multi part fixture reference
I have workpieces that are processed in successive cuts along a continuous piece of flat bar and then a chop saw separates them; each individual workpiece length now varies slightly.
The next operation, multiple workpieces are mounted to a fixture plate by alignment dowels and screws.
Since the WP edge does not reference it's prior operation, the fixture plate must provide the G54 reference point.
Is there an optimum way to create a G54 reference point on a fixture plate?
The fixture plate would need to be imported into the CAM with the parts (or rather the other way around) and the parts must be referenced to the fixture plate G54.
I use SprutCam and this sounds like an opportunity for a mudslide.
Is there a better way?
Re: multi part fixture reference
Yep, working out the details on this myself. However, I'm using Fusion 360.
On my fixture soft-jaw, I machined in a .25" x .25" x .125" deep indicator box so that the soft jaws can easily be set up and aligned. Working out the details on how best to do this in the CAM section based on probing for location where the parts "actually" end up when in the fixture.
http://www.cnczone.com/forums/tormac...980-g59-p.html
Re: multi part fixture reference
I always reference to one top corner of the fixture plate, usually the left-front. When I machine the fixture plate, I bolt it to the machine, with the X/Y/Z zeroes set to avout -.020" INSDIE the left and front edges, and 0.02" BELOW the top surface. I then take a finish cut along the front and left edges, then face the top surface with a Face mill, to bring them to zero. Then, simply machine the fixture features. When making parts, mount the fixture square to the table, and zero to the same corner, and you're ready to go.
Regards,
Ray L.
Re: multi part fixture reference
If I am doing one part or 4 parts I will put a tooling hole at the front left corner of each part. Then I can check against absolute X Y zero if I feel the need to check parts for location.
If I'm making small parts, I'll make 2 fixtures so I can have one in the machine working and one on the bench being loaded.
Re: multi part fixture reference
So If I understand this,
The advantage of a fixture based work offset, oppose to a workpiece offset, is that the fixture offset has reference to a part feature, whereas the workpiece offset references itself.
A reference point on the fixture plate (corner or hole) is set/declared for G54 work offset, for example.
The fixture plate will have points with holddowns,stops or pins that reference G54 when built.
There fixed points constrain the work piece parts and assumes the referenced to G54.
Parts all reference G54 by an offset that varies according to its position on the fixture plate.
This G54 offset absolute value is critical and must be established during initial holddown, stop or pin placement in CAM.
The G54 offset value should be a short round number and not like 1.245824, to prevent truncated position errors.
The CAM will permit multiple copies of the initial part; beware of truncated offset values after many copies.
The CAM, part separation feature, for copied parts will automatically calculate the G54 offsets.
Re: multi part fixture reference
Sounds like you got the concept right. Perhaps you're overthinking it a little bit. When you make the fixture you will establish the relationship between the reference feature (G54 XYZ0) and the features that locate the parts. In CAM just move the XYZ0 accordingly and then pattern the part at the required spacing for your array of parts.
