Z axis Plunge

[ciaranallen93]

Hello All,



Im pretty new here so please bear with me. We recently set up a HeavyMill from 3DTek and aftrer limited success also purchased a Masso G3 to boost our machining capabilities.

We have had some teething issues with the machine, most of which are just down to user error and lack of understanding of the tooling that we are using.

We have had an issue that i dont think can be explained by tooling though. Running an adaptive clearing toolpath the machine works great and then randomly it will plunge in to the stock (18mm Birch Ply) and also completely through the wasteboard (18mm MDF).

After the first failure, I reprogrammed the tool path - changed feeds and speeds etc - and retried it, but it seemed to fail again in exactly the same spot.

I will upload G code and a few images but any help and advice would be appreciated. Tool was a 1.5inch/12.5mm 2 straight fluted endmill.

 

[cncnutz]

Hi CiaranAllen93

Welcome to the forum. Sorry to hear you are having a problem.

I looked at the Gcode and the last Z axis command before the line you indicate is Line 44947 which instructs the Z axis to move to -7.5mm.

N24720 Z-7.5

Unfortunately I cannot see from the photo what Axis height Masso was set at as it is at the top of the screen assuming the photo was taken when the machine was stopped and the Z axis was still buried in the table. For future reference is you use CTRL+P to capture the screen it will copy the entire screen to the USB flash drive and you can upload the image. Easier than getting your phone out and deal with the photo later.

Do you recall what height the Z axis was at when it was busily cutting into the spoilboard? I'm wondering if you are loosing steps on the Z axis.

Could you share a screen print of the Z axis settings please?

Cheers Peter

 

[ciaranallen93]

Hi Peter,

Thank you so much for the swift reply!! It is much appreciated.

Unfortunately when the bit plunged, i pressed ESC on the keyboard, lifted the z axis and turned the machine off and went home for the evening. Was a bit tired to do more trouble shooting.

Thank you for the CTRL+P tip. I will use that in the future if i have any further issues.

I can confirm though from measuring the stock, that the movements before the bit plunged fully through the piece were at -17mm which is worrying if it was only supposed to be at -7.5 as per the g-code.

It also went pretty much the whole way through the waste board so it seems to have lost steps at least twice. I just didn't notice the first loss.



Cheers, Ciaran

 

[cncnutz]

Hi Ciaran

When you look at the Gcode the deepest it should have gone is -16.877mm

(T1 D=12.7 CR=0. - ZMIN=-16.877 - FLAT END MILL)

I'm sorry to say you will have more trouble because there is no way you got through 18mm of plywood and another 18mm of spoilboard without something seriously wrong. On the + side it should be easy to find. Start with the z axis settings. For example if your acceleration is set wrong you will loose steps especially in the up movements causing the Z axis to sink lower and lower as it goes. Likewise if you have a mechanical issue. Gravity helps the Z axis descend but it's no help when lifting the axis.

Cheers Peter

 

[ciaranallen93]

Hi Peter,

Thanks again for the reply.

Z axis settings are as follows:

Motoristance Per Revolution: 1.0mm

Drive: Pulses per Revolution: 1900

Maximum Feedrate: 600.00mm/min

Acceleration: 50.0mm/sec^2

Travel Minimum: -200.00mm

Travel Maximum: 0.00mm

Backlash: 0.00mm

 

[cncnutz]

Hi Ciaran

I'm not familiar with the heavy mill that you have so don't know what to expect. @breezy would be the man for that if memory serves as he set up the one for his local mens shed.

I think the acceleration looks very reasonable for the maximum speed of the axis at 1/12th the maximum so I don't think that is the issue. Some people crank theirs right up which doesn't work but your looks good.

Mine is more aggressive at 1/8th maximum speed. (Don't increase yours as increasing your speed it will only make things worse.)

I looked on line for Heavy mill and it looks like there is a belt drive between the stepper and the leadscrew. Have you checked that the setscrews are not loose and slipping on the shafts. That would cause this issue as well.

Cheers Peter

 

[breezy]

Ciaran,

Unless Ben has changed the dimensions of the Heavy Mill and the steppers your settings are wrong

Quote from CiaranAllen93 on May 29, 2020, 8:28 pm

Z axis settings are as follows:

Motoristance Per Revolution: 1.0mm Don't have access to BMS Heavy Mill so can't check but is is not 1.0mm

Drive: Pulses per Revolution: 1900 2000 - 200 steps/rev * 10 micro step

Maximum Feedrate: 600.00mm/min Could be faster - don't remember what I set BMS HM to

Acceleration: 50.0mm/sec^2 Also can be increased - don't remember what I set BMS HM to

Travel Minimum: -200.00mm Unless Ben has increased the clearance height this should -100mm

Travel Maximum: 0.00mm

Backlash: 0.00mm

COVID lockdown is preventing me from visiting the Bicton Men's Shed where I could check the settings of the Z axis. When I setup the BMS Heavy Mill I had the acceleration and speed set too high and the stepper made horrible grinding noises.

Get the calibration and max travel corrected and your problem will more than likely be fixed.

Regards,

Arie.

Edit: Peter you beat me to it again.

I looked on line for Heavy mill and it looks like there is a belt drive between the stepper and the leadscrew. Have you checked that the setscrews are not loose and slipping on the shafts. That would cause this issue as well.

I had to file a flat on the leadscrew to prevent the pulley from screwing off, set screw engages into the turned down thread and when the motor reverses the pulley moves up the lead screw.

 

[ciaranallen93]

Hi Arie,



Thanks so much for the reply. Havn't been able to get in touch with Ben. Seems he is away or probably having a well deserved break from me annoying him with questions.

When i installed the Masso on to the Heavymill setup, i downloaded a file of masso settings curated by 3DTek and uploaded it onto the machine so i can only assume they are correct.

Just tried a different toolpath after a weekend mulling over what it could be and had the same issue. DRO said 7.2mm but bit was around 18mm below top surface of the stock.

Have also spoken to Ryan, the UK Sales guy - I'm based in London, UK - and he didn't know what it could be either.



My train of thought at the moment is that it is a bug in the Masso, or potentially a fault within the z axis stepper.



Cheers, Ciaran

 

[breezy]

Claran,

If the DRO is saying 7.2mm but the bit moved 18mm, that is a sure sign that the axis is not calibrated and that the settings are way, way off.

Have you calibrated the Z axis?

What is the physical travel of your Z axis (from top to the bottom of the leadscrew)?

Could you take a screenshot (Control + P, MASSO will dump a BMP file onto your USB stick) of all your axes setups and upload them so that we can check the settings.

Regards,

Arie.

 

[breezy]

@ciaranallen93

Ciaran,

Haven't heard from you, wondering how you are going with this problem?

Managed to get to the BMS router today and got a screen dump of the Z axis, see attached.

Try these settings, you will have to adjust Distance per Revolution to suit your gear ratio and leadscrew / nut combination, also backlash is dependent on tightness of the drive belt - leave it at zero.

Regards,

Arie.

 

[scollins]

Hi Arie,

I share a workshop with Ciaran and unfortunately, we haven't got any further with this problem, The same plunge issue happened on a much simpler 2d version of the design. Attached are the settings we have used for X, Y & Z axis, my understanding is that Ciaran downloaded them from 3Dtek who recommended them for the Masso. I will change to the settings you have recommended and run the job again now.



Thank you for helping us!



Sam

 

[breezy]

@scollins, @ciaranallen93

Sam, Ciaran,

Looking at your settings they seem strange for a 3DTek Heavy Mill.

I think you are going to have further problems.

Please supply details about your steppers and the drives you are using. Steps per revolution and micro stepping or driver type/name. Also how far does the gantry move in the X & Y for one revolution of the stepper and what is the length of the Z axis.

With that info I can give you basic settings BUT you must calibrate distance travelled per revolution with the wizard BEFORE running any cut program.

It is most important that the machine is calibrated, you can't plug in values and expect it to cut accurately.

As a test of the Z axis calibration, get a block of known dimensions place it on the bed and zero the Z axis to the top of it, then move the Z axis to the bed and read off the Z axis DRO does it match the block?

I'm in Western Australia 8 hours ahead of you, if you get the info back to me by midday your time I can supply some setting for you to try, before I call it a day.

Regards,

Arie.

 

[masso-support]

Hi Sam,

Thank you for your email to Support. I am answering here in the hope that it help others in the future as well as yourself.
Basically I agree with Arie regards your calibration settings.

Since you line in the UK it is possible that the machine has slightly different parts which require different calibration figures. Usually a calculated value will get you very close but your values are wildly off so something is not right.

The first thing I notice is the Pulses per revolution. You have a figure of 1900. If we assume a standard stepper motor of 200 steps per revolution you have microstepping of 9.5 which I have never seen or heard of. I'm not sure what drive you are using with your motors but from the 3DTek website it looks like a G540 which has microstepping of 10 which would give you 2000 steps per revolution. Of course you may have a different drive with your machine and I don't know everything but 9.5 still doesn't sound right.

As Arie says you need to run the calibration on all axis as the manufactures settings may get you close to right but calibration will work out the correct values for you.
Each machine will be slightly different due to manufacturing variations in Leadscrew tolerances.

Check the Belt on the Z axis is not loose and the timing pulleys are not slipping.

1mm for the resolution seems a little low as well for the lead as the belt drive seems to gear the leadscrew down and a visual of the screw makes it look larger than a 1mm lead to my eye. If it is a multistart screw that will double or triple the visible lead. It's vert difficult to tell from the opposite side of the world.

I downloaded the calibration settings from 3DTek and they do match what you posted but I honestly think they are wrong for your setup.

If you can provide some technical information about your setup it should be easy to figure out your problem.

• What drives are you using and what is the microstepping setting on them?
  
• What is the lead on the Z axis leadscrew
  
• What is the gear ratio from the stepper to the leadscrew?
  

With this information we can figure out what the values should be to start with and you can fine tune it.

Cheers Peter

 

[breezy]

Peter,

1mm for the resolution seems a little low as well for the lead as the belt drive seems to gear the leadscrew down and a visual of the screw makes it look larger than a 1mm lead to my eye.

Check post #10 you will see that BMS's Heavy Mill Z axis resolution is 1.07696mm so the pulley ratio and leadscrew has been designed to give 1mm resolution. Also their settings for X & Y are way off, the DTPR and PPR are short by a factor of 5 compared to BMS's settings.

I'm awaiting Sam or Ciaran to post the values that I asked for to provide some basic settings.

Regards,

Arie.

 

[masso-support]

Thanks Arie,

It was just a guess looking at a photo. The timing pulley on a photo I saw looked to have a larger pulley on the leadscrew than on the motor because the belt seemed to be V shaped.
I assumed that the Z axis was geared down. :-0

And I've just realized the error on my thinking. If it is geared down 2:1 then a 2mm lead would be 1mm which makes sense now.
Just as well one of us is awake, speaking of which I am off to bed.

Cheers
Peter

 

[ciaranallen93]

Hi All,

Thank you so much for the replies. I'll do my best to provide all the information you have asked for.

The driver we are using is a Gecko g540 drive. The stepper motors on all axis are 340 oz. in

From measurement, the z axis can move 95.5mm from its zero position at the top of the motion.

The x and y axis move 50mm per revolution of the motor.

The leadscrew is 12 threads per inch and seems to have about 1mm of backlash (i can move the z axis up by 1mm without turning the screw) if thats the correct terminology.

I am waiting to hear from Ryan at 3DTek to see about the gear reductions as requested and will post again once i have the information.



EDIT: BACKLASH ON Z AXIS WAS DUE TO A BOLT NOT BEING PROPERLY TIGHTENED



Thanks all again for the help. It is very much appreciated. Looking forward to getting this thing carving!



Cheers,

Ciaran

 

[masso-support]

I was going to say that 1mm was huge backlash.

It would be quicker to count the teeth on the motor and leadscrew pulley. The belt doesn't matter. Just post the teeth on each pulley.

Cheers Peter

 

[ciaranallen93]

Hi Peter,

Correct, I have counted and there are 10 teeth on the gear attached to the motor and 20 on the gear attached to the lead screw.

Cheers,

Ciaran

 

[masso-support]

Go with Aries figures of 1mm distance per revolution and 2000 pulses per revolution.

Then run the axis calibration wizard to fine tune the final distance per revolution.

Cheers Peter

 

[breezy]

@ciaranallen93

Ciaran,

Ok, your machine is the same as the BMS's so I'm attaching screenshots of the various setup screens. Copy the settings and then calibrate each axis using the wizard. Try to get the longest distance when moving each axis. I attached a tape measure to the bed, aligned to 100mm mark, moved to 1100mm mark and entered 1000mm into the wizard. Once you have done that, issued a MDI command to move 1000mm, check and adjust calibration by changing last digit of DTPR up or down to correct if short or long.

I noticed that you have set X & Y minimum distance to a negative value any reason for this? BMS's values are shorter than yours because of space restrictions. Photos of machine are available on Bicton Men's Shed - 3DTEK Heavy Mill

Regards,

Arie.