Controller not following G Code?

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Controller not following G Code?

Postby xclimberx » Sat Jan 28, 2012 5:42 pm

Hi all,
I'm new to the forums and need some help.

I have a Shark Pro, running Aspire 3.5 and have a tool path designed to cut holes in the bed or spoil board of the router to allow for fastening work down.
The tool path is set to do profile cuts, inside the line, conventional cutting. I am using 1/4" end mill to cut 5/16" holes in the table. When i get to the 13th hole and the cut of the diameter is complete the gantry moves Y+ backward approx. 0.125" as the Z axis is moving Z+ to the safe distance. Now the hole is oblong. What is going on?

I'm not using a drill pattern as a 5/16" drill will not fit in the chuck of the router. So I'm profile cutting the holes.

I have done the following...
1) I've re-calculated the tool path multiple times, and reloaded the tool path multiple times.
2) I've re-run the tool path and now have hole 14 oblong.
3) I've read through the G Code and looked at the code and there is NO code moving the gantry in the Y+ position.
4) I've run the firmware updater.
5) I have the latest Control Panel SW 1.5.0.22.exe
6) I have loaded the latest Post Processors CNCShark-USB_NewArcs_inch.pp and the others.

Anyone have any ideas what is going on? I can't keep cutting oblong holes in my table. It's a simple circle drawn and duplicated using the array tool in Aspire.
Rich
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Re: Controller not following G Code?

Postby tonydude » Sat Jan 28, 2012 10:34 pm

Can you upload the aspire file so someone can look at it?
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Re: Controller not following G Code?

Postby Buc » Sat Jan 28, 2012 10:57 pm

Rich,

Calculate your tool paths by creating pocket toolpaths. (Not profile toolpaths).

Buc
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Re: Controller not following G Code?

Postby xclimberx » Sun Jan 29, 2012 1:11 pm

Tony,
Here's the Aspire file and the G Code. On the Aspire file ignore the two holes farthest left. I'm focusing on just the array at this point.

I've used an oririn offset of X -2.0, Y -2.0 because the spoil board on the shark is bigger than the functioning tool area. When I set ZERO on the Shark I use a position of X 2.0, Y 2.0 and Z 0.0.

I've added comments into the GCode where the oblong holes are ocurring and I do not see a command for the gantry to move Y+.

Thanks in advance for taking a look.

Rich
Attachments
Spoil Board GCode.zip
Spoil Board crv & GCode files
(460.73 KiB) Downloaded 195 times
Last edited by xclimberx on Sun Jan 29, 2012 1:19 pm, edited 2 times in total.
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Re: Controller not following G Code?

Postby xclimberx » Sun Jan 29, 2012 1:16 pm

Buc,
Thanks for chiming in too! This is really quite simple and I haven't even started to carve yet. :?

I'm the curious type so I'm going to dig into everything. Why do you suggest using pockets? Past experience or did I miss something in the yards of documentatin that Vectric supplies. It is very good documentation by the way and I may not understand how CNC is MEANT to opperate and I may be miss-using a function.

Willing to learn...

Rich
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Re: Controller not following G Code?

Postby Buc » Mon Jan 30, 2012 2:54 pm

Rich,

I pocket cut my because I choose to do it that way. There is nothing wrong with profiling. I added [RAMPS] to your tool path. Checked the add ramps box, and clicked on the radio button for (SPIRAL). Added this to your Aspire file. Profile_Ramps_Spiral. Give it a try. I reccommend using a scrap piece to test it out first. You may have to play with the hole dia. to get the desired finished hole size.

Buc
Attachments
Drill path spoil board.zip
(985.59 KiB) Downloaded 213 times
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Re: Controller not following G Code?

Postby xclimberx » Tue Jan 31, 2012 8:23 pm

Talked to the guys at Nextwave yesterday.

After a long discussion on many things we decided that I'd take a look at the Y lead screwa and check the connector set screws to make sure they were tight.
They are tight.

I also quized them on a topic I saw here in the forums about grounding. I prepared a grounding harnes for the CNC. All 3 steppers are grounded back to the power supply now. We weren't certain that this is causing anything or not.

I've got the table back on and leveled again. Tomorrow I'll give the machine a run.

Buc had modified my tool path. I've examined it and I will do two things tomorrow.
1) run the old tool path on a scrap board.
2) run the Buc's modified tool path on on a board as well.

I'll report back tomorrow.
Rich
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Re: Controller not following G Code?

Postby xclimberx » Wed Feb 15, 2012 1:11 pm

Well, my report back is delayed by a few days as the trial cutting and troubleshooting took a little longer than I imagined.

The problem:
While using my Shark Pro to cut/machine holes in the bed for a hold down system I experienced oblong holes. I thought the gantry was moving in the Y+ direction causing the holes to be 1/8" out of round.

The cause:
This was discovered by mere coincidence. In a few runs of the last test cuts, I was cutting holes using a pocketing tool path and then back to the profile cutting tool path. Both resulted in the same oblong holes.
I was standing alongside my machine viewing the cutting down through the top of the Kent CNC dust shoe I have mounted on my machine. I glanced up as the Z Axis was making it’s plunge and noticed that the Z Axis was rotating on the two bearing rods that bridge between the gantry upright arms.
The dust shoe bristles are stiff enough to cause deflection in the Z Axis and rotate the axis alignment so that the end mill bit is cutting at an angle and not perpendicular to the table leaving the hole oblong.

The solution:
1.This is yet to be discovered. I’ve got a call into Kent CNC to see if there is a softer bristle available for the dust shoe.
2.I’m going to contact Nextwave to see if the Pro Plus gantry risers are made of a different material.

I think the Shark Pro is made of HDPE material which is a soft plastic type material. I believe the Shark Pro Plus is made of UHDPE which is a harder material and may resist the twisting effect of the Z Axis on the bearing rods.
I machined other holes in a scrap piece of wood without the dust shoe on the machine and the holes were as designed. ROUND.
Rich
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Re: Controller not following G Code?

Postby rungemach » Wed Feb 15, 2012 5:53 pm

Hello Rich

Since you covered the bases of loose set screws on the couplers etc, I think you have run into a design issue with the non-HD large sharks. The flex in the bearing rods in the gantry are a known issue which has been addressed in the design of the HD model. I have an older shark pro and changed the bearing rods to the "supported" type a long time ago. The plastic gantry side plates are not really much of the problem, nor is the construction of the z axis itself. The main culprit is the long plain unsupported y axis bearing rods and how they are mechanically loaded when the router is cutting. If you change to a supported type bearing, the great majority of the flexing will go away, with a little more to be gained by strengthening the z axis itself. The y axis has a similar issue, but not quite as pronounced as the x axis due to how the loads are applied.(IMHO). The think you can do in the meantime is take light cuts at moderate speeds to lessen the cutting force on the bit, and be sure any dust collection system you are using is not loading the gantry due to the weight or pull of the dust hose as well as the brush.

I recently redid the retrofit to move the whole z axis up a little rather than have it centered between the bearing rods. I was able to machine the required 1/2 inch aluminum plates on the reinforced shark.(taking shallow cuts, not the full half inch at once) My machine retains the original plastic gantry sides although the z axis now has an aluminum skeleton as part of the refit process. Attached is a picture of the new aluminum z axis skeleton, as well as a picture of the machine.

There has been talk on the group here about whether a retrofit of some kind may be offered for the non-HD machines. The last I remember was that the factory is busy with other projects like the 4th axis. It would be good to get an update from NWA on this issue.
Attachments
shark z frame front.jpg
shark retrofit z axis skeleton
shark z right asm.jpg
z axis and x axis bearing rods
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Re: Controller not following G Code?

Postby xclimberx » Wed Feb 15, 2012 6:44 pm

Hi Rungemach,

WOW! That is exactly what I am battleing. I''ve been taking small shallow cuts. It helps but the weakness of the Y axis bearinig rods is what I struggle with. I'm going to have to work on the dust shoe some to reduce the bristles or see if I can get a smaller bristle diameter to put into the dust shoe. Running without a shoe is really messy. I'm not in for the mod to the Y axis at this time. It seems you've found your solution. I may contact you in the future about the files to make this mod.

Just out of couriosity, what did hardware for the mod cost? Do you think the skeleton for the Z could be machined out of the same plastic the Shark is made of?

Rich
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