Shopbot PRT standard Zeroing

[KetchikanSignpro]

Hey all,

I'm having problems with my Shop-bot PRT Standard. Occasionally my cart will shimmy or shudder and it drags my zeroing off. iv oiled my roller bearings cleaned the tracks, restarted the control box. I slowed my speed to see if that made a difference , it didn't help. I'm carving into 2" HDU with a new bit with minimal drag against the tool. Does anyone have any recommendations as to why my machine might be doing this? The shop-bot tech that i spoke to was unhelpful in diagnosing my problem. he did say the drive motors them self are nearly bullet proof so i'm not sure where to turn.

Thanks

Trevor

 

[Techman]

sound like dropped steps.

To much pressure on the cutter?

What is the ipm and spindle speed?

Bullet proof does not mean they will lose their steps. They mean the motors are strong euf to take a beating power wise. Faster speeds means lower torque. That will cause missed steps.

 

[KetchikanSignpro]

sound like dropped steps.

To much pressure on the cutter?

What is the ipm and spindle speed?

Bullet proof does not mean they will lose their steps. They mean the motors are strong euf to take a beating power wise. Faster speeds means lower torque. That will cause missed steps.

My first opinion is that is the motors as well but i'm just unsure as to what drive motor it really is. I can hardly reproduce the problem it happens at vary random times.

I don't think i'm running to much pressure against the cutter it sounds and looks like its cutting at a decent pace, i even slowed down my feed rate to be sure of this, I'm currently at 200 ipm and 20k spindle speed.

Thanks

Trevor

 

[3dsignco]

I was having the same problem with mine.. Did you recently do an update or install a new version of their SB program.. I had to go back and install an earlier version of the SB program and that fixed my issues.. I think they screwed up some of the codes on the newer software versions and it was not keeping the proper timing on the Z axis causing a "chugging" effect on the Z.

 

[letterman7]

I'm currently at 200 ipm and 20k spindle speed.

Trevor

Even with a new bit on a Standard that's a little quick for Signfoam. I just did the same thing and mine slowed dramaticly; I wasn't thinking and let the machine decide what it wanted to do. Usually I'll put a two-pass on most of my carved stuff - you can do it quicker and with less stress to the motors. Check your grounds, too. Take all the connectors apart, clean them out and put 'em back together. Update your software again - sometimes it takes a couple times before it's "right". 3D may be right, though I personally haven't seen those issues due to software. And I'll state it again - check all your grounds, even the one to the control box. Last week I was routing PVC and it generated so much static that it affected the control lines and really screwed up the file. Wound up putting a #4 wire to the end of the board and to a known ground on the 'Bot and hanging over the router with a can of anti-stat spray...

 

[KetchikanSignpro]

I was having the same problem with mine.. Did you recently do an update or install a new version of their SB program.. I had to go back and install an earlier version of the SB program and that fixed my issues.. I think they screwed up some of the codes on the newer software versions and it was not keeping the proper timing on the Z axis causing a "chugging" effect on the Z.

This sounds like my exact problem i did recently update to the newest version, I hate to go back as im vary happy with some of the new features. but sounds like what i may have to do.

Ill also try slowing my speeds down to the default tool settings of 100 IPM but it seams really slow to me.

Thanks for the help, hopefully i can fix it, i only have one more chance to get it right or i'm out of material >.<

Thanks

Trevor

 

[SebastienL]

I wasn't thinking and let the machine decide what it wanted to do.

LOL, that's funny. Machines do what they are told to do! In my years of experience with CNC machines of all kind, I have yet to see a machine decide for itself! And I have yet to see a machine crash all by itself, despite the "yes it did" of the many operators i've pissed by pointing what they did to make the machine crash.

Anyway, imo, i think you should cut in 2-3 passes, if not 4. If the machine is "Shuddering" in certain materials, and not others then for sure it is a stepper motor skipping because of to much force.

if it skippping in 1/8 pvc, then something is wrong with the machine..

 

[John L]

How did you create the toolpath file? Have you ran the toolpath file in simulation/preview mode to see if the problem is replicated there before you commit to the expensive stuff?

Is the computer that controls the CNC connected to the internet? A stall is sometimes caused by windows updates, net data communication, checking for emails, etc. etc.

Do you have dust collection? Have you reviewed your installed grounding path, through the dust hose, to ground? HDU is very "staticky" when shaved up into dust. Do you ever hear a crack or a pop noise while cutting? I have heard static discharge once before when my ground came disconnected on one end.

It is possible to miss steps even in HDU. How deep of a pass are you taking in the 2" foam? I usually cut HDU between 2.5"-3" per second taking about 3/8-1/2" of material most times. But this is somewhat dependent on bit size, bit type, 2D vector cuts versus 3D work, etc.

The recent software update is obviously suspect if you didnt have trouble before that but there are lots of possibilities.

 

[letterman7]

LOL, that's funny. Machines do what they are told to do! In my years of experience with CNC machines of all kind, I have yet to see a machine decide for itself!

:Big Laugh I guess I should have elaborated... I let the defaults that I had programmed set the passes and speeds rather than changing them for the material at hand...

and yes, machines will crash by themselves, whether it's due to static charge, outside influences (lightening, for instance) or a sudden memory dump from the spooler. Happens quite a bit... and yes, I've been around CNC's for a number of years as well.

 

[KetchikanSignpro]

How did you create the toolpath file? Have you ran the toolpath file in simulation/preview mode to see if the problem is replicated there before you commit to the expensive stuff?

Is the computer that controls the CNC connected to the internet? A stall is sometimes caused by windows updates, net data communication, checking for emails, etc. etc.

Do you have dust collection? Have you reviewed your installed grounding path, through the dust hose, to ground? HDU is very "staticky" when shaved up into dust. Do you ever hear a crack or a pop noise while cutting? I have heard static discharge once before when my ground came disconnected on one end.

It is possible to miss steps even in HDU. How deep of a pass are you taking in the 2" foam? I usually cut HDU between 2.5"-3" per second taking about 3/8-1/2" of material most times. But this is somewhat dependent on bit size, bit type, 2D vector cuts versus 3D work, etc.

The recent software update is obviously suspect if you didnt have trouble before that but there are lots of possibilities.

Hey guys thanks for all the input

My computer is connected to the network pulling the cut file off of my design computer, maybe i will try running it locally off of a thumb drive. and turning off my connection.

I have ran it and preview and the problem doesn't replicate itself, im using Delcam Artcam pro for tool path programing.

I checked my grounds on the table and for my dust collection, they both seam to be fine. i haven't heard any static discharge.

I was cutting at 200IPM at .5 inches at a time.

Thanks

Trevor

 

[KetchikanSignpro]

@#$%^$^ mother $#^%@^&& son of a %$#&^$@!..... It did it again.... luckily its only on cheap material i was using to test.

100 IPM 1/2in step down 85% step over 20k spindle speed. cleaned every plug, restarted both boxes, disconnected from internet ran tool file from desktop, disabled screen saver, downgraded software... still got a shimmy in both x cart and y cart...

 

[SebastienL]

Is it the same path your using or is this another tool path?
How old is your machine, maybe a motor mount is loose?

 

[KetchikanSignpro]

Is it the same path your using or is this another tool path?
How old is your machine, maybe a motor mount is loose?

new path, same problem, happed at another random spot not relevant to the prior tries. The machine is about 6 years old i believe.

 

[SebastienL]

Try cutting a square and measure it to see if it is actually square. this will give you a clue if something is out of wack.

You can also check if there is play in the racks an pinions. When off, you shouldn't be able to move the gantry or the head at all. If it moves just a little bit, you have play in the gears that need to be readjusted.

I've had the same problem a while back. One of the x motor was not working. Turned out the driver card for this motor was fried. But you say both x and y.

 

[KetchikanSignpro]

checked for square was off about an 1/8 of an inch adjusted it and cut a simple file for another job, seamed to do fine, ill try my problem file after lunch i think.

 

[letterman7]

Are you using a spindle or a router? It's a real off chance that if you have a spindle it could be sending a high frequency spike back through the motors and screwing with the signal from the processer... but that's real rare.

 

[Techman]

I was cutting at 200IPM at .5 inches at a time.

with 85% overlap?? ..Its too much.... I was told my machine would do some unusual high speed cutting with outrageous overlaps and deep step downs too. In reality it will not. I found that many will say their machine will almost get up and load itself too. In reality they are living in fantasy land. reduce the overlap and reduce the IMP's a reasonable amount and see if it runs any better.

Run your machine from the chips it creates. Good chips means good speeds. Dust means something is off. Missed steps means something is off.

 

[Just Another Sign Guy]

LOL, that's funny. Machines do what they are told to do! In my years of experience with CNC machines of all kind, I have yet to see a machine decide for itself! And I have yet to see a machine crash all by itself, despite the "yes it did" of the many operators i've pissed by pointing what they did to make the machine crash.

QUOTE]

well i've got to agree and disagree here. the majority of problems that i run into with router problems or trainer router operators the majority of the problems are o/e operator error.

however i ahve seen machines do completely unexpected things. there are many reasons for this and you work through from the most common cause to the rarest until you isolate the issue and correct it.

many times with shopbots what i find is that ppl buy them put them in their shops and think they are good to go..sometimes that works...sometimes it doesnt. you need a separate circuit ideally.
i've seen shops running extreme lengths of cabling for communications...all of these thigns can create problems.

the list of problems with cnc routers can be endless. you isolate the issue, start with the most likely cause of the issue and work down the line until you have solved the issue.

 

[SebastienL]

Letterman7, DanStriker

I'm sorry my statement was a liitle misunderstood. What I ment was that machine don't program themselves. I have never seen a machine add a line in the program to make it dive headlong in the vice or table. I have, however, often seen operator not double check their work and forget to adjust a tool offset or use the wrong workpiece zero, wich, I'd say, is responsible for 99% of the crash I've seen.

That being said, I did see machines do some weird things that I was never able to explain...

 

[GC3]

Did you figure out the problem?

I would check the pinions...make sure they are tight, more than once this type of problem has been traced to loose pinion gear on the stepper shaft. Maybe time for new gears?

Also if your control computer is a older model you may not have enough RAM to run at the speeds you want...look on the bot forum about this. I have a older prt and had problems losing steps at the top end of run/jog speeds so we got a new computer with 8gb ram and can now run at max speeds run/jog with no problems....