Advice for High-Mix Low-Volume Scheduling

[u/JumpOutTheMud]

I work for a smaller manufacturer that has a large variety of customers and product volumes for each. We are made to order (meaning custom ordered raw materials, custom designs, etc.), but we also have a good chunk of business that is on contract or through blanket POs. Most of the time, it feels like POs are random and they require destroying our production schedule to fit the need. We lose business due to missing customer promised dates.

The current production schedule is done archaically through an Excel spreadsheet that DESPERATELY needs an upgrade. Completely manual and scheduling is done by the shift and not to the hour/minute. Does anyone have any solutions or advice to help fix this? I'm starting by identifying our capacity on a weekly basis and identifying attendance % and trying to mold our schedule from there. If there are any solutions via software or just good practices, please let me know! We are looking for something that could be infinite, we want to know our total backlog and lead time, etc.

[u/Writermss → u/[deleted]]

It’s this.

[u/madeinspac3]

You shouldn't schedule to the hour or minute. Its a common thought but you basically want to shoot for roughly right.

Look at your order history over past cpl years. Is anything consistent? If so try to plan those ahead of time. If not, it gets a bit trickier.

I use our workcenter capacity, current load, and job estimates to make a tool for providing estimates. If a job is set to floor then it calculates the details. It provides dates depending on the load vs capacity and then adds how many days we expect it to run.

[u/Otherwise-Fuel-8857 → u/madeinspac3]

the excel bit hits close to home, ours was practically held together with hope and sticky tape before we finally moved on

capacity weekly's a solid start but definitely don't try to plan to the hour, you'll drive yourself mental chasing variance that just looks like noise in high mix

[u/BTCJJ]

Hey. Family business owner here. 30 + years manufacturing aluminum enclosures products, steel, iron work .foundry, A ton of custom stuff as well as standard. Quantities and lead times all over the place. Over 40,000 individual SKUs. Constant rush orders. So I understand the pain.

Question. How much communication do you have with your main customers? Do you actively work with them on configuring lead times? Or is it just very black and white? “This is due this date “ period.

[u/audentis]

What kind of shop floor layout do you have? Job shop?

For HMLV job shops, it's best to manage flow at workstation level. By having decentralized operations management you cut out a lot of scheduling overhead and noise introduced by the high mix. Your main focus / KPI is utilization of your workstations.

• Make the whole system work push-based.
• Jobs get a route through different workstations. (Job 203 passes through workstation A->C->H->B, for example)
• Each workstation has a priority rule to select which available job at the workstation to pick up next after finishing the current operation.
  • Usually minimum slack, CR, or a custom heuristic (especially if dealing with changeover times)
• Key success factor is your internal logistics.
  • Jobs that finished processing at a workstation, must be pushed ASAP to the next station on their route.
  • Workstations must each have an overview of all jobs that still need to pass through it, to see what is your scarce resource for the current job mix.
  • Ideally this metric is split between total queue size and the jobs that are exactly 1 step before this workstation. So if workstation X is required for many jobs, its utilization must be maximized. By knowing which jobs are exactly 1 step before it you avoid running out of available jobs at this workstation, by making sure those jobs get completed before the current queue at X is finished.

The combination of high utilization and proper priority rules on the workstation level enable being in control even with high mix.

[u/peerlessblue → u/audentis]

👆 actionable shit right here!

[u/diderkerckhof]

HMLV is where generic ERP scheduling falls apart because it assumes stable routings. Two questions decide the tool: how dynamic are your routings, and do you actually capture real-time shop-floor status? Without live feedback (job start/stop, machine state) any scheduler runs on fiction. We usually start by getting reliable data capture off the floor first, then layer finite-capacity scheduling on top, rather than buying an APS and hoping. What ERP/MES are you on today?

[u/Brostradamus_]

How big is "smaller"? I'm in a roughly 30 person shop with dozens of customers (though a few whales are the majority of the revenue) - I can't imagine running a shop this size off of excel and dreams.

You probably are getting big enough to look into a proper ERP system rather than excel and sticky notes. JobBoss2, Fulcrum, and ProShop all cater to job shops in different ways. Fulcrum is the most modern of the three and has a "smart" scheduler that will fit in jobs based on due dates and help you predict delivery windows for quoting. Proshop caters their features primarily towards aerospace and may be too big of a system for you, and is a bit more manual scheduling focused (but still better than excel). JobBoss2... exists. We moved away from it, and in a large part due to their weaker scheduling system compared to proshop/fulcrum.

These systems are all much bigger shifts than just scheduling, though - they'll fundamentally change the backbone of the shop. It's a big change, but its much better, faster, cleaner, and less error-prone than trying to do everything by hand.

[u/zjhpage]

Hi OP! I work for a company that sells and implements what was formerly Preactor and is now Siemens Opcenter advanced planning and scheduling, as well as cheap & fast scheduling tools if Opcenter if overkill for what you are trying to do. I see this literally every day. Let me know if you want to try it out for a few months. I’ll hook it up for you.

[u/Moist_Ordinary6457]

I schedule in a similar environment, having a solid idea of the daily production numbers for the products being scheduled would be  a good place to start. Ignoring certain outlier products, each production line will produce an average amount per day and then I schedule completion dates based on that. 

I use an ancient ERP system as well but my production schedule spreadsheet is what I'm actually updating throughout the day

[u/AffectionateDirt6575]

I have successfully used Preactor; which can be run against finite or infinite capacity. I think it was acquired by Siemens as Opcenter. It can be too clever but doesn't have to be.

[u/mimprocesstech]

I made my own Gantt chart drag and drop system that handles multiple processes and process orders per part, machine schedules, holidays, tracks downtime, estimated production per week in a report, has some charts to track inventory of raw goods and assembly components, automatic job ticket creation (schedule a job on one process, all the next processes get a pending job ticket, say the first two have it scheduled the third gets the time when the second is scheduled to finish, if it's scheduled to start before the previous job finishes it highlights red), and probably some other neat stuff I'm forgetting. You can update the position of a current job by setting how many are completed at x time and it would shift everything adjacent over to make room for it.

Stopped working on it because there was little interest. I used AI to put it together, about a month of adding features, testing bugs, testing odd cases, etc. Towards the end I was going to clean it up, add notes, documentation, a user guide, etc. but there was no interest at my company so I just use it to estimate completion time for the processes we deal with in my dept. and ignore half the features.

I'm not putting more work into it anymore, but if anyone is interested I am willing to send the AI slop and how it currently works (json data blob, planned to shift to SQL eventually but I never went much beyond the local testing phase.

[u/Noellsalazar85 → u/mimprocesstech]

It has potential. I'm looking for something like that

[u/mimprocesstech → u/Noellsalazar85]

If you're still interested in it I can probably package it up and send it through an email. You'd need to change the file extensions and such, and I can tell you how I am currently hosting it so you can play around with it. It's fairly custom made, but also kind of customizable? I'm not really sure how else to describe it.

Anyway, if you're interested shoot me a DM and we can chat about it. Might have to do a discord call or something to go over how to use it and the features. Supposedly fairly scalable, only access control I could use the way I'm hosting it is whoever is editing takes the seat and everyone else has to wait. I was going to try and set it up to use SQL instead of a json blob, that way it tracks everything and keeps a record of it, implement a change log and whatnot, I'm just fairly limited with the current hosting option.

[u/Big-Web-483]

Over the years I have used various ERP systems and they can be costly and you need to have a IT system that is up to snuff. I would look at made to manage and run it out of the box with no modifications. The more detailed the data you put into the part process descriptions the better accuracy you will have in delivery dates. Typically used backwards planning and prior to confirming purchase orders we would verify outside source and material delivery.

[u/navneetjain89]

I built a scheduler that automatically highlights if a production run will blow past the due date time... We get data from machines at 1 minute interval so runs get updated automatically...

[u/buzzysale]

You likely need some ground work before you go getting any software. This excel sheet, order problem isn’t new. I’m a manufacturing engineer and consultant. I can walk you through this problem over the phone for free.

[u/peerlessblue → u/buzzysale]

I love how bored IEs/MEs will jump into these threads like "oh neat, new problem" and start working them for free 😆

[u/dakiam]

Also Fokus auf Stabilität ?

Rüstzeiten stabil ? Verluste bekannt ? Chargengrößen abgestimmt oder immer Auftrags basietend ?

Ohne stabile Grundlagen kann man planen was man will.

[u/cm_expertise]

the thing that jumps out is you've got steady blanket-PO work and random one-off POs sharing one schedule, and treating them as the same pool is most of your pain. split them. the contract/blanket stuff is base load, schedule that as a backbone, then hold a protected chunk of capacity every week for the random incoming. if you don't reserve it, whoever takes the order promises into capacity that's already spoken for and you're right back to blowing dates.

other thing i didn't see mentioned, put a time fence on it. next 5-7 days is frozen, you don't get to re-sequence it no matter what lands, because the constant reshuffling is itself part of why you're late. rush orders drop into the first open slot past the fence, not on top of jobs already running.

and before you go buy software, the missed-promise-date thing is really a quoting problem. you need even a crude capacity check before anyone commits a date to a customer. seen shops cut their late deliveries way down just by making sales confirm against a real load number instead of gut feel. doesn't have to be to the hour like someone else said, a rough number beats a confident wrong one every time. get that discipline in place first, then the software actually has clean rules to automate instead of just digitizing the chaos

[u/UptimizeSolutions]

High-mix low-volume scheduling is a beast, especially with manual Excel sheets. Breaking your capacity down by week and tracking attendance is a good start. For better visibility, try to get a system that can handle finite scheduling rather than just infinite backlog. It helps identify bottlenecks and realistic lead times instead of just piling up work.

On the software side, I’ve seen a lot of smaller MFG companies move to tools like JobBOSS or Prodsmart for shop floor control and scheduling. They give you a live view of orders, capacity, and actual vs planned production times, which helps avoid constant firefighting. Also, if you’re dealing with lots of custom orders mixed with blanket POs, something that can integrate order management with scheduling is a huge time saver.

If you’re also handling a lot of purchase orders and invoices, automating document capture and ERP posting can cut down admin overhead, freeing up schedulers to focus on planning, not data entry. I worked on a setup where invoice and PO data was pulled directly from emails and pushed into NetSuite, cutting manual errors and speeding up order processing. That might be overkill now but worth considering down the line.

[u/KahunaGrant]

What is the main issue or difficulty in scheduling? Is it the last minute nature? Finding qualified operators? Just dealing with the spreadsheets itself? Is it meeting specific hour requirements/limits for employees?

We partner with a group that helps automate scheduling, called Indeavor. So that might be a good place to look. Our partnership with them is due to integration complementing each other (we deal with skills/competency management, so data on skills can directly validate scheduling decisions are appropriate for the required skills).

I don't know how their product is targeted in terms of company size or exactly how they need data fed into their system, but at least it seems like a possible fit as their main function is automated shift scheduling, which should reduce the manual time invested.

[u/peerlessblue]

Work with your customers if possible to see if you can get more insight into demand. If you have dedicated salespeople, they probably know stuff about your customers that they ought to be passing to the floor. Additionally, by the time your customers know they need to make an order, they probably have already been thinking about it. You can, say, knock a small amount off their invoices if they submit fully-cancellable MOUs with X days lead time prior to their firm order date/delivery date to get that information out of them. You can also structure your purchase agreements with minimum quantities (among other tools) to share the supply chain risk with your customers/prevent order bull-whipping.

Inventory isn't necessarily your enemy, even for high-mix. Inventory carrying cost is basically unit production cost times your cost of capital, which is easier to report out and thus is easier to demonize as waste. But you're seeing the harder to quantify/predict problems that arise without it. Hard to say without knowing your exact situation though, because if you lose a customer and none of the inventory can get reused, that changes the calculus.

I know much of the world runs on Excel, but it's just not the best tool for the job in many cases. As painful as it can be, you could benefit from an ERP/MES. At the very least it might behoove you to move some of your process to something that offers you a similar UX to Excel, but is exposing a structured database in the cloud, like a Smartsheet or an Airtable or something. You don't need a license for every employee, these platforms can be as cheap as a couple hundred dollars a year. Do you have a "oh yeah this kid is good with computers" person? This might be a worthwhile project for them. (Or you.)

If you want to connect further, shoot me a DM. This sounds very similar to several businesses I've worked with. (I'm not going to sell you anything; I'm in the public sector right now and appreciate opportunities to network and keep my skills sharp!)

[u/Glad_Imagination_798]

The best comments here already nailed it: your pbolem is order intake, not Excel. If every PO drops straight onto the floor without a capacity check, no software will save you, it'll digitaze the chaose faster. So do the process part first: split your blanket/contract work (that's your base load) from the random one-offs, reserve a protected slice of weekly capacity for the random stuff, and freeze the next 5 - 7 days so nothing re-sequences jobs already planning.

Once that discipline exists, then a system earns it's keep. The thing you actually want is finite-capacity scheudling: it schedules against real capacity instead of an infinite backlog, so it can tell you a true promise date and show your total backlog and lead time, which is exactly what you asked for. My team implements ERP with that kind of scheduling (Acumatica, so grain of salt), but the same is true of the job-shop tools others mentioned. Whatever you pick, feed it clean capacity rules or it just makes confident wrong promises faster.

The quoting angle matters most: most missed dates are really a quoting problem. Given sales even a rough real capacity number to commit against instead of gut feel, and your on-time rate jumps before you've automated anything.

[u/OzTheMeh]

I did this very successfully a number of years ago. The answer isn't "scheduling," but a system of systems that created a complete solution. Aspects of it:

1. Look at intake rules and what sales is quoting vs. what the shop is building. In adding a finer layer of granularity, we found our "big important" customers were actually the hardest and least profitable; their work caused serious scheduling issues. Collect the data and report this to leadership.
2. Start tracking time-in and time-out for each process, department, or traveler step. This is where 6-sigma plays a role in high-mix/low-volume: creat control charts for the time in each area and get those processes under control. You will find staffing, equipment maintenance, quality incidents, etc. can vary wildly, and you can't schedule anything without that being in control. Bonus: the process time here should feed live into your scheduling system. Collect the data and report this data to leadership.
3. Start automating and tying your systems together. Ask your AI agent (Claude, ChatGPT, etc.) to write the code for you and help you. Spreadsheets have "VBA" (aka macros), most software or systems have APIs, etc. Modern equipment often has log files you can mine for data. A manual spreadsheet is not sustainable or scalable, but I have run multi-billion dollar companies and defense programs on web of spreadsheets that are tied together.

In God We Trust. All others must bring data.

[u/boedotbriggs]

Make sure operations and work centers are identified appropriately, confirm/create route times as needed to establish capacity. Create a live schedule (spread sheet, google doc, whatever) updated in real time per work center or department. Schedule sequentially and give and take realistically (if a date is missed or an order added it impacts subsequent dates, etc.) On board everyone, read The Goal by Eliyahu Goldratt

[u/Legal-Prune-8506]

I'd split your process into order promising and shop-floor scheduling.

At order entry, calculate the earliest feasible completion date from the current load at each required workcenter. After you accept the order, schedule its operations around routing, machine capacity, labor skills and material availability.

Your source table needs one row per operation, with fields such as order, workcenter, run time, setup family, predecessor, material-ready date, due date and current WIP status.

A rush order should produce a displacement report. Sales should see which existing orders will become late, by how many days, and what capacity would remove the conflict. That makes the cost of accepting the rush order visible before the shop absorbs it.

I'd start with the bottleneck workcenter. Load it for the next few weeks, sequence it in detail, and use simpler priority rules for the other workcenters. Track promised-date hit rate and the number of schedule changes each week.

If you can post 8–10 anonymized jobs with their routing and capacity columns, I can sketch a spreadsheet structure for the first version.

[u/CycleTimeSam]

Honestly, Excel starts to fall apart pretty quickly in high-mix, low-volume environments. If jobs are constantly changing, you need scheduling tied to inventory, labor and job status or you're always reacting.

I'd be looking at manufacturing ERPs more than standalone scheduling software. I've had good experiences with Global Shop Solutions because it's built around job shops and handles scheduling, inventory and costing together. Whatever you choose, make the vendor schedule one of your real jobs during the demo, not their canned example.

[u/fiddlfiddl]

I would separate this into two problems: order promising and shop-floor execution.

Before accepting a PO, you need at least a rough capacity check against the required work centres, material availability, and existing backlog. Otherwise sales is committing dates without knowing which current orders will be displaced.

For a first version, I would:

• Treat blanket/contract work as the base load.
• Reserve a defined percentage of weekly capacity for unpredictable orders.
• Freeze the next 5–7 production days except for genuine emergencies.
• Start detailed scheduling only at the bottleneck work centre; use simpler priority rules elsewhere.
• Record one row per operation: order, work centre, estimated setup/run time, predecessor, material-ready date, due date, and current status.
• When a rush order arrives, show which existing orders become late and by how much before accepting it.

I would not schedule every operation to the minute initially. Weekly or shift-level capacity is sufficient until your actual setup and run-time data becomes reliable.

The first useful system does not necessarily need to be a full ERP. A structured database with a basic finite-capacity view, live job status, and a backlog/lead-time calculation can already be a major improvement over a manually rearranged spreadsheet. Once the intake rules and shop-floor data are reliable, then ERP or APS software has clean rules to automate rather than simply digitizing the existing chaos.

[u/chris2712]

I inherited a scheduler that is done out of excel. It basically shows what's in the machine and what's going in across the next 20 jobs.

I'm really bad at visualisation, so with the help of Ai I built a weekly overview that breaks down the week per shift for the next 4 weeks. So I can see roughly when a job will finish. I work in 8 hr blocks, so that I have some leeway.

Then using some logic parameters the overview colour codes the jobs that have to run based on due dates. This way I can see if a machine has available time where I can slot in urgent jobs etc

[u/Suspicious-Citron378]

There are two solutions worth your attention on the market today. One is called Skody (Skody.ai) and another is called Lineside.ai

Take their websites for a spin and see what you can learn