Inventables Community Forum

Bump stop and x and y zeroing

Hi I am looking for help setting up a bump stop I think it’s called or right angle piece in left corner that I can put my wood in and it will always be zero but I can’t figure out how to do so. I’ve looked on YouTube and I can’t figure it out completely, I currently eyeball x and y on the piece but would like to be more accurate and faster than that. Please if anyone could help I would appreciate it.

Lots of information already posted about using a bump stop.

Some results are shown below;

https://discuss.inventables.com/search?q=bump%20stop

Video on subject https://youtu.be/IwkVDzseCxs

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I’ve read most of them but I still don’t quite understand I am new to this sorry. I think what I’m confused about is the g codes and if I screw a piece of wood down all the way down the x and y axis how would I cut it and tell g code what I did. Thanks again. Sorry if you don’t understand what I’m saying.

Can you try again?

Okay so let’s say I put piece of wood down the x axis and y axis and screw it down so it doesn’t move, home my machine then type in g28 under the settings it’ll move to the location correct? Then what

If you want to use G28, you’ll have to set the location.
Home.
Move to where you want G28 into be.
Send G28.1

From then on, G28 will be at that location (home first).

That said, despite what you’ll hear and read on the forum, G28 is an unnecessary step. Set your zero, and it will remain until you set a different zero.

Assuming you have homing switches installed and they are towards you and to the left when machine is viewed from the front:

  • Screw down a piece of sheeting slightly closer to you and further left, say by 2"
  • Carve a rectangle, with path set to inside, with machine zero as your work zero, this will create your bump stop.
    => consistent (within the precision of your switches) work zero, just Home and Go (re-zero Z though) :slight_smile:

Then G28 and G30 can be used as two different parking spots

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So your using the home switches as your zero and cut a square on that x and y plane. So starting out from 0,0 my machine will be up against the homing switches until it starts to cut. Am I reading that right.

Basically yes, it is one way but not the only one.

I for instance have my switches left/far back but dont use bump stops so dont need a fixed work zero position.
So to use a bump stop similar to what you intend to do I must use G28 or G30 to make a persistent offset from my machine zero.

  • Home machine
  • Move to my intended work zero position
  • Call G28.1 to set that position
  • Carve a rectangle to make my bump stop, to that position. (Cut inside of path)

Now I have a fixed reference off my switches and can call G28 to go directly to my bump stop zero. (Z need to be set individually)

Okay thanks your all your help.

When I cut a rectangle for the bump stop wouldn’t the bit diameter come into play.

No, the corner of the rectangle is at 0,0 (make sure to include a relief dogbone). That will be at the center of the endmill.

Okay thanks so I would cut the square on path instead of inside or outside of line correct

Cut Inside.

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Yup

I used to set the zeros the same way that you have been doing it. I bought a triquetra touch plate (https://triquetra-cnc.com/) and it has made my carving a lot easier.to set up. It also facilitates bit changes by letting me change the z0 position very accurately

This may help

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In addition to the other helpful hints offered here, I would like to add some thoughts as a relatively new person to this field who has had to struggle through some of the issues that may seem obvious to those with more experience.

  • when you set up your bump stock, it will be the guide for all future cuts - if this is off, all cuts will be off. There is play in the y-axis of the machine when it is turned off, and it is very easy for the y-axis to be at a slightly different angle every time it is turned on. To correct this, put in stops on both sides of the y-axis rails in the very back so that you can push the gantry all the way back (BEFORE YOU TURN ON THE MACHINE) and have a relatively stable y-axis cut after cut. I push the gantry back and hold it it in place before turning on the machine. I can feel a few “clicks” in the machine as the stepper motors are engaging. After a few seconds there are no more clicks and I can let go. The y-axis is now in a position that is stable and reproducible.
  • after homing the device, toggle the device over and set your G28 to the place you want to be your work zero (in the Machine Inspector, type in G28.1). This will be your work zero for every cut you use your bump stock for.
  • After doing this, cut the bump stock, cutting on the inside of your line. (Make sure that the bump stock is thinner than the material you are clamping so that the clamps that go over the bump stock can hold the material) This way, the bump stock will be on the same orientation as the machine arm time after time. I did not do this on the first bump stock I made and I had drift between the right and left sides of my cuts of up to about 0.25 inches or so, depending on the starting position of the gantry. I also like to cut a small circle centered a 0,0 so that there is a small notch in the corner of the bump stock. Otherwise your material to be cut will not settle in to that corner well
  • A G30 command is helpful if you want to be able to switch out your material and repeat the carve again on a new piece. Toggle the machine to where you want it and then type G30.1 into the machine inspector. I like to have the z-axis up high here so that the spindle raises as it goes to G30. This does 2 things. It makes it easier to change the bits between cuts and raising the z-axis makes it less likely that the spindle will cross a clamp and break a bit as it moves into park (I have done that a few times). I have also drawn a line on my waste board between my G28 and G30 so I can try to avoid putting clamps crossing that line to hopefully further bit breakage
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Before shutting down I park it at my g28 which is near front left. Be fore start up I measure both sides to the from uprights and set evenly. Then when turned on homing is somewhat quick.
I don’t have the patience for it to home from the rear of 1000 machine.
All your points are valid and will be helpful to newbies here in the community.