MASSO Air Cut

robb

Robb
Environment: CNC Router/mill - 2.2Kw Spindle - Hardwoods only - MASSO G3 controller (Config file version 3.42.2) and V-Carve Pro 10.18.0. I have the correct post processor installed - (FYI only: I use Imperial measurement).

I have a weird occurence taking place. At a point in the job the Z-Axis changes from a negative to a positive position. For instance, I have a test file: testing.crv (which is just the word' Testing') which uses a Carbide V60 degree, 3F Trend .57" dia' bit and is in the Toolbase using appropriate vendor settings. The depth of cut for this file, at maximum, is 0.125". The size of the material is 6" X 4" X .75" and is Oak. I first Home the machine correctly, I have then set the job 'Home', bottom left and at the material surface with all axis at 0. I start the job and all goes swimmingly until the bit completes part of the text 'TEST'. It should go to the 'i' and it does but, the Z axis has now risen from the correct depth (in the Gcode for the previous 't') to a positive position and, consequently, it air cuts the rest of the letters 'ing'.

I have a correctly set up machine. The spoilboard has been surfaced and checked for level by measuring the distance between the spoilboard surface (all four corners and center) and the bottom of the spindle at a set height. The X axis gantry is level across the entire table. The whole system is only a month old and has, virtually, no usage other than setup and testing. I have configured the controller using the latest software update direct from MASSO. The Z-axis is correctly setup and has been checked using MDI to ascertain that a command results in a correct postioning of the Z axis. Homing work correctly and V-Carve 'appears' to be creating accurate measurements and Gcode using the MASSO/Vectric post processor.

Here's a thing: As the Z axis moves into a positive position during the test job I hit the E-Stop. The Z axis on the MASSO is showing a correct position as -0.0825" at the time I stopped the job but, the position of the bit is, clearly, above the surface of the material at about the same value but a positive value of 0.0825" (approximate, as it is difficult to measure accurately).

I have been working with my CNC vendor to try and resolve this anomoly. Mechanically, all is in order. I thought that this Forum might be a good place to ask for help as this may be a MASSO or V-Carve 'problem'. I am also posting a similar message at the Vectric website forum.
 

cncnutz

CNCnutz
Staff member
Hi Robb

It sounds like you are loosing steps either through a mechanical issue or you have speed and acceleration set wrong in the Z axis setup.

Could you share a screen Print of you Z axis settings. Bring them up on screen and press CTRL+P and it will put a picture of the screen onto your USB flashdrive that you can upload here.

Cheers

Peter
 

robb

Robb
Hello and thank you for your reply. I attach the Z-axis config screen. FYI: X axis and Y axis are both positioning accurately. The only problem I have with the entire set up is the Z axis. One thing I did notice was about a 1/16" (.0625") play in the Z spindle carriage. The Z axis is controlled by a stepper and belt and this operates a long thread that passes through a plastic (not sure what the plastic is but, it is incredibly strong) block that is bolted to the plate that carries the actual spindle. The thread moves this block up and down. I removed the spindle and using a piece of wood as a lever I tried to lift the carriage to see if there was any problem. That's when I noticed this play. The vendor tells me that the weight of the carriage assembly and spindle balances that small amount of play. It may be right and I have no evidence to prove the contrary. The vendor is sending me a replacement block 'just in case'.

I've incuded a PDF file that provides a lot of information for this particular test job. I hope you find it helpful.
 

Attachments

  • Z-Problem.pdf
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breezy

Arie
Staff member
@robb

Looking at your carriage assembly I would be correct in saying that you have 3DTEK Heavy Mill.

If so your settings for the Z axis are wrong. Does the stepper grind/growl with rapid moves, if so this is sign of missed steps.

The question I have is what drivers/steppers are you using?

If you are using Gekko 540 and 200step motors as the Bicton Men's Shed's Heavy Mill is, then these are approx settings that you could start at. I can't check our settings until I go to shed again (Monday). Our settings are in metric.
  • Pulses / revol = 2000
  • Max feedrate = 15in/sec
  • Acceleration = 1in/sec^2
  • Travel Min = -4 in
  • Travel Max = 0

The Acme thread in the nut should be tight to turn and there should be no noticeable backlash. If you are getting movement in the carriage, check that the bearings are installed correctly, they control the up/down movement of the Acme thread.

Regards,

Arie.
 

robb

Robb
Hi there and thanks very much for taking the time to respond to my message.

You are correct. It is a 3DTEK Heavy Mill. Gecko 540 and 200 stepper motors. 2.2Kw Spindle - MASSO G3 controller (Config file version 3.42.2) and V-Carve Pro 10.18.0. I have the correct post processor installed.

The bearings are correctly installed with the flanges facing each other. The bearings are brand new and in good order. I have appropriate tension on the drive belt and the gears are 10 teeth stepper -ear and 20 teeth thread-gear. The stepper motor is like everything else, brand new. There is no grinding or any sounds that would cause concern. Everything moves smoothly and I can't detect any mechanical problem in that area of activity. I've taken Z-axis carriage down to check for visible marks/damage to any of the Z-axis parts. All okay (to my eye). There is a bit of slack in the thread/block mating. If you read my first message you will see I mention this play. 3DTEK is sending me a new drive block. Plastic block with female thread. I'm sure your aware of what it is. I am being pedantic as I do not want to mislead and cause further problems.

I made a video of the problem in action. If you would like to view it go to www.wessexmillwork.com and scroll to the footer. Click on the Wessex Millwork logo to view the short video.

I've just swapped out a Y axis motor with the Z axis motor. When I ran the job the result, sadly, is the same as in the video. At least I know the stepper motors are, probably, not the problem.

I am grateful for any help offered as I need to get this working and paying its way.
 

breezy

Arie
Staff member
Robb,

Watched the video, it seems to me that you are losing steps on the downward motion. Because you are machining hard wood there is quite a lot of force required to push the cutter into the wood.

The solution to this is to slow down the Z axis in the MASSO settings.

Run your code again and when finished, in MDI issue Z0 command, check to see if the tool is still zeroed.

The grinding/growling noise I was referring to is from the motor, not mechanical from the carriage. Zero the Z axis to the worktable and in MDI issue a series command to move the head up and down rapidly from top to bottom of the travel, it should be quiet, then check is it still zeroed.

The values that I gave in my previous post came from a discussion on the 3DTEK forum. I can't remember offhand what setting we have on our machine but they are similar values. Get the machine working correctly at a slower speed and then adjust it upwards in small steps.

Regards,

Arie.
 

robb

Robb
Hi Mr Breezy, or should I call you Sir Breezy?

Your solution worked perfectly.
  • Pulses / revol = 2000
  • Max feedrate = 15in/sec
  • Acceleration = 1in/sec^2
  • Travel Min = -4 in
  • Travel Max = 0

The above is the magic charm which I applied last evening. I watched in amazement (remember, I've been through a very frustrating period since building this machine so, I'm entitled to be amazed) as the machine did exactly what I had 'asked' it to do. After it completed I had a bourbon and then ran another job which, before your advice was applied, had never completed. It went like a dream. I got a little excited after that and broke a Ballnose but, hey what the heck!

I am very grateful to you and Mr CNCNutz, on this forum and other forums, for taking the time to offer advice, which I have very much appreciated. I hope to reciprocate in the future and contribute to the forum.

Thanks again. Have a great weekend.
 

breezy

Arie
Staff member
Quote from Robb on December 12, 2019, 9:09 am

Hi Mr Breezy, or should I call you Sir Breezy?

I received the "Breezy" nickname some 60 years ago when I was at school because it rimed with my surname.

Regards,

Arie.
 
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