Two grippers, same part mass, very different overhang

RachelBarnes0609 · 26 Mar 2025, 23:18 UTC

Closed
RA
RachelBarnes0609
I'm reviewing two UR5e tooling offers for a cast housing. One holds it close to the flange; the other uses long fingers and an adapter. Both suitability notes quote only the housing mass. What information should be in the review before we compare prices? I don't want to ask the supplier a question so broad they just resend the brochure.

17 replies

HE
HenryBarnes0525
Replying to RachelBarnes0609

Request the complete loaded tool's mass and centre of gravity relative to the flange, with the geometry that produced those values; the bare housing isn't the assembly

23 points
RA
RachelBarnes0609
Replying to HenryBarnes0525

That gives me a concrete request, thanks. Their totals don't include hose fittings either. I'll ask for an itemised assembly and the held-part position.

9 points
HE
HenryBarnes0525
Replying to RachelBarnes0609

Include the proposed operating movement in the assessment too, since a static mass comparison won't cover every load the robot and tooling see

11 points
AA
AaronBaker0436
Replying to RachelBarnes0609

Have the integrator check the assembly against the manufacturer's applicable load guidance, including moments and inertia where required. Long fingers can matter even when the total mass looks comfortable.

15 points
HE
HenryBarnes0525
Replying to AaronBaker0436

And ask who owns that check in the quote; a tool supplier's yes and a robot supplier's maybe don't add up to one responsible acceptance

25 points
JA
JaneBaker0510
Replying to RachelBarnes0609

Can the close-in tool release the housing where you need it? Geometry isn't automatically better because it's shorter

0 points
HE
HenryBarnes0525
Replying to JaneBaker0510

Good point, I was concentrating on loading; reach and release access need checking for both complete proposals as well

18 points
RA
RachelBarnes0609
Replying to JaneBaker0510

The longer fingers clear a lip on our receiving nest. The short tool would need a nest alteration. That's in a footnote I hadn't connected to the comparison.

12 points
HE
HenryBarnes0525
Replying to RachelBarnes0609

Then price that alteration and have its locating function reviewed, otherwise the short tool's apparent saving excludes work required to make it usable

19 points
DI
DineshBrooks0821
Replying to RachelBarnes0609

Check service access to the tool connections too. More precisely, ask maintenance whether either arrangement can be inspected and replaced as intended. A fitting trapped behind the adapter can make a minor cable fault a much longer interruption.

21 points
RA
RachelBarnes0609
Replying to DineshBrooks0821

Maintenance has the drawings now. I've added the nest change and connection access to our questions. Neither supplier has yet assessed the complete loaded arrangement against the intended job.

2 points
JA
JaneBaker0510
Replying to RachelBarnes0609

Then neither offer is ready for a technical sign-off, however tidy the part-mass comparison looks

16 points
RA
RachelBarnes0609
Replying to JaneBaker0510

Purchasing has separated commercial comparison from the outstanding technical review. We still need the suppliers' assembly data. I can explain the hold now without claiming one tool is unsuitable.

4 points
HE
HenryBarnes0525
Replying to RachelBarnes0609

Ask them to identify any assumptions in those data, especially the housing orientation; a centre-of-gravity figure without its reference frame is a pain to use

16 points
AA
AaronBaker0436
Replying to HenryBarnes0525

A labelled assembly drawing helps there. It should show the flange reference and the held housing location so the reviewer can reproduce the supplier's calculation basis.

15 points
HE
HenryBarnes0525
Replying to AaronBaker0436

Yes, and keep the tool-only and tool-with-part configurations explicit if both are relevant to the robot setup; don't leave somebody guessing which total to enter

12 points
DI
DineshBrooks0821
Replying to HenryBarnes0525

Make the accepted assembly information part of the replacement process. Otherwise a future adapter or finger change can leave the documented load configuration describing tooling that is no longer installed.

20 points

Discussion closed

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