to do this also. I'm working with tech support on this also. Thank you. -Guy
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  #14  
Old 05-22-2020, 08:49 AM
Ken Rychlik Ken Rychlik is offline
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If you have someone pull front to back on the gantry on one side while you watch the ruler, you will probably see that the gantry will rock back and forth a little. Probably as much or more than the issue you are noticing. I had a different center drive machine and replaced it with a dual drive machine for the same purpose. It is worse when actually cutting and under a load. As for the factory top having square cuts, I would think they cut those on a different machine, but you can ask.

If you do you test in the center of the machine, it should be the best there being over the drive.

I think the smallest they make with dual drive is the stinger 3x4

Take care. Ken
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  #15  
Old 05-23-2020, 09:17 PM
Guylaro Guylaro is offline
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Hi Ken. No the gantry does not rock back and forth at all. It’s really all nice and tight but not too tight to have any racking or binding anywhere. -Guy
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  #16  
Old 05-24-2020, 09:31 AM
Ken Rychlik Ken Rychlik is offline
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That's a good sign if it's tight. Have you cut any parts and measured that they come out as expected?
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