help with new machine setup

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Jtucker7000
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help with new machine setup

Post by Jtucker7000 »

I recently bought an old DHC plasmacam table and I'm fitting new motors and mach4 to it only using the gantry, gears, and timing pulleys. I did this previously with the 98z model and was successful, so with a newer version I figured this would have been easy but I'm having issues getting parts to cut the correct size and any arc or circle is shaky. I assume it would be a mechanical issue so I've taken apart and rechecked every set screw, as well as apply loctite. The follower bearings are all tight and seem in good condition. The gear rack looks fine and the spur gears I believe are pressed on same as the larger timing pulley. I drew a line on the shaft and gears for those and don't see any signs of them moving, I see nothing out of the ordinary. This is my first time using clearpath servos so I'm not sure if they could be causing problems. The Y-axis moves really smooth but it looks like the X-axis sort of stutters as its cutting an arc so I assume what ever is causing that is the issue, just not sure if its mechanical, motor tuning, or something else. I went through the tuning setup for each of the motors initially they completed fine but after tightening belts and tension the larger axis that I suspect is the issue doesn't always complete tuning so I intend to contact clearpath tomorrow to see if there is a sizing issue, but the motors seem to move the gantry with ease at speeds as high as 600 ipm. jogging seem smooth its just when running a file or anything at lower speeds it doesnt move smooth.

I've placed the easyscribe in the torch which shows really fine detail and ran small squares and circles I've tried different acceleration numbers as low as 10 all the way to 150 and regardless I get nearly identical results any where on the table. I usually set acceleration at 35 and the velocity at 350. I spent about 16 hours tweaking things and I'm just at a loss to what is the cause. I've tried turning on and off CV feed rate, using exact stop, Mach4 is setup with Arc Center mode and distance mode as absolute. Squares or rectangles look near perfect but anything with a curve is shaky or deformed.

I've set the steps per inch by measuring a 2"x2" square and then using the step calculator. I get perfect results on a 2x2" square but if I cut something longer like 20" Im seeing the x axis be off by and 1/8" and the y axis by 1/16" but I don't see any out of position warnings from clearpath, Its all very strange.

Below is the motor and gear combinations I have, I've never understood how to calculate the resolution of the machine. The current steps per inch I'm using are around 848 I don't have the exact number in front of me

X - axis
clear path CPM-SDSK-2321S-RQN 492oz/in peak torque
800 pulses per revolution (I asked clearpath earlier about this and they said the encoder is 12,800 counts per revolution but has a commandable resolution of 800 and changing the resolution wouldn't increase precision.
Motor Timing Pulley 15 teeth
Larger Timing pulley 60 teeth
pinion gear
diameter - 1.296
48 teeth
Hicon 7766 motion controller, Mach4, Neuron THC

That's as much relevant information I can think of and I'm hoping someone way smarter than me has an easy solution or at least something different to try.
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Re: help with new machine setup

Post by adbuch »

I would be interested to see some photos of your setup.
Thanks,
David
Jtucker7000
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Re: help with new machine setup

Post by Jtucker7000 »

Here’s some pictures of the table and some pictures showing the problems

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Re: help with new machine setup

Post by adbuch »

My suggestion would be to install a sharpie pen holder to your torch and program your table to draw some large squares and perhaps some large circles on either your metal of some paper taped down to the metal sheet on the table. I would start with running at very slow speeds and watch your gantry and carriage motion very closely for any signs of binding or other unusual motion. Post some photos of your large squares and circles showing the orientation on your table (x and y directions) so we can get a better sense of your actual situation.
David
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Re: help with new machine setup

Post by acourtjester »

From the image attached you have a binding or slippage in the movement of one axis. This is clear in the fact that where a axis changes direction where the arrows are pointing. When making a circle each of the 2 axis change direction twice, where this happens you get a bind/slippage in the drive assembly. Something in the drive assembly is slipping that is causing your problem. It can be the motor pulley or another pulley or gear. with the power on the motors push and pull against the X with your hand to see if it moves slightly. Then do the same with the Y axis, one will move and that is the one to check out. Using a sharpie as David suggested will show this, just place the tip on paper and do like I describe above and the sharpie will show a short mark. Easyscribe is great but has resistance to movement a sharpie does not. Be sure the circle is correctly drawn as sometimes they can be short arcs not a continuous line as some software make them.
bad circle A.jpg

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Re: help with new machine setup

Post by adbuch »

I agree with Tom. This is most likely something binding up or slipping - belt, gear, pulley, etc. If you run your test program as I described above using a sharpie running at slow speed this will most likely be helpful in locating the exact source of our problem.
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Re: help with new machine setup

Post by weldguy »

Looking at your circle i am with these guys. My guess is that a setscrew that attaches one of the gears to a shaft is loose and when the motor changes direction the shaft turns inside the gear until the loose setscrew contacts the other side of the flat spot on the gear shaft and you loose that small amount of motion. Be sure all setscrews are tight on the flats of the shafts. I like to use Loctite 243 also.
Also it appears as though your pierce delay is too long and your putting a lot of heat into those pierce locations. I would use lead ins and shorten your pierce delay so it is no longer than needed to pierce the material and this will make your consumables last longer also.
Jtucker7000
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Re: help with new machine setup

Post by Jtucker7000 »

My first thought Is always mechanical as well. Reading post over the years it seems to be a common occurance. All the gears are pressed onto the shafts with the exception of the motors. They have 2 set screws and I removed those with heat and see no sign of slipping. The shafts are completely round so no flat side. The pressed gears and pulleys i simply made a mark on the gear itself and the shaft and kept checking to see if it appeared to slip. The table uses cam follower bearings to ride on and those all seem to move freely but maybe at higher speeds they bind? I’ve never known those to fail that way usually they just start to squeak. I spoke with clear path and they said all the same things about mechanical binding or slipping, but also suggested that occasionally the auto tune can’t produce a smooth motion in all cases and manual tuning may be necessary. I plan to have them manually tune the motors later this week and see if results improve. I’m trying to rig up a pen holder as well as suggested. I’ve tried in the past and usually feel what I’ve fashioned is never sturdy enough to not be an additional wobbly component. As for the cutting setting I had all lead ins turned off because I was using the scribe and a made a handful cuts at really low speeds with the torch so I didn’t bother to mess with THC I was mainly checking if the cut looked them same without the scribe just in case it dragging was causing issues. I appreciate all the help so far, I’m sure it will some mechanical component that I’m just not seeing.
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Re: help with new machine setup

Post by weldguy »

Thats very strange but it sounds like you have a good handle on making sure nothings slipping. I would be surprised if it was motor tuning and definitely curious to know what the issue was.
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Re: help with new machine setup

Post by Wendle »

Not sure if this may help but. do you have a ramp speed adjustment??
In other words when your torch comes to a change of direction it slows down and takes torch wobble out.
If so try slowing it down some. This is different than cutting speed.
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Re: help with new machine setup

Post by acourtjester »

Jtucker to check the bearing disconnect to motor wiring from the controller and move the table along the X and Y axis at a fair speed and distance. the should move smoothly. The reason for disconnecting the motor wiring is they have dynamic braking due to the Permanent Magnet in the motor and they will stop you from moving them then release to move again.
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Re: help with new machine setup

Post by adbuch »

acourtjester wrote: Wed Jun 15, 2022 4:40 pm Jtucker to check the bearing disconnect to motor wiring from the controller and move the table along the X and Y axis at a fair speed and distance. the should move smoothly. The reason for disconnecting the motor wiring is they have dynamic braking due to the Permanent Magnet in the motor and they will stop you from moving them then release to move again.
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