Running issue

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Kafi
Posts: 6
Joined: Thu Jan 01, 2015 7:33 pm
Model of CNC Machine: Stepcraft 840
Location: South West, United Kingdom

Running issue

Post by Kafi »

Hi,
I am hoping someone can help me with an issue I seem to be having. I have attached a photo to better illustrate the issue. As can be seen the initial roughing cut, 3.175mm EM, starts well then after a time the cut shifts to the left and continues. This is the 3rd time this has happened with no real reason that I can see.
My machine is a Stepcraft 840 which has been recently maintained, cleaned and re-greased. The Aspire program seems to be ok with no issues during the preview. If I cut out a smaller model I do not have the problem, not that I have seen on the few I have made during this issue.
At the moment I have no idea if it is a machine problem or a program issue. Any thoughts, suggestions or guidance would be much appreciated.

Many thanks.

Kafi
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IMG_0088.jpg

ohiolyons
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Re: Running issue

Post by ohiolyons »

If I understand your question this has been reported and responded to on multiple occasions. What we see as “random” let’s go cut somewhere else is the program optimizing the cutting process.

I agree and it use to drive me crazy too. There are things you just have to accept.
John
CNC in Kettering, Ohio

Kafi
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Joined: Thu Jan 01, 2015 7:33 pm
Model of CNC Machine: Stepcraft 840
Location: South West, United Kingdom

Re: Running issue

Post by Kafi »

Hi John,

Thanks for the reply. So basically what you are saying is there is nothing that can be done about this? I take it that it is a program issue and not a machine one? If that is the case surely there must be a way of 'tweaking' the cutting paths to minimize all the red line none cutting paths to reduce the potential of this happening?

Regards,
Sonny

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dealguy11
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Re: Running issue

Post by dealguy11 »

What I see in your picture is a machine issue, not an Aspire issue. It appears as if the machine is shifting the entire model to the left. This indicates lost steps on your machine. This is not the same thing as the behavior where it works on a portion of the carving, then moves to another place on the carving to continue.
Steve Godding
D&S Artistic Woodworking http://www.dsartisticwood.com

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scottp55
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Re: Running issue

Post by scottp55 »

+1 on the Lost Steps.
Every machine is different.
You may have to lighten up pass depth,
or tweak your feeds and speeds for Your machine for a lighter load.
Looks like it lost position in X(?), and then when second pass(?) started,
It was cutting in uncut wood that it thought it had already cut...which just made it worse.

Oh...Welcome to the Forum!!
scott
"Buy your second machine....First"
common cnc saying


scott

Kafi
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Joined: Thu Jan 01, 2015 7:33 pm
Model of CNC Machine: Stepcraft 840
Location: South West, United Kingdom

Re: Running issue

Post by Kafi »

Hi Scott,

Thanks for the reply. I agree about it moving in X as my Zero was well left of start. I am only cutting 1mm at the moment but I can see how a lighter cut will make a difference, that will be my next try. As far as feeds and speeds go is there a tried and trusted method to use to work this out? I am currently using what Aspire gives me as I am a bit in the dark with the best way to go, should I 'tweak' and substantially increase run times or hope I am not over stressing the tool or machine?

+1 on the Lost Steps? Sorry I don't understand that one.

Sonny

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TReischl
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Re: Running issue

Post by TReischl »

Kafi wrote:
Fri Oct 23, 2020 2:28 pm
Hi Scott,

Thanks for the reply. I agree about it moving in X as my Zero was well left of start. I am only cutting 1mm at the moment but I can see how a lighter cut will make a difference, that will be my next try. As far as feeds and speeds go is there a tried and trusted method to use to work this out? I am currently using what Aspire gives me as I am a bit in the dark with the best way to go, should I 'tweak' and substantially increase run times or hope I am not over stressing the tool or machine?

+1 on the Lost Steps? Sorry I don't understand that one.

Sonny
There is no tried and trusted method for your machine because it is basically underpowered. From pics of your machine it looks like it has maybe Nema 17 stepper motors on it. Those type of machines are mostly meant for engraving, not milling. Sure you CAN mill on them, at incredibly low feed rates and depth of cuts.

This is something that makes my blood boil. There are a slew of folks selling "cnc machines" without providing any specifications of what they can or cannot do. I am willing to bet there are lots of machines sitting in shops and garages buried under piles of stuff because they do not perform the way the buyer expected they would. It is like most of these people employ marketing types that have lots of hype to make up for the lack of performance in the machines being sold.
"If you see a good fight, get in it." Dr. Vernon Jones

Kafi
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Model of CNC Machine: Stepcraft 840
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Re: Running issue

Post by Kafi »

Thank you all,

I have taken the the advice and reduced my depth of cut and it seems to have done the trick. Thanks TReischl for your comment and I agree, I am currently saving up for a new bigger and more capable machine. As I am now enjoying building in Aspire and making my own models I think it is time I had a machine that will allow me to do what I need to do.

Many thanks all.

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scottp55
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Re: Running issue

Post by scottp55 »

Glad you have it temporarily sorted :)
(+1 just meant I agreed with Steve)

Is the machine I looked up in pic your machine?
Specs say Maximum speed is about 2 IPS(Inch Per Second)...

I wouldn't run near maximum speed until I KNEW from tests with various bits
that I wouldn't lose position(lost steps+machine thinks it's somewhere it's Not).
Make sure none of your bits in database that you use exceed maximum speed,
BUT you've already lost position, so I'd do some Air Cuts(cut nothing but air),
and after the test run, make sure that machine returns exactly to Home position!

Maybe start at 50% max speed air cut.....then work up feed gradually in air to find air limit.
THEN try shallow cuts(or if small bit...50% Diameter of bit) at maybe 50% of the good air cut.
And then gradually work up again to find Your machine's limits?
There IS no easy way :(

Tweaking feeds and speeds for each bit and material is again trial and error to start.
You want feeds and speeds to give Chips(Not sawdust) so chips carry heat away from the bit.
Bit can stay at room temp(or slightly warm to touch)
and you can cut all day once "Sweet Spot" is found, and bit will stay room temp to the touch.
https://www.precisebits.com/tutorials/c ... speeds.htm

With a little time and testing, you'll fairly soon find out what your machine Sounds and Feels like when you're in the sweet spot. Then you can dial in new cutters and materials fairly fast. :)

After searching the Forum(and even better a Google search starting with "Vectric Forum" and topic)
And you'll find virtually every topic under the moon has been talked about. :)
THEN ask away on forum if you don't find anything or have a problem.
Everybody was a beginner Once!!
Don't know what I would have done when I started without this forum's help!

Hope I hit everything?
Again.....Welcome!
scott
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2020-10-23 11_15_05-STEPCRAFT D.840 CNC Machine (Self-Assembly Kit) _ Stepcraft, Inc.jpg
"Buy your second machine....First"
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scott

Kafi
Posts: 6
Joined: Thu Jan 01, 2015 7:33 pm
Model of CNC Machine: Stepcraft 840
Location: South West, United Kingdom

Re: Running issue

Post by Kafi »

Scott,

Many thanks for all your help, I will be taking your advice and spending a quiet day air cutting. I really have the bug now but you are correct about using the forum to sort problems as 'you don't know what you don't know' until it goes wrong!

Stay well and thanks for the welcome,

Sonny

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scottp55
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Re: Running issue

Post by scottp55 »

Thanks Sonny :)
Yep....VERY addictive!
Originally Loved the Accuracy aspect the most,
But because I can't hand carve worth a darn (except organic smoothing and such)..
Now I'm HOOKED on the 3D aspect!! :)

I think you'll pic up the lingo and limits of your machine quickly...and then Love it too!

Air cutting will just give you a rough idea of limits(and start your "comfort zone")
before cutting your material. Scraps come in really handy for testing!
Chip Charts and usually manufacturers will give a chip size range for a ballpark starting point,
but so long as you're getting a good cut with chips, and bit stays cool...
you're usually good to go. :)

Enjoy it :)
scott
"Buy your second machine....First"
common cnc saying


scott

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