How to make this 22" long part on a 18" travel machine..

swatkins · Oct 7, 2014

Working with BOBcad V27 and a Bridgeport Boss that I have converted.. The boss machine has 18 x 12 work area and I need to make a new throat plate for my 26" DoALL band saw. This is a very simple part that is 22 inches long. 4 inches wide with a 2.24 radius on one end, square on the other and a slot down the middle for the blade to move through, this is a power table model and the table moves back and forth.

At first I thought I could just program the part and cut 18 inches and then move the part and make a program to cut the last 4 inches. When looking at the tool paths the program wants to cut around the entire perimeter of the part so that leaving the blank long, to make the completed part 22", would result in the blank be cut at the 18" mark.

Is there a better way to program this part? Bob file for this part

Steve

Red James · Oct 7, 2014

This is why every 'machinist' needs to know some programing. Just edit your program to cut in near the right end of travel, profile, then stop and rapid up near the end of its travel on the other side.

quadman2007 · Oct 7, 2014

I agree with Red James, either modify the code by hand or break the lines in BOBcad.

RTM · Oct 7, 2014

How do you plan on holding the part? Will you be clamping to the table?

Instead of selecting the top surface to machine, instead extract edges of the surface on another layer then break them accordingly to fit in your envelope. I'm doing a similar job right now, a 60" part on a 40" machine. I am working with a solid model so I'm using a 3D roughing operation with a boundary to keep it contained. The finish 2D milling is all done with geometry extracted from the model, broken up into manageable sections.

swatkins · Oct 7, 2014

Red James said:
This is why every 'machinist' needs to know some programing. Just edit your program to cut in near the right end of travel, profile, then stop and rapid up near the end of its travel on the other side.

I agree, thats the reason I'm working through this program.. That computer makes my hand work look like a 5 year old was turning the handles

Computers are here to stay so I'd better get with the program

swatkins · Oct 7, 2014

RTM said:
How do you plan on holding the part? Will you be clamping to the table?

Instead of selecting the top surface to machine, instead extract edges of the surface on another layer then break them accordingly to fit in your envelope. I'm doing a similar job right now, a 60" part on a 40" machine. I am working with a solid model so I'm using a 3D roughing operation with a boundary to keep it contained. The finish 2D milling is all done with geometry extracted from the model, broken up into manageable sections.

I had planned on making the stock longer on each end and clamp in to the table.. The Boss machine has a large table but it's designed not to move very far in each axis to prevent table tipping, like on a regular mill. I was also using .500 thick stock, the part is .460 thick and then flipping the part and mill off the excess.

This is my second attempt at making a part with BOBcad so I'm a novice at 3d drawing. I drew the part using solids and extracting the parts not needed. I have not seen a "boundary" discussed in the training videos so far so I haven't a clue on making a boundary, yet

Lots more studying to do.,..

jrmach · Oct 7, 2014

RTM is steering you in the right direction.Do you need help with tool paths ?

upnorth5axis · Oct 7, 2014

Ask AL he knows all about BOB

swatkins · Oct 7, 2014

jrmach said:
RTM is steering you in the right direction.Do you need help with tool paths ?

Not just yet, thanks... I need to read and watch a little more so I can have intelligent questions

I'm not used to drawing with solids and need to figure out a few things.. All these years I've line drawn and not really looked into programming a machine. While it's not perfect, I just finished making a sign with the mill and Bobcad.

jrmach · Oct 7, 2014

swatkins said:
Not just yet, thanks... I need to read and watch a little more so I can have intelligent questions

I'm not used to drawing with solids and need to figure out a few things.. All these years I've line drawn and not really looked into programming a machine. While it's not perfect, I just finished making a sign with the mill and Bobcad.

Good Gawd,,,something went wrong with your thread here

swatkins · Oct 7, 2014

jrmach said:
Good Gawd,,,something went wrong with your thread here

I know pitiful ain't it, using a mill to cut wood.... In my defence it was the only way I was going to get the wife off my back and learn if the darn mill could actually do something...

I promise to do better

mjk · Oct 7, 2014

Why not finish or start with a blank that is 4" then just do the end radius detail and slot?

jrmach · Oct 7, 2014

swatkins said:
I know pitiful ain't it, using a mill to cut wood.... In my defence it was the only way I was going to get the wife off my back and learn if the darn mill could actually do something...

I promise to do better

Actually I was referencing your Picture size takes up 4 feet of my 18 inch screen.

swatkins · Oct 7, 2014

jrmach said:
Actually I was referencing your Picture size takes up 4 feet of my 18 inch screen.

Looks like we're going to need a bigger screen....

Sorry fixed it for you.

swatkins · Oct 7, 2014

mjk said:
Why not finish or start with a blank that is 4" then just do the end radius detail and slot?

Couple of reasons..

First I was going to cut it out of a piece of plate I have on hand.

Second If I were to do as you suggest it would be faster, for me, to just put the blank on the rotary table and cut the radius and then freehand a slot on the mill. This is more of a project for me to learn the Bobcad program and different ways of drawing the parts.

mjk · Oct 7, 2014

Part of "having experience" is knowing what the limitations of your machine are and how they affect your tooling choices, machining sequence and in this case "cooperation" with your software.
With each combination of the above many members of PM choose different ways to complete a part.
For you combining X travel limits and the software wanting to cut across your part is one combination of a limit.
These limits don't eliminate you from doing the part, just require you to take a different approach than someone else to complete.

No doubt you'll need at least 2 setups to complete your part.
Work from the finished part backwards knowing what that entails and create the drawing/drawings and programs to accomplish it.

If all you have to do is draw a part and load it in the machine and push a button.....monkeys could do it

Evan if you had a machine with 40" of X travel, you would have to be creative with how to hold a part your cutting the entire perimeter

Mike

swatkins · Oct 7, 2014

mjk said:
Evan if you had a machine with 40" of X travel, you would have to be creative with how to hold a part your cutting the entire perimeter

Mike

I had though that the best way to hold this part was to use a piece of stock that was thicker than the part, clamp it to the table on both ends and in the middle of both sides. Of course the clamps will be out of the exterior tool path. After the first side of the part was cut I would then flip the part over and use a 2 inch facing mill to cut the excess off the back and bring the part to size.

Should work fine... Right?

mjk · Oct 8, 2014

If that was a production part, your extra material cost could become an issue along with the extra machine time to create the final thickness.
But for one it should work.

If the part is made out of a material that can be welded without a problem , and the welding won't affect post processing(painting,plating, anodizing), I try and use thru bolts to fasten a part like that to the table.
After machining , fill them up and machine flush
If the holes can be placed in an area that are not a concern OR can be later drilled and tapped to create an added function to the part, leave the holes in.

swatkins · Oct 13, 2014

jrmach said:
RTM is steering you in the right direction.Do you need help with tool paths ?

A quick couple of questions...

I have designed another part, a bracket, and today I successfully cut a pair of them in one setup. The operation consisted of a roughing pass, finish pass, center drill, drill and a chamfering pass. After slogging through making this part my mind is a little fried

One thing I noticed, and can not find out where to change, is the tool would always complete a rotation and then lift and re-plunge to the new level. I was taking .050 cuts and stepping down to .450 part depth. I can see no reason for the tool to rise and if it would just move on down to the new level on each pass it would save a significant amount of time.. How can I change this?

I have also looked into boundaries in an effort to complete the 22" table insert.. So far the only place I find boundaries options are when a 3d tool path is chosen. Can you point me to information on setting a boundary on this 2d mill operation?

jrmach · Oct 13, 2014

You do not say what kind of tool path you tried.I would suggest you try a Profile tool path with Contour Ramping for your pattern.

For the second part of your question,I am trying to figure out why and where you need a 2D Boundary.If for an "open pocket"you would use the Advanced Pocket or Advanced Pocket/Adaptive Rough tool path and you would use dotted lines on your open end.

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